Cost Study for Phase Two Small Engine Emission Regulations
Cost Study for Phase Two Small
Engine Emission Regulations
Draft Final Report
Submitted to
U.S. Environmental Protection Agency
Office of Mobile Sources
2565 Plymouth Road
Ann Arbor, MI 48105
October 25,1996
submitted bv
Lit-Mian Chan
and
Christopher S. Weaver, P.E.
Engine, Fuel, and Emissions Engineering,
9812 Old Wissery Place, Suite 22
Sacramento, CA 95827 USA
ph. (916) 368-4770
fax (916) 362-2579
David Goldbloom-Helzner, Tom Uden,
Kelly Connolly, Barry Galef, and
Isabel Reiff
ICF Consulting Group
9300 Lee Highway
Fairfax, VA 22031-1207
ph. (703) 934-3599
fax (703) 218-2668
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Cost Study for Phase Two Small Engine Emission Regulations
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CONTENTS
1. INTRODUCTION [
1.1 Phase 1 Emission Standards 1
1.2 Phase 2 Emission Standards 2
1.3 Scope and Approach of Cost Study 2
PART I BOTTOM UP COST ANALYSIS FOR NON-HANDHELD EQUIP-
MENT ENGINES 5
2. NON-HANDHELD ENGINES 6
2.1 Operating Principle of Small Four-Stroke Engines- 6
2.2 Side-Valve Versus Overhead-Valve Engines 8
2.3 Emissions Levels for Small Non-Handheld Eneines 11
2.4 Emission Control Technologies for Four-Stroke Non-Handheld Engines 12
3. COST ANALYSIS FOR CONVERTING SIDE-VALVE TO OVERHEAD-VALVE
ENGINES 18
3.1 Analysis of Parts Used in Side-valve and Overhead-valve Engines 18
3.2 Cost of Converting from SV to OHV 23
4. COST ANALYSES FOR IMPROVING SIDE-VALVE ENGINES 31
4.1 Improvement in Combustion and Intake Systems ....... 31
4.2 Improvement in Spark Ignition and Timing 33
4.3 Optimization in Valve Timing and Cam Design 34
4.4 Improvement in Piston and Ring Designs 35
4.5 Improvement in Manufacturing Variability 38
4.6 Improvement in Carburetor 39
5. COST ANALYSES FOR IMPROVING OVERHEAD-VALVE ENGINES 41
5.1 Improvement in Combustion and Intake Systems 41
5.2 Improvement in Piston and Ring Designs and Bore Smoothness 43
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PART n BOTTOM UP COST ANALYSIS FOR HANDHELD EQUIPMENT
ENGINES 45
6. HANDHELD ENGINES 46
6.1 Operating Principles of Small Two-Stroke Engines 46
6.2 Causes of Emissions from Two-Stroke Engines 48
6.3 Emission Levels for Handheld Two-Stroke Engines Meeting EPA Phase 1
Emission Standards 49
6.4 Emission Control Technologies for Small Two-Stroke Engines 50
7. COST ANALYSIS FOR CONVERTING TWO-STROKE
TO FOUR-STROKE ENGINES 59
7.1 Comparison of Two-stroke and Four-stroke Engines 59
7.2 Cost Analysis 63
8. COST ANALYSIS FOR IMPROVING TWO-STROKE ENGINES 68
8.1 Two-Stroke Engines with Improved Scavenging 68
8.2 Two-Stroke Engines with Stratified Scavenging 69
9. COST ANALYSIS FOR TWO-STROKE ENGINES
WITH CATALYST 72
9.1 Two-Stroke Engines with Catalyst 72
9.2 Improved Engine Designs with Catalyst : 74
PART HI EQUIPMENT COSTS, USER COSTS AND CONSTRAINTS 75
10. COST ESTIMATE TO ADAPT EQUIPMENT TO MODIFIED ENGINE TECH-
NOLOGIES 76
10.1 Non-Handheld Equipment 77
10.2 Modifications to Handheld Equipment due to Engine Changes 81
11. USER COSTS - 87
11.1 Fuel Cost Savings 87
11.2 Lifccvclc Maintenance Savings 90
12. CONSTRAINTS 93
12.1 Rule-Related Constraints 93
12.2 Manufacturer-Related Constraints 99
12.3 Technology-Related Constraints 102
13. SUMMARY 1°5
14. REFERENCES 108
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APPENDICES
APPENDIX A
ELECTRONIC CONTROL SYSTEMS AND EXHAUST
AFTERTREATMENTS TECHNOLOGIES FOR NON-HANDHELD ENGINES
APPENDIX B
EXPLODED VIEW AND PARTS OF
NON-HANDHELD AND HANDHELD ENGINES
APPENDIX C
ADDITIONAL TECHNOLOGIES TO REDUCE
EMISSIONS IN HANDHELD ENGINES
APPENDIX D
DETERMINING HIGH, INTERMEDIATE, AND LOW VOLUME
ENGINE FAMILIES FOR NON-HANDHELD AND HANDHELD ENGINES
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LIST OF FIGURES
Figure 1: Diagrams to illustrate the operating principles of four-stroke engines with side-
valve and overhead-valve configurations 7
Figure 2: Illustrations for a side-valve (L-head) and an overhead-valve (I-head) arrange-
ments and combustion chambers 8
Figure 3: The valve train and operation for a side-valve engine 9
Figure 4: Operation of the valve train for an overhead-valve engine with a push rod
design 10
Figure 5: Mechanical layout of a typical overhead-valve, overhead-camshaft four-stroke
engine 10
Figure 6: A 1978 Honda overhead-valve, overhead-camshaft engine 11
Figure 7: CARB 199S certification data compared to EPA Phase 1 non-handheld engine
standards 12
Figure 8: Effect of air-fuel ratio on SI engine emissions 13
Figure 9: Typical effect of ignition timing on SI engine emissions and power output. ... 15
Figure 10: Combustion rate vs. crank angle for conventional and "fast-burn" combustion
chambers 16
Figure 11: Operation of a two-stroke, loop scavenged engine . 47
Figure 12: CARB 1995 certification data compared to EPA Phase 1 handheld engine
standards 50
Figure 13: Schematic to illustrate the stratified scavenging approach in a two-stroke
engine 52
Figure 14: Exploded view of the Ryobi four-stroke engine. 60
Figure 15: Exploded view of a Ryobi two-stroke engine 61
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LIST OF TABLES
Table 1; Phase 1 Emission Regulations for Small Spark-Ignition Engines 1
Table 2: Statement of Principles (May, 1996) on Phase 2 Emissions Levels for Class DH,
IV, and V Engines (Handheld Equipment) 2
Table 3: Engine Modification Technologies Addressed in Study. 3
Table 4: Major lawn mower engines with 5 to 6 hp 19
Table 5: Information on the additional parts for the B&S Europa OHV engine as
compared to the Quantum SV engine 20
Table 6: Comparison of similar components for a side-valve engine and an overhead-
valve engine 21
Table 7: Comparison of the weights for the cylinder heads and cylinders for a side-valve
engine and an overhead-valve engine 21
Table 8: Comparison of number of milling and boring operations in the cylinder head and
cylinder for SV and OHV engines 22
Table 9: Comparison of number of drilling and tapping operations in the cylinder head
and cylinder for SV and OHV engines 22
Table 10: Estimation of manufacturing costs for Class I OHV engine parts made in-
house 23
Table 11: Estimation of incremental variable manufacturing cost for Class I OHV engines
compared to SV engines 24
Table 12: Estimated fixed costs for the change from SV to OHV class I engine 25
Table 13: Estimated cost of emission testing. 26
Table 14: Summary of the variable and fixed costs for converting SV to OHV Class I
engines 28
Table 15: Estimated fixed costs for the changes in improving combustion chamber and
intake systems 32
Table 16: Estimated fixed costs for the changes in improving spark ignition and
timing 33
Table 17: Estimated fixed costs'for optimizing valve timing and cam design for SV
engines • 34
Table 18: Incremental variable manufacturing cost for improving piston and ring design
and adding exhaust valve stem bushing for SV engines 36
Table 19: Estimated fixed costs for the changes in improving piston and ring designs for
SV engines 37
Table 20: Summary of the variable and fixed costs for improving piston and ring designs
for SV engines 37
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Table 21: Estimated fixed costs for the changes in improving manufacturing variability
for SV engines 3£
Table 22: Summary of the variable and fixed costs for improving manufacturing
variability for SV and OHV engines 39
Table 23: Estimated fixed costs to reduce manufacturing variability in carburetors 40
Table 24: Summary of the total added manufacturing and fixed costs for improving
carburetor for SV and OHV engines 40
Table 25: Estimated fixed costs for the changes in improving combustion chamber and
intake systems for OHV engines 42
Table 26: Estimation of incremental variable manufacturing cost for improving piston and
ring designs for OHV engines 43
Table 27: Estimated fixed costs for the changes in improving piston and ring designs for
SV engines 44
Table 28: Summary of the variable and fixed costs for improving piston and ring designs
for SV engines 44
Table 29: Average emission levels for handheld equipment engines that meet EPA Phase
1 and CARB Tier I standards 50
Table 30: Information on the additional parts for the Ryobi four-stroke engine as
compared to the two-stroke engine 62
Table 31: Estimation of incremental variable manufacturing cost for four-stroke engine
compared to two-stroke engine 64
Table 32: Estimation of manufacturing costs for four-stroke engine parts made in-
house . 65
Table 33: Estimated fixed costs for converting two-stroke to four-stroke engines for
handheld equipment 66
Table 34: Summary of the total added manufacturing and fixed costs for converting 2-
stroke to 4-stroke handheld engines o5
Table 35: Estimated fixed costs for two-stroke engines with improved scavenging. ..... 69
Table 36: Manufacturing costs for additional parts for two-stroke engine with stratified
scavenging 70
Table 37: Estimated fixed costs for two-stroke engines with stratified scavenging 71
Table 38: Summary of the variable and fixed costs for 2-stroke \frith stratified scav-
enging 71
Table 39: Manufacturing costs for additional parts for two-stroke engine with catalyst. .. 73
Table 40: Estimated fixed costs for two-stroke engines with catalyst 73
Table 41: Summary of total hardware/assembly costs and fixed costs for two-stroke
engines and catalyst 74
Table 42: Summary of total hardware/assembly costs and fixed costs for improved two-
stroke engines with catalyst two-stroke engines with stratified scavenging and
catalyst, and 2-stroke to 4-stroke conversion with catlyst 74
Table 43: Features of the Modified Engines that Might Result in Equipment Changes. .. 76
77
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Table 45: Cost of Equipment Changes for Rear Engine Rider as a Result of SV to OHV
Conversion.
78
Ta6I& Cost of Equipment Changes for Lawn Tractor as a Result of SV to OHV
Conversion.
79
Table 47: Cost of Equipment Changes for Lawn and Garden Tractor as a Result of SV
to OHV Conversion. . 80
Table 48: Cost of Equipment Changes for Generator Sets as a Result of SV to OHV
Conversion. 80
Table 49: Cost of Equipment Changes for Pumps as a Result of SV to OHV Conversion.
81
Table 50: Comparison of equipment parts for a 2-stroke and a four-stroke engine 82
Table 51: Estimated equipment fixed costs for converting 2-stroke engines to 4-stroke en-
gines. 83
Table 52: Incremental variable costs for handheld equipment equipped with catalyst 84
Table 53: Incremental variable equipment cost for adding catalytic converter to hand-held
equipment 85
Table 54: Estimated equipment fixed costs for handheld engines with catalyst 86
Table 55: Summary of hardware/assembly and fixed costs to modify handheld equipment
to add catalytic converters 86
Table 56: Commercial Class I Non-handheld Lifetime Fuel Cost Savings by Engine
Modification . 89
Table 57: Residential Class I Non-handheld Lifetime Fuel Cost Savings by Engine
Modification 90
Table 58: Commercial Handheld Lifetime Fuel Savings by Engine Modification 89
Table 59: Residential Handheld Fuel Cost Savings by Engine Modification 91
Table 60: Oil service costs for tractor engines 92
Table 61: Characterization of Class II Non-handheld Engine Manufacturers 99
Table 62 Incremental Variable and Fixed Costs for Modifications to Non-Handheld
Engines 106
Table 63 Increment Variable and Fixed Costs for Modifications to handheld Engines ... 106
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1. INTRODUCTION
The U.S. Environmental Protection Agency (EPA) has determined that nonroad equipment and
engines contribute significantly to emissions and air pollution. A particular focus is on small
spark-ignition (SI) engines that power equipment such as lawnmowers, hedge trimmers, generator
sets, and small pumps. In an effort to reduce these emissions, EPA is taking steps to phase-in
emission reduction regulations on small SI engines. The California Air Resources Board is also
pursuing a phased-in approach for reducing emissions from utility engines.
1.1 Phase 1 Emission Standards
EPA published Phase 1 emission reduction regulations for small spark-ignition (SI) engines on
July 3, 1995. These regulations contain exhaust emission standards for new small SI engines at
or below 19 kilowatts (25 horsepower) in five classes (Table 1). The small SI engine are divided
into five classes corresponding to handheld equipment engines and non-handheld equipment
engines.
Table 1: Phase 1 Emission Regulations for Small Spark-Ignition Engines.
Engine
Class
Displacement
(cc)
Equipment
Type
HC+NOx
(g/kw-hr)
HC
(g/kw-hr)
CO
(g/kw-hr)
NOx
(g/kw-hr)
I
<225
non-hand-
held
16.1
—
469
—
n
>225
non-hand-
held
13.4
—
469
—
in
<20
handheld
—
295
805
5.36
IV
>20 & <50
handheld
—
241
805
5.36
V
>50
handheld
—
161
603
5.36
These standards must be met by new engines by model year 1997. In-use deterioration is not
considered in Phase 1. In the rulemaking, EPA evaluated the cost implications of the emission
levels on industry (EPA, May 1995). The EPA Phase 1 standards are similar to the emission
reduction (Tier 1) standards set by the California Air Resources Board (CARB).
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1.2 Phase 2 Emission Standards
From 1993 to Februaiy 1996, EPA participated in a regulatory negotiation process involving
government, industry, and environmental groups to develop Phase 2 emission regulations for
small SI engines. In subsequent efforts, a Statement of Principles (SOP) was developed on
handheld engines. This SOP proposes Phase 2 deteriorated certification standards for handheld
engine, to be met at the useful life hours (Table 2).
Table 2: Statement of Principles (May, 1996) on Phase 2 Emissions Levels for Class ID, IV, and
V Engines (Handheld Equipment).
Engine
Class
HC + NOx
(g/kW-hr)
CO
(g/kW-hr)
Useful Life (Hours)
Consumer/Commercial
m
210
80S
50/300
IV
172
805
50/300
V
116
603
50/300
These levels for Class m, IV, and V engines will be proposed as straight, rather than averaging
standards; thus, each engine produced would have to meet these levels. EPA will propose that
these levels be phased in over four years beginning with model year 2002, as follows:
Model Year Percent of Production
2002 20%
2003 40%
2004 70%
2005 100%
An SOP is being developed for the non-handheld engines.
13 Scone and Approach of Cost Study
The purpose of this cost study is to provide further cost-benefit analysis for the rulemaking(s)
for Phase 2 standards for small (<19 kilowatts) spark-ignition engines used in handheld and non-
handheld equipment The effort was to determine the incremental costs incurred by manufactur-
ers oyer the Phase 1 baseline costs to reduce emissions further to meet Phase 2 emission
standards. In the study, data sources consulted included:
(1) Regulatory Impact Analysis and Regulatory Support Document for Emission Standards
for New Nonroad Spark-ignition Engines at or Below 19 Kilowatts;
(2) regulatory negotiation task group reports;
(3) EPA alternative technology assessment reports;
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(4) CARB technical review report;
(5) cost, emissions, technology, useful life, and deterioration factor (DF) information from
a variety of engine manufacturers;
(6) engine data from the Power Systems Research ENGLNDATA database;
(7) conversations with engine and equipment manufacturers, distributors, and retailers; and
(8) inhouse literature
Some sections of the study on handheld equipment engines were based on cost analyses
performed for CARB in support of technology reviews of Tier n. It should be noted that some
of the manufacturer information was classified as confidential business information, but was
guaranteed by EPA and its contractors to not be used in this study.
The primary approach used in this study was to perform a bottom-up analysis to estimate the
incremental costs for modifying or changing an engine to reduce emissions below Phase 1 levels.
The scope includes engines used in both handheld and non-handheld equipment. The types of
costs estimated include variable hardware costs (e.g., materials), production costs (e.g., tooling),
and fixed costs (e.g., research and development). The bottom-up approach builds up the cost
estimate based on the hardware, production, and fixed costs associated with individual engine
parts that will be needed or modified. In some cases, the actual engines were purchased and
taken apart to determine the need for additional or modified parts. The cost estimates were based
without reference to similar estimates developed by engine manufacturers.
The bottom up cost approach focused on six engine technology modifications identified by EPA
as the most likely technologies that will be used by engine manufacturers to reduce emissions
from Phase 1 standards (Table 3). The three technology modifications that apply to non-handheld
equipment (engine classes I and II) are improved side-valve (SV) design, conversion to overhead-
valve (OHV) design, and improved overhead-valve design. The three technologies that apply to
handheld equipment (engine classes IE, IV, and V) are improved two-stroke design, conversion
of two-stroke to four-stroke design, and a two-stroke design with a catalyst.
Table 3: Engine Modification Technologies Addressed in Study.
Engine
Class
Equipment
Engine Modification Technologies Addressed in
Study
Class I and
n
Non-
Handheld
Improved Side-valve Design
Improved Overhead-valve Design
Conversion of Side-valve to Overhead-valve Design
Class 01,
IV, and V
Handheld
Improved Two-Stroke Design
Stratified Charge and Catalyst Design
Conversion of Two to Four-Stroke Design
The study is organized into three parts. Part I provides a bottom up cost analysis for non-
handheld equipment engines (engine classes I and II). Within Part I, there are several chapters.
Chapter 2 presents a description of small non-handheld equipment engines using the four-stroke
engine, and a discussion of technical feasibility issues and emission rates. The remaining
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chapters in Part I provide a cost analysis for converting side-valve to overhead-valve engines
(Chapter 3), a cost analysis for improving side-valve engines (Chapter 4), and a cost analysis for
improving overhead-Valve engines (Chapter 5).
Part II of the study provides a bottom up cost analysis for handheld equipment engines (engine
classes III, IV, and V). Within Part n, there are several chapters. Chapter 6 presents a
description of small two-stroke engines including technical feasibility issues and emission rates.
The remaining chapters in Part II provide a cost analysis for converting two-stroke to four-stroke
engines (Chapter 7), a cost analysis for improving two-stroke engines (Chapter 8), and a cost
analysis for a two-stroke engine with a catalyst (Chapter 9).
Part HI of the study provides cost estimates that may be incurred by the equipment manufacturer
to adapt or redesign equipment to incorporate a modified engine technology (Chapter 10). For
example, a modified engine that results in a larger engine may not fit under the hood of a lawn
tractor. Part III also addresses user costs (Chapter 11) associated with using a modified engine.
The user costs consisted of the incremental costs associated with fuel saving or consumption, and
increased/decreased maintenance. Chapter 12 discusses various constraints that can potentially
impact engine costs. Rule-related constraints include issues such as lead time and phase-in
schedule, and timing for retiring old equipment Manufacturer-related constraints include issues
such as the effect of different production volumes and market penetration. Technology-related
constraints include issues such as the feasibility of the technology and its possible use in various
equipment applications. Chapter 13 summarizes the study and discusses limitations. References
are provided in Chapter 14.
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PARTI
BOTTOM UP COST ANALYSIS FOR NON-HANDHELD
EQUIPMENT ENGINES
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2. NON-HANDHELD ENGINES
Almost all small engines used in non-handheld equipment are small, air-cooled, reciprocating
Otto-cycle engines using gasoline fuel. These small engines are primarily of the four-stroke
design (in contrast to two-stroke designs usually used in handheld equipment) either using side-
valves (SV) or overhead-valves (OHV). This chapter discusses the operating principles and
different valve configurations of small four-stroke engines. The rest of Part 1 - non-handheld
engines (Chapters 3, 4, and 5) present incremental cost analyses of SV to OHV conversion,
improving SV design, and improving OHV design.
2.1 Operating Principle of Small Four-Stroke Engines
Figure 1 illustrates the operating principle of a four-stroke engine with a SV configuration (top
diagrams), and an OHV configuration (bottom diagrams). As this figure shows, engine operation
takes place in four distinct steps, which are intake, compression, power, and exhaust. Each step
corresponds to one "stroke" of the piston, or 180° of crankshaft rotation. During the intake
stroke, the intake valve opens to admit a mixture of air and fuel, which is drawn into the cylinder
by the vacuum created by the downward motion of the piston. Diagram a in Figure 1 shows the
piston near the end of the intake stroke, approaching bottom-dead-center. During the
compression stroke, as shown in diagram b, the intake valve closes, and the upward motion of
the piston compresses the air-fuel mixture into the combustion chamber between the top of the
piston and the cylinder head.
The compression stroke ends when the piston reaches top-dead-center. Shortly before this point,
the air-fuel mixture is ignited by a spark from the spark plug, and begins to bum. Combustion
of the air-fuel mixture takes place near top-dead-center, increasing the temperature and pressure
of the trapped gases. During the power stroke (diagram c), the pressure of the hot burned gases
pushes the piston down, turning the crankshaft and producing the power output of the engine.
As the piston approaches bottom-dead-center again, the exhaust valve opens, releasing the pent-
up burned gases. Finally, during the exhaust stroke (diagram d), the piston once more ascends
toward top-dead-center, pushing the remaining burned gases in the cylinder out the open exhaust
port as it does so. Near top-dead-center again, the exhaust valve closes and the intake valve
opens for the next intake stroke. Thus, combustion and the resulting power stroke occur only
once every two revolutions of the crankshaft in a four-stroke engine.
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(i) Side-valve engine
EXHAUST
VALVE
CLOSED
PISTON
CONNECTING
ROD
CRANKSHAFT
CAMSHAFT
(a) INTAKE
EXHAUST
VALVE
CLOSED
INTAKE
VALVE
CLOSED
EXHAUST
VALVE
OPEN
INTAKE
VALVE
CLOSED
BURNED
GASES
OUT
(ft) COMPRESSION
(c) POWER
(
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LONG FLAME TRAVEL CLEARANCE
L-HEAD l-HEAO
Source: (Crouse and Anglin, 1986)
Figure 2: Illustrations for a side-valve (L-head) and an overhead-valve (I-head) arrangements and
combustion chambers.
2.2 Side-Valve Versus Overhead-Valve Engines
The mechanical systems required by four-stroke engines to open and close their intake and
exhaust valves at the optimal time make these engines relatively complex to manufacture as
compared to a two-stroke engine design. Two different types of valve arrangements are generally
found in small four-stroke engines. These are the SV configuration (or L-head) and the OHV
configuration (or l-head) as shown in Figure 2. Each valve arrangement, discussed below,
requires a different type of valve train.
Side-Valve Engines
Most four-stroke engines found in non-handheld equipment use a SV configuration. In the SV
engine, the valves are below the cylinder head of the cylinder block (see the top diagram in
Figure 1). Figure 3 shows the valve train and operation of a SV engine. As this figure shows,
the gear in the crankshaft drives the cam gear, which in turn rotates the cam lobes on the
camshaft to push the valve lifters to lift the valves during the intake and exhaust strokes. This
makes it possible to eliminate the push rods and rocker arms, and drive the valves directly from
the camshaft, thus reducing the height of the engines and costs.
To accommodate the location of the valves in the engine block, the intake and exhaust ports for
a SV engine must be located at the bottom of an extension of the combustion chamber, which
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VALVE
SPRING '
RETAINER
TIMING MARK
SPRING
VALVE
LIFTER
VALVE
GUIDE
EXHAUST OR
INTAKE PORT
Source: (Crouse and Anglin, 1986)
if CRANKSHAFT
ie > />*»!
CAM
SPRING RETAINER
CYLINDER BLOCK
VALVE LIFTER
VALVE SPRING
VALVE GUIDE
OIL PASSAGE
CAMSHAFT
CAM
VALVE
LOBE
Figure 3: The valve train and operation for a side-valve engine.
projects out of the line of the cylinder bore (see the top diagram of Figure 1). This results in a
long, flattened combustion chamber. High surface to volume ratio, longer flame propagation
distance and longer combustion time characterize this type of combustion chamber.
Overhead-valve Engines
In the OHV engine, the valves are located in the cylinder head (see the bottom diagram of
Figure 1). There are several types of OHV engines, depending on the location of the camshaft.
The common camshaft location for small engines is similar to that for SV engines - at the bottom
of the cylinder near the crankshaft (see Figure 4). As shown in Figure 4, the camshaft is gear-
driven by the crankshaft, and cam followers in the cam assembly translate the circular motion
to linear motion. This linear motion is imparted to pushrods, which act on the rocker arms to
open the valves.
An alternative OHV design locates the camshaft in the cylinder head, as shown in Figure 5. This
design is common in high performance engines, such as those typically found in motorcycles.
For this design, the valves are opened by lobes on the camshaft, which is driven at one-half en-
gine speed by a sprocket and chain arrangement from the crankshaft. The camshaft lobes press
on the valve followers, pushing up on the rocker arms, and causing the valves to open appropri-
ately at every second crankshaft revolution. The camshaft, valve linkage, crankshaft bearings,
and pistons are lubricated by oil pumped from the oil sump at the bottom of the crankcase
through a series of oil galleries. Since the camshaft is located above the cylinder, and both
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SPRING
COMPRESSED
ROCKER
ROCKER-ARM arm ROCKS
SHAFT (PIVOT)
PUSHROO
PUSHED
UP
VALVE
LIFTER
RAISED
ROCKER ARM BACK
SPRING
EXPANDED
VALVE OPEN
PUSHROD
DOWN
VALVE CLOSED
Source: (Crouse and Anglin, 1986)
Figure 4: Operation of the valve train for an overhead-valve engine with a push rod design.
cylinder head
intake valve
intake pott
spark plug hole
cylinder
piston
timing chain roller
connecting rod
camshaft timing sprocket
rocker arms
camshaft
exhaust valve
exhaust port
valve guide
timing chain
crankshaft timing gear
crankshaft
oil sump
Figure 5: Mechanical layout of a typical overhead-valve, overhead-camshaft four-stroke engine.
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Cost Study for Phase Two Small Engine Emission Regulations
1. Crankshaft
2. Camshaft
3. Clutch
4. Output shaft
5. Chain tension roller
0. Oil guide
7. Oil separator
Source: (Intertec, 1995)
Figure 6: A 1978 Honda overhead-valve, overhead-camshaft engine.
valves are controlled by a single cam, this is a "single overhead camshaft" (SOHC) engine. In
some advanced four-stroke engines, the intake and exhaust valves are controlled by separate
camshafts. Since it requires two camshafts, engines with this design are called double overhead
cam (DOHC) engines. Because of their cost and complexity, DOHC engines are not expected
to be used in utility equipment. In 1978, Honda introduced an OHV, SOHC engine for
equipment applications. The schematic for this engine is shown in Figure 6.
With the EPA Phase 1 regulations taking effect in model year 1997, and the California Air
Resources Board (ARB) Tier I utility equipment regulations in 1995, some engines have been
redesigned to use an OHV configuration. More than 100 OHV engin& models were certified with
ARB in 1995.
23 Emissions Levels for Small Non-Handheld Engines
There are some data on emission levels for small non-handheld engines that meet EPA Phase 1
emission standards. Figure 7 shows the emissions certification data from non-handheld equip-
ment engines.
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EPA Phase 1 Standards for Class I Engines
\ Phase 1 Standards for Class II Engines
6 8 10 12 14
HC+NOx (g/kw-hr)
Figure 7: CARB 1995 certification data compared to EPA Phase 1 non-handheld' engine
standards
2.4 Emission Control Technologies for Four-Stroke Non»Handheld Engines
Small non-handheld engines pose unique problems for emission control. Because they are often
used in low-cost equipment, some emission control technologies used in automotive applications
(e.g., fuel injection and computer control) may not be economically feasible for these engines.
The different duty cycles imposed by the different applications in which these engines are used
may also pose challenges for emission control development.
Potential emission control measures for four-stroke small engines include relatively inexpensive
engine modifications such as changes to valve arrangements, air-fuel mixture optimization,
optimization of ignition timing, and combustion chamber improvements. Measures to reduce
manufacturing variability and deposit formation in the combustion chamber can also play a
significant role. More advanced technologies such as electronic control systems and catalytic co-
nverters have also been demonstrated on engines in this size range, but are considered too
expensive for widespread application. Such technologies are not treated in this study, but a
discussion of electronic control systems and aftertreatment technologies is provided in Appendix
A for completeness' sake.
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Engine Modifications
Emissions from gasoline engines can be reduced through changes in the engine design and
combustion conditions. Some of the important engine design and combustion variables that affect
emissions include valve arrangements (e.g., side, overhead), the air-fuel ratio X, ignition timing,
the level of turbulence in the combustion chamber, and the amount of exhaust gas recirculation,
if any. Through appropriate engine design and control strategies, engine-out pollutant emissions
can be reduced substantially. This involves complex tradeoffs between engine complexity, fuel
economy, maximum power, and emissions.
Side-valve and Overhead-valve
Arrangements - Use of a side-
valve configuration in small four-
stroke engines simplifies the de-
sign of the valve train cylinder
head, thus reducing manufacturing
costs. The presence of the exhaust
port in the cylinder block means
that the side-valve engine has
poorer cooling characteristics than
an overhead-valve engine, howev-
er. Thus, the side-valve engine
needs to run with a richer air/fuel
mixture to prevent the engine from
overheating, and at a lower com-
pression ratio to prevent knock.
The richer air/fuel mixture re-
quired by the side-valve engine
causes it to produce higher HC
and CO emissions compared to
overhead-valve configuration.
Also, the combustion chamber design of the side-valve engine provides a greater wall surface
area and larger crevices for unburned fuel/air mixture to settle in. Sfece the flame is unable to
penetrate these crevices, the unburned fuel in them becomes unburned HC emissions in the
exhaust.
1.0
Air/Ft* Ratio (i)
Figure 8: Effect of air-fuel ratio on SI engine emissions
Air-fuel ratio - The air-fuel ratio has an important effect on engine power output, efficiency, and
pollutant emissions. Figure 8 shows the typical variation of pollutant emissions with X for a
spark-ignition engine. At Xs below 1.0, there is too little oxygen to react fully with the fuel, so
that CO and HC emissions increase. NOx emissions show a peak in the vicinity of X = 1.1,
where flame temperatures are high and excess oxygen is available. For leaner mixtures, flame
temperature decreases, since the chemical energy from the ^-me amount of fuel must heat a
greater mass of gas. Flame speed also decreases as the mixture oecomes leaner, and ignition be-
comes more difficult, until combustion quality degrades to ar unacceptable levels, with an ac-
companying increase in fuel consumption and HC emissions. This is known as the "lean ignition
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14.
limit". The exact location of the lean ignition limit varies considerably, depending on the ignition
system, combustion chamber design and engine rotational speed.
In the absence of emission controls, small engines are generally calibrated for maximum power
output, which occurs at an air-fuel ratio somewhat rich of stoichiometric (X between about 0.85
and 0.9). This rich mixture provides the maximum power output for a given engine size, and the
excess fuel reduces the exhaust temperature - decreasing thermal stress on the engine. This is
especially important in high-powered air-cooled engines. The rich air-fuel ratio required for
maximum power output increases fuel consumption and HC emissions relative to those at
stoichiometric conditions, and greatly increases CO emissions.
Because of the importance of air-fuel ratio control for emissions, fuel metering systems play a
crucial role in the emission control system for Otto-cycle engines. Two types of metering
systems are commonly used: carburetors and fuel injection. In automobiles, the use of
carburetors has been completely supplanted by fuel injection systems, due to their greater
precision and stability. Such systems are too expensive for small engines, however, which
continue to rely on carburetors.
In a carburetor, air going into the engine is accelerated in one or more Venturis, and the pressure
differential in the venturi throat is used to draw fuel into the airstream and atomize it In modem
carburetors, this simple principle is supplemented by devices to provide mixture enrichment at
idle and under full-load conditions, as well as during cold starts.
Carburetors are unable to maintain precise air-fuel ratio control under all conditions, and are
subject to "drift" or change over time. They are not suitable, therefore, for applications which
require precise and invariant air-fuel ratio control. This is one of the most important factors
affecting the deterioration in Otto-cycle emissions with time, and reducing this drift without
excessively increasing costs is one of the major challenges facing the small engine industry.
Exhaust Gas Recirculation - Dilution of the incoming charge with spent exhaust affects
pollutant formation. In four-stroke engines, this technique is achieved through exhaust gas
recirculation (EGR). The effect of exhaust gas dilution is similar to that of excess combustion
air - by diluting the combustion reactants, the flame temperature ana flame speed are reduced.
A given volume of exhaust gas generally has a greater effect on flame speed and NOx emissions
than the same quantity of excess air (Heywood, 1988), due to the greater heat capacity of the
C02 and H20 contained in the exhaust and the reduced oxygen content of the charge. As with
excess combustion air, too much exhaust gas recirculation leads to unacceptable variability in
combustion, misfire, and increased HC emissions. The degree of exhaust gas dilution that can
be tolerated before combustion begins to degrade depends on the ignition system, combustion
chamber design, and engine speed. In general, ignition systems and combustion chamber designs
which improve performance with lean mixtures (so-called "lean-burn/fast bum" combustion
systems) also improve performance with high levels of exhaust gas dilution.
Combustion Timing - The time relationship between the motion of the piston and the com-
bustion of the charge has a major effect on both pollutant emissions and engine efficiency. For
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maximum engine efficiency, combustion should be timed so that most of the combustible mixture
burns near or slightly after the piston reaches the top-dead-center. A mixture that burns late in
the expansion strokedoes less work on the piston, decreasing fuel efficiency. A. mixture that
burns before TDC increases the compression work that must be done by the piston, and thus also
decreases efficiency. Since the combustion process takes some time to complete, it is necessary
to compromise between these two effects.
The timing of the combustion pro-
cess is determined by the timing of
the initial spark, the length of the
ignition delay while the initial
spark grows into a kernel of flame,
and the rate of flame propagation
through the combustion chamber.
The flame propagation rate, in
turn, is controlled by the geometry
and turbulence level in the com-
bustion chamber. Of these, only
the timing of the initial spark is
subject to control without rede-
signing the engine. The greater
the ignition delay and the slower
the flame propagation rate, the
earlier (or more advanced) the
initial spark must be to maintain
optimum combustion timing. For r T ical effec[ of iplition liming on SI engine
tyP «"emissions and power output,
mum or MBT (minimum for best
torque) spark advance is usually about 20 to 4QC crankshaft rotation before TDC. The MBT
spark advance is also a function of engine speed - at higher speeds, a greater angular advance
is required, since the ignition delay time remains roughly constant
The portions of the air-fuel mixture that burn at or before TDC account for a disproportionate
part of the NOs emissions, since they remain at high temperature for relatively long periods. To
reduce NOx emissions, it is common to retard the ignition timing somewhat from MBT in emis-
sion-controlled engines. Moderately retarding the ignition timing also helps to reduce hydro-
carbon emissions. Excessively retarded ignition timing, however, increases HC emissions,
reduces power output, and increases fuel consumption, as Figure 9 shows.
Combustion Chamber - To reduce knock and improve efficiency, it is desirable to minimize the
time required for combustion. This can be done by designing the combustion chamber to
maximize flame speed and burning rate and/or minimize the distance the flame has to travel.
Figure 10 compares typical values of the fraction of fuel burned and its derivative, the
combustion rate, for conventional and "fast-bum" combustion chambers. In the conventional
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chamber, the flame spreads radial-
ly outward at a relatively slow
rate, giving a relatively long com-
bustion time. To avoid having too
much fuel burn late in the expan-
sion stroke, it is necessary to ad-
vance the timing so that a signifi-
cant part of the fuel burns before
TDC.
With the "fast-burn" chamber, the
flame spreads rapidly due to tur-
bulent effects, giving a higher
combustion rate and shorter com-
bustion duration. With the shorter Figure 10: Combustion rate vs. crank angle for conven-
combustion time, MBT combus- tional and "fast-burn" combustion chambers,
tion timing is more retarded than
for a conventional engine. Since significant combustion does not take place until after TDC, the
compression work is reduced, efficiency is increased, and NOx and HC emissions are lower.
There is also less fuel burned during the later stages of the expansion stroke, which contributes
to better efficiency. Finally, reducing the combustion time reduces the time available for the re-
maining unburned mixture to undergo pre-flame reactions and self-ignite, which cause knock.
Reducing the tendency of an engine to knock allows an increase in compression ratio, further
increasing efficiency.
It should be noted that the combustion characteristics occurring in a "fast-burn" combustion
chamber directly contrast those occurring in the combustion chamber of a side-valve engine, in
which the combustion is characterized as a "slow-burn" process due to chamber configuration.
However, there are ways to improve the combustion chambers in side-valve engines to reduce
emissions, as well as to improve the engine performance. Xia and Jin (1991) showed that an
oblique dish-shaped combustion chamber, which was designed to raise the compression ratio and
burn a leaner mixture without being limited by knock, reduced the HC and CO emissions by 47
and 35 percent, respectively. The fuel consumption was also reduced by an average of 10%, and
the exhaust temperature was also reduced by about 10%.
Ignition systems - The type of ignition system used, and especially the amount of energy deliv-
ered, have an important effect on the ignition delay and subsequent combustion. For any given
flammable mixture, there is a minimum spark energy required for ignition. Both the minimum
ignition energy and the ignition delay are lowest for stoichiometric air-fuel mixtures, and increase
greatly as the mixture becomes leaner or more diluted with exhaust gas. The minimum ignition
energy also increases with increasing gas' velocity past the spark plug. Increasing the spark
energy beyond the minimum required for ignition helps to reduce both the average length and
the variability of the ignition delay.
-30 20 -10 0 10 a »
Crank-Angle Degrees ATDC
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High ignition energies are attained by increasing the spark gap (and thus the breakdown voltage)
and by increasing the stored energy available to supply the arc. The former approach is the more
effective of the two. To supply the necessary voltages, transistorized coil and distributorless elec-
tronic ignition systems are increasingly used. Driven by an electronic computer, these can also
provide very flexible control of ignition timing. Electronic ignition timing control systems have
been developed for small engines, but have not yet experienced wide commercial application, due
largely to their costs. These are in the range of $10-15 per engine, compared to about $3 for
typical small engine ignition systems (R.E. Phelon Co, 1995).
Anticipated Phase 2 Emissions Control Technologies for Non-Handheld Engines
The Phase 2 emission standards defined in the Statement of Principles would not require a
reduction in new engine emissions compared to the Phase 1 emission standards, but would
require that engines continue to meet the emission standards for a defined "useful life" period,
and not only when the engines are r.ew. Thus, the major area of focus in meeting the Phase 2
standards will be oh reducing deterioration in emissions performance over time, rather than on
achieving the lowest possible emissions from new engines. Among the approaches that
manufacturers may employ to achieve the Phase 2 standards are: improvements in SV engines,
conversion from SV to OHV, and improvement in OHV engines. The cost implications of each
of these approaches are analyzed in Chapters 3 through 5.
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3. COST ANALYSIS FOR CONVERTING SIDE-VALVE TO
OVERHEAD-VALVE ENGINES
This chapter addresses the incremental costs of conversion from side-valve (SV) to overhead-
valve (OHV) engines in non-handheld equipment. The methodology is based on a "bottom up"
cost analysis comparing SV and OHV engines, including the differences in parts count and
manufacturing operations. To ensure that these estimates were grounded in reality, we procured
and disassembled one SV and one OHV engine in order to count and weigh the parts and to
count the machining operations necessary to produce each one. Although the resulting cost
analysis is based on a comparison of class I engines, we also adapted the analysis to consider the
cost implications of converting a class II engine (see end of section 3.2).
3.1 Analysis of Parts Used in Side-valve and Overhead-valve Engines
Currently, OHV engines have a larger number of parts to manufacture than SV engines. To
estimate the incremental cost of converting a side-valve engine design to OHV, it is necessary
first to characterize the differences between them. These differences include the number and type
of parts, the casting and machining operations necessary to produce these parts, and any
differences in assembly requirements. To assure a firm basis for our comparison of SV and OHV
engines, we purchased and dismantled two similar engines: one an SV configuration and the other
an OHV. We then compared the number of parts in each engine, weighed the parts to determine
the differences in material requirements, and noted the machining operations that had been used
to produce each part.
Engine Selections
We analyzed the costs of converting from SV to OHV configuration for a Class I popular lawn
mower engine with around five horsepower. After reviewing specifications in the sales literature,
and information from a small engine service manual (Intertec, 1995a), we determined that there
are five major manufacturers producing vertical shaft, OHV engines with about 5 hp. These are:
Briggs & Stratton (B&S), Honda, Kawasaki, Kohler and Tecumseh. The general specifications
for the engine models from these manufacturers are shown in Table 4. Exploded views for
several of these engines from the Intertec manual are shown in Appendix B. Exploded views for
the Honda and Kawasaki engines are not available in the manual. However, part manuals giving
an engine parts breakdown for the Honda GXV140 engine and for the last Honda SV engine
model G100 are included in the Appendix B.
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Table 4: Major lawn mower engines with 5 to 6 hp.
Briggs & Stratton
Honda
Kawasaki
Kohler
Tecumseh
Model
Quantum
I/C 12G700
Europa,
99700
GXV 140
FC 1S0V
C5
VLXL
OVRM
55
Horsepower
5
5
5
5
5
5.5
5.5
Displacement (cc)
190
147
140
153
180
207
172
Valve Arrangement
SV
OHV
OHV
OHV
OHV
SV
OHV
Weight (lb)
30
35
26
29
n/a
26
25
Height (mm)
247
260
261
271
n/a
263
269
Length (mm)
318
319
n/a
394
n/a
316
308
Wide (mm)
334
389
n/a
294
n/a
369
393
List Price
243
334
280
n/a
n/a
230
305
As shown in Table 4, only B&S and Tecumseh produce both SV and OHV engines in the 5 to
6 hp range. Based on a review of engine sales data, it was decided that the B&S engine pair was
the best choice for the analysis. The SV engine in this pair was the B&S model 12 "Quantum"
engine, while the OHV engine was the B&S model 997 "Europa". The model 12 is produced
and sold in extremely large numbers, primarily for lawnmower use, while the model 997 is
produced in smaller numbers, mostly for industrial and commercial applications, and is provided
with a number of "quality" features not found in the model 12. In addition to the OHV
configuration, these features include several that are not related to the choice of valve
configuration, such as the use of a separate oil pump and pressure-lubricated crankshaft bearings.
These features are intended to provide a longer operating life. Since the latter features are not
related to the valve configuration (and are not found on OHV engines intended for the consumer
lawnmower market, such as Honda's), we did not include the costs attributable to these features
in the analysis.
Comparing the exploded views of the B&S and Tecumseh engines (in Appendix B) reveals that
there are many common components between the SV and OHV engines. This suggests that these
manufacturers have made use of the SV engine parts whenever possible when developing the
OHV engines. However, it was necessary to physically examine the parts and/or review the part
numbers to confirm the similarity. This was one of the reasons we decided to purchase the
selected engines, and disassemble them for our analysis. After deciding which engines to use
for comparison, we purchased the selected engines from a local B&S dealer. The parts lists for
these engines were also obtained from a distributor, and are included in this report as Appendix
B.
Additional Parts - After disassembling the engines, we counted and recorded the parts found in
each one. Using this information, and confirming with the parts lists, we compiled a list of
additional parts used in the OHV engine that are not found in the SV engine. This list is shown
in Table 5. For each of the parts in Table 5, we estimated whether it would be more cost-
effective to manufacture or purchase. The small parts, such as screws and nuts, were assumed
to be purchased, while the larger and more specialized parts such as the rocker cover, rocker
arms, push rod guide, and push rods would most likely be manufactured in-house. We weighed
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Table 5. Information.'on the additional parts for the B&S Europa OHV engine as compared to
the Quantum SV engine.
Item
Unit
Manufacturing
Process
Part Material
Weight
(lb)
Rocker Cover
1
stamping
low-carbon steel
5/16
Rocker Arm
2
stamping
low-carbon steel
3/32
Push Rod Guide
1
stamping
low-carbon steel
1/32
Push Rod
2
precision grinding
low-carbon steel
1/32
Rocker Cover Gasket
1
Purchased from suppliers
Valve Cap
2
Lock Screw
2
Valve Seal
1
Valve Stem Bushing
1
Pivot Nut
2
Pivot Stud
2
the manufacturer-produced parts and determined the manufacturing processes required. This
information is also presented in Table 5.
Besides the additional parts found in the valve train, the B&S OHV engine also has an oil pump
assembly which is not found in the SV engine. After closely examining the OHV engine, it was
determined that the pressurized lubrication system does not affect the valve train, which is still
lubricated by splash lubrication as in the SV engine. The oil pump assembly in the OHV engine
is used only to lubricate the crankshaft bearings. Thus, we concluded that oil pump and pressure
lubrication system are not related to the choice of valve configuration, but have been included
to provide longer engine life (i.e. "quality"). Honda, Kawasaki, Kohler and Tecumseh OHV
engines used in lawnmowers have only splash lubrication systems. Since it is not necessary to
have a pressurized lubrication system in a lawnmower engine, we did not consider the parts in
the pump assembly as required parts for producing an OHV engine.
Manufacturing Differences in Parts - Besides the additional parts, there are also differences in
manufacturing processes and requirements for similar components whkn comparing SV and OHV
engines. These are due mainly to the differences in the valve train configuration. Significant
differences in terms of manufacturing processes and material requirements were observed in the
cylinder head and cylinder block. These differences are summarized in Table 6. We counted
the number of machining operations, such as milling, boring, drilling, and tapping, required for
each piece, and weighed the components to determine the material requirements. The weights
for the cylinder heads and cylinder blocks for these engines are tabulated in Table 7. The
cylinder head and cylinder for the OHV engine required an additional 7/8 lb of aluminum alloy.
Although the engine displacement is smaller for the OHV engine, additional material was
required to create the push rod passage in the cylinder block (see part number 1 for both engines
in Appendix B).
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Table 6: Comparison of similar components for a side-valve engine and an overhead-valve
engine.
Component
SV
OHV
Cylinder Head
Simple
- no intake and exhaust ports
Complex
- intake/exhaust ports, valve seats, etc.
Cylinder + Crankcase
Cylinder: Complex
- intake and exhaust ports, valve seats, etc.
- cylinder liner
Cylinder: Simple
- no intake and exhaust ports
- only cylinder liner
Crankcase: no significant differences
Crankcase: no significant differences
Crankshaft
no significant differences
no significant differences: counterweight
is slightly bigger
Connecting Rod
no significant differences
no sign.ficant differences: shorter and
wider
Piston & Rings
no significant differences
no significant differences: combustion
chamber on piston top
Valves
use nickel-stainless steel exhaust
could use less expensive stainless steel
valve due to cooler environment
1 Cylinder and crankcase are one unit for these engines.
The numbers of milling/boring operations for
the cylinder head and cylinder block for SV
and OHV engines are tabulated in Table 8.
As this table shows, the OHV engine requires
one more milling/boring operation than the
SV engine. The drilling and tapping opera-
tions for the cylinder heads and cylinders for
these engines are listed in Table 9. As this
table shows, a total of 21 drilling and tapping
operations are required for each engine.
Thus, there is no difference in the number of drilling and tapping operations required. For drill
holes without tapping, the cylinder head and cylinder for the SV engine required 10 drill holes
while the OHV engine required 1^ drill holes. However, the table ihows that two drill holes
each in the cylinder head and cylinder of the OHV engine are not used! This left only one addi-
tional drill hole as actually required for the OHV engine as compared to the SV engine. The
reasons for the unused drill holes in the OHV cylinder and cylinder head are not clear, but may
be related to use of common tooling or for auxiliary equipment.
In summary, about one pound of added material, one additional milling operation and one
additional drilling operation are required for the cylinder head and cylinder of the OHV engine
as compared to those for the SV engine. This information was used later to estimate the added
material and labor costs for these components in addition to the costs for the added materials.
Table 7: Comparison of the weights for the
cylinder heads and cylinders for a side-valve
engine and an overhead-valve engine.
Item
Weights (lb)
SV
OHV
Difference
Cylinder
Head
1 5/16
1 15/16
5/8
Cylinder
4 1/2
4 3/4
1/4
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Table 8: Comparison of number of milling
and boring operations in the cylinder head
and cylinder for SV and OHV engines.
Table 9: Comparison of number of drill-
ing and tapping operations in the cylinder
head and cylinder for SV and OHV en-
gines.
Item
SV
OHV
Cylinder Head
Top
n/a
1
Bottom
none
1
Intake Port
n/a
2
Exhaust Port
n/a
1
Cylinder
Top
1
1
Intake Port
2
n/a
Exhaust Port
2
n/a
Total for Cylinder and
Cylinder Head
5
6
| SV
OHV |
Cylinder Head
Spark plug
1
1
Rocker box fastener
n/a
4
Intake port
n/a
2
Drilled
Exhaust port
n/a
2
and
Rocker Pivot.
n/a
2
Tapped
Auxiliary
4
4 .
Total
5
15
Cylinder head fas-
8
4
tener
Drilled
Only
Lube oil passage
n/a
1
Valve stem
n/a
2
Unused
0
2
Total
8
9
Cylinder
Cylinder head fas-
8
4
tener
Drilled
and
Intake port
2
n/a
Exhaust port
2
n/a
Tapped
Auxiliary
4
2
Total
16
6
Lube oil passage
n/a
2
Drilled
Only
Valve stem
2
2
Unused
0
2
1
Total
2
6
1 Total
Both
1 Pieces
DriUdU and Tapped
21
21
Drilled Only
11
15
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3.2 Cost of Converting from SV to OHV
The cost analysis includes an estimate of the incremental variable manufacturing costs (e.g.
materials and assembly labor) and fixed costs (e.g. tooling and engineering design) due to the
change from SV to OHV. The incremental costs per engine produced are affected both by the
size of the engine (i.e. class I or class II) and the number of engines produced. The cost analysis
given in this and subsequent chapters in Part I is based on a class I engine model. A discussion
of how these costs would differ for a class II engine is given at the end of each cost section.
Cost estimates are also developed for a range of different annual production levels representing
high, intermediate, and low volumes: 1.2 million engines per year, 200,000 engines per year, and
35,000 engines per year. The high-volume line represents a high-volume line for a class I
manufacturer. The intermediate volume line can represent a high-volume line for a class II
manufacturer. Further basis for these numbers is provided in Appendix D.
Variable Manufacturing Costs (Materials. Components, and Labor)
Variable manufacturing costs are those that are proportional to the number of engines produced.
They include manufacturing labor, purchased parts, and raw materials. The changes in variable
manufacturing costs due to changing from SV to OHV would include the additional cost of
material and labor for machining the cylinder head and cylinder block, the additional costs of
material and labor for producing those new parts that would be produced in-house, and the addi-
tional costs to purchase those new parts that would be purchased from outside suppliers.
Table 10: Estimation of manufacturing costs for Class I OHV engine parts made in-house
Rocker Cover
Rocker Arm
Push Rod
Guide
Push Rod
Cylinder Head
& Cylinder1
Process
Stamping
Stamping
Stamping
Precision
Grinding
Diecasting
Material
Low Carbon
Steel
Low Carbon
Steel
Low Carbon
Steel
Stainless Steel
A1 Alloy
Weight (lb)
0.313
0.094
0.031
0.031
0.875
Weight+ 10%Scrap
0.344
0.103
0.034
' 0.034
0.963
Material cost S/lb*
0.40
0.40
0.40
2.00
1.00
Material cost S/pait
0.138
0.041
0.014
0.069
0.963
Labor minutes
1
1
1
1.5
3
Labor cost S/hr
15
15
15
25
25
Direct Labor S/pait
0.25
0.25
0.25
0.63
1.25
Overhead @40%
0.10
0.10
0.10
0.25
0.50
Total labor+OH/pait
0.35
0.35
0.35
0.88
1.75
Total mfg. cost/part
0.49
0.39
0.36
0.94
2.71
1 Incremental manufacturing cost compared to SV engine components
2 Given the relatively small contribution of material costs to the incremental cost, it was not expected that any
volume savings (small vs. bulk) would appreciably change the incremental cost estimate.
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Table 10 shows our estimate of the production costs for the parts that wouljJ produced in-house.
Estimates of material costs were based on ranges quoted by metal suppliers contacted by
telephone. Actual 'material prices fluctuate from day to day, but costs of $0.40 per pound for
low-carbon steel and $1.00 per pound for aluminum alloys are typical (Capital Steel Co., 1996).
Estimates of labor time requirements were developed with the assistance of standard references
on manufacturing cost estimation (Ostwald, 1984; Winchell, 1989). Stamping will take less time
than precision grinding. Die casting and subsequent machining would take the longest time,
accounting for the milling and drill/tapping operations.
The costs of hourly labor include wages and fringe benefits. We estimated these at $15 per hour
for relatively unskilled tasks such as operating the stamping press. According to the 1992 Census
of Manufactures, average 1992 hourly wages in SIC 3524 (Lawn and Garden Equipment) were
$10.71. Allowing for inflation and 30% for fringe benefits, this would be about $16 per hour
in 1996, which is consistent with our estimates. Labor for more skilled operations, such as a
precision grinding, milling, and drilling were estimated at $25 based on the average rates for
machinists.
Table 11: Estimation of incremental variable manufacturing
cost for Class IOHV engines compared to SV engines.
The labor overhead rate for small
engine manufacturing was assumed
to be 40 percent of the cost of
direct labor used on emission
related components (Lindgren,
1977).
Table 11 shows our estimate of the
total change in variable manufac-
turing costs per engine due to the
change from SV to OHV. In
addition to the costs of manufac-
turing the parts, the total change in
variable costs also includes the
purchase cost of those additional
parts obtained from outside suppli-
ers. Our estimates of the prices
for each of these are shown in
Table 11. The costs of purchased
parts were estimated based on our
own experience,, conversations
with part suppliers, and conversa-
tions with other knowledgeable
parties in the small engine industry
(e.g. Conley, 1996; Huffman,
1996). In addition to the increased
part costs, we estimate that the more complex cylinder head and valve train would require three
Cost/Piece
Pieces/Engine | Total
Rocker Cover
0.49
1
0.49
Rocker Aim
0.39
2
0.78
Push Rod Guide
0.36
t
0.36
Push Rod
0.94
2
1.89
Rocker Cover Gasket
0.25
1
0.25
Valve Cap/key
0.10
2
0.20
Lock Scrfcw
0.05
2
0.10
Valve Se%l
0.10
1 ¦
0.10
Valve Stem Bushing
0.30
1
0.30
Pivot Nut
0.25
2
0.50
Pivot Stud
0.25
2
0.50
Cylinder Head & Cylinder
*71
1
2.71
Total Parts Cost
8. IS
Added Assembly Labor
Labor minutes
3
Labor Cost, Mir
15
Direct Labor Cost, S
0.75
Overhead @40%, $
0.3
Total Labor + OH, $
1.05
Total Added Variable Manufacturing Cost
9.23
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25
ext-a minutes of assembly labor, costing $1.05 with overhead (Ostwald, 1984; Winchell, 1989).
The total change in variable manufacturing costs, therefore, comes to $9.23.
Since the variable costs are expressed on a per-engine basis, there would be relatively little
difference in these costs between the large and small manufacturer. Because of learning-curve
effects and economies of mass production, we would anticipate that the actual variable costs for
the large manufacturer in the 1.2 million engine case would be slightly smaller, but these
differences are difficult to quantify without much more detailed information.
Fixed Costs
Fixed costs are costs that must be
incurred to produce an engine
model, regardless of the number of
units produced. Fixed costs asso-
ciated with the conversion from
SV to OHV include engineering
design and testing costs; the costs
of the special tooling, molds, and
other equipment needed to produce
the changed or additional parts; the
costs of changing the production
line to accommodate the changes
in the assembly process and in the
size and number of parts; and the
costs of updating paits lists and
technical manuals to reflect the
changed design. Table 12 shows
the estimated fixed costs due to
changing from SV to OHV at each
of the three production levels
considered.
Since all of the major small engine
manufacturers are presently pro-
ducing OHV engines for at least
part of their product line, there
would be no need for research and
development to develop this tech-
nology. Thus, no costs are alloca-
ble to R&D. However, we esti-
mate that the necessary changes in
engine design would require the
efforts of about four engineers for
Table 12: Estimated fixed costs for the change from SV to
OHV class I engine.
Case 1
Case 2
Case 3
Engineering Costs
Engineering tabor + OH
(4 years @ $100,000)
400,000
400,000
400,000
Number of Tests
400
400
400
Test Cost ($).
300
300
300
Testing costs
120,000
120,000
120,000
Other engineering
100,000
100,000
100,000
Total Engineering
620,000
620,000
620,000
Technical support
Training/Tech. Pubs
500,000
200,000
200,000
Tooling Costs
New Master Dies
Cylinder head
60,000
60.000
60,000
Cylinder block
40,000
40,000
40,000
Connecting rod
15,000
15,000
15,000
Piston
25,000
25,000
25,000
Crankshaft
25,000
25,000
25,000
Rocker arm
30,000
30,000
30,000
Rocker cover
50,dp0
50,000
50,000
Push rod guide
10,000
10,000
10,000
Setup changes
100,000
50,000
50,000
Total tooling
355,000
305,000
305,000
Total Engine*Specific
1,475,000
1,125,000
1,125,000
Amortized aver 5 yrs
379,211
289,229
289,229
New Machine Tools
980,000
230,000
90,000
Amortized over 10 yis
152,704
35,054
13,717
Total Fixed Cost/Yr
531,915
324,283
302,946
Annual Production
1,200,000
200,000
35,000
Fixed cost/engine
0.44
1.62
8.66
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26
about one year. This estimate is based on consideration of the technical requirements and the
length of process necessary for the design change (B&S, 1996). For typical engineering salaries
and overhead rates, the cost of an engineer working full-time for a year (including salary, bene-
fits, physical and administrative overhead, and other costs) is estimated to be about $100,000.
This is a conservative estimate for the small engine industry based on the benefits/overhead in
the automobile industry (with which the small engine industry competes for engineering talent).
With this loaded engineering cost, the total cost of engineering staff time for engine redesign
would be about $400,000.
Additional costs would be incurred for testing of
prototype engines, special materials, travel, and other
similar expenses associated with the design changes.
We estimate that engine calibration would require
about 200 emission tests per engine model and
another 200 tests for durability and reliability. We
estimated the manufacturer's cost per test at about
$300, based on the analysis in Table 13. This is also
consistent with the lower end of the range of testing
costs obtained in discussions with several independent
test laboratories. At $300 per test, the 400 emission
tests would cost about $120,000. We estimated that
the costs of test engines, travel, test materials and so
forth would amount to another $100,000, so that the
total engineering design costs would be about
$620,000. These costs would not be greatly different
between the three different production levels.
Changes in the engine hardware would require corre-
sponding changes in the company's technical support
services - service manuals, technical training, etc. A source at Honda (1996) indicated that the
costs of completely revising technical documentation and training dealers for a major engine
change were of the order of $500,000, while the costs of issuing a technical bulletin for a minor
change were around $10,000. Based on this information, we estimated the technical support costs
for the SV to OHV conversion at $500,000 for the high volume engine line, and at $200,000 for
the smaller-volume engine lines. The costs are lower for the smaller lines, as these would have
fewer manuals to print and fewer dealers to train.
The production changes involved in going from side-valve to overhead-valve would also require
tooling costs. The main tooling costs would be the production of new master designs for the dies
used to cast the cylinder head, cylinder block, connecting rod and piston. After discussing with
some die manufacturers (Spec Cast, Prince Machine and Muller Weingaren 1996), we estimate
these costs at $60,000 for the cylinder head, $40,000 for the cylinder block, and $15,000 and
$25,000 for the much simpler connecting rod and piston castings, respectively. New masters
would also be required for the stamping dies for the new stamped parts. Stamping dies are more
expensive than the casting dies. Based on our conversations with stamping die manufacturers
Table 13: Estimated cost of emission
testing.
Capital Cost
Analyzer bench
100,000
Dynomometer
50,000
Test cell
50,000
Misc. Instruments
60,000
Total Capital Cost
260,000
Amortized 5 yrs @ 9%
66,844
Operating Costs
Test engineer (1/2)
50,000
Technician
60,000
Supplies/Repairs
40,000
Total Annual Cost
216,844
Tests/day
3
Tests/yr
750
Cost/test
289
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(Hess-MAE and Sheffield Progressive 1996), we estimate $10,000, $30,000, $50,000 for push
rod guide, rocker arm, and rocker arm cover dies, respectively.
Note that we have not included any costs for the actual production of new casting dies, but only
the master designs from which the dies are produced. That is because casting dies wear out and
must be replaced periodically in any event, so that their replacement with a new design would
not necessarily involve any incremental cost except for the new master.
The few additional machining operations required for the OHV cylinder and cylinder head would
not likely require new machine tools, but it would be necessary to change fixtures, jigs, and
material handling equipment and to modify production line flow to incorporate the new and
changed parts and the new assembly procedures. The costs of these changes include mostly labor
and engineering time, retraining costs, and the cost of lost production while the assembly line is
down. These are lumped together as "setup" in the table. Setup costs are difficult to estimate,
as they are highly plant- and process-specific. We estimate these costs setup cost at $50,000 for
the two lower-volume engine lines, and $100,000 for the high volume engine line, based on our
judgement of the relative complexity of the changes needed. Smaller-volume engines tend to be
produced using more flexible procedures, so that the production changes are easier to
accommodate.
Total engine-specific costs (excluding the costs of new machine tools) are totalled at $1,475
million for the large volume engine line, and $1,125 million for the two smaller volume engine
lines. These costs were amortized over five years at a cost of capital of 9%. The five year
amortization period reflects the typical time between model changes. The assumed 9% cost of
capital is consistent with information from the industry. Capital costs would not be much
different between the large- and small-volume production cases, as even most small-volume
engine manufacturers are divisions of large companies, and thus have access to relatively low-
cost capital.
In addition to the engine-specific costs, the production of the new parts in-house would require
that some new machine tools be purchased (assuming that all existing machine tools are fully
utilized). For the high-volume engine line, we estimated that ten new 50-ton stamping presses
would be required for the stamped parts, at $50,000 each. This estinfcte is based on an assumed
throughput of two stampings per press per minute, with the presses operating two shifts for a
total of 14 hours per workday. We also estimate that 12 new CNC grinders would be required
for the pushrods, at a cost of $40,000 each. These estimates are based on typical price ranges
for machine tools given by industry sources. The total cost of the new machine tools required
would be $980,000 for the 1.2 million engine per year line. For the 200,000 engine per year
case, we estimate that three presses and two grinders would be required, for a total cost of
$230,000. For the 35,000 unit case, we assumed that the stamped parts would be produced in
batches, requiring only one new press and one grinder for a total of $90,000.
The costs of the new machine tools required were amortized over 10 years at 9%. Ten years is
about the economic lifetime of a machine tool before it is either worn out or made obsolete by
advancing technology.
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The total amortization of the fixed Table 14: Summary of the variable and fixed costs for
costs amounts to about $532,000 converting SV to OHV Class I engines,
per year for the 1.2 million unit
case, $324,000 per year for the
200,000 unit case, and $303,000
for the 35,000 unit case. Dividing
by the number of units produced
per year results in fixed costs of
$0.44 per engine for the 1.2 million unit model, $1.62 per engine for the 200,000 unit model, and
$8.66 for the 35,000 unit model. Table 14 shows a summary of the hardware/assembly costs and
fixed costs for converting SV to OHV Class I engines for the three cases.
Adapting the Cost Estimate for Class II Engines
We expect that the conversion of a class II engine may have larger incremental costs than a class
I engine. In terms of variable costs, the material mass requirements for engine parts made in-
house would be roughly triple those of a class I engine (based on engine dry weight comparison
of a 5 hp and 14 hp engine). This would add $2.67 per engine to the costs, giving a total
material cost per engine of $4.01. The labor to make the parts is expected to be the same. The
prices of purchased parts would also increase to reflect the increased material requirements. We
estimate this increase at about 50%, based on the ratio of material cost to total cost for the parts
made in-house. The cost of purchased parts would thus increase by $.98. The total change in
variable cost would then be about $3.65 per engine, bringing the total variable cost to about
$12.88.
The fixed costs for developing the engine design and changing the production process would be
essentially the same for the larger class II engines. The costs of preparing master dies, for
example, are determined more by the complexity of the part than by its size. Similarly,
differences in parts size would not have a significant effect on machine tool costs, as the parts
would still be within the size range for standard machine tools. A more significant effect would
result from the lower production volumes typical for class II engines, which commonly range
from 35,000 to 200,000 engines per year (i.e. the two lower production ranges considered in our
analysis). The fixed costs per engine would thus be around $1.62 at 200,000 engines per year,
and $8.66 at 35,000 engines per year.
Possible Developments to Reduce Incremental Conversion Costs
The incremental costs estimated above for shifting and SV engine design to OHV do not account
for possible cost savings due to redesign and re-engineering of production processes to take
advantage of improvements in manufacturing techniques. Many existing SV engine designs are
quite old, and incorporate old manufacturing technology. By redesigning the engine (i.e., fewer
parts) and its production processes, manufacturers might be able to achieve significant savings
in production costs, and a number of engine manufacturers are doing so. Advances in material
Case 1
Case 2
Case 3
Total Added Manufacturing Cost
9.23
9.23
9.23
Fixed Costs
0.44
1.62
8.66
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29
minimization or the use of lighter and cheaper materials could reduce costs further. In some
cases, manufacturers have indicated that the cost savings equal or even exceed the incremental
costs due to the charge from SV to OHV. We have not attempted to account for these potential
savings in this report.
Possible Cost Saving Through Learning Curve Effect
The incremental cost for converting from SV to OHV should be less for every year of production
as a result of the phenomenon known as the "learning curve." A general 'rule of thumb* used
by EPA in the past (EPA, January 1996) is that for every doubling of production, the costs are
reduced by 20 percent. This is primarily applicable to variable (labor, material) costs. For
example, in the second year of production (assuming same production) the variable costs should
be reduced by 20 percent over the first year. In contrast to variable costs, fixed capital costs are
usually one time costs spread over several years and therefore are not subject to the rule.
However, high-volume engine lines may experience this type of cost reduction for some fixed
costs because the engine dies are often replaced more than once a year (see Chapter 12
discussion on retirement of manufacturing equipment). This cost savings learning curve is
applicable to the other engine modificaiton technologies.
Possible Actions bv Small Manufacturers to Reduce Costs to Convert SV to OHV
There may be only a few manufacturers in the non-handheld engine market that can be
characterized as small manufacturers. Most small engine manufactures with small market share
(Wisc-Teledyn, Kawasaki) are medium to large companies with the ability to afford extensive
capital investment. We expect that any actual small engine manufacturer, faced with the prospect
of having to convert a SV family line to an OHV family line, may not go about it the same way
as it had in the past in producing the SV family line. We anticipate that the small engine
manufacturer may make certain decisions to reduce the costs of this conversion. For example,
the small engine manufacturer may not be able to afford the capital investment necessary to
purchase new machine tools to make their own cylinder head and block (which is necessary for
a new OHV design). Also, even if the small manufacturer wants to purchase the machine tools,
the small manufacturer will likely have to pay a higher interest rate for capital investment.
Consequently, the small manufacturer may contract for services from a machine tool company
to produce the cylinder head and block. The machine tool company may be able to make these
engine parts cheaper because the company's big machines can be used for several jobs from other
clients. Even with the markup from the machine tool company, the small manufacturer could
gain modest savings per engine.
Additionally, the small manufacturer may purchase a license for an OHV engine design rather
than incur the engineering labor to develop the design itself. Although this is a one time cost,
saving per engine could occur in reduced engineering design costs. Also, instead of incurring
the costs for developing new training/technical/catalogue publications, the small manufacturer
may purchase and adapt the publications from the licensing company. This could perhaps have
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additional savings over the estimated costs for a small manufacturer to develop their own
tiaining/technicai/catalogue publications. Finally, the small manufacturer may find ways to
consolidate low-profluction lines by modifying a higher production engine (i.e., add governor or
have smaller stroke to make lower power engine line from higher power engine). We assume
that some of the above cost savings decisions would be implemented by a small manufacturer.
ICF Consulting Group & Engine, Fuel, and Emissions Engineering, Inc.
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31
4. COST ANALYSES FOR IMPROVING
SIDE-VALVE ENGINES
This chapter presents the cost analysis for improvements in side-valve engine technology.
Potential improvements in SV engine technology to reduce emissions include:
• improvement in combustion and intake systems
• improvement in spark ignition and timing
• optimization of valve timing and cam design
• improvement in piston and ring designs
• improvement in manufacturing variability
• improvement in carburetor
Similar to the cost analysis for the SV to OHV conversion, we assessed the incremental variable
and fixed costs for each of these technologies. For all technologies except the carburetor
improvement, we based our analysis on the same three scenarios considered in the preceding
chapter: engine models with production of 1.2 million, 200,000, and 35,000 units per year,
respectively. Since a single carburetor model may be used on many engine lines, we analyzed
only a single scenario for carburetor improvements. This scenario assumed annual production
of four million units per year for a manufacturer with a large market share.
4.1 Improvement in Combustion and Intake Systems
Since the conditions in the intake system affect the combustion process, combustion and intake
systems are treated together in the research, design and development processes. Minor changes
in the intake and combustion chamber design for SV engines can produce a more homogeneous
mixture and better combustion, thus helping to reduced emissions. Improvements in this area
would not affect the number of parts used in the engine, but only the geometry of the existing
parts. Examples would include a new combustion chamber geometry with smaller surface to
volume ratio and/or with a squish band to improve mixing, or changing the geometry of the
intake to induce more swirl to the combustion chamber. These changes are not expected to affect
variable production costs significantly. (Although engine manufacturers might choose to take
advantage of the opportunity to combine parts or substitute newer production processes where
these would be profitable, any such changes would be highly engine-specific, and we have not
attempted to account for them.) Although material requirement might change slightly, these
changes could be in either direction, and would likely be minimal in either case. Thus, the only
quantifiable costs incurred as a result of combustion and intake system improvements would be
the fixed costs of changing the production process.
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Table 15 shows the estimated
fixed costs associated with each
engine production .level. The
design challenges in developing an
improved combustion and intake
system for an SV engine are mod-
est. We estimate that this devel-
opment would require about one
person-year of engineering time, at
a cost of about $100,000. Engine
calibration would require about
100 emission tests per engine
model, with another 100 tests for
durability and reliability assess-
ment. At $300 per test, the emis-
sion tests would cost about
$60,000. Other engineering-relat-
ed costs such as model building,
special materials, test engines, and
travel are estimated at $25,000.
Changes in the design of the com-
bustion chamber and intake sys-
tems would require a one-time cost
to revise parts and stocks listings.
Based on the information from
Honda (1996), we estimated that
these changes would cost about
$20,000, or the equivalent of two
service bulletins.
Table 15: Estimated fixed costs for the changes in improv-
ing combustion chamber and intake systems.
- *se 1 Case 2 Case 3 |
Engineering Costs |
Engineering labor + OH
(1 year @ $100,000).
100,000
100,000
100,000 I
Number of Tests
200
200
200
Test Cost ($)
300
300
300
Testing costs
60,000
60,000
60,000
Other engineering
25,000
25,000
25,000
Total Engineering
185,000
185,000
185.000
Technical support
Training/Tech. Pubs | 20,000 20,000 20,000
Tooling Costs
New Master Dies
Cylinder head
25,000
25,000
25,000
Piston
25,000
25,000
25,000
Total Tooling
50,000
50,000
50,000
Machine Tool Setup
50,000
25,000
25,000
Total Engine-Specific
305,000
280,000
280,000
Amortized over 5 yrs
78,413
71,986
71,986
New Machine Tool
0
0
0
Amortized over 10 yrs
0
0
0
Total Fixed Cost/Yr
78,413
71,986
71,986
Annual Production
1,200,000
200,000
35,000
Fixed cost/engine
0.07
0.36
2.06
Changes in combustion chamber and intake system geometry would involve tooling costs. The
main tooling costs would be the production of new master designs $pr the dies used to cast the
new cylinder head and piston with improved combustion chamber designs. Based on information
from die manufacturers (Spec Cast, 1996; Prince Machine, 1996; Muller Weingaren, 1996) we
estimated these costs at $25,000 for the cylinder head die, and $25,000 for the piston casting.
We also estimated that it would cost $50,000 and $25,000 to change the machining fixtures for
the high-volume line and the two low-volume lines, respectively. No new machine tools would
be required.
Total engine-specific costs are estimated at $305,000 for the 1.2 million unit case, and $280,000
for the 200,000 and 35,000 unit cases. These costs were amortized over five years at 9%. The
total amortized fixed costs amount to about $78,400 per year for the 1.2 million unit case and
$72,000 per year for the other two cases. Dividing by the number of units produced results in
fixed costs of $0.07 per engine for the 1.2 million unit case, $0.36 per engine for the 200,000
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Cost Study for Phase Two Small Engine Emission Regulations
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unit case, and $2.06 per engine for the 35,000 unit case. The costs for similar modifications to
a class II engine would be the same.
4.2 Improvement in Spark Ignition and Timing
Table 16: Estimated fixed costs for the changes in improv-
ing spark ignition and timing.
Similar to the case of combustion
chamber and intake systems im-
provement, changes in spark igni-
tion and timing would not require
additional parts or extensive en-
gine redesign. The spark timing
can be changed by changing the
location of the stator and flywheel
key on the crankshaft. Spark
ignition can be enhanced by using
a different spark plug or ignition
module. The differences in cost to
the engine manufacturer of chang-
es in ignition modules or spark
plugs are difficult to predict, and
would be small in any case.
Changes in ignition timing would
involve only fixed costs. Our cost
estimates are shown in Table 16.
The development work to optimize
the spark ignition system and
ignition timing was estimated to
require about four person-months
of engineering time, and about 100
emissions tests. Other engineer-
ing-related costs were estimated at $10,000. Costs of changing technical documents were
estimated at $20,000, or the equivalent of two service bulletins. No new tooling would be
required, but some changes in the setup of the existing tooling would be needed to accommodate
the changed location of the flywheel key. Total engine-specific costs are estimated at $103,000
for the 1.2 million unit case, and $98,000 for the other two cases. Amortizing these costs over
five years at a cost of capital of 9%, and dividing by the annual production results in fixed costs
of $0.02 per engine for the 1.2 million unit case, $0.13 per engine for the 200,000 unit case, and
$.72 per engine for the 35,000 unit case. The costs for similar modifications to a class II engine
would be the same.
Case 1
Case 2 Case 3
Engineering Costs
Engineering labor + OH
(1/3 year @ $100,000)
33,000
33,000
33,000
Number of Tests
100
100
100
Test Cost ($)
.300
300
300
Testing costs
30.000
30,000
30,000
Other engineering
10,000
10,000
10,000
Total Engineering
73,000
73,000
73,000
Technical support
Training/Tech. Pubs 20,000 20,000 20,000
Tooling Costs
Machine Tool Setup
10,000
5,000
5,000
Total Engine-Specific
103,000
98,000
98,000
Amortized over S yrs
26,481
25,195
25,195
New Machine Tools
0
0
0
Amortized over 10 yis
0
0
0
Total Fixed Cost/Yr
26,481
25,195
25,195
Annual Production
1,200,000
200,000
35.0OO
Fixed cost/engine
0.02
0.13
0.72
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4.3 Optimization in Valve Timing and Cam Design
Optimization in valve timing and cam design would generally require only research, design and
development costs. In our discussions with one engine manufacturer, however, it was indicated
that it might be necessary to change the camshafts in some engine models. These models use
nylon cam lobes that are pressed onto a steel tube or rod, and the concern is that the nylon may
not be durable enough to ensure stable emissions over the useful life of the engine. Camshafts
are traditionally made of cast iron, which must then be machined to exact dimensions. Some
recent engines, such as the Ryobi hand-held four-stroke, use powder-metal camshafts, however.
This process is less expensive than casting and machining a cast iron camshaft, and should give
dimensional accuracy at least equal to that of the press-fit nylon cam lobes and much better
durability. We were not able to estimate the variable cost differences between a powder-metal
camshaft and the present nylon/steel camshaft with any accuracy, due to lack of information
about the production process for the latter. Since the powder-metal part would be made to final
shape in a single operation, without machining, there should be a saving on labor compared to
the present design. Material costs for the two designs would be similar. Thus, we would expect
a small net reduction in variable
Table 17: Estimated fixed costs for optimizing valve timing
and cam design for SV engines.
costs with the powder-metal part.
For conservatism, however, we
have assumed a zero savings in
variable costs.
Our estimates of the fixed costs
involved in optimizing valve and
camshaft design are tabulated in
Table 17. Development of the
optimum valve timing and design
of the powder-metal camshaft are
estimated to require about one year
of engineering time, at a cost of
$100,000. About 200 emission
tests would be required, at a cost
of $60,000. Other engineering-
related costs (prototype camshafts,
other tests, etc.) were estimated at
$25,000. Total engineering costs
are estimated at $185,000.
Molds for powder-metal forming
are less expensive than for die-
casting or stamping, ranging from
$3,500 to $8,000 (Monaich, 1996).
We assumed a cost near the top of
this range. The cost of altering
the production process to accom-
Case 1 Case 2 | Case 3
Engineering Costs
Engineering labor + OH
(1 year @ $100,000)
100,000
100,000
100,000
Number of Tests
200
200
200
Test Cost ($}
300
300
300
Testing costs
60,000
60,000
60,000
Other engineering
25,000
25,000
25,000
Total Engineering
185.000
185,000
185.000
Technical support
Training/Tech. Pubs | 20,000 J 20.000 20,000
Tooling Costs
New Master Dies
Camshaft
8,000
8,000
8,000
Total Tooling
8,000
8,000
8,000
Machine Tool Setup
20,000
10,000
10,000
Total Engine-Specific
233,000
223,000
223,000
Amortized over 5 yrs
59,903
57,332
57,332
New Machine Tools
565,000
282,500
141,250
Amortized over 10 yrs
88,038
44,019
22,010
Total Fixed Cost/Yr
147,941
101,351
79,341
Annual Production
1,200,000
200,000
35,000
| Fixed cost/engine
0.12
0.51
2.27
ICF Consulting Group & Engine, Fuel, and Emissions Engineering, Inc.
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Cost Study for Phase Two Small Engine Emission Regulations
35
modate the change in camshaft production methods are estimated at $20,000 for the high-volume
engine line, and $10,000 for the low-volume lines. Thus, the total engine-specific costs are esti-
mated at $233,000 ftii: the 1.2 million unit case and $223,000 for the other two.
The switch to powder-metal production would require a substantial investment in new production
machinery. The cost of the presses to compact the green molds ranges from $50,000 to $190,000
(Fulesday; 1996). We estimated that one press would be required for the 1.2 million unit case,
at a cost of $190,000. The cost of the sintering furnace is about $300,000 (C.I. Hess, 1996).
Powder metal hoppers and handling equipment would add about $75,000, for a total cost of
$565,000. For the 200,000 unit case, we assumed that production would be split between two
similar engine lines, so that the total cost allocable to each line would be $282,000. For the
35,000 unit case, we assumed that it would be split four ways, so that the cost allocable to one
line would be $141,000 (In most cases, manufacturers will produce more than one engine line,
making it economic to share powder-metal parts production between lines. Where that is not the
case, the manufacturer would probably choose to contract with an external supplier to produce
the parts). Total fixed cost amortization amounts to $148,000, $101,000, and $79,000 per year
for the 1.2 million, 200,000, and 35,000 unit cases, respectively. Dividing by the number of
units, the fixed costs would be $0.12, $0.51, and $2.27, respectively. These costs would not be
significantly different for a class II engine.
4.4 Improvement in Piston and Ring Designs
In order to assure that an engine would meet emission requirements throughout its lifetime, one
manufacturer (Briggs and Stratton, 1996) indicated that it is necessary to reduce the amount of
lubricating oil that enters the combustion chamber past the piston rings and along the valve
stems. This oil contributes to the formation of carbon deposits, which degrade the combustion
and emission characteristics. Reducing the oil loss into the combustion chamber would therefore
improve emissions durability, as well as reducing maintenance costs to the consumer. This will
require higher manufacturing tolerances to produce better quality piston and ring packages. The
same manufacturer indicated that in order to produce a better quality piston it would be necessary
to change from a die-cast piston to one produced by permanent-mold casting. This would require
procuring the pistons from an external supplier. The manufacturer estimated the incremental cost
of the permanent-mold piston as about $1.50 to $2.00, and that of the ring package at about
$0.50. For our cost analysis, we took the midpoint of the manufacturers' estimated range of
piston costs, or $1.75.
Some SV engines have valve stem bushings only on the intake valve stem, and not on the
exhaust valve stem. To reduce the amount of oil entering the combustion chamber along the
exhaust valve stem, it would be necessary to add a bushing to the exhaust valve stem as well.
We estimate the cost of the bushing at $0.30. We also assume that it would take an additional
one-half minute of labor to account for handling and pressing the bushing into the cylinder block.
The resulting cost estimates are summarized in Table 18.
ICF Consulting Group & Engine, Fuel, and Emissions Engineering, Inc.
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Cost Study for Phase Two Small Engine Emission Regulations
36
Fixed cost estimates are summarized in Table 19.
We estimate that the development of the im-
proved engine and ring package and the exhaust
valve bushing would require about one person-
year of engineering time, plus extensive durability
testing. We estimate the cost of the durability
testing at $100,000. About 100 emission tests
would also be required, so that total testing costs
would be about $130,000. Other engineering
costs are estimated at $15,000, for a total engi-
neering cost of $245,000. Training and technical
support costs are estimated at $20,000, or about
enough to send out two service bulletins.
Table 18: Incremental variable manufactur-
ing cost for improving piston and ring de-
sign and adding exhaust valve stem bushing
for SV engines.
Cost/
Piece
Pieces/
Engine
Total
Piston
1.75
1
1.75
Piston Rings
0.50
1
0.50
Valve Bushing
0.30
1
0.30
Total Parts Cost
2.55
Added Assembly Labor
Labor Minutes
0.5
Labor Cost, $/hr
15
Direct Labor, $
0.125
Overhead @40%, S
0.05
Total Labor +OH, $
0.175
Total Added Variable Manufacturing
Cost
2.73
The changes in the piston would require matching
changes in the connecting rod design, thus mak-
ing necessary a new master die for the connecting
rod. Fairly extensive changes to the assembly
and component handling processes would also be
required to accommodate the changes in piston
and ring pack design, and to press the exhaust valve stem bushing into the exhaust port. These
changes are estimated to cost $50,000 for the 1.2. million unit case, and $25,000 for the two
lower-volume cases. Thus, the total engine-specific costs are estimated at $330,000 for the 1.2
million unit case, and $305,000 for the other two cases. Amortizing these costs over five years
at a cost of capital of 9%, the total amortized fixed costs amount to about $85,000 per year for
the 1.2 million unit case and $78,000 per year for the other two. Dividing by the number of
units produced results in fixed costs of $0.07 per engine for the 1.2 million unit case, $0.39 per
engine for the 200,000 unit case, and $2.24 per engine for the 35,000 unit case. Table 20 shows
a summary of the hardware/assembly costs and fixed costs for improving piston and ring designs
for SV engines for the three cases.
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Cost Study for Phase Two Smail Engine Emission Regulations
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Table 19: Estimated, fixed costs for the changes in
improving piston and ring designs for SV engines.
Case l
Case 2 j Case J
Engineering Costs
Engineering labor+OH
{) year ® Si00,000)
100,000
100,000
100.000
Emission Testing
30,000
30,000
30,000
Durability Testing
100,000
300,000
loaooo
Total Testing costs
130,000
130,000
130,000
Other engineering
15,000
15,000
15,000
Total Engineering
245,000
245,000
245,000
Technical support
TrainingfTech. Pubs
20,000 | 20,000 | 20,000
Tooling Costs
New Master Dies
Connecting Rod
15,000
15,000
15,000
Total Tooling
15,000
15,000
15.000
Machine Too J Setup
50,000
23,000
25,000
Total Engire-Specific;
330,000
305,000
305.000
Amortized over 5 yrs
84,841
75,413
78,413
J New Machine Tools
0
0
0
| Amortized over 10 yrs
0
0
0
|Total Fixed Cost/Yr
94,841
78,413
78,4.3
j Annual Production
1,200,000
200.00ft
35,00# n
[ Fixed cost/engine
0,07
0.39
231
Table 20: Summary of the viable and
fixed costs for improving piston and ring
designs for SV engines.
Case 1 .
Case 2
Case 3 j
Total Added
Manufacturing
Cost
2.73
2.73
2.73
Fixed Costs
0.07
0.39
2:24 |
!CF Consulting Group & Engine, Fuel, and Emissions Engineering. Inc.
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Cost Study for Phase Two Small Engine Emission Regulations
38
4.5 Improvement in Manufacturing Variability1
To meet the proposed emission
durability requirement, it will be
essential to reduce manufacturing
variability by tightening manufac-
turing tolerances, and by having a
good quality control program. To
achieve tighter tolerances may
require a reduction in throughput,
thus requiring additional machines
to meet the same production level.
More precise assembly operations,
and more frequent quality inspec-
tion will also slow down the as-
sembly processes, requiring more
workers to produce a similar
throughput. Additional people and
quality control machines and tools
would be needed for the QA/QC
program. We considered all these
requirements in our cost analysis.
Since it is based mainly on manu-
facturing practices and processes,
the cost analysis for this improve-
ment is applicable for both the SV
and OHV engines.
As shown in Table 21, we esti-
mated that it the reduction in variability would require the efforts of about one engineer (industri-
al/research) for about one year, which translated to about $100,000. These efforts would go into
identifying and correcting the sources of manufacturing variability. The costs of engineering tests
to identify the source and consequences of manufacturing variability are estimated at $60,000.
Other engineering costs such as special supplies and tools, test materials and so forth are
estimated at $25,000. We also estimated that the setup costs to implement these changes in the
production process would be about $100,000 for the 1.2 million unit case and 50,000 for the
other two cases.
Adding all these costs up, the total engine specific costs are about $285,000 for the high-volume
and $235,000 for the two lower-volume cases. Amortizing these estimates over five years at 9%
Table 21: Estimated fixed costs for the changes in improv-
ing manufacturing variability for SV engines.
Case 1 Case 2 Case 3
Engineering Costs
Engineering labor + OH
(1 year @ $100,000)
100,000
100,000
100,000
Testing costs
60.000
60,000
60,000
Other engineering
25,000
25,000
25,000
Total Engineering
185,000
185,000
185,000
Technical support
Training/Tech. Pubs 0 0 0
Tooling Costs
New Master Dies
None
0
0
0
Total Tooling
0
0
0
Machine Tool Setup
100,000
50,000
50,000
Total Engine-Specific
285,000
235,000
235,000
Amortized over 5 yrs
73,271
60,417
60,417
Add'l Machines and QA
355,000
100,000
38,000
Amortized over 10 yrs
55,316
15,582
5,921
Total Fixed Cost/Yr
128,587
75,999
66,338
Annual Production
1,200,000
200,000
35,000
Fixed cost/engine
0.11
038
1.90
1 Note that the improvement in manufacturing variability does not include tightening the manufacturing tolerance
for the carburetor. Manufacturing variability for the carburetor is addressed separately in the next section as
improved carburetors are assumed to be used in both SV and OHV engines. Therefore, the number of annual
production would be different, and hence, the cost estimates would be different.
ICF Consulting Group & Engine, Fuel, and Emissions Engineering, Inc.
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Cost Study for Phase Two Small Engine Emission Regulations
39
capital rate, the total engine specific costs are $73,000 for the high-volume case and $60,400 for
the two other lower-volume cases.
It would be necessary for the manufacturer to purchase additional machine tools to compensate
for the reduction in throughput. We estimated the reduction in throughput at 30%. For the 1.2
million unit case, we estimated that this would require the equivalent of 5 vertical CNC
machining centers at $55,000 each, plus about $80,000 in QA/QC equipment. For the 200,000
unit case, we estimated the requirement at 1 CNC machining center plus $45,000 in QA/QC
equipment, and for the 35,000 unit case at 1/4 of one CNC machine plus $25,000 in QA/QC
equipment. These costs were amortized over ten years at 9%. The total amortized fixed costs
amount to $129,000 per year for the 1.2 million unit case, $75,000 per year for the 200,000 unit
case, and $66,000 per year for the 35,000 unit case. Dividing these costs by the annual produc-
tion gives fixed costs per engine of $0.11, $0.38, and $1.90, respectively. These costs would be
essentially the same for a class II engine.
We also assumed that it would require one
addition skilled labor minute per engine or
about $0.35 to perform the QfiJQC program.
This variable manufacturing cost is shown in
the summary table (see Table 22).
4.6 Improvement in Carburetor
One critical engine part that would especially
require tighter manufacturing tolerances is the
carburetor. Manufacturing variations in the carburetor directly affect the air-fuel ratio, and thus
the engine emissions and performance. The reduction in carburetor variability was not included
in the previous section, but is treated separately here. Since the same carburetor model is often
used on several different models of engines, carburetor production volumes are considerably
higher than those of individual engine models. While some of the largest engine manufacturers
make their own carburetors, many engine makers buy their carburetors from specialized suppliers
such as Walbro, who are thus able to achieve substantial economies H>f scale. For this analysis,
we assumed that the improved carburetor would be used in both low-volume and high-volume
models, and in both SV and OHV engines. Thus, the annual production engines would be much
greater than 1.2 million engines. We assumed that these improved carburetors would be used
in 4 million engines (see Appendix D for basis).
Similar to the improvement in manufacturing variability, reducing manufacturing tolerances in
the carburetor would require reduced machining throughput, increased care in the assembly opera-
tion, and frequent quality inspection. As shown in Table 23, we estimated that the reduction in
manufacturing variability would require the efforts of about two industrial/research engineers for
one year. The costs of testing to establish the causes and effects of manufacturing variability
were estimated at $60,000. Other engineering costs such as test engines, travel, test materials
Table 22: Summary of the total added
manufacturing and fixed costs for improving
manufacturing variability for SV and OHV
engines.
Case 1
Case 2
Case 3
Total Added Man-
ufacturing Cost
0.35
0.35
0.35
Fixed Costs
0.11
0.38
1.90
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Cost Study for Phase Two Small Engine Emission Regulations
40
and so forth were estimated at $25,000. Table 23: Estimated fixed costs to reduce manu-
Changes to the technical documentation for facturing variability in carburetors,
the carburetor were estimate at $20,000.
The cost of a new master die for the die-cast
carburetor body was estimated at $60,000,
based on a discussion with Walbro engineers.
Changes to the assembly line, materials and
components handling were estimated at
$100,000. Adding all these costs up, the total
carburetor model-specific cost is about
$465,000. Amortizing these estimates over
five years at 9% capital rate, the total model-
specific fixed cost is $156,000. In addition to
these costs, we assumed that the change to
more precise machining processes would
require about one million dollars in capital
investment. Amortizing this estimate over a
ten year period and at a 9% capital rate, the
fixed cost for these machines would be about
$156,000. Dividing the sum of the fixed
costs by the annual production volume, the
fixed cost per carburetor is $0.07.
We also assumed that it would require one
addition skilled labor minute per unit or about
$0.35 to perform the QA/QC program. This
cost is also reflected in Table 24, which is a
summary of total hardware/assembly costs and
fixed costs for tightening manufacturer tolerances for the carburetor.
Table 24: Summary of the total added manufac-
turing and fixed costb for improving carburetor
for SV and OHV engines.
Case 1
Total Added Manufacturing Cost
0.35
Fixed Costs
0.07
Case 1
Engineering Costs
Engineering labor + OH
(2 year @ $100,000)
200,000
Number of Tests
200
Test Cost ($)
300
Testing costs
60,000
Other engineering
25,000
Total Engineering
285,000
Technical support
Training/Tech. Pubs | 20,000
Tooling Costs
New Master Dies
Carburetor
60,000
Total Tooling
60,000
Machine Tool Setup
100,000
Total Model-Specific Costs
465,000
Amortized over S yrs
119,548
New Machine and QA/QC
1,000,000
Amortized over 10 yrs
155,820
Total Fixed Cost/Yr
275,368
Annual Production
4,000,000
Fixed cost/engine
0.07
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October, 1996
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Cost Study for Phase Two Small Engine Emission Regulations
41
5. COST ANALYSES FOR IMPROVING
OVERHEAD-VALVE ENGINES
This chapter presents our cost analysis for the improvements in overhead-valve engine tech-
nology. OHV technologies improvements considered in this study were the following:
• improvement in combustion and intake systems
• improvement in piston and ring designs, and in bore finish
We assessed both variable and fixed costs three cases: 1.2 million engines per year, 200,000
engines per year, and 35,000 engines per year. The basis for these numbers is discussed in
Appendix D.
5.1 Improvement in Combustion and Intake Systems
In general, OHV engines are able to operate at a leaner air/fuel ratio than SV engines due to their
better cooling and airflow characteristics. Also the combustion characteristics are generally better
than those of SV engines, due to die smaller surface-to-volume ratio in the OHV combustion
chamber. However, additional emission reductions may still be realized by operating at an even
leaner air/fuel ratio, and by optimizing the combustion chamber geometry and intake airflow
characteristics. In order to operate on a lean mixture, it is necessary to have a better prepared
mixture by inducing more swirl in the intake manifold, and by designing a better squish area to
induce more turbulent flow, and hence, better mixing during combustion.
The incremental costs of improving the combustion and intake systems are essentially due to the
fixed costs of research, design and development, and changes in production tooling. As in the
case of SV engines, combustion and intake system improvements are not expected to affect
variable costs, since they would require only modifications of existing engine parts, and would
not add new parts or assembly processes. Examples would include a new combustion chamber
with a smaller surface to volume ratio and/or with a squish band, and a change in intake system
geometry to induce more swirl in the combustion chamber to improve combustion characteristics.
Although changes in part geometry might have some minor impact on material requirements,
these impacts are very difficult to predict, and could involve either an increase or a decrease in
material. For this analysis, we have assumed no impact on material or assembly labor
requirements.
The estimated fixed costs of improving the combustion and intake systems are tabulated in
Table 25. We estimated that about two engineer-years would be required to carry out the
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Cost Study for Phase Two Small Engine Emission Regulations
42
research, development, and design
work involved in improving com-
bustion and intake'systems for
OHV engines. This is twice the
estimate for the SV engines.
Since small engine manufacturers
have more experience with SV
than OHV engines, we assumed
that more engineering effort would
be required to first convert to
OHV and then to improve the
OHV engine design.
Extensive emission testing would
be required to develop the opti-
mized intake and combustion
chamber. This was estimated to
require 200 emission tests, at $300
each. Other engineering-related
casts such as test engines, prot-
otyping, travel, test materials and
so forth were estimated at $25,000.
The total engineering costs would
then be $285,000. These costs
would not be greatly different
between any of the engine cases.
The cost of changes to parts lists
and other technical documents was
estimated at $20,000, or about the
cost of two technical bulletins.
Table 25: Estimated fixed costs for the changes
ing combustion chamber and intake systems
engines.
in improv-
for OHV
[ Case 1
Case 2 | Case 3
Engineering Costs
Engineering labor + OH
(2 years @ $100,000)
200,000
200,000
200,000
Number of Tests
200
200
200
Test Cost (S)
300
300
300
Testing costs
60,000
60.000
60,000
Other engineering
25,000
25,000
25,000
Total Engineering
285,000
285,000
285,000
Technical support
Training/Tech. Pubs | 20,000 20,000 20,000
Tooling Costs
Mew Master Dies
Cylinder head
60,000
60,000
60,000
Piston
25,000
25,000
25,000
Total Tooling
85,000
85,000
45,000
Machine Tool Setup
50,000
25,000
25,000
Total Engine-Specific .
440,000
415,000
415,000
Amortized over 5 yrs
113,121
106,693
106,693
New Machine Tool
0
0
0
Amortized over 10 yrs
0
0
0
Total Fixed Cost/Yr
113,121
106,693
106,693
Annual Production
1,200,000
200,000
35,000
Fixed cost/engine
0.09
0.53
3.05
Tooling costs to implement the geometric changes would include thfe costs of new master dies
for the cylinder head and piston. The costs for the cylinder head and piston master dies for an
OHV engine are estimated at 560,000 and $25,000, respectively, based on our conversations with
die makers (Spec Cast, Prince Machine and Muller Weingaren, 1996). The costs of the necessary
changes in the production process, jigs, transfer equipment, etc. are estimated at $50,000 and
$25,000 for the high-volume and the two lower-volume cases, respectively. Thus, the total
engine-specific costs are estimated at $440,000 for the 1.2 million unit case, and $415,000 for
the 200,000 and 35,000 unit cases. These costs were amortized over five years at a cost of capi-
tal of 9%. No new inachine tools would be needed, so the total amortized fixed costs amount
to $113,000 per year for the 1.2 million unit case and $107,000 per year for the other two.
Dividing by the number of units produced results in fixed costs of $0.09 per engine for the 1.2
million unit case, $0.53 per engine for the 200,000 unit case, and $3.05 per unit for the 35,000
unit case.
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Cost Study for Phase Two Small Engine Emission Regulations
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5.2 Improvement in Piston and Ring Designs and Bore Smoothness
In OHV engines, as in SV engines, it may be
necessary to reduce the amount of lubricating
oil that enters the combustion chamber in
order to reduce the formation of carbon de-
posits. These deposits increase HC emissions
and degrade combustion. This may require
improvements in the design of the piston and
piston rings (note that OHV engines already
have valve stem seals on both the intake and
exhaust valves, so that these would not consti-
tute an added cost). Improvements in the
roundness and finish of the cylinder bore may
also be needed. According to one engine manufacturer we consulted (Briggs and Stratton, 1996),
the development effort to produce a better piston and ring package for an OHV engine would be
similar to that for an SV engine. For our cost analysis, we assumed that permanent-mold cast
pistons and better ring package would be required to improve the piston and ring designs. The
pistons were assumed to be obtained from an outside supplier, at an additional cost of $1.75.
The additional cost of the better quality ring package was estimated at $0.50 (Table 26).
The estimated fixed costs for the piston and ring improvements in the OHV case are similar to
those estimated for the SV case, which were documented in Table 19. The main differences are
that we assumed an investment in new machine tools due to reduced throughput in the cylinder
boring process resulting from the need for improved bore roundness and finish. For the 1.2
million unit case, this was estimated to require the equivalent of four new boring machines at
$100,000 each. For the 200,000 unit case, one boring machine was assumed, and 1/4 of a boring
machine for the 35,000 unit case. The resulting cost estimates are shown in Table 27. Table 28
shows a summary of the hardware/assembly costs and fixed costs for improving piston and ring
designs, and improving bore finish for OHV engines for the three cases.
Table 26: Estimation of incremental variable
manufacturing cost for improving piston and
ring designs for OHV engines.
Cost/
Piece
Pieces/
Engine
Total
Piston
1.75
1
1.75
Piston Rings
0.50
1
0.50
Total Added Variable Manufacturing Cost
2.25
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Cost Study for Phase Two Small Engine Emission Regulations
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Table 27: Estimated fixed cos for the changes in improv
ing piston and ring designs for OHV engines.
Case 1 | Case 2 Case 3
Engineering Costs
Engineering labor + OH
(2 years @ $100,000)
100,000
100,000
100,000
Emission Testing
30,000
30,000
30,000
Durability Testing
100,000
100,000
100,000
Testing costs
130,000
130,000
130,000
Other engineering
15,000
15,000
15,000
Total Engineering
245,000
245,000
245,000
Technical support
Training/Tech. Pubs 20,000 | 20,000 20,000
Tooling Costs
New Master Dies
Connecting Rod
15,000
15,000
15,000
Total Tooling
15,000
15,000
15,000
Machine Tool Setup
50,000
25,000
25,000
Total Engine-Specific
330,000
305,000
305,000
Amortized over 5 yrs
84,841
78,413
78,413
New Machine Tool
400,000
100,000
25,000
Amortized over 10 yrs
62,328
15,582
3,896
Total Fixed Cost/Yr
147,169
93,995
82,309
Annual Production
1,200,000
200,000
35,000
Fixed cost/engine
0.12
0.47
2.35
Table 28: Summary of the vari-
able and fixed costs for improving
piston and ring designs for OHV
engines.
Case 1
Case 2
Case 3 ]
Total Added
Manufacturing
Cost
2.25
2.25
2.25
Fixed Costs
0.12
0.47
2.35 |
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PART II
BOTTOM UP COST ANALYSIS FOR HANDHELD
EQUIPMENT ENGINES
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6. HANDHELD ENGINES
Except for battery-electric or cord-electric equipment, nearly all small engines used in handheld
equipment (e.g., chainsaw, trimmers) use the crankcase-scavenged two-stroke design.
Additionally, a four-stroke handheld engine, used in trimmer equipment, has been developed and
is now on the market. The distinction between two-stroke and four-stroke small engines is an
important one for emissions, as two-stroke engines tend to emit much greater amounts of
unburned hydrocarbons (HC) and particulate matter (PM) than four-stroke engines of similar size
and power. The high PM emissions are due to the fact that lubricating oil is mixed with fuel in
two-stroke engines. Two-stroke engines also display markedly poorer fuel economy than four-
strokes, but tend to have higher power output, quicker acceleration, and lower manufacturing
costs. Because of their advantages in performance and manufacturing cost, two-stroke engines
are used extensively in small equipment where this is permitted by emission regulations.
The reasons for using two-stroke engines include compactness and the ability to operate in a
variety of positions, including upside down, as well as better power-to-weight ratio and lower
manufacturing cost. These engines range from 20 to 100 cc displacement. Recently, a handheld
engine and equipment manufacturer, Ryobi, has introduced string trimmers powered by a four-
stroke engine with overhead-valves. The Ryobi four-stroke engine is discussed later in the
chapter. Recently, Honda also announced that it will introduce a small four-stroke engine for
applications in handheld equipment, but details of this engine are not yet available.
The operating principles, emission characteristics, and emission control technologies for small
four-stroke engines were discussed in Chapter 2. This chapter discusses the general operating
principles, emission characteristics, and emission control technologies for two-stroke engines, and
for lightweight four-stroke engines suitable for handheld use.
6.1 Operating Principles of Small Two-Stroke Engines
A two-stroke small engine can be much simpler mechanically than a four-stroke engine. The
operating principles are very simple as well. Blair (1990) provides an excellent and very thor-
ough discussion of two-stroke engine design and operation. Four stages in the combustion cycle
of a simplified two-stroke engine are shown in Figure 11. In the first stage (Figure 11a), near
the top of the compression stroke, the compressed charge in the cylinder is about to be ignited
by the spark plug. At the same time the partial vacuum created by the rising piston draws fresh
air-fuel mixture into the crankcase. Ignition is followed by combustion, and the pressure of the
hot burned gases forces the piston down. As the piston approaches the bottom of the cylinder,
the exhaust port in the wall of the cylinder is uncovered, and the combustion gases "blow down"
into the exhaust port (Figure 1 lb).
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4
Figure 11: Operation of a two-stroke, loop scavenged engine.
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As the piston gets closer to the bottom of its stroke, the transfer ports are uncovered, and air-fuel
mixture from the crankcase is forced into the cylinder (Figure 1 lc). The pumping force required
to move the air-fuel mixture is provided by the downward motion of the piston. Since the
exhaust port is still open, the burned gases are pushed from the cylinder by the pressure of the
incoming charge. In the process, however, some mixing between the exhaust gas and the charge
takes place, so that some of the exhaust is retained in the cylinder, and some of the fresh charge
is emitted in the exhaust. As the piston again rises for the next compression stroke, it closes First
the transfer port and second the exhaust port - trapping the remaining charge in the cylinder.
Before the exhaust port closes, however, the rising piston pushes some of the charge in the
cylinder out into the exhaust (Figure 1 Id).
Since the gas exchange processes in a two-stroke engine are controlled by its piston and ports,
the complex valve gear, camshaft, and related mechanisms needed in a four-stroke engine are not
needed. For this reason, two-stroke engines are easier and cheaper to manufacture than four-
stroke engines.
6.2 Causes of Emissions from Two-Stroke Engines
In small two-stroke engines, the major sources of unburned hydrocarbon emissions are the loss
of unburned charge out the exhaust ports during scavenging, and hydrocarbon emissions due to
misfire or partial combustion at light loads. The fraction of the total charge fed to the cylinder
that is trapped to participate in the combustion process is known as the "trapping efficiency".
At full load, trapping efficiency for a chainsaw engine may be as low as 55% (Blair, 1990) -
implying that 45% of the fuel-air mixture supplied to the engine is emitted unburned in the
exhaust (Hare et al, 1974; Batoni, 1978; Nuti and Martorano, 1985).
Under light-load conditions such as idle, the flow of fresh charge is reduced, which increases the
trapping efficiency. However, scavenging efficiency is also reduced, allowing substantial
amounts of exhaust gas to be retained in the cylinder. This high fraction of residual gas can
cause incomplete combustion or misfire. Misfiring or incomplete combustion cycles are the
source of the "popping" sound commonly produced by two-stroke engines at idle and light loads,
as well as the problems that these engines often have in maintaining stable idle. These unstable
combustion phenomena are major sources of HC emissions under idle and light-load conditions
(Tsuchiya et al, 1983; Abraham and Prakash, 1992; Aoyama et al, 1977).
Another source of the high HC and CO emissions typical of two-stroke engines is the air-fuel
ratio, which is normally set very rich compared to (e.g.) four-stroke automotive engines. For
conventional carburetted two-stroke chainsaw engines, the mixture is usually set around 12:1 by
weight, compared to a stoichiometric air-fuel ratio of 14.7:1. This increases the maximum power
output from the engine, and helps to limit the engine temperature, as well as providing easier
starting. Since there is insufficient oxygen present in the cylinder to fully bum all the fuel to
CO2, however, substantial amounts of CO and HC are emitted in the exhaust.
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The source of the high level of particulate emissions characteristic of two-stroke engines is the
lubricating oil that is added to the fuel to lubricate the crankcase parts. Since the crankcase is
used as a pump, it cannot contain a pool of oil to lubricate the bearings as well. Thus, lubricat-
ing oil is mixed into the fuel instead. When the fuel is atomized in the carburetor and vaporizes,
the less-volatile oil is left as a mist of oil droplets in the air-fuel mixture. Some of these droplets
contact the cylinder walls, the crankshaft bearings, and other parts that require lubrication. Most
of the oil, however, is carried into the combustion chamber along with the air-fuel mixture. The
oil in that part of the air-fuel mixture that is not trapped and burned appears as particulate matter
in the exhaust. Even the oil that is trapped often fails to burn completely. The presence of
condensed oil droplets in the exhaust is responsible for the two-stroke's characteristic white or
blue smoke emissions.
Since two-stroke SI engines usually retain significant exhaust gas in the cylinder and run at rich
air-fuel ratios, flame temperature and NOx concentrations are usually low. Measures to reduce
CO and HC emissions from two-strokes, to the extent that they result in leaner air-fuel ratios, are
likely to increase NOx emissions.
63 Emission Levels for Handheld Two-Stroke Engines Meeting EPA Phase 1 Emission
Standards
Since engine emissions have only recently been regulated, emission data are scarce, and are
generally available only for new engines in proper running condition. The limited data available
are presented in this section.
Figure 12 shows emissions certification data for California 199S model handheld utility equip-
ment engines. These engines were certified to California Tier I standards, which are similar to
EPA's Phase 1 emission standards. The average emission levels for these certified engines are
shown in Table 29.
An interesting observation on the emission data in Figure 12 is that the emissions for the only
engine with displacement greater than 50 cc were quite low. These data were for a 56 cc blower
engine manufactured by Stihl. Discussions with a Stihl engineer revealed that the blower engine
is designed to run leaner than other engines. This engine can affor&to run leaner without fear
of overheating, since the blower provides a very high flow of cooling air.
To meet the EPA Phase 1 or the California Tier I standards, most handheld equipment engines
required enleanment in fuel/air mixture, improvements in fuel metering, changes in ignition tim-
ing, and improved cooling. Some engines required minor design changes as well. To achieve
additional reductions in HC and CO emissions, small two-stroke engines may require advanced,
engine modifications and/or use of aftertreatment devices.
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EPA Phase 1 Standards for Class III Engines
0
0 0
0 <*»°
s
& 0 99
0
8 & 0
0
0
w O
3° 8
Kngin» Size
O < 20 cc
O 20-50 cc
~ > 50 cc
EPA Phi ise 1 Standards for Class IV Engines
EPA Phase 1 S tandards for Class V Engines
100 150 266 250 300 3&0
HC (g/kw-hr)
Figure 12: CARB 1995 certification data compared to EPA Phase 1 handheld engine standards.
Table 29: Average emission levels for handheld equipment engines that meet EPA Phase 1 and
CARB Tier I standards.
Eng. Disp.
(cc)
THC
(g/Kw-hr)
CO
(g/Kw-hr)
NOx
(g/Kw-hr)
Engine Displacement: < 20 cc
18.0
220
422
1.1
Engine Displacement: 20 • 50 cc
31.8
186
418
1.6
Engine Displacement: > 50 cc
56.0
89
254.7
3.55
6.4 Emission Control Technologies for Small Two-Stroke Engines
Compared to small non-handheld engines, small handheld engines pose even more difficult
problems for emission control. These handheld engines are frequently used in situations that
demand multi-position capability, which may not currently be conducive to certain engine
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modification technologies (e.g., four-stroke handheld). The engines must remain lightweight,
therefore certain weight intensive emission controls would not be feasible. Additionally, the
contact proximity of-the handheld engine to the operator poses issues for heat generation using
certain technologies (e.g., catalytic converters). Also, the tolerances for the two-stroke have to
be more exact and there is generally less flexibility in redesign of the handheld versus the non-
handheld small engine.
Technologies potentially applicable to reducing small two-stroke engine emissions can be grouped
into the following categories:
• improved scavenging characteristics;
• combustion chamber modifications;
• improved ignition systems;
• exhaust aftertreatment technologies;
• conversion to four-stroke engines;
• improverr . nts in engine lubrication; and
• advanced fuel metering systems.
The application of some of these technologies to small engines to reduce exhaust emissions have
been reported in a number of studies, and there is now significant practical experience with some
of these techniques. The emission control technologies that are within the scope of this study
- scavenging control, stratified scavenging, improvements in the combustion chamber,
improvement in spark ignition, exhaust aftertreatment, and conversion to four-stroke - are
discussed below. Other technologies are presented in Appendix C.
Scavenging Control Technologies
In a two-stroke engine, the exhaust and intake events overlap extensively, as the piston finishes
its downward stroke and begins its movement from the bottom of the cylinder to the top. As the
piston approaches the bottom of the cylinder, exhaust ports in the walls of the cylinder are
uncovered. When this happens, the high pressure combustion gases blow out through the exhaust
port. As the piston gets closer to the bottom of its stroke, the intake ports are opened and fresh
air or air-fuel mixture is blown into the cylinder while the exhaust ports are still open. Piston
movement timing (measured in crank angle) and cylinder port configuration are the major factors
controlling the scavenging process. The ideal situation would be to retain all of the fresh charge
in the cylinder (high trapping efficiency) while exhausting all of the spent charge from the last
cycle (high scavenging efficiency). These two goals conflict. In production engines, the cylinder
ports and timing are generally designed for high scavenging efficiency, in order to achieve
maximum power output and smoother idle, at the expense of higher short-circuiting losses and
HC emissions. It is possible to reconfigure the intake and exhaust ports to fine-tune the
scavenging characteristics for lower emissions, but this involves significant trade-offs with engine
performance. Another way to increase trapping efficiency, with minimum impact on
performance, is to apply exhaust charge control technology.
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Exhaust charge control technology modifies the exhaust flow by introducing one-way control
valves in the exhaust, or by making use of the exhaust pressure pulse wave. Using the exhaust
pressure pulse wave to control intake and exhaust flow usually requires a fairly long exhaust
pipe, and is effective only for a restricted range of engine RPM. For this reason, one-way control
valves are usually used to control the exhaust flow rate in small engines. The critical variable
parameter for exhaust charge control techniques is the contraction ratio, which is defined as the
ratio of the restricted exhaust passage area regulated by the valve to the unrestricted exhaust
passage area. The effectiveness of these techniques is measured by the delivery ratio, which is
the ratio between the mass of air-fuel mixture actually delivered to the engine and the mass of
air-fuel mixture contained by the engine displacement volume at ambient conditions.
Figure 13: Schematic to illustrate the stratified scavenging approach in a two-stroke engine.
Stratified Scavenging
Stratifying the charge in a two-stroke engine can reduce scavenging losses and HC emissions.
One stratified scavenging approach is shown in Figure 13. In this approach, a supply of pure air
is first introduced into the cylinder during the start of the scavenging process, to displace the
exhaust gas, and is then followed later by a rich fuel/air mixture to support combustion. Con-
trolled by reed valves, the secondary air supply can be inducted either through transfer passages
M : EXHAUST MUFFLER
«p: spark plug
F, : PISTON
TV : THROTTLE VALVE
AW : AIR FILTER
C :CARBURETTOR
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or through the crankcase. The simplest approach is to pre-fill the transfer passages between the
crankcase and combustion chamber with pure air, inducted separately from the air-fuel mixture
entering the crankcase.
Ideally, with stratified scavenging, most of the charge lost from the cylinder will be pure air or
a very lean air-fuel mixture. Thus, scavenging losses are minimized. However, it is impossible
to obtain a perfect "two-layer" charge (pure air, and rich fuel/air mixture), while accurately
supplying the right amount of pure air to effectively displace the exhaust gas during the actual
scavenging process at different load/speed conditions. Thus, there will still be some fresh fuel/air
charge scavenged out the exhaust port(s) with the stratified scavenging approach. A number of
researchers have tested different designs based on the stratified scavenging concept, and their
designs are discussed in Appendix C.
Improvements in the Combustion Chamber
Combustion chamber and piston configurations can be improved to induce more turbulent motion
to improve mixing during the compression stroke, as well as to control the flow direction of the
fresh charge to minimize losses due to unburned fuel. Using improved combustion chamber and
piston configurations with more swirl and squish can also minimize the formation of pocket or
dead zones in the cylinder volume where burned gases can become trapped and escape
displacement or entrainment by the fresh scavenging flow. Laimbock et al. of Graz University
of Technology (GUT) in Austria have designed a "jockey-cap" shape like combustion chamber
which concentrates the squish area only above the exhaust port (Laimbock and Landerl, 1990).
This "jockey-cap" type combustion chamber is designed to force the fresh charge to flow over
the spark plug, which improves the cooling and allows the engine to run leaner without pre-
ignition.
Recently, Kawasaki modified the combustion chamber of a 25 cc chainsaw engine to increase
the power output to overcome the power loss due to retarding the exhaust timing for HC and
NOx emission reductions (Tamba S. et al, 1995). A 48% HC emission reduction and 85% CO
emission reduction were achieved through enleanment and retarding exhaust timing. Some other
minor modifications, such as combustion chamber and exhaust port modifications, and improved
cooling, were also incorporated to overcome engine and exhaust gas temperature rise due to the
leaner mixture, and power loss problems. The Kawasaki study showed that there is still a lot of
room for engine modifications for small engines to reduce emissions.
Improvement in Spark Ignition and Timing
The effect of ignition timing on two-stroke engines is essentially the same as on four-stroke
engines. Retarding ignition timing beyond the minimum for best torque (MBT) point reduces
power and increases fuel consumption, but reduces NOx and (within limits) HC emissions. Re-
tarding ignition timing, especially at high loads, may offer a means of recovering much of the
increase in NOx emissions that will otherwise result from using a leaner mixture in low-emission
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two-stroke engines. Advancing ignition timing at light load reduces HC emissions in direct fuel-
injected engines by reducing the dispersion of the fuel cloud. The cloud is therefore less likely
to contact the walls'of the combustion chamber. This reduces the amount of unbumed HC
produced by the quenching effect at the combustion chamber walls, as well as the filling of
crevice volumes with unburned mixture. The unburned HC due to flame quenching and crevice
volumes are major sources of HC exhaust emissions. With better combustion quality at advanced
ignition timing, CO emissions are also reduced. NOx emissions, however, are increased with
advanced ignition timing.
Researchers at ITRI have used a dual spark plug ignition in a scooter two-stroke engine to
determine the effects on engine torque and unbumed HC emissions (Huang et al, 1991). It was
reported that the engine with dual spark plugs yielded lower HC emissions and better engine
torque at low and medium engine load conditions. The improvements were believed to be due
to the increase in combustion speed and the decrease in mixture bulk quenching effect when the
dual plug ignition was used. However, ITRI's findings also showed that using additional spark
plugs did not improve the high unbumed HC emissions under idling or light-load conditions.
Exhaust Aftertreatment Technologies
The use of aftertreatment technologies such as thermal oxidation and catalytic converters can
provide additional control of emissions beyond that achievable with engine and fuel-metering
technologies alone. Catalytic converters have been demonstrated on a limited basis in small two-
stroke engines.
Thermal Oxidation - Thermal oxidation is used to reduce emissions of HC and CO by
promoting further oxidation of these species in the exhaust. This further oxidation usually takes
place in the exhaust port or pipe, and may require the injection of additional air to supply the
needed oxygen. Substantial reductions in HC and CO emissions can be achieved through thermal
oxidation if the exhaust can be maintained at a high enough temperature long enough. The
typical temperature levels required for HC and CO oxidation are about 600 and 700 °C
respectively. Although these requirements are difficult to meet for small engines with typical
short exhaust systems, the technique has been demonstrated in a biodified small four-stroke
engine by introducing secondary air into the stock exhaust manifold upstream of the engine
muffler. Air injection at low rates into the stock exhaust system was found to reduce emissions
by -as much as 77% for HC and 64% for CO (White et al, 1991). However, this was effective
only under high-power operating conditions. In addition, the high exhaust temperatures required
to achieve this oxidation would substantially increase the skin temperature of the exhaust pipe.
Oxidation Catalyst - Like thermal oxidation, the oxidation catalyst is used to promote further
oxidation of HC and CO emissions in the exhaust stream, and it also requires sufficient oxygen
for the reaction to take place. Some of the requirements for a catalytic converter to be used in
two-stroke engines include high HC conversion efficiency, resistance to thermal damage^
resistance to poisoning by sulfur and phosphorus compounds in the lubricating oil, and low light-
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off temperature. Additional requirements for catalysts to be used in two-stroke engines include
extreme vibration resistance, compactness, and light weight.
Catalytic converters available for small engines use either metal or ceramic substrates. Although
metal substrates have many advantages - especially resistance to vibration and shock -they are
considerably more expensive. "Ballpark" pricing data from industry sources suggest that a
catalytic converter based on a ceramic substrate should cost the engine manufacturer about five
dollars per unit, while the cost of a metal substrate would be about four times as high. Although
most available test data are on metal substrate catalysts, ceramic substrate suppliers have
developed mounting techniques which they believe will allow catalytic converters using these
substrates to give durability and performance similar to those of the metal substrate units.
Recently, Coming and Engelhard have presented results indicating that the durability
requirements of two-stroke engine can be met with the ceramic catalyst substrates with improved
mounting systems (Reddy et al., 1995).
Application of catalytic converters to two-stroke engines presents a problem, because of the high
concentrations of HC and CO in their exhaust. If combined with sufficient air, these high
pollutant concentrations result in catalyst temperatures that can easily exceed the temperature
limits of the catalyst. These high temperatures also pose a hazard of fire or personal injury to
equipment users. Temperature limits for catalytic converters are similar for metal substrate and
ceramic substrate catalysts - both begin to suffer damage at about 1000 °C. Thus, application
of catalytic converters to two-stroke engines requires either limiting the air supply to limit
pollutant oxidation and the resulting exotherm, or engine modifications to reduce the
concentration of pollutants in the exhaust before the catalyst.
A number of researchers have applied oxidation catalytic converters to small two-stroke engines.
Researchers at Graz University of Technology, 1TR1 in Taiwan and several other organizations
have all published data on the application of catalytic converters in small two-stroke engines
(Mooney et al., 1975; Engler et al., 1989; Burrahm et al., 1991; Laimbock and Landerl, 1990;
Laimbock 1991; Hsien et al, 1992; Pfeifer et al., 1993; Gulati et al., 1993; Castagna et al., 1993).
Some of these studies are discussed in Appendix C.
As a result of this research, catalytic converters have been used on opmmercial production two-
stroke motorcycles and mopeds in order to meet emissions standards in Taiwan, Switzerland, and
Austria. Experience with these systems in consumer use has shown them to be acceptable,
except that special heat shielding is necessary to protect the passengers from contact with the
catalyst housing, which can have a skin temperature exceeding 500 °C. In Europe, catalytic
converters have also been available since 1989 on production model chainsaws - with the primary
intention to reduce inhalation of hydrocarbon emissions by the operators. These are presently
an expensive option, found mostly on professional saws.
Stihl Production Chainsaws Equipped with Catalytic Converters - Stihl is selling three models
of chainsaws equipped with catalytic converters. The engine sizes of these chainsaws range from
49 to 77 cc. The average weight increase for these catalyst chainsaws ranges from 0.44 to 0.66
lbs (0.2-0.3 kg). Emission results obtained from Stihl for a 70 cc chainsaw with enleanment (air-
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fuel ratio of 16:1) and catalytic converter showed HC emissions reduced by 85% (from 114 to
13.4 g/kW-hr), and CO emissions reduced by 45% (from 590 to 255 g/kW-hr). However, even
with heat shields and'1 mixing ambient air with exhaust, Stihl reported that the maximum exhaust
gas stream and skin temperatures were 530 and 300°C, respectively. These temperatures
exceeded the US Forest Service's allowable temperature limits, which are 246°C for exhaust gas
temperature and 289°C for skin temperature. In addition, these catalytic converters add about
$100 to the price of the chainsaw. The added cost is said to be due to the costs for the catalytic
element and its support, additional heat resistant material for the muffler, additional structural
material for cooling and redirecting hot gases, and development and tooling costs. These latter
probably account for the largest share of the increase, due to the very small volume of units over
which they are spread.
Husavama "E-Tech" Two-Stroke Engines with Catalytic Converters - Recently, Husqvama has
issued several press releases on its "advanced two-Stroke engine", so called "E-Tech" engines,
to be used in trimmers. This engine will be used in conjunction with a "lower-temperature"
catalytic converter. Husqvama claims that the E-Tech engine have the potential to reduce
combined HC+NOx emissions by 60% compared to EPA Phase 1 standards. Husqvama indicates
that these reductions are achieved by means of a better scavenging process and the use of a
catalytic converter. However, as of today, no emission data were publicly available for this
engine.
Other Catalyst Research on Two-Stroke Engines - United Emission Catalyst (UEC) has
investigated the use of catalysts in leaf blowers to determine the maximum reduction of HC and
CO emissions possible using a catalyst size limited to that which will fit in a standard muffler
housing (Hobbs, 1995). A leaf blower engine was tested with and without catalyst at idle and
WOT conditions. Emission results with a 64 cell catalyst showed 58% and 50% reduction in HC
emissions at idle and WOT conditions, respectively. The CO emissions were reduced by 25%
at idle and 49% at WOT conditions. However, the exhaust outlet temperature was increased
from 95 to 145°C at idle, and 250 to 370 °C at WOT.
Pfeifer et al. (1993) also studied the effects of catalytic converters on exhaust HC, smoke and
PM emissions for two-stroke motorcycle engines. The results showed that the catalytic converter
not only reduced HC emissions, but PM emissions as well. Thus, thduse of catalytic converters
on two-stroke engines will significantly reduce PM emissions and smoke as well as HC and CO
emissions.
Additional catalytic converter developments are described in Appendix C.
Conversion to Four-Stroke Engines
As discussed previously, four-stroke engines inherently produce less HC, CO, and particulate
emissions than two-stroke engines. Therefore, one way to reduce emissions from small
equipment using two-stroke engines is to convert the equipment to use four-stroke engines if the
applications of the equipment permit. In California, nearly all of the two-stroke engines used in
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non-handheld equipment were replaced by four-stroke designs after the CARB Tier I emission
regulations took effect, and the same is expected to occur in the rest of the U.S. when EPA's
Phase 1 standards become effective. However, in order to use four-stroke engines in handheld
equipment, the engine has to match the performance advantages of a two-stroke engine. These
include high power to weight ratio, compactness, and multiposition operating ability. Since four-
stroke engines have more mechanical parts, the cost to produce them is higher. In order to be
competitive, the cost of the four-stroke engine would need to be comparable to or less than that
of the advanced or improved two-stroke engines that could also meet possible Phase 2 standards.
Rvobi Four-Stroke Engine - Ryobi has certified a string trimmer powered by a four-stroke
engine to meet CARB Tier I emission standards. This innovative 26 cc four-stroke engine, which
uses overhead-valve and exhaust gas recirculation (EGR) technologies, was the result of many
years of research and development work within Ryobi. The engine is rated at 0.75 to 1 hp, and
has an expected life of about 100 to 200 hours. Ryobi also reports that it can build handheld
four-stroke engines up to 3 horsepower. Recently, Honda announced that it will offer a small
four-stroke engine for handheld equipment in 1997. However, no detailed information was given
regarding the engine.
Emission Levels - The Ryobi four-stroke engine is the first and only handheld four-stroke
gasoline engine certified by CARB to meet the Tier I emission standard. The certified emission
data are 493 g/kW-hr for CO, 37.5 g/kW-hr for HC, and 4.0 g/kW-hr for Nox emissions. The
HC and CO values were determined with the carburetor set in the rich/rich position, and the NOx
value was determined with the carburetor set in the lean/lean position.
Ryobi is continuing to refine the engine by limiting carburetor adjustments, as well as using
different cam designs and valve timing to control NOx emissions without EGR. The reason for
investigating other means to control NOx emissions is that reports indicate the EGR passage in
the engine might plug when the carburetor is set at the rich/rich position.
Ryobi also tested the four-stroke engine with a catalytic converter. The results showed that HC,
CO and NOx emissions were reduced further. A substantial reduction in NOx emissions was
observed (from 4.2 to 0.7 g/kW-hr). However, as with other research on catalytic converters for
two-stroke engines, the skin and exhaust temperatures were increased qnd exceeded the US Forest
Service limits. All these results indicate that more testing is necessary with different emission
control approaches to reduce the CO emissions while maintaining the NOx emissions or vice
versa.
Cost and Weight - Compared to a similar 31 cc two-stroke model that Ryobi offers, the four-
stroke string trimmer costs about 50 to 80% more at retail, depending on the design features, and
it weighs about 2 to 3 lbs more based on the same specifications. Ryobi also reported that the
differential weight can be reduced to less than 0.6 lbs by retooling some injection molded and
die cast components.
Engine Features - Ryobi has incorporated many features to reduce the weight and parts in this
engine, which in turn make it more compact and less expensive to produce. The innovative
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design of the cylinder head assembly, which includes the miniature overhead-valve train and EGR
passage, allows it to tolerate high speeds and loads. Many of the valve train parts, including the
intake and exhaust " valves and followers, are interchangeable to reduce manufacturing and
inventory costs. A simple gear-lobe-follower assembly is used to control the valve timing instead
of the typical two-lobe camshaft used in many engines with overhead-valve configurations.
A small passage is drilled between the intake and exhaust ports to provide EGR. An accelerator
pump is also used in this engine to keep the carburetor from going too lean during acceleration.
The engine uses the splash lubrication method to lubricate the crankshaft bearing, piston/cylinder
and valve train assembly. While Ryobi tried to design the current string trimmer to have
multiposition operating ability, field tests have shown that the engine begins smoking and oil
drips from the air filter when the trimmer is operated for a few minutes with the exhaust side
down. However, the string trimmers do come with a split boom design, which allows the
operator to adjust the front part of the trimmer to perform edging while still keeping the engine
upright.
Current Status - Ryobi has indicated that it is ready and willing to license its four-stroke engine
design to other manufacturers. It has been reported that Ryobi is involved in licensing
discussions with several manufacturers, and at least one company is buying Ryobi four-stroke
trimmers to be sold under its own brand name.
With Ryobi's demonstration of the feasibility of using small four-stroke engines on string
trimmers, many handheld engine and equipment manufacturers are believed to be considering
four-stroke engine technology as one of their research and development alternatives to produce
low emission handheld equipment, at least for those applications that do not require total
multiposition operating ability. These applications include string trimmers and blowers, but not
chainsaws. Small four-stroke engine technology is well developed and understood in motorcycle
and non-handheld equipment applications. Thus, it will not be surprising to see other four-stroke
engines emerging for handheld equipment as one of the viable technologies to meet the emission
regulations.
ICF Consulting Group & Engine, Fuel, and Emissions Engineering, Inc.
October, 1996
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Cost Study for Phase Two Small Engine Emission Regulations
59
7. COST ANALYSIS FOR CONVERTING TWO-STROKE
TO FOUR-STROKE ENGINES
This chapter presents the cost analysis for converting two-stroke engines used in handheld
equipment to four-stroke engines. This includes estimates of the incremental variable
manufacturing costs (e.g. materials and assembly labor) and fixed costs (e.g. tooling and
engineering design) due to the change from two-stroke to four-stroke engines. Since the fixed
costs per engine are strongly affected by the production volume, cost estimates were developed
for two cases: one with a production volume of 400,000 units annually, and the other with a
production of 90,000 units. The basis for selecting these production levels is given in Section
7.2.
7.1 Comparison of Two-stroke and Four-stroke Engines
As discussed in Chapter 6, four-stroke engines tend to have more engine parts than two-stroke
engines, due to the need for a valve train assembly to control the flow of air/fuel mixture into
the combustion chamber and the flow of exhaust gases out of the chamber. In two-stroke
engines, these functions are accomplished by the piston covering and uncovering ports in the
cylinder wall. The valve train assembly adds substantially to the parts count, as well as to the
weight of the engine. In order to estimate the incremental cost of converting two-stroke engines
to four-stroke engines, it was necessary first to characterize the differences between them. Using
data developed in a previous study (Chan and Weaver, 1996), we were able to determine the
number of additional parts, the difference in material requirements, and the differences in
machining operations used to produce each part for a small four-stroke engine and a small two-
stroke engine.
The four-stroke engine that we investigated was the one used in the Ryobi Model 920 string
trimmer. The Ryobi engine is the only production four-stroke engine that is presently used in
handheld equipment. The two-stroke engine that we used for comparison was the one in the
Ryobi Model 720 string trimmer. Exploded views of these engines are shown in Figure 14 and
Figure 15, respectively. The parts lists for these engines were also obtained from a distributor,
and are included in Appendix B.
Recently, Conley et al. (1996-1, 1996-2, 1996-3) have published three papers on the research,
design and development, as well as the emission and performance characteristics, of the Ryobi
four-stroke engine. The information in these papers was also used in our cost analysis, along
with the data we developed.
ICF Consulting Croup & Engine, Fuel, and Emissions Engineering, Inc.
October, 1996
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Cost Study for Phase Two Small Engine Emission Regulations
60
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-------
Cost Study for Phase Two Small Engine Emission Regulations
61
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Figure 15: Exploded view of a Ryobi two-stroke engine.
JCF Consulting Croup & Engine, Fuel, and Emissions Engineering, Inc.
October, 1996
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Cost Study for Phase Two Small Engine Emission Regulations
62
Additional Parts - After disassembling the engines, we counted and recorded the parts found in
each one. Using this information, which was confirmed against the parts lists in Appendix B,
we compiled a list df' major parts used in the four-stroke engine that were not found in the two-
stroke engine. This list is shown in Table 30. The only major part found in the two-stroke but
not in the four-stroke engine was the reed valve assembly in the intake system. We did not
include this in our analysis to off-set other minor parts (e.g. washers, screws etc) that were found
in the four-stroke engine but not in the two-stroke. For each of the parts in Table 30, we
estimated whether it would be more cost-effective to make or purchase. The small parts, such
as pivot screws and nuts, were assumed to be purchased, while the bigger and more specialized
parts such as the rocker cover, rocker arms, push rod, push rod guide, cam gear and so on would
most likely be made in-house. We weighed the manufacturer-produced parts and determined the
manufacturing processes required. This information is also presented in Table 30.
Table 30: Information on the additional parts for the Ryobi four-stroke engine as compared to
the two-stroke engine.
Item
Unit
Manufacturing Process
Part Material
Weight (lb)
Rocker Box Cover
1
stamping
low-carbon steel
5/64
Rocker Ann
2
stamping
low-carbon steel
1/64
Push Rod
2
precision grinding
low-carbon steel
1/64
Push Rod Guide
2
stamping
low-carbon steel
1/128
Rocker Box
1
die casting
A1 alloy
7/64
Oil Pan
1
die casting
A1 alloy
1/4
Cam Bracket
1
powder metal
low-carbon steel
3/64
Cam Follower
2
powder metal
low-carbon steel
1/64
Cam Gear
1
powder metal
low-carbon steel
1/8
Crank Gear
1
powder metal
low-carbon steel
1/64
Valve Cover Gasket
1
Lock Screw
2
Pivot Nut
2
Purchase from suppliers
Spring Retainer
2
Valve
2
Spring
2
Other Differences in Parts - Besides the additional parts, there are also differences in
manufacturing processes and requirements for similar components when comparing two-stroke
and four-stroke engines. Significant differences in terms of manufacturing processes and material
requirements were observed in the cylinder head and cylinder block. The cylinder head and
cylinder for small two-stroke engines are generally made as one unit, while four-stroke engines
have a separate cylinder head. The weight of the four-stroke cylinder/head assembly was found
to be about 5/16 lb more than that for the two-stroke engine. This information was used later
to estimate the added material cost for these components.
ICF Consulting Group & Engine, Fuel, and Emissions Engineering, Inc.
October, 1996
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Cost Study for Phase Two Small Engine Emission Regulations
63
7.2 Cost Analysis
The cost analysis includes an estimate of the variable and fixed costs. We developed incremental
cost estimates for a high-volume engine family in a large market share manufacturer and for a
high-volume engine family in a small market share manufacturer. The number of engines in a
high-volume engine family for large manufacturers (termed Case 1) was determined to be
400,000 units. This number is based on sales information from the PSR database for four of the
largest handheld engine manufacturers. The number of engines in a high-volume engine family
for small market share manufacturers (termed Case 2) was determined to be 90,000 units. This
number is also based on sales information from the PSR database for two typical small handheld
engine manufacturers. Further basis for both these numbers is provided in Appendix D.
Variable Manufacturing Costs (Materials. Components, and Labor)
Table 32 shows our estimate of the production costs for the parts that would produced in-house.
The data and assumptions on raw material costs and labor costs in this analysis are similar to
those that we used in the cost analysis for non-handheld equipment given in Part I. Table 31
shows our estimate of the total change in variable manufacturing costs pter engine due to the
change from two-stroke to four-stroke. In addition to the costs of manufacturing the parts in-
house, the total change in variable costs also includes the purchase cost of those additional parts
obtained from outside suppliers. Our estimates of the prices for each of these are shown in
Table 31. Purchase cost estimates were discussed with a knowledgeable industry source, who
confirmed their accuracy (Conley, 1996).
Table 31: Estimation of manufacturing costs for four-stroke engine parts made in-house.
Part
Vil«i Cow
Rodir
Aim
Mi Rod
Pu* Rod
Guide
Rocker
Arts Ban
OUPsa
Cam Bnektf
Cm FoMohw
CieGar
Craafc Cenr
Cjrttodar
Hod*
Cyttntfar
Procesa
Stamping
Sumpiat
precision
pnMttot
ftampiaf
die caiting
die-castiii|
Powder Metal
Powder Metal
fowder Metal
Powder
Metal
Die Castini
Material
Low Carton
Steel
Lav Cuban
Steel
Low Caftan
Sted
Low Caitoa
Sted
AJ Alloy
AJ Alloy
Low Carton
Steel
Low Caiton
Sted
Low Cartwa
Sted
Low Carbon
Sied
Al Alloy
Weight m
0.313
0016
0.016
0.0U
0.43ft
0.250
00*7
0.063
0.123
0.063
0.320
Wjt+IO%Scnp
0.344
0.017
0.017
Q.0»
aiSL
0175
o.osa
^069
0.138
0069
0.352
Maierial cos Vlb'
0.4O
0.40
0.40
0.40
LOO
1.00
0.40
0.40
040
0.40
1.00
Material Coal {Vpan}
a i3i
0.007
0.007
0.00)
0.481
0273
0.011
0.021
O.QS5
0021
0.332
Labor nai&utes
0J
D.J
1.5
0J
as
03
0L5
0J
as
as
3
Labor cost Via
IS
IS
IS
IS
IS
13
IS
15
IS
IS
25
DL Cofi Vpan
QUJ
an
0 63
0.13
0.13
0.L]
0.13
an
0.13
ais
1.25
Overhead »40»
aas
0.QJ
025
0.0}
0.09
0.05
0.QS
0.05
005
o.os
0.50
TotaJ cost/pan
an
an
an
an
an
0.11
an
an
Oil
an
1.75
Totti cm/part
U1
Mt
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ill
lift
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In addition to the increased costs of parts, we estimate that the more complex cylinder head and
the new valve train would require three extra minutes of assembly labor, costing $1.05 with over-
head. The total change in variable manufacturing costs, therefore, comes to $9.93.
ICF Consulting Croup &. Engine, Fuel, and Emissions Engineering, Inc.
October, 1996
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Cost Study for Phase Two Small Engine Emission Regulations
64
Since the variable costs are
expressed on a per-engine
basis, there would - be little
difference in these costs be-
tween the 400,000 and the
90,000 unit cases. Because of
learning-curve effects and
economies of mass production,
we would anticipate that the
actual variable costs for the
400,000 unit case would be a
little smaller, but these differ-
ences are difficult to quantify
without much more detailed
information.
Table 32: Estimation of incremental variable manufacturing
cost for four-stroke engine compared to two-stroke engine.
Cost/Piece Pieces/Engine Total
Rocker Box Cover
0.31
1
0.31
Rocker Arm
0.18
2
0.36
Push Rod
0.88
2
1.76
Push Rod Guide
0.18
2
0.36
Rocker Box
0.66
1
0.66
Oil Pan
0.45
1
0.45
Cam Bracket
0.20
t
0.20
Cam Follower
0.20
2
0.41
Cam Gear
0.23
1
0.23
Crank Gear
0.20
1
0.20
Valve Cover Gasket
0.25
1
0.25
Lock Screw
0.05
2
0.10
Pivot Nut
0.1
2
0.20
Spring Retainer
0.05
2
0.10
Valve
0.50
2
1.00
Spring
0.25
2
0.50
Cylinder Head & Cylinder
2.10
1
2.10
Total Parts Cost
8.88
Added Assembly Labor
Labor minutes
3
Labor Cost $/hr
15
Direct Labor $
0.75
Overhead @40%
0.3
Total Labor + OH
1.05
Total Added Variable Manufacturing Cost
9.93
Fixed Costs
Our estimates of fixed costs
are presented in Table 33.
Although Ryobi is selling four-
stroke engines for the handheld
equipment, and Honda has
announced that it will have one
four-stroke model for handheld
equipment in 1997, other en-
gine manufacturers will still
require quite extensive re-
search, design and develop-
ment work before they can
market their own four-stroke engines for handheld equipment This is especially true for those
handheld engine manufacturers that have been dealing with only two^troke engines for decades.
The development work required to convert a two-stroke engine to four-stroke operation was
estimated to require about three engineer-years of effort, costing about $300,000 with overheads.
The estimated cost was based on information from Ryobi's experience, and the assumption that
the next manufacturers will benefit (i.e., less engineering design) from Ryobi's effort. The costs
for the emission testing would also be fairly high, since it would require more testing to develop
a new engine than to improve an existing one. We estimated that the development would require
500 emission tests at $300 per test, for a total of $150,000. Additional engineering-related costs
of $100,000 were estimated to cover prototype development, test engines, travel, test materials
and similar costs. The total engineering cost was estimated at $550,000. These costs would not
be greatly different between the 400,000 and the 90,000 unit cases.
ICF Consulting Group Jc Engine, Fuel, and Emissions Engineering, Inc.
October, 1996
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Cost Study for Phase Two Small Engine Emission Regulations
65
Table 33: Estimated fixed costs for converting
two-stroke to four-stroke engines for handheld
equipment.
Changing an engine line would also require
extensive expenditure for technical support,
training and publications. We assumed it
would cost about $500,000 for the high-vol-
ume model and $200,000 for the low-volume
model. This is consistent with information
from Honda (1996) on the costs of technical
support for a major engine modification.
Tooling costs would include the costs of new
master dies for die-casting the cylinder head,
cylinder block, oil pan, connecting rod, piston,
and crankshaft; and new stamping dies for the
rocker cover, rocker arm, and push rod guide.
New molds would also be needed foe powder
metal forming of the cam bracket, cam fol-
lower, cam gear and crank gear. Cost esti-
mates for these dies were based on our con-
versations with industry sources, as referenced
earlier in Part I. Total tooling costs would
amount to about $300,000 for the 400,000
unit case and $250,000 for the 90,000 unit
case. This includes setup costs estimated at
$100,000 and $50,000, respectively. The
setup cost includes the changes in the assem-
bly process, material handling, jigs, fixtures,
machine settings, etc. needed to integrate the
new machines into the assembly flow (similar
to SV to OHV conversion).
Total engine specific costs were estimated at
$1,350,000 for the high-volume model, and
$1,000,000 for the low-volume model. These
costs were amortized over five yeah at a cost
of capital of 9%. The total amortized fixed
costs amount to about $347,000 per year for
the 400,000 unit case and $257,000 per year
for the 25,000 unit case. The costs of new
machine tools (stamping presses, powder-
metal forming machines, and die-casting
machines) were estimated at $2,225 million
for the 400,000 unit case, and $730,000 for
the 90,000 unit case. Amortizing these costs
over a ten-year period at a 9% capital rate, the new machine costs per year were $347,000 for
the high-volume case and $111,000 for the low-volume case. Summing all the fixed costs and
Case 1 Case 2
Engineering Costs
Engineering labor + OH
(3 years @ $100,000)
300,000
300,000
Number of Tests
500
500
Test Cost ($)
300
300
Testing costs
150,000
150,000
Other engineering
100,000
100,000
Total Engineering
550,000
550,000
Technical support
Training/Tech. Pubs 500,000 200,000
Tooling Costs
New Master Dies
Cylinder head
30,000
30,000
Cylinder block
30,000
30,000
Connecting rod
10,000
10,000
Piston
10,000
10,000
Crankshaft
15,000
15,000
Rocker Cover
10,000
10,000
Rocker Arm
10,000
10,000
Push Rod Guide
10,000
10,000
Oil Pan
15,000
15,000
Cam Bracket
15,000
15,000
Cam Follower
15,000
15,000
Cam Gear
15,000
15,000
Crank Gear
15,000
15,000
Setup changes
100,000
50,000
Total tooling
300,000
250,000
Total Engine-Specific
1,350,000
1,000,000
Amortized over S yrs
347,075
257,092
New Machine Tools
2,225,000
730,000
Amortized over 10 yrs
346,700
111,258
Total Fixed Cost/Yr
693,775
368,350
Annual Production
400,000
90,000
Fixed cost/engine
1.73
4.09
ICF Consulting Group <£ Engine, Fuel, and Emissions Engineering, Inc.
October, 1996
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Cost Study for Phase Two Small Engine Emission Regulations
66
dividing by the number of units produced results in fixed costs of $1.73 per engine for the
400,000 unit case, and $4.09 per engine for the 90,000 unit case.
Table 34 is a summary of total hard-
ware/assembly costs and fixed costs for con-
verting two-stroke to four-stroke engines for
handheld equipment.
Actions bv Small Manufacturers to Reduce
Costs to Convert from Two- to Four-Stroke
Engines
Table 34: Summary of the total added man-
ufacturing and fixed costs for converting 2-
stroke to 4-stroke handheld engines.
Case 1
Case 2
Total Added Manufactur-
ing Cost
9.93
9.93
Fixed Costs
1.73
4.09
There may be only a few manufacturers in the
handheld engine market that can be ch^ acterized as small manufacturers. Most small engine
manufactures with small market share (T cumseh, Kioritz) are medium to large companies with
the ability to afford extensive capital investment. We expect that any actual small engine
manufacturer is less likely to make this two- to four-stroke conversion than a large manufacturer
because of the costs for designing and manufacturing a new technology engine and because of
the additional costs of redesigning the equipment to handle the different size and weight of the
four-stroke engine. Even if we assume that the small manufacturer will make the conversion
from two- to four-stroke, the manufacturer may not go about it the same way as it had in the past
in producing the two-stroke family line. We anticipate that the small engine manufacturer may
make certain decisions to reduce the costs of this conversion. For example, the small engine
manufacturer may not be able to afford the capital investment necessary to purchase new machine
tools to make their own cylinder head and block (which is necessary for a new 4-stroke design).
Also, the small manufacturer may not have the engineering labor to pursue the extensive design
effort to develop this new and complex engine. Consequently, the small manufacturer may
purchase the four-stroke engines from a larger handheld engine manufacturer. On balance
between savings both capital and engineering labor and the need to purchase the engines, the
small manufacturers may realize a modest savings over manufacturing the engines themselves.
Also, the small manufacturer may not have to incur costs for developing new train-
ing/technical/catalogue publications if they purchase and adapt the publications from the
manufacture that sold them the engines. This could perhaps result in additional savings over the
estimated costs for a small manufacturer to develop training/technical/catalogue publications. We
assume that some of the above cost savings decisions would be implemented by a small
manufacturer.
ICF Consulting Group & Engine, Fuel, and Emissions Engineering, Inc.
October, 1996
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Cost Study for Phase Two Small Engine Emission Regulations
67
8. COST ANALYSIS FOR IMPROVING
TWO-STROKE ENGINES
This chapter presents our incremental cost estimates for improvements in the scavenging of two-
stroke engines by optimizing the designs of the piston, ports, and combustion chamber; and for
the application of stratified scavenging using a throttle valve. Again, we assumed that a large
handheld manufacturer (case 1) had a high-volume engine line of 400,000 units and a small
handheld manufacturer (case 2) had a high-volume line of 90,000 units (see Appendix D for
basis).
8.1 Two-Stroke Engines with Improved Scavenging
Substantial HC emission reductions can be realized by optimizing the piston and port designs to
reduce scavenging losses. The use of better piston and port designs, such as the GPB's deflector
piston/port designs (Blair, 1996); and/or the use of an optimized combustion chamber, such as
the GUT "Jockey-cap" combustion chamber (Laimbock and Landerl, 1990) can also allow the
use of a leaner mixture without jeopardizing.the engine performance. A leaner mixture and better
combustion characteristics result in lower HC and CO emissions. Thus, a two-stroke engine with
optimized piston, port, and combustion chamber designs, along with a better quality carburetor,
could be a potential option to meet the Phase 2 emission standards or even more stringent
standards. It would also provide a less harsh environment for an oxidation catalyst to perform
its job by reducing engine out HC and CO emissions. Therefore, we have developed a cost
analysis based on these improvements.
Optimization of piston, port, and combustion chamber designs wouldyiot require additional parts
or machining processes, but only refinements in the design of existing parts. The effect on
variable manufacturing costs, therefore, will be very small, and could be either positive or
negative. For purposes of this analysis, we assume that the design changes would not affect
variable costs, but only the fixed costs of production.
Fixed Costs
Our estimates of the fixed costs of optimizing piston, port, and combustion chamber designs are
shown in Table 35. The design of an improved two-stroke handheld engine is somewhat more
complex than the design for an improved side-valve non-handheld engine because of the tighter
tolerances needed on a smaller engine. Also, the designer has less flexibility in what can be done
ICF Consulting Group & Engine, Fuel, and Emissions Engineering, Inc.
October, 1996
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Cost Study for Phase Two Small Engine Emission Regulations
68
with a two-stroke design, and may, therefore, Table 35: Estimated fixed costs for two-stroke
need additional effort. We estimate that the
development of an" optimal design would
require about two engineer-years, at a cost of
about $200,000 for labor and overheads.
Emission testing costs were estimated at
$90,000. Other engineering-related costs such
as prototype engines, travel, test materials and
so forth are estimated at $50,000. The total
engineering cost is estimated at $340,000.
These costs would be nearly the same for
either the 400,000 or the 90,000 unit cases.
Updating the parts lists and similar informa-
tion to incorporate the redesigned parts is
estimated to cost $20,000. New master dies
would be required for the cylinder/cylinder
head, piston, and carburetor. Costs of these
dies were estimated based on our conversa-
tions with industry sources and die makers
(Spec Cast, 1996). Set-up costs of $50,000
for the high-volume case and $25,000 for the
low-volume case were also estimated. Total
engine specific costs would be $525,000 for
the high-volume model, and $500,000 for the
low-volume model. These costs were amor-
tized over five years at a cost of capital of
9%. The total amortized fixed costs amount
to about $135,000 per year for the 400,000
unit case and $129,000 per year for the 90,0-
00 unit case. Dividing these estimates by the
number of units produced results in fixed costs of $0.34 and $1.43, respectively.
engines with improved scavenging.
Case 1 Case 2
Engineering Costs
Engineering labor + OH
(2 year @ $100,000)
200,000
200,000
Number of Tests
300
300
Test Cost ($)
300
300
Testing costs
90,000
90,000
Other engineering
50,000
50,000
Total Engineering
340,000
340,000
Technical support
Training/Tech. Pubs 20,000 20,000
Tooling Costs
New Master Dies
Cylinder/Cylinder Head
40,000
40,000
Piston
15,000
15,000
Carburetor
60,000
60,000
Total Tooling
115,000
115,000
Machine Tool Setup
50,000
25,000
Total Engine-Specific
525,000
500,000
Amortized over 5 yrs
134,974
128,546
New Machine Tool
0
0
Amortized over 10 yrs
0
0
Total Fixed Cost/Yr
134,974
128,546
Annual Production
400,000
90,000
Fixed cost/engine
0.34
1.43
8.2 Two«Stroke Engines with Stratified Scavenging
A well designed stratified scavenging system in a two-stroke engine with optimized piston, port,
and combustion chamber designs can be expected to reduce full-power HC emissions by 30%
to 50%. In this section, we estimate the incremental costs for a stratified scavenging system.
Variable Manufacturing Costs
The stratified scavenging approach would involve changes in the air system to prefill the transfer
ports with air instead of air-fiiel mixture. This would require adding new hardware to the engine,
and would thus increase variable costs. Our estimate of these variable costs is shown in
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Table 36: Manufacturing costs for additional
parts for two-stroke engine with stratified scav-
enging.
Table 36. As shown in the table, we estimat-
ed that the throttle valve would cost about
$0.50 from an external supplier, and we
assumed another $0.50 for extra fittings. We
also estimated that it would require one min-
ute of added labor time (costing $0.58 with
overhead) for handling and assembling the
added parts. These costs would be roughly
the same for both high and low volume cases.
Fixed Costs
Our estimates of fixed costs are tabulated in
Table 37. The fixed costs for the develop-
ment of two-stroke engines with optimized
piston, port and combustion chamber designs,
improved carburetor, and a stratified scaveng-
ing system would be about the same as those
for the optimized two-stroke engines without stratified scavenging. For this case, however, we
estimated that 400 emission tests would be required instead of 300, since more tests would be
needed to develop the stratified scavenging system. The costs for technical support, training, and
publications were estimated to be higher as well - $100,000 for the high-volume model and
$50,000 for the low-volume model. This is intermediate between the costs of a technical bulletin
and those of a complete revision to engine documentation.
Cost/
Piece
Pieces
/Engine
Total
Throttle Valve
0.50
1
0.50
Other Fittings
0.50
Total Parts Cost
1.00
Added Assembly Labor
Labor minutes
1
Labor Cost S/hr
25
Direct Labor $
0.42
Overhead @40%
0.17
Total Labor + OH
0.58
Total Added Mfg. Cost
1.58
Total engine specific costs were estimated at $635,000 for the high-volume model, and $560,000
for the low-volume model. These costs were amortized over five years at a cost of capital of
9%. The total amortized fixed costs amount to about $163,000 per year for the 400,000 unit
case, and $144,000 per year for the 90,000 unit case. Dividing these estimates by the number
of units produced results in fixed costs of $0.41 per engine for the high volume case, and $1.60
per engine for the low volume case.
Table 38 is a summary of hardware/assembly costs and fixed costs ^for two-stroke engines with
stratified scavenging.
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Table 37: Estimated fixed costs for two-stroke
engines with stratified scavenging.
Case 1
Case 2
Engineering Costs
Engineering labor + OH
(2 year @ $100,000)
200,000
200,000
Number of Tests
400
400
| Test Cost (S)
300
300
Testing costs
120,000
120,000
Other engineering
50,000
50,000
Total Engineering
370,000
370,000
Technical support
Training/Tech. Pubs
100,000
50,000 •
Tooling Costs
New Master Dies
Cylinder/Cylinder Head
40,000
40,000
Piston.
15,000
15,000
Carburetor
60,000
60,000
Total Tooling
115,000
115,000
Machine Tool Setup
50,000
25.000
Total Engine-Specific
635,000
560,000
Amortized over 5 yrs
163,254
143,972
New Machine Tool
0
0
Amortized over 10 yts
0
0
Total Fixed Cost/Yr
163,254
143,972
Annual Production
400,000
90,000
Fixed cost/engine
0.41
1.60
Table 38: Summary of the variable and
Fixed costs for 2-stroke with stratified scav-
enging.
Case 2
Case 3
Total Added Manufactur-
ing Cost
1.58
1.58
Fixed Costs
0.41
2.60
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9. COST ANALYSIS FOR TWO-STROKE ENGINES
WITH CATALYST
A catalytic converter can be added to a two-stroke engine to reduce emissions. However, the use
of catalyst technology alone may not be sufficient to meet both emission limits and the U.S.
Forest Service limits on exhaust temperature. If a catalytic converter with a high efficiency were
used, the exothermic energy released by the oxidation of HC and CO would be very high. The
resulting catalyst temperature would exceed the thermal limits of the catalytic converter (roughly
1.000 °C), as well as exceeding the USFS limits on exhaust and skin temperatures. If a catalytic
converter with a low efficiency were used, the emission reductions might not be sufficient to
meet the standards in the Statement of Principles for EPA Phase 2 regulations of handheld
engines. Thus, the key requirement in each of these approaches is to reduce the engine-out HC
and CO emission levels to the point that a catalytic converter can survive in the exhaust without
overheating, and if possible to achieve an overall lean or stoichiometric air-fuel ratio in the
exhaust to maximize catalytic converter efficiency. It is then possible to rely on the catalytic
converter to bring the remaining HC and CO to levels well below the applicable standards.
A wide variety of emission control measures and design features could be used to achieve the
further reduction in engine-out HC and CO emissions needed to allow the catalytic converter to
survive in the exhaust. Some of these measures have already been discussed in previous
chapters. Since it is not always clear what technology a manufacturer would use in conjunction
with the catalyst technology, we assessed the costs only for the application of the catalyst
technology. These costs can then be combined with the cost estimates for improved two-stroke
engines with or without a stratified scavenging system, or with those for converting to a four-
stroke engine. As in the previous chapters, a manufacturer with a large market share (case 1)
was assumed to produce 400,000 engine per year, and a manufacturer with a small market share
(case 2) to produce 90,000 engines (see Appendix D for basis).
9.1 Two«Stroke Engines with Catalyst
Variable Manufacturing Costs - The use of catalyst in a two-stroke engine would require some
hardware or variable costs, such as the costs for the catalyst and heat shield. These variable costs
are tabulated in Table 39. As shown in the table, we estimated that the ceramic catalyst would
cost about $4.00 (Allied Signal and United Emission Catalyst, 1996). If a metallic catalyst is
used, we estimated that the cost would be doubled (i.e. $8.00). The costs of the heat shield and
the heat-resistant muffler are accounted for in the equipment cost analysis given in Chapter 10,
and are not duplicated here to avoid double-counting.
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Table 39: Manufacturing costs for additional
parts for two-stroke engine with catalyst.
Ceramic
Metallic
Catalyst
4.00
8.00
Added Assembly Labor
Labor minutes
1
1
Labor Cost $/hr
25
25
Direct Labor $
0.42
0.42
Overhead @40%
0.17
0.17
Total Labor + OH
0.58
0.58
Total Added Mfg.
Cost
4.58
8.58
Table 40: Estimated fixed costs for two-stroke
engines with catalyst.
We estimated that the catalytic converter
production would require one minute of added
labor time (costing $0.58 with overhead) for
handling and the relatively straightforward
assembly of added pans (Ostwald, 1994,
Winchell, 1989) performed by skilled labor.
These costs would be applicable to both high
and low volume models.
Fixed Costs - Our estimates of the fixed costs
involved in applying a catalytic converter to
a two-stroke engine model are shown in
Table 40. We estimate that the development
effort would require about two engineer-years
of work, costing $200,000 with overhead.
The relatively large amount of effort required
is due to the lack of existing experience with
catalytic converters. The number of emission
tests would be more than that needed for a
minor redesign, but perhaps less than for a
major redesign (two to four stroke). We as-
sumed a total of 400 emission tests at a cost
of $120,000 for baseline, prototype and other
emission testing. Other engineering-related
costs were estimated at 50,000. The costs for
technical support, training, and publications
were estimated at $100,000 for the high-
volume model and $50,000 for the low-vol-
ume model, reflecting the need for safety and
technical training of service personnel, as well
as changes in parts lists and similar docu-
ments.
The addition of a catalytic converter to a two-
stroke engine would not in itself require any
tooling costs. The changes in the design of
the muffler, heat shield, and other components
of the engine-powered equipment would
involve tooling costs, but these are addressed
separately in Chapter 10. Thus, the total en-
gine-specific costs would be about $470,000 for the high-volume model, and $420,000 for the
low-volume model. These costs were amortized over five years at a cost of capital of 9%,
resulting in annual fixed costs of $121,000 and $108,000, respectively. Dividing these estimates
by the number of units produced results in fixed costs of $0.30 per engine for the 400,000 unit
model, and $1.20 per engine for the 90,000 unit model.
| Case 1 Case 2
Engineering Costs
Engineering labor + OH
(2 year @ $100,000)
200,000
200,000
Number of Tests
400
400
Test Cost ($)
300
300
Testing costs
120,000
120,000
Other engineering
50,000
50,000
Total Engineering
370,000
370,000
Technical support
Training/Tech. Pubs 100,000 50,000
Tooling Costs
Total Engine-Specific
470,000
420,000
Amortized over 5 yrs ^
120,833
107,979
New Machine Tool
0
0
Amortized over 10 yrs
0
0
Total Fixed Cost/Yr
120,833
107,979
Annual Production
400,000
90,000
Fixed cost/engine
0.30
1.20
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Table 41 is a summary of total hardware/assembly Table 41: Summary of total hard-
and fixed costs for two-stroke engines with a catalytic ware/assembly costs and fixed costs for
converter. two-stroke engines and catalyst.
9.2 Improved Engine Designs with Catalyst
As discussed previously, a catalytic converter could
be combined with any of the other advanced two-
stroke options considered in this report to achieve
even lower emissions. Table 42 summarizes the total hardware/assembly costs and fixed costs
for the combination of the catalytic converter with optimized scavenging, stratified scavenging
system, and the two-stroke to four-stroke conversion .
Table 42: Summary of total hard-
ware/assembly costs and fixed costs for
improved two-stroke engines with cata-
lyst, two-stroke engines with stratified
scavenging and catalyst, and 2-stroke to
4-stroke conversion with catlyst.
Case 1
Case 2
Improved 2-Stroke Engine with Catalyst
Hardware/Assembly
Costs
$4.58'
$8.582
$4.58'
S8.582
Fixed
0.64
2.63
2-Stroke Engines with Stratified Scavenging
and Catalyst
Hardware/ Assembly
Costs
$6.16'
S10.162
$6.16'
S10.162
Fixed
0.71
2.80
2-Stroke to 4-Stroke Engine Conversion with
Catalyst
Hardware/Assembly
Costs
$14.51'
S18.512
$14.51'
$18.512
Fixed
2.03
5.29
1 with ceramic substrate catalytic convener
2 with metallic substrate catalytic converter
Case 1
Case 2 |
Hardware/Assembly
Costs
$4.58'
$8.582
$4.58'1
S8.5821
Fixed
0.30
1.201
1 ceramic substrate
metallic substrate
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PART HI
EQUIPMENT COSTS, USER COSTS AND CONSTRAINTS
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10. COST ESTIMATE TO ADAPT EQUIPMENT TO MODIFIED
ENGINE TECHNOLOGIES
The types of engine modification technologies evaluated in Parts I and II may have impacts on
the design of equipment. Some equipment may be sensitive to engine orientation, weight, size,
location of exhaust/air filter/oil disposal, higher engine exhaust heat, and other factors. In this
chapter, the types of changes in equipment design/production and the associated costs are
examined.
For the six technologies examined in this study, Table 43 presents some features (e.g., size,
weight) of the modified engines that might result in downline equipment changes.
Table 43: Features of the Modified Engines that Might Result in Equipment Changes.
Engine Modification
Features of the Modified Engines thai Might Result in
Equipment Changes
Convert SV to OHV
(NHH)
OHV taller, weighs more, but in terms of width, two single
cylinder SV in opposed configuration is roughly equal to
V-Twin OHV
Improved SV (NHH)
None expected
Improved OHV
(NHH)
None expected
Convert Two to
Four-Stroke (HH)
Currently four-stroke weighs perhaps 2-3 pounds more, but still
under 8 pounds total; more bulky
Improved Two-Stroke
(HH)
None expected
Added Catalyst to
Two-Stroke (HH)
More bulky and new heat source from catalyst
Based on this table, it is not expected that any costs will be incurred by the equipment
manufacturer by installing improved two-stroke, improved SV, or improved OHV. Thus, the
remaining focus is on the three remaining engine modification technologies.
Any changes in equipment as a result of an engine change or modification depend on the
equipment application. Consequently, the major applications in each engine class were identified
using the Power Systems Research ENGINDATA database and to a lesser extent, on the CARB
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certificat; iatabase. Table 44 lists the applications that made up a large segment of the engines
sold or thw. nad a large number of engine families/models. Additionally, the listing includes
minor applications that may require different equipment iesign changes than those of the major
application equipment. Based on this listing, we focusea on manufacturers of lawn and garden
equipment, generators, and pumps. Some other equipment (e.g., golf cart) which are similar to
certain lawn and garden equipment may require similar changes. The following cost analyses
first addresses non-handheld equipment and then handheld equipment.
Table 44: Major applications of small engines, by engine class.
(of total)
(of total)
(of total)
(of
(of
mower/comm turf
81.5%
tractor
53.0%
trimmer/cufr
NA
trimmer/cufr
80.0%
chain saw
53.2%
tiller/snowblower
8.1%
mower/comm turf
12.2%
chain saw
11.5%
mower
29.0%
generator
2.7%
generator
10.8%
blower/vacuum
4.8%
snowblo-
17.7%
compressor/wash
1.1%
snowblower
5.7%
pump
1.2%
pump
1.1%
golf cart
3.5%
leaf blower
0.5%
tiller
2.5%
shredder
0.5%
outboard engine
2.1%
sprayer
0.1%
compressor/washer
1.8%
wood splitter
0.1%
pump
1.6%
mixer
0.1%
welder
1.5%
plate compactor
0.1%
shredder/chipper
0.8%
other
4.0%
4.5%
2.5%
0.0%
Total
100.0%
100.0%
NA
100.0%
100.0%
Source: PSR database (sales data for 1993)
Note: sales for classes I & II do not include exported engines, or engines sold directly by engine distributors
10.1 Non-Handheld Equipment
We contacted over ten equipment manufacturers, representing a variety on non-handheld
applications, however, only a few responded or could provide the desired equipment modification
or cost information.
Walk Behind Lawnmowers
Currently, most walk behind lawnmowers use SV technology. Conversion from side-valve to
OHV is viewed as incurring little if no additional costs because there is extensive room over the
blade area to mount the slightly larger OHV and also the engines also are not enclosed in a
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covering. The mounting pads would not need to be changed. SV and OHV are sometimes
interchanged with very minor changes within model lines. (MTD conversation, September 1996).
Rear Engine Rider
In rear engine riders, the engine is usually exposed (i.e., not covered by hood). Because the
OHV is taller than the SV, the OHV engine will need to be reoriented 90 degrees from the
traditional side-valve so that the cylinder is parallel to the center line of the equipment. This
affects several equipment features including the mounting holes, the controls, the exhaust, and
the oil drains (John Deere conversation, September 1996). The cost impact of these and other
factors are summarized in Table 45.
Table 45: Cost of Equipment Changes for Rear Engine Rider as a Result of SV to OHV
Conversion.
Change
Action
Cost
Change in Mounting Holes
Change blanking die to add
4 holes
$40,000-$ 100,000 for die
and tooling per equipment
line
Control Wires Longer Be-
cause of Reorientation
Need additional material
Minor
Modified Exhaust/Air Filter
Positioning
New tooling by exhaust
supplier and new materials
$10,000 to $100,000 de-
pending on extent of tool-
ing; material costs direcdy
passed to consumer
Study of Vibration
R&D
probably one time cost for
all engine families
Relocate Oil Drains
Punch blanking hole in die
or install drain tube on
engine
$10,000 per equipment line
for die or $2 to OEM per
piece of equipment
Source: Conversations with John Deere and American Yard Products
Lawn Tractor
Lawn tractors (approximately 9-16 hp) usually have a hood covering over the engine. Because
of the greater length of the OHV, the hood will need to be lengthened. This can be an expensive
change. Usually, it-requires, a new injection molding die to create a redesigned plastic hood.
Costs for a hood modification range from $300,000 to 1.5 million dollars per equipment line
(John Deere conversation September 1996 and American Yard Products conversation September
1996). Typical equipment dies last 3-10 years and produce upwards of 250,000 units. Other
costs are similar to the rear engine rider though additional baffling will be needed. The costs are
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delineated in Table 46. Although not usually included in lawn tractors, a fuel shutoff solenoid
valve may be required to prevent any bleeding of gas into the muffler and any resulting explosion
or flaming in the ntttffler after the equipment is turned off. This may occur more in OHV
engines because OHV engines tend to run leaner and hotter. However, the cost for the solenoid
is not included below in the cost for lawn tractors.
Table 46: Cost of Equipment Changes for Lawn Tractor as a Result of SV to OHV Conversion.
Change
Action
Cost
Hood Lengthen
New master die and tooling
$300,000 - $1,500,000 per
equipment line
Change in Mounting Holes and
Brackets
Change blanking die to add 4
holes
$40,000-$ 100,000 for die and
tooling per equipment line
Control Wires Longer Because of
Reorientation
Need additional material
Minor
Modified Exhaust/Air Filter Posi-
tioning
New tooling by exhaust supplier
and new materials
$10,000 to $100,000 depending
on extent of tooling; material
costs directly passed to consumer
Study of Vibration
R&D
probably one time cost for all
engine families
Relocate Oil Drains
Punch blanking hole in die or
install drain tube on engine
$10,000 per equipment line for
die or $2 to OEM per piece of
equipment
Additional Baffling
Tooling
$20,000-$30,000
Source: Conversations with John Deere and American Yard Products
Lawn and Garden Tractors
For lawn and garden tractors, (typically 18-25 hp), the OHV willVnot have to be reoriented
because the cylinder head is always facing forward. Therefore, mounting holes would not be an
issue. Additionally, there is typically room under the hood to handle a V-twin OHV engine.
However, additional baffling will be needed. Also, the fuel shutoff solenoid is added to prevent
explosion in muffler and flame from muffler. The costs are delineated in Table 47.
S nowblower/Tiller
The costs for adapting a snowblower/tiller to use an OHV in place of a SV was estimated to be
approximately one-third the cost of adapting the lawn tractor (American Yard Products
conversation, September 1996).
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Table 47: Cost of Equipment Changes for Lawn and Garden Tractor as a Result of SV to OHV
Conversion.
Change
Action
Cost
Modified Exhaust Positioning
New tooling by exhaust supplier
and new materials
$10,000 to $100,000 depending
on extent of tooling; material
costs directly passed to consumer
Study of Vibration
R&D
probably one time cost for all
engine families
Relocate Oil Drains
Punch blanking hole in die or
install drain tube on engine
$10,000 per equipment line for
die or $2 to OEM per piece of
equipment
Redesign Baffle
Tooling
$20,000-530,000
Fuel Shutoff Solenoid
Add/integrate equipment
$8-15 to OEM
Source: Conversations with John Deere and American Yard Product
Generator Sets
Generator sets are usually encased in a frame that holds the engine and other parts of the
generator set. For some generator set lines, the taller OHV may require that the frame or cage
around the generator set be redesigned, developed, tooled, and fabricated. Often, the fuel tank
will also need to be redesigned and the muffler relocated. Table 48 lists the costs of these
changes per equipment line. At least six months would be needed to implement this change
(John Deere conversation, September 1996).
Table 48: Cost of Equipment Changes for Generator Sets as a Result of SV to OHV Conversion.
Change
Action
Cost |
Expand Frame, Redesign Fuel
Tank, and Relocate Muffler
Redesign, develop, tool, fabricate
$100,000 per equipment line
Source: Conversation with John Deere
Pumps
Like the generator sets, some pumps that are encased in a frame or cage may need to be
redesigned, developed, tooled, and fabricated. Often, the fuel tank will also need to be
redesigned and the muffler relocated. Table 49 lists the costs of these changes per equipment
line. At least six months would be needed to implement this change (John Deere conversation,
September 1996).
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Table 49: Cost of Equipment Changes for Pumps as a Result of SV to OHV Conversion.
Change
Action
Cost
Expand Frame, Redesign Fuel
Tank, and Relocate Muffler
Redesign, develop, tool, fabricate
$50,000 per equipment line
Source: Conversations with John Deere
10.2, Modifications to Handheld Equipment due to Engine Changes
With few exceptions, manufacturers of handheld equipment produce their own engines. Thus,
engine modifications and equipment modifications are likely to be closely coordinated. Engine
modifications that are likely to require a change in equipment design include the conversion from
two-stroke to four-stroke engines, and the addition of a catalytic converter to two-stroke engines.
In our judgement, internal improvements to the two-stroke engine are not likely to require
changes in the equipment design.
Two-stroke to four-stroke conversion - Four-stroke engines are currendy larger and heavier
than two-stroke engines. On nearly all string trimmers and hand-held blowers, the engine is
enclosed in a set of injection-molded plastic components, which together make up the external
body of the equipment. Chainsaws would also be included in this group, however, the chainsaw
will not be specifically mentioned because of questions about the feasibility of using a four-stroke
engine on applications that require multipositional capability. The significant change in engine
size and shape due to changing to four-stroke operation will require changes in the design of the
trimmer and blower. This will require new injection molds, at a minimum, and may require
additional material as well. This additional weight is a concern given the equipment is weight
sensitive and the four-stroke already weighs more than the two-stroke. On the other hand,
backpack blowers, portable pumps, and similar equipment generally do not enclose the engine
in plastic. For most of these units, the only equipment change needed would be a minor change
in the design of the stamped metal retaining strap attached to the engine.
We compared the external plastic components used in the Ryobi two-stroke string trimmer with
those used in the Ryobi four-stroke trimmer. The results of this comparison are shown in
Table 50. Analysis of the changes is complicated by the fact that some changes were obviously
made for purposes of styling and/or user comfort, and were not directly attributable to the change
from two-stroke to four-stroke design. The design changes also succeeded in eliminating one
component (the stamped steel muffler shield) by increasing the size of the engine cover, and
reducing the number of injection-molded components in the starter housing and shaft support
from three to two. The total weight of injection molded components increased by 9.5 ounces.
In our view, neither the elimination of the two parts nor the increase in weight of the injection-
molded parts between the Ryobi four-stroke trimmer and the earlier two-stroke trimmer are
attributable to the change from two-stroke to four-stroke operation. Instead, these were
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attributable to design and
styling improvements that
are normally incorporated
with any new model.
The change from two-
stroke to four-stroke opera-
tion will also require some
changes in the design of
the muffler, as the location
of the exhaust discharge
from the engine is different
between the two designs.
A typical muffler consists
of three stamped sheet
metal pieces joined togeth-
er. While it might be
possible to accommodate
the change in location with
a change in only one of
these pieces, we anticipate
that a change in all three
pieces would be required in most cases. This would require changes in the three stamping dies
used to make these pieces. In the case of the Ryobi engines, the change from two-stroke to four-
stroke also made possible the incorporation of an integral spark arrestor into the muffler, thus
adding two more components: a stamped steel plate and a section of metal screen. These were
not counted as an incremental cost due to the change, since they represent a product enhancement
rather than a change made necessary by the change from two-stroke to four-stroke.
Based on our comparison of the two Ryobi models, no incremental variable costs are assignable
to the equipment changes required to accommodate the four-stroke engine. However, the changes
in the design of the muffler stamping would require new stamping dies, and the changes in the
design of the air cleaner cover, fan housing cover, and engine cover fa)uld require new injection
molds. These would not be required for pumps and backpack blowers. The engine cover for
pumps and backpack blowers is stamped metal strap, which would require a new stamping die.
No new machine tools would be required, since only the shape of the components is changed,
and not the number or basic manufacturing processes. We estimate that about six months of
engineering time would be required to make the needed design changes and confirm the
performance of the modified designs (three months for the pumps and backpack blowers).
Although the needed changes are straightforward, they would involve a significant amount of
detail. Miscellaneous engineering-related costs would include performance and safety testing and
similar costs. These are estimated at $20,000 for chainsaws, trimmers, and handheld blowers,
and $10,000 for backpack blowers and pumps. The estimated costs for the technical publications
and training are consistent with an independent cost estimate for a minor engine/equipment
modification (Honda, 1996). Detailed cost estimates are shown in Table 51.
Table 50: Comparison of equipment parts for a 2-stroke and a
four-stroke engine.
Part
Weight (oz)
Material
Manufacturing
Process
2-Stroke
4-Stroke
Air-Cleaner Cover
2
3
Plastic
Injection Molding
Shroud Extension and Stand
2.5
n/a
Plastic
Injection Molding
Starter/Fan Housing Assembly
9.5
8.5
Plastic
Injection Molding
Throttle/Handle Housing
(left/top)
1.5
6
Plastic
Injection Molding
Throttle/Handle Housing
(right/bottom)
1.5
6
Plastic
Injection Molding
Clutch Cover
2
n/a
Plastic
Injection Molding
Muffler Cover
5
n/a
L.C. Steel
Stamping
Engine Cover
n/a
5
Plastic
Injection Molding
Muffler
8.5
8.5
L.C. Steel
Stamping
Total Parts Number
8
6
Total Weight: Plastic
19
28.5
Total Weight: L.C. Steel
13.5
8.5
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Table 51: Estimated equipment fixed costs for converting 2-stroke engines to 4-stroke engines.
Fixed Costs
Chainsaws, Trim-
Backpack Blowers
mers etc.
and Pumps
Case 1
Case 2
Case 1
Case 2
Engineering Costs
Engineering labor (person year)
0.5
0.5
0.25
0.25
Engineering labor + OH
50,000
50,000
25,000
25,000
Number of Tests
0
0
0
0
Test Cost ($)
250
250
250
250
Testing costs
0
0
0
0
Other engineering
20.000
20,000
10,000
10,000
Total Engineering
70,000
70,000
35,000
35,000
Technical support
TrainingTech. Pubs
20,000
20,000
10,000
10,000
Tooling Costs
New Injection Molds
Air Cleaner Cover
5,000
5.000
0
0
Fan Housing Cover
20,000
20,000
0
0
Engine Cover
10,000
10,000
0
0
New Stamping Dies
Muffler, Top
5,000
5,000
5,000
5,000
Muffler, Bottom
5,000
5,000
5,000
5,000
Muffler, Baffle
5,000
5,000
5,000
5,000
Engine Retainer Strap
5,000
5,000
Setup changes
20,000
20,000
10,000
10,000
Total tooling
70,000
70,000
30,000
30,000
Total Engine-Specific
160,000
160.000
75,000
75,000
Amortized over 5 yrs
41,135
40,603
19,282
19,032
New Machine Tools
0
0
0
0
Amortized over 10 yrs
0
0
0
O1
Total Fixed Cost/Yr
41,135
40,603
19,282
19,032
Annual Production
400,000
90,000
400,000
90,000 1
Fixed cost/engine
0.10
0.45
0.05
0.21 j
The costs of sheet metal stamping dies can range from $5,000 for a simple die to substantially
higher (Conley, 1996). Since the muffler components are all relatively simple stamping, we
estimated a die cost of $5,000 each. Injection molds can also range from $5,000 for a simple
one up to much higher costs. The mold for the air cleaner cover would be simple* while that for
the fan housing is more complex, and that for the engine cover is of intermediate complexity.
These costs were estimated at $5,000, $20,000, and $10,000, respectively. Adjustments to other
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tooling and new jigs to accommodate the changed size and shape of the parts are estimated to
cost an additional $20,000 ($10,000 for the backpack blowers and pumps).
Catalytic converters in two-stroke engines - The addition of a catalytic converter to a two-
stroke engine would also require changes in the design of various equipment (including trimmer,
chainsaw, blower). The catalytic converter would be incorporated into the muffler, necessitating
changes in the design of all three of the muffler stamping. Since the exhaust temperature will
also increase greatly, it will be necessary to change the muffler material from the present low-
carbon steel to a more expensive alloy steel such as 405 (chromium alloy) or 304 (nickel-
chromium alloy) that will retain its strength at higher temperatures. We estimate that this will
double the material costs for the muffler to about $0.80 per pound. A local metal supplier (ABC
supply, 1996) quoted prices of $0.80 per pound for cold-rolled 1080 low-carbon steel sheet, and
$1.50 per pound for 304 alloy sheet, about twice as much. Large buyers are able to obtain much
lower prices (Am. Metal Market, 1996). Quotes for 405 alloy sheet were not available, but the
cost is expected to be considerably lower, due to its lower alloy content, and we estimate it at
$0.80 per pound in large volume. The resulting increase in cost of 0.40 cents per pound
compared to low-carbon steel, multiplied by the 8.5 ounce weight of the muffler, gives an
increase in material cost of $0.23 per piece (Table 52).
Table 52: Incremental variable costs for hand-
The higher muffler temperature will require a
change in the thermal design of the equipment
as well. Presently, a single metal muffler
cover serves as a heat shield to prevent direct
contact with the hot muffler. Based on prac-
tices used with catalytic converters in two-
stroke motorcycles, we expect that manufac-
turers would add a second heat shield around
the muffler cover. This would require design
changes in the air cleaner cover and the fan
cover assembly as well, to accommodate the
increased size of the muffler/heat-shield
assembly and to provide adequate cooling air
to this assembly. The additional heat shield
is assumed to be stamped out of low-carbon
steel (since its temperature is less than that of
the muffler, high-temperature steel is not
required). The weight of the heat shield would be similar to that of the present muffler cover.
The resulting variable manufacturing costs are also shown in Table 52. The added assembly
labor to attached the heat shield would amount to about $.175, giving a total increase in the
variable manufacturing cost of $0.90 (Table 53).
The fixed costs involved in modifying hand-held equipment models for catalytic converter use
would include about one year of engineering labor and testing to ensure safe design of the high-
temperature components. Testing and related costs are included under "other engineering".
Significant safety-related changes to consumer manuals and documentation would also be needed.
held equipment equipped with catalyst.
Heat Shield
Muffler
Process
Stamping
Stamping
Material
L.C. Steel
Alloy-Steel
Weight (lb)
0.313
0:531
Wgt+10%Scrap
0.344
0.584
Material cost S/lb
0.40
0.401
Material Cost (S/part)
0.138
0.234
Labor minutes
1
0
Labor cost $/hr
15
15
DL Cost S/part
0.25
0.00
Overhead @40%
0.10
0.00
Total cost/part
0.35
0.00
Total equip, cost/part
0.49
0.23
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The costs of the needed training and Table 53: Incremental variable equipment cost for
documentation changes are estimated at adding catalytic converter to hand-held equipment.
$100,000, which is intermediate between
the costs for a major engine change
($500,000) and those of a technical sup-
port bulletin ($20,000) (Honda, 1996).
Tooling costs would include new injection
molds for the air cleaner cover and fan
housing cover, and new stamping dies for
the heat shield, muffler cover, and the
three components of the muffler itself.
Detailed cost estimates are shown in
Table 54. Setup costs would include the
changes needed in the assembly line, jigs,
handling equipment, etc. to accommodate
the added components and assembly oper-
ations.
Since the heat shield would be an added component, it would require an additional stamping
press capacity to produce it. We estimate the press cycle time at 30 seconds, based on typical
values (Amstead, Ostwald, and Begemand, 1976). Allowing for two shifts, and seven hours of
production per shift, this is equivalent to about 1500 parts per shift. Thus, 400,000 parts per year
for a high-volume line (case 1) would require all of the capacity of one press, running two shifts,
while 90,000 parts per year for a low-volume line (case 2) would require about 25% of one
press's capacity (we assume that the remaining capacity would be used on other engine lines).
A 50-ton stamping press costs about $50,000 (Chew, 1996), so we assessed machine tool costs
of $50,000 for the high-volume case, and $15,000 for the low-volume case (the latter allowing
for some loss of production due to die changes between runs of different parts).
A summary of hardware/assembly costs, and fixed costs to modify various handheld equipment
(e.g., trimmer, chainsaw, blower) to add catalytic converters is given in Table 55.
Cost/
Piece
Pieces/
Engine
Total
Parts Cost
Heat Shield
0.49
1
0.49
Alloy-Steel Muffler
0.23
1
0.23
Total Parts Cost
0.72
Added Assembly Labor
Labor minutes
0.5
Labor Cost $/hr
15
Direct Labor S
0.125
Overhead @40%
0.05
Total Labor + OH
0.175
Total Added Variable Equipment Manu-
facturing Cost
0.90
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Table 54: Estimated equipment fixed costs for
handheld engines with catalyst.
Case 1
Case 2
Engineering Costs
Engineering labor (person
year)
1
1
Engineering labor + OH
100,000
100,000
Number of Tests
0
0
Tesft Cost
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11. USER COSTS
This chapter addresses user costs associated with using a modified engine. The user costs consist
of the incremental costs associated with fuel saving and maintenance.
11.1 Fuel Cost Savings
Engines designed to meet Phase 2 emission regulations will have the added benefit of decreased
fuel consumption, leading to decreased lifecycle fuel costs to the consumer.
For engines used in non-handheld equipment, three pollution control measures are studied: (1)
improved side-valve technology, (2) improved overhead-valve technology, and (3) conversion
from side to an overhead-valve system. Improved side-valve design is estimated to reduce fuel
consumption by 5-10 percent. This fuel range of decreased fuel consumption is consistent with
a technical study that measured a 6.4 percent fuel reduction with improved side-valve design (Xia
and Jin, 1991). The improved design will burn fuel more completely and bum less fuel while
maintaining power output similar to the non-optimized design.
Improved overhead-valve engines incorporate many of the same changes as improved side-valve
engines. Therefore, it is reasonable to assume a similar fuel consumption savings of 5-10
percent.
The fuel savings associated with converting from side to overhead-valve design are more
significant than those of the improved designs described above. Overhead-valve engines are
inherently cleaner burning than side-valve designs. Compared to side-valve engines, overhead-
valve engine combustion is more complete, emitting fewer hydrocarbons in the form of unbumed
gasoline. This results in increased fuel economy. Engine manufacturer literature suggest 30-40
percent fuel savings and an estimate by one equipment manufacturer (John Deere, Conversation,
September, 1996) was between 25 and 50 percent fuel consumption reduction. Thus, we assumed
35 percent
For engines used in handheld equipment, three technologies are considered:
(1) improved two-stroke design (stratified charge), (2) improved two-stroke with catalyst, and (3)
two-stroke to four-stroke conversion. The estimate of fuel savings for improved two-stroke
design is 15-20 percent based on the relationship between emission reduction and fuel reduction.
The addition of a catalyst should not affect the fuel savings on an improved two-stroke. For two
to four-stroke conversion, Ryobi is currently the only company that currently markets a handheld
four-stroke engine. Four stroke designs are inherently cleaner burning and notably more fuel
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efficient than two-stroke designs. Ryobi estimates a fuel savings of 30 percent with two to four-
stroke conversion.
Table 56 and Table 57 present expected savings for class I non-handheld engines for commercial
and residential use, respectively. The data for average engine lifespan, average annual use,
average engine horsepower, and baseline fuel consumption rate used based on a 1990 CARB
study (ARB, 1990).
To determine the fuel consumption rate of the modified engine, the baseline fuel consumption
rate was multiplied by the fuel saving percent. To determine the lifetime fuel cost for an
unmodified engine (second row from bottom), the baseline fuel consumption rate was multiplied
by the average lifespan, the average usage, the average horsepower and the price of gasoline get
the baseline lifetime fuel cost. Then, to determine the lifetime fuel cost for a modified improved
engine (third row from bottom), the improved fuel consumption rate (as determined above) was
multiplied by the average lifespan, the average usage, the average horsepower and the price of
gasoline get the baseline lifetime fuel cost. The resulting lifetime fuel savings (bottom row) was
determined by subtracting the improved lifetime fuel costs from the baseline lifetime fuel cost.
In these calculations, the price per gallon was $0,765 which was the refinery price to endusers
excluding federal and state taxes. The price was the average for 1995 from the Energy
Information Administration Petroleum Marketing Monthly, September 1996. Also, a gasoline
density of 6.25 pounds per gallon was used to determine the fuel consumption on a per gallon
basis.
The tables show that most of the fuel savings axe in the commercial applications because of the
longer lifetime use hours than residential applications. The largest savings were $220 from the
side-valve to overhead-valve conversion.
Table 58 and Table 59 detail cost savings for typical handheld engines (classes IE, IV, and V).
The data for average engine lifespan, average annual use, average engine horsepower, and
baseline fuel consumption rate used in Table 58 and Table 59 were based on a 1990 CARB study
(ARB, 1990).
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Table 56: Commercial Class I Non-handheld Lifetime Fuel Cost Savings by Engine Modification
Commercial Non-Handheld
Improved Side Valve
Improved Overhead Valve
Conversion Side Valve to
Overhead Valve
Average Lifespan (yrs)
3
3
3
Average Usage (hrs/yr)
320
320
320
Average Horsepower
4
4
4
Baseline SV/OHV Fuel Consumption (gal/hp-hr)
022 for SV
0.145 for OHV
0.22 for SV
Fuel Savings %
7.5%
7.5*
35%
Improved Fuel Consumption (gal/hp-hr)
0.2
0.135
0.145
Improved Lifetime Fuel Costs (S)
$597
$394
$426
Baseline Lifetime Fuel Cost ($)
$646
$426
$646
Lifetime Fuel Savings ($)
$49
$32
$220
Gasoline price was $0,765 per gallon which was the average refinery price to end user for 199$; source from Energy Information Administration
Source: Baseline fuel use data provided by 1990 CARB study "California Exhaust Emission Standards and Test Procedures for 1994 and
Subsequent Model Year Utility and Lawn and Garden Equipment Engines". December 1990.
Table 57: Residential Class I Non-handheld Lifetime Fuel Cost Savings by Engine Modification
Residential Non-Handheld
Improved Side Valve
Improved Overhead Valve
Conversion Side Valve to
Overhead Valve
Average Lifespan (yn)
7
7
7
Average Usage (hrs/yr)
20
20
20
Average Horsepower
3.5
3.5
3.3
Baseline SV/OHV Fuel Consumption (gal/hp-hr)
0.22 for SV
0.145 for OHV
0.22 for SV
Fuel Savings %
7 5%
7.5%
35%
Improved Fuel Consumption (gal/hp-hr)
02
0.133
0.143
Improved Lifetime Fuel Costs ($)
$76
$50
$34
Baseline Lifetime Fuel Cost (S)
$82
$54
$82
Lifetime Fuel Savings ($)
$6
$4
$28
Gasoline price was $0,765 per gallon which was the average refinery price to enduser far 199S; source from Energy Information Administration
Source: Baseline foe) use data provided by 1990 CARB study "California Exhaust Emission Standards and Test Procedures for 1994 and
Subsequent Model Year Utility and Lawn and Garden Equipment Engines". December 1990.
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Table 58: Commercial Handheld Lifetime Fuel Savings by Engine Modification.
Commercial Handheld
Improved Two-Stroke
(either improved scav-
enging or stratified scav-
enging)
Two-Stroke to Four-Stroke
Improved Two-Stroke with
Catalyst
Average Lifespan (yn)
22
2.2
22
Average Usage (hrs/yr)
261
261
261
Average Horsepower
3
3
3
Baseline 2- Stroke Fuel Consumption (gal/hp-hr)
022
0.22
0.22
Fuel Savings %
17.5*
30%
17.5*
Improved Fuel Consumption (gal/hp-hr)
0.18
0.15
0.18
Improved Lifetime Fuel Costs (S)
$235
$200
$235
Baseline Lifetime Fuel Cost ($)
$285
$285
$285
Lifetime Fuel Savings ($)
$50
$85
$50
Gasoline price was $0,765 per gallon which was the average refinery price to enduser for 1993; source from Energy Information Administration
Source: Baseline fuel use data provided by 1990 CARB study "California Exhaust Emission Standard* and Test Procedures for 1994 and
Subsequent Model Year Utility and Lawn and Garden Equipment Engines'*, December 1990.
Table 59: Residential Handheld Fuel Cost Savings by Engine Modification.
Residential Handheld
Improved Two-Stroke
(improved scavenging or
stratified scavenging)
Two-Stroke to Four-Stroke
Improved Two-Stroke with
Catalyst
Average Lifespan (yn)
5
5
5
Average Usage (his/yr)
9.5
9.5
9.5
Average Horsepower
1.5
1.5
1.5
Baseline 2-Strolce Fuel Consumption (gal/hp-hr)
0.22
0.22
022
Fuel Savings %
17.5*
30*
17.5*
Improved Fuel Consumption (gal/hp-hr)
0.18
0.15
0.18
Improved Lifetime Fuel Costs (S)
$10
$8
$10
Baseline Lifetime Fuel Cost (S)
$12
$12
$12
Lifetime Fuel Savings ($)
$2
$4
$2
Gasoline price was $0,765 par gallon whicft was the average refinery prtea to enduser tor 1995; source: Energy Information
Administration
Source: Baseline fuel use data provided by 1990 CARB study "California Exhaust Emission Standards and Test Procedures for 1994
and Subsequent Modal Year Utility and Lawn and Garden Equipment Engines', December 1990.
11.2 Lifecvcle Maintenance Savings
Improved side and improved overhead-valve designs, and improved two-stroke designs will likely
have maintenance costs slightly lower than the original unmodified engines. This decrease in
maintenance costs is due to the improved design allowing less oil into the combustion chamber.
This leads to less carbon being deposited in the combustion chamber and decreases engine oil
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consumption. Also, class I side-valve improvements will result in less carburetor fixes.
Commercial users would be more likely to notice such minor reduction in maintenance costs,
because their more..intensive equipment use leads to shorter maintenance intervals. More
dramatic differences in maintenance costs are associated with a change in engine technology,
such as converting from a side to overhead-valve configuration.
Overhead-valve engines have significantly lower maintenance costs than comparable side-valve
designs (John Deere, Conversation, September, 1996). The merits of overhead-valve designs for
both class I and class n engines include increased engine life (e.g., valve life), less frequent
replacement of parts, and longer intervals between maintenance. The oil service costs provided
by John Deere in Table 60 demonstrate these merits for premium tractor equipment. In this case,
the air and liquid-cooled overhead-valve designs decrease maintenance costs per hour by 66 and
90 percent respectively from side-valve designs. The two major maintenance items considered
are oil replacement and valve adjustment. These maintenance practices are undertaken more
often by commercial engine users. Commercial users run their engines for much longer periods
of time, and do so more frequently. The maintenance intervals prescribed by the manufacturer
are based on hours of service. Residential users may not undertake maintenance as consistently
as commercial users, and do so less often if proper service intervals are observed.
Table 60: Oil service costs for tractor engines.
Engine Design
OU Replacement
Interval (hn.)
Expected Equipment
Life (hn.)
Lifetime Oil Service
Coit (I)
Oil Service Cart, 1
per 750 hour* (2)
Side-valve
25
7S0
s UOO
$ UOO
Overhead-valve, Air Cooled
30 - 100 (assume 75)
uoo
S 800
S 400
Overhead-valve. Water
Cooled
230
3,500
S 560
$ 120
Source: John Deere
(1) - Oil change cost - S40/service (Wicks Repair. Alexandria. VA)
(2) • For comparison purposes, developed cost for 750 hours
Valve train adjustments are generally required once over the lifetime of an engine. This service
costs approximately $50 (Wicks Repair, Alexandria, VA). For a premium side-valve engine, the
service is required within the first 100 hours of use. Premium overhead-valve engines require
the service in the first 1,000 hours of use (John Deere, Conversation, September, 1996). Users
of commercial equipment with side-valve engines will have the cost and inconvenience of
servicing their engines much sooner than users of commercial equipment with overhead-valve
engines. Perhaps, because of the long time before an overhead-valve engine needs adjusting, the
commercial user of overhead-valve equipment may not even incur the cost of valve readjustment.
Similarly, many residential users may not use an overhead-valve engine to the point where it
requires a valve adjustment, thereby avoiding the cost and inconvenience of the service. A
residential user would almost certainly use a side-valve engine to the point where it requires an
adjustment.
For handheld equipment engines, improved two stroke engine will reduce oil consumption and
minimize oil and carbon deposits in the chamber. This results in probably some, but not a
significant reduction in maintenance. Similarly, the engine with stratified charge and a catalyst
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will have a small reduction of maintenance due to the stratified charge design. Finally, the
conversion of two to four stroke design may result in somewhat additional maintenance
reductions than the other improvements to the handheld engines because of the reliability of four
stroke designs.
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12. CONSTRAINTS
This chapter explores the sensitivity of the engine incremental cost data (provided in the bottom
up engine analyses Parts I and H) by considering other possible constraints that may affect the
cost of the engine. It addresses rule-related constraints, manufacturer-related constraints, and
technology-related constraints. We focused on the six technologies studied in this report. There
is some uncertainty in determining the influence of these constraints on the estimated costs per
engine because it is not clear what types or combinations of technology modifications the
manufacturers will use to achieve emission reductions. It is also not clear which engine families
will be modified with the different technologies. This chapter addresses these constraints through
general discussions, by making certain assumptions to enable quantitative analysis, by
characterizing the engine manufacturers data, and by providing various illustrative examples.
12.1 Rule»Related Constraints
This section describes how some of the implementation features of the Phase 2 regulations may
affect the cost of the engines. The implementation features that could affect engine costs include
the lead time provided to meet the Phase 2 regulations and the phase-in schedule which
determines the percentages of engines that must comply each year with the emission regulations.
For handheld engines, the anticipated implementation is for model year 2002 with a four year
phase period as follows:
Model Year Percent of Production
2002 20
2003 40
2004 70
2005 100
For non-handheld-engines, the phase in period has not been defined, however, for the purposes
of this analysis of rule-related constraints, we have assumed the following phase-in penod for
engines that need major design changes (i.e., conversion of class U side-valve to clean durable
OHV) to comply with the emission standards.
Model Year Percent of Production
2001 50
2003 75
2005 100
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The effects of rale-related constraints (e.g., lead time) on the costs of engines depends on a
number of different factors including:
• the assumption about the start time for manufacturers (when Phase 2 regulations are
promulgated or when manufacturer is informed of/or agrees to emission reduction levels);
• level of experience/preparation of the manufacturer (e.g., advanced R&D) to implement
engine changes;
• manufacturer resources;
• number of engine families/models that need to be modified;
• the timing for typical replacement/retiring of dies, tooling equipment, training manuals,
training, etc,
• ability of the manufacturer to use/adapt capital equipment to manufacture the modified
engine;
• the type or combinations of engine modifications necessary to meet emis: svels;
• industry structure to integrate engine with equipment; and
• extra lead time to develop certain newer technologies.
The following topics regarding rule-related constraints are covered: start time, lead time, possible
cost impacts of phase-in schedule, factors that affect the early retirement of equipment and
tooling, possible early retirement costs, and strategy/challenges to meet phase-in schedule.
Start Time
A cost analysis of rule-related constraints also depends on the start of the lead time for the Phase
2 regulations. For this analysis, we assume that lead time for complying with the Phase 2
regulations starts in mid 1997, the official date of the expected final rulemaking. This start date
is also reasonable because the Statement of Principles was completed in May 1996 for handheld
engines and the SOP for non-handheld engines is currently being drafted.
Lead Time
We conducted a brief evaluation to determine if adequate lead time is provided to comply with
the Phase 2 regulation. Presumably, some manufacturers are already\planning engine modifica-
tions to comply with the CARB 1999 Tier II emission regulations on utility engines. EPA Phase
2 will have an implementation date several years after the CARB implementation date.
The typical product development cycle for small engine and equipment includes several steps
including concept development, feasibility, preliminary design, final design, qualification, pilot
production, and production. Varying amounts of lead time will be required depending on the
level of redesign/replacement required, the emission levels that need to be achieved, and the
durability and performance requirements of the engine. Also, several layers of testing may be
required for system integration. The projected lead-time for a single engine family is typically
two to fpur years. (Technology Task Group, September 1995.) The lead time necessary for
specific engine modification technologies is another area of great disagreement
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For adding a catalyst to two-stroke handheld engines, scavenging losses must be reduced.
Industry has made some progress in minimizing the other problems associated with packaging,
high exhaust and steface temperature, durability of the catalyst because of excessive heat,
vibration, and possible contamination. For example, Husqvama had recently announced
(Husqvama Newsbrief, 1996) development of an advanced two-stroke engine that reduces
scavenging losses and that features a low temperature catalyst. This technology will be available
on a range of Class IV trimmers, edgers, hedge trimmers and blowers in 1997. Also, chainsaws
and mowers have been equipped with catalytic converters in Europe, however, Europe does not
have the temperature standards from the U.S. Forest Service. CARB asserts that catalysts will
be ready on utility equipment by 1999, the implementation year of the Tier II regulations. In
contrast, the Power Equipment Manufacturers Association (PEMA) has asserted in comments to
CARB (CARB, January 1996) that a catalyst for handheld is not ready until formidable issues
are addressed (e.g., heat management) and catalyst will not be feasible until various techniques
are perfected to reduce scavenging losses. PEMA states that more lead time is needed. In terms
of making a lead time assumption for this study, we believe that because some additional R&D
is needed across the engine manufacturing industry, lead time for production may be 3-4 years
for one engine family. Given a start time of mid 1997 and an initial phase-in date of 2002, the
manufacturer would have just sufficient time to add a catalyst to one or more of its engine
models.
Concerning two to four-stroke conversion, Ryobi's development of a lightweight four-stroke
engine for handheld applications provides some guidance on lead time. Ryobi generally
developed their four-stroke handheld engine over a period of about 6-8 years (Ryobi Newsbrief,
199S). However, acceptance and spreading of this technology throughout the industry is an issue.
Ryobi has signed an agreement with Toro to produce four-stroke trimmers and is discussing
licensing the technology to other manufacturers. The Ryobi engine, however, will not be able
to be used in certain multiposition applications (e.g., chainsaw). Honda has recently developed
a four-stroke handheld that could be used in multiposition applications. PEMA points out that
more lead time is needed because the Ryobi engine may not meet certain emission reduction
levels (e.g., Tier II) and confirms the problem of using a Ryobi-type engine in chainsaws. In
terms of making a lead time assumption, we believe that because of the newness of the two to
four-stroke technology, a lead time of 4-5 years for production of one engine family will be
needed. Given a start time of mid 1997 and an initial phase-in dat^of 2002, the manufacturer
may not have sufficient time to design and produce a four-stroke engine in the first year of the
Phase 2 implementation unless efforts started before mid 1997.
In terms of conversion of non-handheld engines from side-valve to overhead valve, most
manufacturers produce some part of their engine lines with overhead valve. The technology is
widely available and depending on the final emission standards, OHV may be used more
extensively. In terms of ^airing a lead time assumption, we believe that because the clean
durable OHV technology is accessible and in use by many non-handheld manufacturers, a lead
time of 2-3 years for one engine family is reasonable. Given a start time of mid 1997 and an
initial phase-in date of 2001 for non-handheld equipment (one year before handheld), the
manufacturer should have adequate time to design and produce one or more lines of OHV
engines. However, assuming the phase-in compliance schedule is 100 percent production volume
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or class I engines and 50 percent production for class II engines, the manufacturers cannot wait
co convert their lines unless a substantial portion of their engines already comply with the Phase
2 emission standard.
It is important to note that for all of the engine modifications discussed above, progress in the
development/production process can be concurrently applied to additional engine families.
Potential Cost Impacts of Phase-In Schedule
There are a couple cost impacts that the proposed rule phase-in schedules may have on engine
manufacturers. First, if engine manufacturers can wait until equipment need replacing before
converting engine models in response to a rulemaking, they can avoid losses associated with
premature retirement of capital equipment. If they cannot wait, and have to discard equ. *ment
such as dies that have remaining useful life, manufacturers lose a percentage of the oital
equipment ccst commensurate to the percentage of remaining useful life of the production
equipment. Secondly, some manufacturers may have to convert a large percentage of the number
of engine models to accommodate the proposed phase-in schedules. In this instance,
manufacturers may incur early and significant equipment and labor costs to accomplish model
conversion in the phase-in schedule.
Factors that Affect the Early Retirement of Engine Manufacturing Equipment and Tooling
The likelihood of needing to discard equipment with useful life is a function of equipment usage.
The most important equipment that may need to be retired are the dies. Dies generally have a
useful life of 100,000 presses, which produce at least 100,000 engines. Manufacturers with large
volume engine lines may have dies that can produce as many as 6 engine parts per press (Briggs
and Stratton, September, 1996) or 600,000 engine parts per die life. Dies that are used to
produce a large number of engines per model last a short time whereas dies used in the
production of low volume engine models last longer. For example, dies used in the production
of a high-volume class I engine model with 1.2 million engines annually are replaced at least
twice and at most twelve times per year. Dies used for an engine model with 35,000 engines
produced per year however, are replaced every three years. Lines smaller than 35,000 engines
will have an even longer years of service.
The maximum amount of time before dies are replaced will influence the likelihood of needing
to retire capital equipment (e.g., dies) early. The impact is discussed for high, intermediate, and
low volume manufacturers.
High Volume Manufacturers. Manufacturers with large market share generally produce engine
models with greater unit volume than medium and small volume manufacturers. These dominant
high-volume engine models for the large handheld or non-handheld manufacturers produce at
least 100,000 engines annually and likely require die replacement at least annually. In the
context of a phase-in schedule, these high-volume engine lines are unlikely to face any problems
of early retirement losses because the dies are replaced so frequently (i.e., several times a year).
Also, because the manufacturer will likely convert the high-volume lines first to comply with the
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phase-in regulation, the manufacturer will suffer no early retirement loss. In addition, any small
or intermediate volume lines in the large manufacturer can be converted at the manufacturers
discretion (i.e., when, the die lifetime use is complete) to avoid eariy retirement costs from these
lines. Finally, any retirement costs will be small when averaged over the total large production
volume of engines.
Intermediate and Low Volume Manufacturers. When Phase 2 emission limits are established in
mid 1997, medium and low volume manufacturers will likely consider modifying engine models
that have dies with no remaining useful life (i.e., dies that have performed 100,000 presses) by
the first year of implementation (e.g., year 2002 for handheld and 2001 for non-handheld). For
small volume manufacturers, losses from early retirement of dies is spread over a significantly
smaller number of total engines produced (i.e., loss per engine is far greater), which makes this
cost more significant. In addition, small manufacturers have far fewer engine models to convert
(generally Five or fewer engine models), which means that there are fewer combinations available
that accomodate the phase-in schedules. Models that are ready for die replacement may not
constitute enough of total production to achieve compliance for some manufacturers, forcing these
manufacturers to scrap dies prematurely in order to comply. Small volume manufacturers would
prefer to wait until dies for all engine models have performed 100,000 presses before conversion.
Medium volume manufacturers have similar conversion concerns, but generally have greater
flexibility through more engine models and quicker die replacement schedules.
Ultimately, the likelihood of needing to discard production equipment with remaining useful life
depends a complex set of variables including engine volume size, the lead time required for the
engine modification, the implementation year of the regulation, and the phase-in schedules.
Possible Earlv Retirement Costs
The type of engine modification will impact the retirement costs. More extensive modifications
typical of SV to OHV and two to four-stroke will potentially incur the most retirement costs.
SV to OHV Conversion of Non-Handheld Engines. In the SV to OHV conversion, there is
concern about the need to retire SV capital equipment. Although machine tooling equipment
originally used for SV can be adapted for use in manufacturing QHV (Briggs and Stratton
conversation, 1996), however, the dies for the SV will have to be retired. These dies typically
cost $25,000 each for a main pait (e.g., cylinder head, cylinder block, crankshaft, piston), and
$15,000 each for other parts (e.g., connecting rod). For the SV to OHV conversion, the side-
valve capital equipment that may have to be retired early per engine model include dies foT
cylinder block, cylinder head, connecting rod, piston, and crankshaft Thus, the maximum total
cost to the manufacturer for retirement of the dies is $115,000 per engine line. If the dies used
in SV engine production have two years of remaining useful life out of three total years of useful
life, manufacturers lose two thirds of $115,000, or $76,000). Using this loss rate and given a
hypothetical medium sized non-handheld manufacturer with approximately 15 engine models,
each producing 35,000 engines per year, the total retirement cost would be $1.14 million over
three years. This would be equivalent to about $0.7 additional cost per engine (based on three
years total sales) as a result of early retiring of capital equipment over a three year period.
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Two to Four-Stroke Conversion To convert a two to four-stroke handheld engine, the two-stroke
manufacturing capital equipment that may have to be retired early per engine model include a
die for cylinder headftjlock ($40,000), die for piston ($15,000), die for carburetor ($60,000), die
for connecting rod ($15,000), die for crankshaft ($25,000), and die for crankcase ($40,000). The
total is $195,000.
Strategy/Challenges to Meet Phase-in Schedule
Most small engine manufacturers, whether big or small, will have a few engine lines that will
dominate the manufacturer's total engine production. Unless a large percent of the engine
production already meets the emission regulations by the time they are implemented, these
dominating engine lines would be expected to be converted first, in advance of the regulations
to meet the compliance phase-in.
The proposed phase-in schedule for non-handheld manufacturers is faster and more dramatic in
the first year of implementation than the handheld. By 2001, class II non-handheld manufactur-
ers must have 50 percent of production in compliance. Generally, SV to OHV conversion for
class II engines may be necessary to achieve compliance. This first year compliance phase-in
is in part based on the assumption that a certain percentage of non-handheld engines are already
overhead valves and will not require conversion. Nonetheless, this phase-in could pose problems
for some manufacturers of Class II non-handheld engines, which will convert many engine
models from side valve to overhead valve. Table 61 illustrates the percent of claaa II
manufacturers' production that was side valve in 1993 according to the Power Systems Research
database. The percentages may have changed in the last several years. The table shows that
manufacturers with the largest market share (58 percent - 2 percent of total Class 2 engine
production) have significant percentages of production that need to be converted from side valve
to overhead valve (24 percent - 100 percent). These manufacturers, however, produce many
models (22 - 39 models), of which a few would likely need new dies before they must be
converted. Also, large volume manufacturers tend to have several other models to choose from
to comply with the phase-in schedules. Smaller manufacturers that have a high percentage of
side valve engines that will require conversion will have significantly fewer engine models (in
some cases only one model). These manufacturers need to convert 50 percent of production by
the year 2001, which may likely require early retirement of dies and a joss on capital investment.
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Table 61: Characterization of Class II Non-handheld Engine Manufacturers.
Percent or rotal Class II
Production for Different
Number of Engine
Models
Percent Side Valve Production
(Representing Percent of Manu-
58.16%
39
87'%
11.97%
19
24%
9.67%
26
7$%
9.02%
22
89%
4.64%
27
85%
1.62%
22
166%
1.45%
3
0%
1.43%
15
0%
0.47%
1
6%
6.43%
4
76%
6.23%
1
166%
0.24%
1
6%
0.2 2%
1
6%
0.14%
1
0%
0.12%
2
37%
6.10%
2
0%
0.07'%
1
100%
0.03%
4
100%
Source: Power Systems Research, 1993.
12.2 Manufacturer-Related Constraints
This section describes the constraints on the engine manufacturing sector to modify the engine
(e.g., convert SV to OHV). The constraints are evaluated in terms of the profile of the engine
manufacturing sector which includes the market dynamics between manufacturers (e.g., big/small,
general/specialty) and the engine family/model structure within these manufacturers. The overall
constraints are stated in terms of their general effect on the costs of producing the modified
engines.
Choice of Technology to Meet Emission Standards
Manufacturers could choose any of the six engine modification technologies evaluated in this
study or perhaps other technologies to meet anticipated Phase 2 emission standards. The type
of technology chosen will certainly influence the compliance costs. Manufacturers may choose
different modification methods to comply. Some modifications will be less expensive than others
(see bottom-up engine analysis Parts I and II for the six technologies studied). Some
manufacturers already manufacturer engines that use such technologies (e.g., OHV) and will meet
Phase 2 emission standards without additional costs. It might be expected that certain
manufacturers that primarily serve the consumer equipment market (i.e., Briggs and Stratton)
where engine/equipment price is a critical factor may pursue the less expensive modifications.
The active competition between Briggs and Stratton and Tecumseh in the consumer equipment
market will support this logic to pursue least expensive options. Other manufacturers that
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produce specialty engines (e.g., Teledyn-Wisc) or prem: m engines (e.g.. Jhler) may choose
to invest in more expensive or extensive technologies tha; enhance the pen /nance or premium
reputation of the engine/equipment as well as meeting the emission standards. The engine
modification pursued by the manufacturer (and therefore the cost) may be influenced by other
reasons including the motivation to pursue efforts that build on past and existing R&D efforts,
on the assets of the manufacturer to pursue new and perhaps unproved technologies, on the
manufacturer's policy and culture concerning changes to the engine, and on manufacturer
knowledge about the application of the engine in the equipment and the preferences by the
equipment manufacturer and the consumer. Assets for R&D may not be entirely a function of
market share, but may also be a function of the wealth of a parent company or its success in
other markets (e.g., Honda).
Manufacturer Size and Eneine Cost
Given the same engine modification undertaken by different manufacturers. cost of the engine
modification can still differ. The size of the manufacturer as expressed in lumber of engines
produced and sold is one factor that will influence the cost of the engine modification to the
manufacturer.
Non-Handheld Manufacturers. The non-handheld category is largely composed of two engine
manufacturers that dominate. Briggs and Stratton and Tecumseh account for over 90 percent of
all class I engines and over 74 percent in class II (all market share percentages from PSR
ENGINDATA database). Two medium-sized manufacturers (e.g. Honda, Lawnboy/Toro) together
make up 9 percent of the class I engines and three medium-sized manufacturers (e.g., Kawasaki,
Kohler, Onan) together make up over 20 percent of the class II engines. The rest of the
manufacturers of either the class I or class II engines represent a very minor part of the market.
All of the six engine modification studies in this report will require additional parts. >ome of
'he parts will be provided by suppliers and others may be produced by the manufactu:er. For
any specific engine modification, it is anticipated that the Briggs and Stratton and Tecumseh will
be able to get large-volume discounts from suppliers and further discounts in purchasing
machining tools to produce some parts in house. These large manufacturers will also receive raw
material discounts (e.g., steel, aluminum) and labor efficiency savings. Companies with more
modest market share will receive smaller discounts and will likdy need to buy a higher
proportion of additional parts from suppliers. The costs for modifying engines for small engine
manufacturers will likely be significant and proportionally much higher than the increase in
engine cost from medium to large engine manufacturers.
Handheld Manufacturers. For the hand-held class IV engines, the market can be characterized
as a two tiered market (e.g., large and small), and therefore the engine volume factors that affect
cost still apply. Class IV is dominated by Poulan, Homelite, Stihl, and Ryobi/Inertia Dynamic
(representing over 90 percent of the market). In the relatively small class V, Homelite and
Poulan, and Tecumseh represent over 90 percent of the market) (PSR ENGINDATA). One
difference in this handheld category is that these manufacturers tend to produce both the engine
and equipment. Perhaps, as compared to the non-handheld manufacturers, this industry structure
to the handheld manufacturers will have closer cooperation and communication in modifying the
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engine and equipment, and therefore, will result in comparatively lower costs to modify an engine
line.
Engine Family and Engine Cost
The cost per engine will depend somewhat on the engine family/model within a single
manufacturer, but when compared with other factors, the engine family/model is not expected to
be a significant variable affecting the engine cost for most of the six technologies examined in
study. It is expected that different size parts will be needed to modify different engine
families/models. Larger parts tend to be more expensive and if produced in-house, larger parts
will require more material and different stamp and die molds. In an SV to OHV conversion,
each engine family will require a different master die for the cylinder head and block. It is not
expected, however, that the cost of making of a master die for one OHV engine family will differ
from the cost of making a master die for another OHV engine family. Different engine
families/models will also require different drill/tap sizes, but the main cost associated with this
is labor which would not change from engine family to engine family. For handheld equipment
engines that use a catalyst, the cost per engine could differ somewhat depending on the engine
family. Catalyst materials are expensive and larger engines require larger amounts of catalyst,
however, the overall difference in cost between the smallest to the largest handheld engines is
not expected to be significant.
Application and Engine Cost
Engines are used in a variety of equipment and applications. It is expected that some changes
to the equipment may be needed to accommodate the modified engine technologies. For
example, it is expected that for all handheld applications, engines with catalysts will need a heat
shield. A further description of these types of changes and their associated costs are outlined in
the bottom-up engine analyses Parts I and II. Additionally, the cost of producing a modified
engine itself for a variety of equipment applications is not expected to changes costs. For
example, a mounting bracket on an OHV engine intended for use on a lawnmower is not
expected to cost more than a mounting bracket on an OHV engine intended for use on a
snowblower.
Transition Costs for Manufacturers
As discussed under rule-related constraints, manufacturers could experience additional costs per
engine from having to prematurely retire capital equipment (primarily dies) that cannot be used
to manufacture the modified engine. Because these retirement costs are dependent on the number
of engine families/models and not on the number of engines produced, the cost per engine
associated with the retired dies would be larger for manufacturers that make a small number of
engines per engine family. For engine manufacturers that embark on the engine modifications
early, market share loss to other manufacturers could be an important short term loss. For
example, an engine manufacturer that switches their engine line from SV to OHV may lose
business from ah equipment manufacturer that still wishes to purchase SV engines. This loss to
manufacturers could be in the tens of millions, however, the manufacturers may not pass on these
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costs immediately because the playing field should level out when all manufacturers have to
comply with the emission reduction regulations.
Costs to Participate in California Market
Manufactures that are heavily involved in the California market may have to pursue more
expensive technology modifications in order to comply with stringent Tier II emission standards.
Such manufacturers would include Briggs and Stratton and Tecumseh. However, if the market
for both California and the rest of the U.S. is large, a manufacture such a Briggs and Stratton
could consider developing separate engine families/models that meet the California Tier II and
the Phase 2 emission standards, respectively.
12.3 Technology-Related Constraints
There are technological constraints associated with the engine modifications considered in this
study. The technological constraints discussed below include issues of technical feasibility,
production feasibility, and market penetration.
There are some limits to the technical feasibility of applying the engine modifications to some
engines and equipment to meet phase 2 emission standards. Some of these are mentioned in the
above section on rule-related constraints and in Part 1 and Part 2 of the study.
On the hand-held side, the constraints on using catalysts include safety concerns due to the heat
generated. Applying a catalyst to a two-stroke engine without reducing scavenging losses will
create great heat. Equipment that emit this heat will not comply with various temperature
regulations (e.g., OSHA and USDA National Forest Service) and other requirements. In Europe,
catalysts are used on handheld equipment because of less stringent temperature requirements.
In the U.S., no examples are yet available which show high emission conversion efficiency and
low temperatures on handheld equipment. However, a number of methods are being explored
to reduce temperatures below a safe limit (Technology Task Group, September, 1995). These
include heat shield (e.g., guard), stratified charge, and fuel scavenging through direct fuel
injection, air scavenging or enleanment. One solution may be to usfc a lower efficiency catalyst
on a smaller size two-stroke. A recent development by Husqvarna may have effectively
addressed the temperature issue (see above discussion in rule-related constraints). The
temperature issue also affects the durability of the engine and equipment The catalyst will also
add weight to the weight-sensitive handheld equipment. However, CARB states (CARB, 1994)
that a catalyst system may only add one pound to the equipment.
Also of concern for a catalyst system is the need for exhaust hardware changes to prevent
flaming out of exhatist, engine control to maintain correct air/fuel ratio, maximum conversion
efficiency of emissions, vibration concerns, and closed loop feedback. According to CARB
(CARB, January, 1996), there are several possible solutions to these issues that can make two-
stroke catalyst engines feasible by 1999, well in advance of the 2002 EPA Phase 2 emission
standards. Six engine families have been certified for CARB Tier I regulation. Numerous
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efforts, past experience, and recent accomplishments in this area of catalyst technology would
seem to suggest that 2002 should give sufficient lead time to achieve emission reductions over
Phase 1 levels.
There are several technical issues in converting two to four-stroke handheld engines. The basic
oil splash system in four-stroke handheld does not permit multipositional use of equipment. The
oil can leak. The lightweight four-stroke technology and design is relatively new (see description
in rule related constraints). Additional R&D can refine this technology and perhaps address the
multiposition-use issue (as possibly addressed by Honda) may necessitate an additional year of
lead time. Extensive licensing of the lightweight four-stroke technology, although unlikely across
the industry, may eliminate this need for additional lead time.
In the non-handheld engine sector, the conversion of SV to OHV is a known and demonstrated
change. The technology conversion has few technical challenges, however, there may be some
minor redesign of certain equipment to address the slighdy heavier and more bulkier engine (see
chapter 10 equipment cost analysis). The conversion of SV to OHV is not expected to need
additional lead time based on technical feasibility issues.
The market penetration ability of the SV to the OHV will be an issue for some applications, but
not for others. Particularly, the consumer SV market in lawnmowers may be difficult to
penetrate. Also, some engine manufacturers that are relatively new to the OHV engine market
with have to compete with more experienced OHV engine manufacturers. In addition, equipment
manufacturers will need time to perhaps redesign their equipment, however, this redesing can not
begin until the engine manufacturer share engine plans or when the new engines become
available. Equipment manufacturers usually redesign equipment in a five year cycle so the
expected lead time for market penetration might be sufficient if the engine manufacturer give
advance notice of engine conversion plans to OHV. However, if the OHV engines are not made
available until the year of implementation, the equipment manufacturers will not be able to
redesign the equipment to be used until the second or third year of implementation.
For the two to four-stroke conversion for handheld equipment, the market penetration into
equipment used in one position (e.g., edger) market should not experience technical barriers.
However, the handheld market that requires multipositional capability (e.g., chainsaw, hedge
trimmer) will be difficult because current four-stroke handheld technology cannot be applied to
multipositional equipment. However, Honda has announced that it will introduce a small four-
stroke engine for handheld application that can be used in multipositions.
The addition of catalyst to a handheld equipment may face slow market penetration because
additional time is needed to redesign the equipment to handle the catalyst and heat management
systems. However, because of the general vertical integration of the handheld engine/equipment
manufacturers, any equipment design changes may be more effectively integrated into the
equipment
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13. SUMMARY
This cost study for Phase 2 small engine regulations determined the incremental costs estimated
to be incurred by engine manufacturers over the Phase 1 baseline. The study addresses small
spark-ignition engines used in handheld and non-handheld equipment. A bottom-up approach
was used to determine the variable hardware/assembly costs and the fixed costs associated with
six engine modification technologies. For non-handheld engines, the technologies included
conversion of side-valve (SV) design to overhead-valve (OHV) design, improved SV design, and
improved OHV design. For handheld engines, the technologies included conversion of two-stroke
design to four-stroke design, improved two-stroke, and two-stroke with catalyst.
Table 62 presents a summary of the variable and fixed costs of the various modifications for the
non-handheld engines. The estimates were developed without using specific engine manufacturer
data on costs. However, manufacturers did provide the technical and manufacturing process
information required to make the estimates. Many other information sources were consulted for
the costs. In many cases, engineering judgement was required. For non-handheld engines, three
engine volume sizes - high (case 1), intermediate (case 2), and low (case 3) - based on engine
data were used for the fixed costs to provide a range of estimates. Several findings appear for
non-handheld engine modifications (engine classes I and II).
• improvements to existing engine design are generally less costly than major design
changes
• the most costly engine modification both in terms of variable and fixed costs is the
conversion of SV to OHV
• modifications that do not require variable costs (improved spark ignition in SV and
improved valve timing in SV) are the least costly options
• incremental cost estimates are highly dependent on the size of the line
• for low-volume lines, the fixed costs tend to approach or exceed the variable costs
• for high-volume lines, the variable costs tend to predominate
Table 63 presents a summary of the variable and fixed costs of the various modifications for the
handheld engines. For handheld engines, two engine volume sizes - high (case 1) and low (case
2) were used for the fixed costs. Several findings appear for handheld engine modifications
(engine classes HI, IV, and V).
• improvements to engine design are generally less costly than major design changes
• the most costly engine modification both in terms of variable and fixed costs is the
conversion of two to four-stroke
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Table 62 Incremental Variable and Fixed Costs for Modifications to Non-Handheld Engines
Engine Modification
Type of Cost
Case 1
(High Volume)
Case 2
(Intermediate
Volume)
Case 3
(Low Volume)
SV to OHV Class 1
Hardware/Assembly
Fixed
9.23
0.44
9.23
1.62
9.23
8.66
SV to OHV Gass II
Hardware/Assembly
Fixed
Not applicable
Not applicable
12.88
1.62
12.88
8.66
Improved SV (Combustion System)
Fixed
0.07
0.36
2.06
Improved SV (Spark Ignition/Timing)
Fixed
0.02
0.13
0.72
Improved SV (Valve Timing/Cam Design)
Fixed
0.12
0.51
2.27
Improved SV (Piston/Ring Design)
Hardware/Assembly
Fixed
2.73
0.07
2.73
0.39
2."5
2.;i
Improved SV (Manufacturing Variability)
Hard ware/Assembly
Fixed
0.35
0.11
0.35
0.38
0.35
1.90
Improved SV (Carburetor)
Hardware/Assembly
Fixed
0.35
0.07
0.35
0.69
0.35
3.94
Improved OHV (Combustion System)
Fixed
0.09
0.53
3.05
Improved OHV (Piston, Ring Design,
Bore Finish)
Hardware/Assembly
Fixed
2.25
0.12
2.25
0.47
2.25
2.35
• for low-volume lines, the fixed costs tend to approach or exceed the variable costs
• for high-volume lines, the variable costs tend to predominate
• modifications that do not require variable costs (improved two-stroke scavenging) are
the least costly options
Table 63 Increment Variable and Fixed Costs for Modifications to Handheld Engines
Engine Modification
Type of Cost
Case 1
(High Volume)
Case 2
(Low Volume)
Two- to Four-Stroke
Hardware/Assembly
Fixed
9.93
1.73
9.93
4 09
Improved Two-Stroke Scavenging
Fixed
0.34
1.43
Improved Two-Stroke Stntified Scavenging
Hardware/Assembly
Fixed
1.58
0.41
1.58
1.60
Improved Two-Stroke Scavenging with Catalyst (Ceramic
Metal)
Hard ware/Assembly
Fixed
4.58/8.58
0.64
4.58/8.58
2.63
Further reductions from the costs estimated in this study may come from improved redesigns
the engines and improved production processes. Warrantee costs to the manufacturer may al
be reduced. Additionally, a learning curve may reduce variable costs for every subsequent ye
of engine line production. Also, costs can be reduced because progress in modifying one engir
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line can be concurrently applied to additional engine families. In this study, however, these
reductions were not incorporated into the cost estimates.
Equipment manufacturers will have to make a variety of changes depending on the type of engine
modification. In the non-handheld equipment, various levels of changes were characterized for
rear engine riders, lawn tractors, lawn and garden tractors, snowblowers, generators, and pumps.
In the handheld equipment, manufacturers will incur fixed or variable costs that are no greater
than one dollar per equipment unit from either adding a catalyst or from replacing a two-stroke
with a four-stroke engine.
The analysis of fuel impacts showed that fuel savings was greatest for major engine modifications
(SV to OHV and two to four-stroke). In commercial applications, the resulting fuel savings may
significantly offset reduce the incremental costs passed on to the consumer due to modifying the
engine and redesigning the equipment. Lifecycle maintenance would be reduced somewhat by
all engine modifications except for the case of a catalyst added to a two-stroke (due to additional
heat). The most prominent lifecycle maintenance is for SV to OHV conversion (from routine
maintenance), however, this may be nullified by more expensive repairs to OHV versus SV.
Early retirement of capital equipment due to an engine modification is dependent on a complex
set of variable including the rule constraints (e.g., phase-in, start time), the type of modification,
the engine class affected, and the profile of the engine lines in the manufacturer. Generally, in
complying with the phase-in schedule, manufacturers with mostly low-volume engine lines will
be more likely to incur early retirement losses of capital equipment than manufacturers with
medium and high-volume lines.
1CF Consulting Group & Engine. Fuel, and Emissions Engineering, Inc.
October, 1996
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Cost Study for Phase Two Small Engine Emission Regulations
106
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Cost Study for Phase Two Small Engine Emission Regulations
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Cost Study for Phase Two Small Engine Emission Regulations
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October, 1996
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APPENDIX A:
ELECTRONIC CONTROL SYSTEMS AND
EXHAUST AFTERTREATMENT TECHNOLOGIES FOR
NON-HANDHELD ENGINES
-------
This appendix discusses in detail electronic control systems and exhaust aftertreatment
technologies for non-handheld engines.
Electronic Control Systems - Electronic control technology for stoichiometric engines using
three-way catalysts has been extensively developed. These systems rely on monitoring the
exhaust competition to adjust the air-fuel ratio entering the combustion chamber. An automotive
lambda sensor can be used for the larger of the small engines operating at, or near stoichiometric
air-fuel ratios (Technology Task Group, 1995).
The main function of the computer in a feedback emission control system is to adjust the air-fuel
ratio to maintain the narrow range needed by the three-way catalyst. In addition to the air/fuel
ratio, modern computer control systems are also used to control many features that were
controlled .by vacuum switches or other devices on earlier emission control systems. These
include spark timing, exhaust gas recirculation, idle speed, air injection systems, and evaporative
canister purging.
The stringent air-fuel ratio requirements for three-way catalyst operation made electronic control
systems necessary. However, the increased precision and flexibility of air-fuel ratio control
made possible by the electronic system can greatly reduce emissions, even in the absence of a
catalytic converter. Many computer control systems also have the ability to "self-diagnose"
problems with the engine and control system to some extent. The capability to warn the
equipment operator of a malfunction and assist the mechanic in its diagnosis may help to
improve the quality of maintenance.
Exhaust Aftertreatment
A useful alternative to controlling emissions within the engine cylinder is to reduce them by
subsequent treatment of the exhaust gas. This allows the combustion process within the cylinder
to be optimized (within some limits) for maximum power and fuel economy, rather than for
reduced emissions. The two aftertreatment technologies that have seen wide use on spark-
ignition engines are air injection and the various types of catalytic converters. The use of
catalytic aftertreatment allows an order-of-magnitude reduction in pollutant emissions compared
to that achievable with engine-out controls alone. In addition, by reducing the need for engine-
out emissions control, the use of a catalytic converter allows power and fuel economy to be
improved at the same time.
Air Injection - The hot exhaust gases expelled from the cylinder of an Otto-cycle engine contain
significant amounts of unburned hydrocarbons and CO. If sufficient oxygen is present, these
gases will continue to react in the exhaust system, reducing the quantities of these pollutants that
are ultimately emitted from the tailpipe. The reaction rate is extremely sensitive to temperature -
a minimum of 600 °C is needed to oxidize hydrocarbons significantly, and a minimum of
700 °C for CO. To-provide the needed oxygen under rich or stoichiometric conditions, air is
injected into the exhaust manifold. In some motorcycle engines, this air is provided by a system
A-l
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of check valves which uses the normal pressure pulsations in the exhaust manifold to draw in
air from outside.
Air injection was first used as an emission control technique in itself, and is still used for this
purpose in many four-stroke motorcycle engines to meet emission requirements. Air injection
can also be used with oxidizing catalytic converters, in order to ensure that the mixture entering
the catalyst has \ greater than one. In vehicles equipped with three-way catalytic converters,
air injection before the three-way catalyst must be avoided, to allow control of NOx emissions.
Thus, in three-way catalyst engines, air injection is used primarily during cold starts, and is cut
off during normal operation.
Catalytic Converters - The catalytic converter is among the most effective exhaust emission
control devices available. By chemically processing the exhaust to remove pollutants, the
catalytic converter makes it possible to achieve much lower emissions levels than are possible
with in-cyUnder techniques alone. Catalytic converters require lead-free fuel, since lead from
the antiknock compounds often used in gasoline forms deposits on the catalyst material. These
deposits "poison" the catalytic converter by blocking the exhaust gases' access to the catalyst.
As little as a single tank of leaded gasoline will significantly degrade catalyst efficiency.
Two types of catalytic aftertreatment are commonly used for automotive engines: oxidation or
"two-way" catalysts and oxidation/reduction or "three-way" catalysts. Oxidation catalysts use
platinum and/or palladium to increase the rate of reaction between oxygen in the exhaust and
unburned hydrocarbons and CO. Ordinarily, this reaction would proceed very slowly at
temperatures typical of engine exhaust. The effectiveness of the catalyst depends on its tempera-
ture, on the air-fuel ratio of the mixture, and on the mix of hydrocarbons present. Highly
reactive species such as formaldehyde and olefins are oxidized more effectively than less-reactive
species. Short-chain paraffins such as methane, ethane, and propane are among the least
reactive hydrocarbon species, and are difficult to oxidize.
Three-way catalyst formulations use a combination of platinum and/or palladium and rhodium.
In addition to promoting the oxidation of hydrocarbons and CO, these metals also promote the
reduction of NO to nitrogen and oxygen. For the NO reduction to proceed efficiently, an
overall rich or stoichiometric air-fuel ratio is required. The efficiency of NOx control drops
rapidly as the air-fuel ratio becomes leaner than stoichiometric. If the air-fuel ratio is
maintained precisely at or just rich of stoichiometric, a three-way catalyst can simultaneously
oxidize HC and CO while reducing NOx. The "window" of air-fuel ratios within which this is
possible is very narrow, however, and there is a tradeoff between NOx and HC/CO control even
within this window.
Figure 1 shows how the efficiency of a typical three-way catalyst varies as a function of air-fuel
ratio. To maintain the precise air-fuel ratio required, modern gasoline cars use exhaust X sen-
sors (also known as oxygen sensors) with computer electronic control systems for feedback con-
trol of the air-fuel ratio. Such systems are also used on at least two BMW motorcycle models
equipped with three-way catalytic converters.
A-2
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In order to perform their function,
the precious metals in the catalytic
converter must be supported in
intimate contact with the exhaust
gas. The most common type of
catalyst support is a single piece
of ceramic (ceramic monolith)
which is extruded to form numer-
ous small parallel channels and
then fired. The exhaust gases
flow lengthwise through the paral-
lel channels, which provide a very
high surface area. Other types of
supports include ceramic bead
beds and cellular structures of
high-temperature metal alloy. The
latter are used primarily in situa-
tions where mechanical or thermal
shock would likely damage the
relatively brittle ceramics.
Figure 1: Effect of air-fuel ratio on three-way catalyst efficiency.
The chemical reactions promoted
by the catalytic converter take
place at the catalyst surface. Because of the cost,, a typical catalytic converter contains only a
fraction of a gram of the catalytic metals. In order to make efficient use of this expensive
material, it is necessary to give it a very high surface area, and to ensure good access by the
exhaust gases to the catalyst surface. The most common and damaging maintenance problems
with catalytic converters are those which reduce the surface area of catalyst exposed. For
example, engine oil will form deposits in the catalytic converter, blocking the pores and
destroying its efficiency. Excessive temperatures can cause the metal crystals to sinter together,
losing surface area, or even partially melt the ceramic. This causes a loss of porosity and a drop
in conversion efficiency. Such high temperatures are most commonly due to excessive
combustible materials and oxygen in the exhaust (due to a misfiring cylinder, for instance, or
air injection with a very rich mixture). These materials will react in the catalytic converter, and
can easily raise its temperature enough to cause permanent damage. Correcting the cause of the
misfire will not restore emissions performance unless the catalyst is replaced.
A-3
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APPENDIX B:
EXPLODED VIEW AND PARTS OF
NON-HANDHELD AND HANDHELD ENGINES
-------
This appendix presents exploded views and part lists of engines from Briggs and Stratton,
Tecumseh, Kohler, Ryobi, and other manufacturers. Figure 2 shows and Briggs and Stratton
side valve engine and Figure 3 shows a discontinued Briggs & Stratton Vanguard 5hp OHV
engine.
B-l
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1. Nut
2. Starter cup
3. Screen
4. Flywheel
5. Baffle
6. Gasket
7. Intake manifold tube
8. Gasket
9. Seal
10. Governor lever
11. Push nut
12. Washer
13. Cylinder block
14. Gasket
15. Breather &
tappet cover
16. Head gasket
17. Cylinder head
18. Shroud
19. Governor shaft
20. Key
21. Crankshaft
22. Camshan
22A. Camshaft, auxiliary
pto gear
23. Tappets
24. Key
25. Connecting rod
26. Piston
27. Piston rings
28. Valve retainers
29. Valve springs
30. Intake valve
31. Exhaust valve
32. Piston pin
33. Clips
34. Governor &
oil slinger
35. Gasket
36. Crankcase
37. Seal
38. Washer
39. Shaft stop
40. Roll pin
41. Auxiliary pto shaft
42. Seal
21 11 23
rU ,, ,,
Figure 2: Exploded view of a Briggs & Stratton Series 12 side-valve engine
B-2
-------
1. Rocker cover
2. Gasket
3. Valve cap
4. Valve retainer
5. Valve spring
6. Valve seal
7. Gasket
8. Exhaust valve
9. Intake valve
10. Lock screw
11. Adjusting nut
12. Rocker arm
13. Stud
14. Push rod guide
15. Push rod
16. Valve lifter (tappet)
17. Cylinder head
18. Head gasket
Fig. BS14—Explod»dvhwetutghm.
1. Cow
2. Gatkct
3. Breather tuba
4. Oil ml
5. CUapboit
6. Governor lmr
7. Nut
8. Pufthsat
9. Wiuhtr
10. Crsakcut
IL Dowd pia
12. Governor shaft
a Guktt
14. l^pptteortr
15. Piitoa rtngi
16. KatiuiuBf rififl
17. Ptaeopin
18. PUtoo
19. Cocoactutf rod
20. Rod cap
2L Cfinkihift
21 G«ar
23. CiQiinil
24. Gownor
25. Gufeet
28. Oilpaa
27. OU seal
20. Oil pump
iocerrotc
29. Outer rob
30. *0* riof
31. Cow
Source: (Intertec, 1995a)
Figure 3: Exploded view of a Briggs & Stratton Series 9 overhead-valve engine.
B-3
-------
Fig. KQ44—Exploded view of cylinder heed end valve system.
1. Rocker arm cover
2. DreMherhoae
3. Breather a**p
4. Gasket
6. Lnckmtt
6. Pivot bull
7. Rocker arm
ft. Stud
9. ru«h rod
10. Vnlve spring retainer
11. Vnlve spring
12. I^ish rnd (jiiide plate
13. Cylinder head
14. Exhaust valve
15. Intake vslv*
Ifl. UAsket
Fig. KQ53—Exploded view of engine. Governor components (7 and 8) am used on some engines.
1. CmnkeMM cover
2. Cnnkihiftittli
3. ffmlier
4. Snap ring
5. Washer
6. Governor ihaft
7. Needle bearings
8. Bushing
9 Governor Rear
10. Spacer
11. Stub «hMft
13. Main bearing
1.1, CnnhnhflA
14. Main heating
)S. Camshaft nmy.
1fl. Compmsion
irlesae spring
17. Dowel
lft. Crankeaae
19. ristmi
20. Pistnn pin
21. Snap ring
22.
-------
Fig. T210—Exploded view of engirt*.
1. flrrnlher emw
St. Rod rnp
2. Gmlwt
21 Crnrifcutiaft
3. m MHl
2-1. Canvweting rnd
4. Brenthrr flltit sbwnl
24. Rrlflirriaff ring
5. Drfitlhrr vjilrt
25. Pinion & pin
-------
'x>> 4
Fig. T311—Exploited of Model QVRM50
engine. Model OVRM40 Is similar.
t. Flywheel nut
2. Belleville wnsker
3. Sorter tup
1. Hy-lied
5. Spacer
fi. Oil-ienl
7. Breather tube
8. Cmnkcane brentlier
ni«y.
9. Washer
10. Governor pholt
11. Governor fpring
12. Gnvernor lever
13. Clfltnp
M. Key
15. Jlmroljim
16. PtaUm ring*
17. Pirton
IB. Cnnnreling rod
Id. Crankshaft
20. Connecting rod ca£
21. Thrust wailier
21 G»fcd
25. CfankeaMeovej-
(l
-------
Source: (Intertec, 1995a)
1. Oil teal
2. Breather cover
3. Breather valve
4. Catket
5. CrankcaM
7. Governor (heft buahing
B. Seal
B. Wither
10. Colter pin
11. WaiKert
] 2 Governor lever
13. Dowel pin
14. Dowel pin
16. Governor the (I
17. Crankthaft
15. Key
19. Connecting rod
20. Pit ton pin
ai. dip*
22. Pitlon
23. Piilon ring*
24. Kty
25. Gear
26. Snap ring
21. C»m»ha!l
28. Comprettion relem
tpring
29. Oil pump drive pin
30. Governor gear
4 flyweight
31. Snap ring
32. Wather
33. Oil aemn
34. Spring
35. 041 pretaur*
relief valve
36. Guket
37. Oil pan
38. Oil eeal
39. Drain plug
40. Oil pump
inner rotor
41. Outer rotor
42. "O* ring
43. Oil putnp cover
I- Rocker cover
2. Lock screw
3. Adjusting nut
4. Rocker arm
6. 3lud
6. Push rod guide
7. Guaket
8. Cylinder head
9. Head gasket
10. Valve cap
11. Valve retainer
12. Valve spring
13. Valve teal
14. Exhaust valve
16. Intake valve
16. Exhaust gasket
17. Puah rod
18. Cam follower (tappet)
«--0 ».
Figure 7: Exploded view of a Briggs & Stratton Vanguard overhead-valve engine.
B-7
-------
FILE IN SECT 2 OF SERVICE MANUAL
. 12G700 to 12G799
Illustrated Parts List
Industrial/Commercial®
Model Series
12G700 to 12G799
TYPE NUMBER
2615
TO FIND
THE CORRECT NUMBER OF THE PART YOU NEED;
FOLLOW THE INSTRUCTIONS BELOW
A. Rater to Engine Modal, Type and Code Number thai is stamped on the blower housing o( engine.
Engine type numbers such as 0123 01 are listed only as 0123 in most instances. The two digits (Qt
ct02, etc.) ta the rtghtcl the space may be required lor more accurate parts identification in soma
instances. Select the Illustrated Parts List covering the correct Model Series and Type Number.
B. Refer to the Illustrations and compare the original part with Illustration. The number next to the
Illustration is the Reference Number. Assemblies Include all parts shown in frames. All parts shown
in assembly Irames having individual reference numbers can be purchased separately.
C. After the Reference Number has been identified, refer lo the Numerical text, where Reference and
Primary Part Number are listed. THE PRIMARY PART IS USED ON ALL TYPE NUMBERS
EXCEPT THOSE TYPE NUMBERS UNOER "NOTE."
D. If a 'Note* appears below the Primary Pari Number, it means that this part differs from the Primary
Pari for certain types. If your Type number Is listed under "Note,* order ihe part referred to at the
•Note."
E. If your Engine Type Number does not appear after any part number listed under 'Note,* use the
Primary Part Number.
F. For Engine Type Numbers not covered by this book, check other Parts Lists having the same
engine model or contact your source of supply.
PRINTED MU.SX
COPYfUGHTO
BRIGGS &STRATTON
-------
12G700 to 12G799
/K)
f?£
It
9
8
1058 OWNER'S MANUAL |
10
~ REQUIRES SPECIAL TOOLS
TO INSTALL SEE REPAIR
INSTRUCTION MANUAL
REF.
O.
PART
NO.
DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
1
2
3
5
494062
399269
*299819
214349
7 *272916
8 495786
9 *272481
9A *272238
10 94650
11 231933
,13 94547
52 *272199
Cylinder Assembly
Bushing
Seal-Oil
Head-Cylinder
Gasket-Cy finder Hd.
Breather Assembly
Gasket-Valve Cover
Gasket-Balfle Plate
Screw-Hex. Head
Tube-fireather
Screw-Cylinder Hd.
Gasket-Intake Elbow
54
284
306
307
94526
94511
224324
94515
337 802592
383
523
89838
495264
524 *280393
525 495265
572 224328
Screw-Hex. Head
Screw-Hex. Head
Shield-Cylinder
Screw-Hex. Head
Plug-Spark
(Resistor Type)
(1-7/8" High, 48 mm)
Wrench-Spark Plug
Cap-On Fill
Seal-Filler Tube
Tube-Oil Fill
Baffle-Cylinder
625 281085 Manifold-Intake
635 66538 Elbow-Spark Plug
842 *260966 Seal-O-Ring
847 495263 Tube-Oil Fill
869 213512 Seat-Intake Vatve
870 213513 Seat-Exhaust Valve
871 262001 Guide-Exhaust Valve
Note
63709 Guide-Intake
Valve
1019 494256 Label Kit
1058 272262 Owner's Manual
iduded in Gasket Set-Part No 497318.
included in Carburetor Kit-Part No. 493762.
Included in Carburetor Gasket Set-Part No. 490937.
0475-2
Assemblies Include all parts shown in frames.
2
64
-------
12G700 to 12G799
REF.
NO.
PART
NO.
DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
12 *272198
15 94720
16 493362
18 493279
20 *399781
22 94220
Gasket-Crankcase
Plug-Oil Drain
Crankshaft
Note
24 222698
25 494058
For Timing Gear Key-
Order Part No.
94388.
Sump-Engine
Seal-Oil
Screw-Hex. Head
Note
94612 Screw-Hex.
Head
One Used in Hole
Nearest Breather.
Key-Flywheel
Piston Assy.
(Standard)
494059 Piston Assy.
(.010* O.S.)
494060 Piston Assy.
(.020-O.S.)
494061 Piston Assy.
(.030" O.S.)
26 493261 Ring Set
(Standard)
493388 Ring Set
(.010* O.S.)
493389 Ring Set
(.020* O.S.)
493390 Ring Set
(.030* O.S.)
27 26026 Lock-Piston Pin
28 298909 Pin-Piston
(Standard)
298908 Pin-Piston
(.005* O.S.)
29 490566 Rod-Connecting
32 94699
262651
262652
262224
93312
262204
46 492B30
47 493737
492349
67072
33
34
35
40
45
227
230
562 92613
592 231082
615 94474
616 262578
741 262598
490743 Rod-
Connecting
(.020*Undersize)
Screw-Connecting
Rod
Valve-Exhaust
Valve-Intake
Spring-Valve
Retainer-Valve
Tappet-Valve
Gear-Cam
Slinger-Oil
Lever-Governor
Washer-Governor
Crank
Bolt-Governor Lever
Nut-Hex.
Fastener
Crank-Governor
Gear-Timing
* Included in Gasket Set-Part No 497316.
• Included in Carburetor Kit-Part No. 493762.
~ Included in Carburetor Gasket Set-Part No. 490937.
0475-3 Assemblies include all parts shown tn frames.
3
-------
12G700 to 12G799
620A
202
619
riEF.
NO.
PART
NO.
DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
98A
188 A
201
202
209
268
493280 Screw-Speed Ad].
94644 Screw-Hex. Head
262579 Link-Governor
262782 Link-Control
262660 Spring-Governor
66986 Casing-Wire
(48* Long)
¦ Note •
If Longer Casing is
Needed, Specify
Length in Inches and
Cut to Required
Length.
269 26099 Wire-Control
(54* Long)
Note
If Longer Wire is
Needed, Specify
Length in Inches and
Cut to Required
Length.
270
271
618
619
620
620A
621
670A
63426
290568
262749
94620
495976
494112
396847
493823
843 272616
Locknut-Casing
Lever-Control
Spring-Return
Screw-Self Tap
Bracket-Control
Bracket-Control
Switch-Stop
Spacer-Bracket
(Includes 2)
Sleeve-Control
* Included in Gasket Set-Part No 497316.
• Included in Carburetor Kit-Part No. 493762.
~ Included in Carburetor Gasket Set-Part No. 490937.
0475-4
Assemblies include all parts shown in frames.
4
64
-------
12G700 to 12G799
124
L2£L
| 131
T
634©
(§)634
125
§134
104
v ' |133
F.
PART
REF.
PART
REF. PART
).
NO.
DESCRIPTION
NO.
NO.
DESCRIPTION
NO. NO.
DESCRIPTION
95
94098
Screw-Round Head
127
•
Plug-Welch
617 *#270344
Seal-Intake Elbow
98
398185
Screw-Idle Adjustment
(Sold in Kit Only).
634
Washer-Shaft
104
•231371
Pin-Float Hinge
130
223470
Valve-Throttle
(Sold in Kit Only).
108
223471
Valve-Choke
131
493267
Shaft-Throttle
955 493869
Screw-Bowl Mtg.
116««
Gasket-Sealing
133
398187
Float-Carburetor
(Standard)
(Sold in Kit Only).
134
•398188
Valve-Needle
Note
118
493765
Valve-Needle
(Includes Seat)
493763 Screw-Bowl
124
94525
Screw-Carburetor
137«4
Gasket-Bowl
Mtg. (High Altitude)
Mounting
(Sold In Kit Only).
975 493640
Bowt-Float
125
494217
Carburetor
141
494218
Shaft-Choke
uded in Gasket Set-Part No 497316.
• included in Carburetor Kit-Part No. 493762.
4 Included in Carburetor Gaskel Set-Part No. 490937.
0475-5 Assemblies include all parts shown in frames.
5
-------
12G700 to 12G799
969^
967
971
163
966
258
REF.
NO.
PART
NO,
DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
REF.
NO.
PART
NO,
DESCRIPTION
163 *272653 Gasket-Air Cleaner
*>36 262461 Link-LockOut
^58 94512 Screw-Hex. Head
423 037S8 Screw-Hex. Head
529 281299 Grommat
621 396847 Switch-Stop
922 262640 Spring-Brake
923 493442 Brake Assembly
942 224494 Bracket-Brake
966 496116 Base-Atr Cleaner
967 491588 Filter-Air
968 281340 Cover-Air Cleaner
969 94120 Screw-Cover Mtg.
871 94121 Screw-Air Cleaner
991 493537 Pre-Filter
* Included in Gaskel Set-Part No 497316.
• Included in Carburetor Kit-Part No. 493762.
~ Included in Carburetor Gasket Set-Part No. 490937.
0475-6
Assemblies include all parts shown in frames.
6
64
-------
12G700 to 12G799
REF. PART
NO. NO. DESCRIPTION
23 492177 Flywheel
37 224511 Guard-Flywheel
38 94619 Screw-Hex. Head
304 493293 Housing-Blower
REF PART
NO. NO. DESCRIPTION
305 94729 Screw-Sem
332 92284 Nut-Flywheel
333 802574 Armature-Magneto
334 94731 Screw-Sem
REF. PART
NO. NO. DESCRIPTION
356 398703 Wir&-Stop
363 19069 Puller-Flywheel
455 224250 Cup-Starter
851 493880 Terminal-Cable
* Included in Gasket Set-Part No 497316.
• Included in Carburetor Kit-Part No. 493762.
~ Included in Carburetor Gasket Set-Part No. 490937.
0475-7 Assemblies Include all parts shown In frames.
7
-------
12G700 to 12G799
:F.
PART
REF.
PART
REF.
PART
.
-------
12G700 to 12G799
i_i: PART
NO.' NO. DESCRIPTION
REF. PART
NO. NO. DESCRIPTION
REF. PART
NO. NO. DESCRIPTION
187 492790 Line-Fuel
(6-3/4" Long)
188 398540 Screw-Tank Mounting
265 213146 Clamp-Casing
1
267 94694 Screw-Sell Tap
284 94511 Screw-Hex. Head
601 93053 Clamp-Hose
670 280512 Spacer-Fuel Tank
949 281136 Guard-Finger
957 397974 Caj>-Fuel Tank
972 497224 Tank-Fuel
* Included in Gasket Set-Part No 497316.
• Included in Carburetor Kit-Part No: 493762.
+ Included in Carburetor Gasket Set-Part No. 490937.
0475-9 Assemblies include all parts shown in frames.
9
-------
12G700 to 12G799
o
0 'o
X'
X
REF. PART
NO. NO. DESCRIPTION
REF. PART
NO. NO. DESCRIPTION
REF. PART
NO. NO. DESCRIPTION
81 223664 Lock-Muffler Screw
300 496106 Muffler-Exhaust
346 93705 Screw-Hex. Head
346A 94602 Screw-Hex. Head
613 94231 Screw-Hex. Head
676 396548 Deflector-Muffler
832 494224 Guard-Muffler
883 *272253 Gasket-Muffler
.
* Included in Gasket Set-Part No 497316.
• Included In Carburetor Kit-Part No. 493762.
~ Included in Carburetor Gasket Set-Part No. 490937.
0475-10 Assemblies Include all parts shown in frames.
10
-------
12G700 to 12G799
977 CARBURETOR
GASKET SET
121 CARBURETOR KIT
F.
NO.
PART
NO.
DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
3 *299816 Seal-03
7 *272916 Gasket-Cylinder Hd.
9 *272481 Gasket-Breather
9A *272238 Gasket-Breather
12 *272198 Gasket-Crankcase
20 *399781 Seat-Oil
52 *272199 Gasket-Intake Elbow
104 *231371 Pin-Float Hinge
'16 Gasket-Sealing
{Sold in Kit Only).
1t8 *493765
121 493762
127 •
134 *398168
137
163 *272653
Valve-Needle
Carburetor KH
Plug-Welch
(Sold In Kit Only).
Valve-Needle
{Includes Seat)
Gasket-Bowl
(Sold In Kit Only).
Gaskel-Air Cleaner
358 497316
524 *280393
617 •~270344
634
842 *280966
883 *272253
977 49Q937
Gasket Set
Seal-Filler Tube
Seat-Intake Elbow
Washer-Shaft
(Sold In Kit Only).
Seal-O-Ring
Gasket-Muffler
Gasket Set-
Carburetor
* mduded in Gasket Set-Part No 497316.
* Included in Carburetor Kit-Part No. 493762.
* Induded in Carburetor Gaskal Set-Part No. 490937.
0475-11 Assemblies Include all parts shown In frames.
11
64
-------
WS-i5.lo.-M5
REPLACES form MS-251B-S/9*
F)U= IN SECT. 2 OF SERVICE MANUAL
99700 to 99799
B
Illustrated Parts List
Model Series
99700 to 99799
TYPE NUMBERS
0100 through 0103,
01 tO through 0118,
0601,0606,
0610,0611,0612,
0614,0615,
0618 through 0626,
0630 through 0638,
0814, 0916, 0918,
0920, 0925, 0934,
0935, 0937, 0938,
0942,0945,
TYPE NUMBERS
3015,3016,
3024 through 3026,
3101,3102, 3103,
3111 through 3120,
3141 through 3143,
3515,3525,3601,
3608 through 3613,
3616,3617, 3620,
3624, 3925, 3641,
3642, 3643, 3650.
TO FIND
THE CORRECT NUMBER OF THE PART YOU NEED:
FOLLOW THE INSTRUCTIONS BELOW
Refer to the Engine Model, Type and Code Number that is stamped on the Wower housing of en-
gine. Engine type numbers such as 0123 01 are listed only as 0123 in most instances. The two
digits (01 or 02, etc.) to the right of the space may be required for more accurate parts identification
in some instances. Select the illustrated Parts List covering the correct Model Series and Type
Number.
Refer to Ihe illuslralions and compare the original part with illustration. The number nexl.to thai-
lustration is the Reference Number. Assemblies include all parts shown in frames. All parts shown
in assembly frames having individual reference numbers can be purchased separately.
C. After the R eference N umber has been identified, refer to Ihe Numerical text, where Reference and
Primary Part Number are listed. THE PRIMARY PART IS USED ON ALL TYPE NUMBERS EX-
CEPT THOSE TYPE NUMBERS UNDER "NOTE.*
D. If a "Note" appears below the Primary Part Number, it means that this part differs from the Primary
Part for certain types. If your Type number Is listed under "Note," order the part referred to at the
"Note."
E. If your Engine Type Number does not appear after any part number listed under "Note," use the
Primary Part Number.
F. For Engine Type Numbers not covered by this booh, check other Parts Lists having the same en-
gine model or contact your source of supply.
PRINTED tN U.S.A.
COPYRIGHT®
-------
99700 to 99799
V> * REQUIRES SPECIAL TOOLS
10 TO INSTALL SEE REPAIR
INSTRUCTION MANUAL 346
1019 LABEL KIT
1058 OWNER'S MANUAL
REF.
PART
REF.
PART
REF.
PART
NO.
NO.
DESCRIPTION
NO.
NO. DESCRIPTION
NO.
NO.
DESCRIPTION
1
494728
Cylinder Assembly
Note
635
66538
Boot-Spark Plug
2
293708
Bushing
231685 Tube-Breather
718
230192
Pin-Cyiinder
3
*299819
Seal-Oil
(Used Before Code
868 *4493661
Seal-Valve
S
496054
Head-Cylinder
Date 93110100).
868A *£272376
Gasket-Valve
(Used After Code Date
13
94547 Screw-Cylinder Hd.
871
262718
Bushing-Guide
92080400).
33
493778 Valve-Exhaust
883 *4272313
Gasket-Exhaust
Note
34
493777 Valve-Intake
1019
495337
Label Kit
494726 Head-Cyl.
35
262716 Spring-Valve
1022
*A272323
Gasket-Rocker Cover
(Used Before Code
40
262552 Retainer-Valve
1023
224588
Cover-Rocker
Date 92080500).
45
262679 Tappet-Valve
1026
493527
Rod-Push
7
Gasket-Cylinder Head
122
281193 Spacer
1029
224111
Arm-Rocker
See Last Pages.
166
94555 Stud-Rocker Arm
1034
224400
Guide-Push Rod
8
494489
Breather Assembly
192
492160 Ball & Screw-
1058
273123
Owner's Manual
9
*272481
Gasket-Breather
Rocker Arm
(Used After Code Date
9A
*272238
Gasket-Breather
238
262499 Cap-Valve
94112000).
10
94650
Screw-Hex.
307
94515 Screw-Hex.
Note
11
231933
Tube-Breather
337
491055 Plug-Spark
272520 Owner's
(Used After Code Date
346
94513 Screw-Hex.
Manual
93103100).
383
19374 Wrench-Spark Plug
(Used Before Code
572
224328 Baffle-Cylinder
Date 94112100).
* Included in Gasket Set-See Ret. No. 358.
A Included in Valve Overhaul Kit-See Ref. No. 1033.
~ Included in Carburetor Gasket Set-Part No. 490937.
2518-2
Included in Carburetor Kit-See Ref. No. 121.
Assemblies include all parts shown in frames.
2
35
-------
99700 to 99799
REF.
PART
REF.
PART
REF.
PART
NO.
NO.
DESCRIPTION
NO.
NO.
DESCRIPTION
NO.
NO. DESCRIPTION
12
*272324
Gasket-Crankcase
26
493782
Ring Set
230
67072 Washer
15
94613
Plug-Oil Drain
(Standard)
284
94511 Screw-Hex.
16
Crankshaft
495268 Ring Set
346
94513 Screw-Hex.
See Last Pages.
(.010 O.S.)
377
93065 Key-Woodruff
18
493901
Sump-Engine
495270 Ring Set
523
Cap-Oil Fill
20
*399781
Seal-Oil
(.020 O.S.)
See Last Pages.
22
94220
Screw-Hex.
495272 Ring Set
524
*280393 Seal-Fill Tube
Note
(.020 O.S.)
525
Tube-Oil Fill
94612 Screw-Hex.
27
262514
Lock-Piston Pin
See Last Pages.
One Used in Hole
28
492765
Pin-Piston
562
92613 Bolt-Carriage
Nearest Breather.
(Standard)
592
231082 Nut-Hex.
25
493781
Piston Assy.
29
493049
Rod-Connecting
615
94474 Pushnut
(Standard)
493689 Rod-Conn.
616
262578 Crank-Governor
495267 Piston Assy.
(.020* Undersize)
741
262598' Gear-Timing
(.010 O.S.)
32
94404
Screw-Conn. Rod
842
*280966 Seal-O-Ring
495269 Piston Assy.
46
493310
Gear-Cam
847
Tube-Oil
(.020 O.S.)
116A
*280891
Seal-O-Ring
See Last Pages.
495271 Piston Assy.
219
493719
Gear-Governor
979
492756 Cover-Oil Pump
(.030 O.S.)
227
492349
Lever-Governor
1024
493884 Pump-Oil
A Included in Valve Overhaul Kit-See Ref. No. 1033.
~ Included in Carburetor Gasket Set-Part No. 490937.
2518-3
Included in Carburetor Kit-See Ref. No. 121.
Assemblies include all parts shown in frames.
3
35
-------
99700 to 99799
125
134
KJ\ 104
133
1011
REF.
PART
REF.
PART
REF.
PART
¦—j
NO.
NO.
DESCRIPTION
NO.
NO.
DESCRIPTION
NO.
NO.
DESCRIPTION
95
94098
Screw-Round Head
125
497718
Carburetor
141
494218
Shaft-Choke
98
398185
Screw-Idle Adjustment
(Used After Code Date
617 •~270344
Seal-Intake Elbow
104
•231371
Pin-Float Hinge
94112000).
634
•~
Washer-Shaft
108
223471
Valve-Choke
494971 Carburetor
V
(Sold in Kit Only)
116
Gasket-Sealing
(Used Before Code
955
494870
Screw-Fuel Bowl
(Sold in Kit Only)
Date 94112100).
(Standard)
118
•497717
Valve-Idle Adjust
127
•
Plug-Welch
Note
(Used After Code Date
(Sold in Kit Only)
496495 Screw-Fuel
94112000).
130
223470
Valve-Throttle
Bowl
: Note
131
493267
Shaft-Throttle
(High Altitude)
•493765 Valve-Idle
133
398187
Float-Carburetor
975
493640
Bowl-Float
Adjust
134
•398188
Valve-Needle
1011
281244
Tube-Vent
(Used Before Code
(Includes Seat)
1091
•281425
Cap-Limiter
Date 94112100).
137
•~
Gasket-Float Bowl
(Used After Code Date
124
94656
Screw-Hex.
(Sold in Kit Only)
94112000).
* Included in Gasket Set-See Ref. No. 358. • included in Carburetor Kit-See Ref. No. 121.
A Included in Valve Overhaul Kit-See Ref. No. 1033.
~ Included in Carburetor Gasket Set-Part No. 490937.
2518-4 Assemblies include all parts shown in frames.
4
-------
99700 to 99799
REF.
PART
REF.
PART
REF.
PART
NO.
NO.
DESCRIPTION
NO.
NO. DESCRIPTION
NO.
NO.
DESCRIPTION
52 *A272487
Gasket-Intake
268
66986 Casing-Wire
423
93758
Screw
98A
493280
Screw Assy.-
(48" Long)
445
494586
Filter-Air
Speed Adjustment
Note
467
493903
Knob
163
*272512
Gasket-Air Cleaner
If Longer Casing is
529
281418
Grommet
164
494729
Manifold-Intake
Needed, Specify
(Used After Code Date
201
262827
Link
Length in Inches; if
93101700),
209
Spring-Governor
Shorter Casing is
Note
See Last Pages.
Needed Order and Cut
281201 Grommet
265
213146
Clamp-Casing
to Required Length.
(Used Before Code
265A
221535
Clamp-Casing
269
26099 Wire-Control
Date 93101800).
267
94694
Screw-Hex.
(54" Long)
535
272533
Filter-Air
258
94512
Screw-Hex.
Note
618
262749
Spring
If Longer Wire is
620
494538
Bracket-Control
Needed, Specify
621
396847
Switch-Stop
Length in Inches; if
922
262640
Spring-Brake
Shorter Wire is
923
493442
Brake
Needed Order and Cut
935
398758
Switch-Interlock
to Required Length.
968
231196
Cover-Air Cleaner
270
63426 Locknut-Casing
970
94577
Screw-Air Cleaner
271
290568 Lever-Control
971
94655
Screw-Shoulder
* Included in Gasket Set-See Ref. No. 358.
A Included in Valve Overhaul Kit-See Ref. No. 1033.
~ Included in Carburetor Gasket Set-Part No. 490937.
251&-5
• Included in Carburetor Kit-See Ref. No. 121.
Assemblies include all parts shown in frames.
5
35
-------
99700 to 99799
REF.
PART
REF.
PART
REF.
PART
NO.
NO.
DESCRIPTION
NO.
NO.
DESCRIPTION
NO.
NO. DESCRIPTION
55
494671
Housing-Rewind
60
393152
Grip-Starter Rope
608
494960 Starter-Rewind
Starter
69
280973
Washer-Spring
Include(s):
56
493824
Pulley-Starter
69A
224322
Washer-Flat
92987 Nut-Hex
57
262594
Spring-Rewind Starter
456
224321
Retainer-Spring
94128 Screw-Hex.
58
280399
Rope-Starter
459
492833
Pawl-Ratchet
946
223294 Guide-Rope
(Cut to 88-5/8")
461
262626
Pin-Shaft
1016
224278 Spacer
59
396892
Insert-Handle
515
262625
Spring-Retainer
* Included in Gasket Set-See Ref. No. 358. • Included in Carburetor Kit-See Ref. No. 121.
A Included in Valve Overhaul Kit-See Ref. No. 1033.
~ Included in Carburetor Gasket Set-Part No. 490937.
2518-6 Assemblies include all parts shown in frames.
6
-------
99700 to 99799
7S9
REF.
NO.
PART
NO.
DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
REF.
NO.
PAFTT
NO.
DESCRIPTION
23 492177
23 A 492175
Flywheel
Flywheel
- Note ¦
24
37
38
304
222698
224511
94608
494961
305
332
94510
92284
492893 Flywheel
Used on Type No(s).
0625, 0626, 0636,
0925.
Key-Flywheel
Guard-Flywheel
Screw-Hex.
Housing-Blower
Used on Engines With
Band Brake.
Note
494962 Housing-
Blow ar
Used on Engines
Without Band Brake.
Stud-Stator Mtg,
Nut-Flywheei
333
334
346
346A
356
94513
94582
398808
802574 Armature-Magneto
93361 Screw-He*.
Screw-He*.
Screw-Hex.
Wire-Stop
Note
496381 Wire-Stop
(Used After Code Date
93060300).
398153 Wire-Stop
(Used Before Code
Date 93080400).
Used on Type No(s).
0110,0610,3111,
3611,3624.
496721 Wire-Stop
Used on Type No(s).
0625.
363 19069 Flywheel Puller
455 224250 Cup-Flywheel
474 492841 Alternaior
482 94512 Screw-Hex.
527 224722 Clamp-Tube
789 494543 Harness-Wiring
Used on Engines
Without Band Brake.
789A 494544 Harness-Wiring
Used on Engines With
Band Brake Except as
Listed Below:
Note
493380 Harness-
Wiring
Used on Type No(s).
0916,3616.
851 221798 Terminal-Cable
941 281206 Cover-Linkage
* Included in Gasket Set-See Rel. No. 358.
A Included in Valve Overhaul Kit-See Ref. No. 1033.
~ Included in Carburetor Gasket Set-Part No. 490937.
Included in Carburetor Kit-See Ret. No. 121.
2518-7
Assemblies include all parts shown in frames.
7
35
-------
REF.
PART
REF.
PART
REF
PART
NO.
NO.
description'
NO.
NO.
DESCRIPTION
NO.
NO.
DESCRIPTION
65
94058
Screw-Guard
601
93053
Clamp-Hose
0920. 0925, 0934,
Mounting
670
280512
Spacer-Fuel Tank
0935, 0937, 0938,
187
296004
Line-Fuel
832
494719
Guard-Muffler
0942,0945,3114,
(23" Long Cut to Suit)
883 *4272313
Gasket-Exhaust
3141,3142, 3616,
Hole
949
281197
Guard-Starter
3620,3625.3641,
393815 Line-Fuel
Note
3642, 3650.
(11" Long Cut to Suit)
281406 Guard-Starter
957
397974
Cap-Fuel Tank
188
398540
Screw-Tank Mounting
Used on Type No(s).
957A
494277
Cap-Fuel Tank
284
94511
Screw-Shoulder
0632,0633, 0634,
9S8
493960
Valve-Shut-Off
300
494717
Muffler-Exhaust
0636, 0637, 0638,
972
494973
Tank-Fuel
346
94513
Screw-Hex.
0814,0916, 0918,
994
493662
Arrester-Spark
346B
93705
Screw-Hex.
* Included in Gasket Set-See Ref. No. 358. • Included in Carburetor Kit-Sea Ref. No. 121.
A Included in Valve Overhaul Kit-See Ref. No. 1033.
~ Included in Carburetor Gasket Set-Part No. 490937.
2518-8 Assemblies include all parts shown in frames.
B
-------
99700 to 99799
REF.
PART
REF.
PART
REF.
PART
NO.
NO..
DESCRIPTION
NO.
NO.
DESCRIPTION
NO.
NO.
DESCRIPTION
22A
94268
Screw-Hex.
544
492921
Armature-Starter
801
492335
Cap-Drive
74
93490
Screw-Hex.
548
492919
Washer Set
802
492922
Cap-End
309
494233
Motor-Starter
782
281127
Gear-Starter
803
492920
Housing-Starter
310
94051
Screw-Hex.
783
261606
Gear-Starter
937
281125
Spline-Starter
510
494147
Drive-Slarter
784
224262
Cover-Gear
938
93941
Retainer-Lock
513
394815
Clutch-Drive
785
272201
Gasket-Cover
* Included in Gasket Set-See Ref. No. 358. • Included in Carburetor Kit-See Ref. No. 121.
a Included in Valve Overhaul Kit-See Ref. No. 1033.
~ Included in Carburetor Gasket Set-Part No. 490937.
2518-9 Assemblies include all parts shown in frames.
9
-------
99700 to 99799
REF.
NO.
PART
NO.
DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
3 *299619
7
9 *272481
9A *272238
12 *272324
20 *399781
52 *4272487
104 *231371
116 •~
116A *280691
118 *497717
Seal-Oil
Gasket-Cylinder Head
See Last Pages.
Gasket-Breather
Gasket-Breather
Gasket-Crankcase
Seal-Oil
Gasket-Intake
Pin-Float Hinge
Gasket-Sealing
(Sold in Kil Only)
Seal-O-Ring
Valve-Idle Adjust
(Used After Code Date
94112000).
¦ Note -
•493765 Valve-Idle
Adjust
(Used Before Code
Date 94112100).
121 497719 Carburetor Kit
(Used After Code Date
94112000).
493762 Carburetor Kit
(Used Before Code
Date 94112100).
127 • Plug-Welch
(Sold in Kit Only)
134 *398188 Valve-Needle
(Includes Seat)
137 Gasket-Float Bowl
(Sold in Kit Only)
163 *272512 Gasket-Air Cleaner
358
524 *280393
617 •~270344
634 •~
842 *280966
868 *4493661
868A *4272376
883 *4272313
977 490937
1022 *4272323
1091 *281425
1033
Gasket Set
See Last Pages. I
Seal-Fill Tube
Seal-Intake Elbow
Washer-Shaft I
(Sold in Kit Only) '
Seal-O-Ring
Seal-Valve .
Gasket-Valve |
Gasket-Exhaust
Gasket Set-
Carburetor i
Gasket-Rocker Cover j
Cap-Limiter
(Used After Code Date
94112000). I
Kit-Valve Overhaul j
See Last Pages.
* Included in Gasket Sel-See Ref. No. 358.
A Included in Valve Overhaul Kit-See Ref. No. 1033.
~ included in Carburetor Gasket Set-Part No. 490937.
2513-10 Assemblies include all parts shown In frames.
10
Included in Carburetor Kit-See Re). No. 121.
35
-------
99700 to 99799
REF.
NO.
PART
NO.
DESCRIPTION
REF. PART
NO. NO. DESCRIPTION
REF.
NO.
PART
NO.
DESCRIPTION
7 *A272314 Gasket-Cylinder Head
(Used After Code Date
92080400).
Note
*A272488 Gasket-
Cylinder Head
(Used Before Code
Date 92080500).
494638 Crankshaft
Note
16
For Timing Gear Key-
Order Part No.
94388.
493725 Crankshaft
Used on Type No(s).
0638, 0938.
494635 Crankshaft
Used on Type No(s).
0118,3025,3111.
494636 Crankshaft
Used on Type No(s).
0114, 3024,3114,
3141, 3142.
494637 Crankshaft
Used on Type No(s).
0100,0102,0103,
0112,0116, 3015,
3101,3103,3120,
3143.
494639 Crankshaft
Used on Type No(s).
0110, 0111, 0115,
3026.
495515 Crankshaft
Used on Type No(s).
0623.
495793 Crankshaft
Used on Type No(s).
0618,0622,0633,
0918, 0945,3525,
.3611, 3617, 3624,
3625.
495794 Crankshaft
Used on Type No(s).
3641.
209
495795 Crankshaft
Used on Type No(s).
0612, 0625, 0626,
0630, 0636; 0916,
0920, 0925, 0935,
0942, 3515, 3601,
3608, 3616, 3620,
3642, 3643.
495796 Crankshaft
Used on Type No(s).
0601, 0606. 0614.
0619, 0621,0632,
0634, 0814, 0934,
3612, 3613, 3650.
495797 Crankshaft
Used on Type No(s).
0610,0611,0615,
0624, 0637, 0937.
262678 Spring-Governor
Note
262657 Spring-Gov.
Used on Type No(s).
0110,0610,0625,
0925, 0945,3111,
3611,3617,3624,
3625.
262659 Spring-Gov.
Used on Type No(s).
0100,0103, 0626,
0636, 0942, 3015,
3016. 3024, 3025,
3026.3101,3103.
3114; 3141, 3142,
3515.3525, 3601,
3608, 3641,3642.
262660 Spring-Gov.
Used on Type No(s).
3143,3643.
262661 Spring-Gov.
Used on Type No(s).
0638, 0938.
262665 Spring-Gov.
Used on Type No(s).
0115,0615, 0637,
0937,3112,3113.
3612, 3613.
262666 Spring-Gov.
Used on Type No(s).
0116, 0619,0622.
358
523
525
262667 Spring-Gov.
Used on Type No(s).
0633, 0916, 0920,
3120.3616, 3620.
262678 Spring-Gov.
Used on Type No(s).
0632. 0634, 0814,
0918. 0934, 0935.
3650.
496055 Gasket Set
(Used After Code Date
92080400).
Note
494963 Gasket Set
(Used Before Code
Date 92080500).
495264 Cap-Oil Fill
(Used After Code Date
92083000).
Note
493950 Cap-Oil Fill
(Used Before Code
Date 92083100).
495265 Tube-Oil Fill
(Used After Code Date
92083000).
Note
647
1033
493952 Tube-Oil Fill
(Used Before Code
Date 92083100),
495263 Tube-Oil Fill
(Used After Code Date
92083000).
Note
493459 Tube-Oil
(Used Before Code
Date 92083100).
496056 Overhaul Kit-Valve
(Used After Code Date
92080400).
Note
495772 Overhaul Kit-
Valve
(Used After Code Date
92080500).
* Included in Gasket Set-See Ref. No. 358.
A Included in Valve Overhaul Kit-See Ref. No. 1033.
~ Included in Carburetor Gasket Set-Part No. 490937.
Included in Carburetor Kit-See Ref. No. 121.
2518-11
Assemblies include all parts shown In frames.
11
35
-------
General Purpose Engine
GXV140
HONDA
Power
Equipment
Parts Catalog
First Edition
May, 1994
AMERICAN HONDA MOTOR CO., INC.
© American Honda Motor Co., Inc. 1994
14ZG90E1
PRINTED IN USA
-------
CYLINDER HEAD
f
ZG93£0200
GXV140
BLOCK NO. E-2
No DESCRIPTION
1 HEAD COUP/ CYLINDER
2 GUIDE, EX. VALVE (OVERSIZE)
3 CLIP, VALVE GUIDE
4 GASKET, CYLINDER HEAD
5 COVER, HEAD
6 GASKET, HEAD COVER
7 PIN A, DCWEL, 10X16
8 BOL1", FLANGE, 6X14
9 BOLT, FLANGE, 8X50
10 PLUG, SPARK (BP4ES NGK)
PLUG, SPARK (BPR4ES NGK)
PLUG, SPARK (BPR5E5 NGK)
PLUG, SPARK (BPR6ES NGK)
TYPE
ENGINE
SERIAL NUMBER
FJROM
TO
Q
T
y
R
- E
HONDA
Q
PART NUMBER
CODE
1
1220Q-ZG9-800
4452470
(1)
122Q5-ZE1-315
1899848
1
12216-IE5-300
2399780
1
12251-ZG9-000
3337821
1
12311-ZG9-800
4428165
1.
12391-ZE7-T00
4J11437
2
94301-10160
GQ582Q6
4
95701-06014-00
2410B84
4
95701-08050-00
2935740
(1)
98079-54841
1455427
(1)
98079-54646
1521756
1
98079-55846
1672443
<1)
98079-56846
1441112
§ AMERICAN HONDA MOTOR CO, 1TO. 1094
Bl
-------
CYLINDER BARREL
ZG33E0300
GXV140
Ref BLOCK NO. E-3
No. DESCRIPTION
AYP „
1 PAN ASSY., OIL (USA-PUSH)
2 GASKET, OIL PAH
3 BARREL CCMP., CYLINDER
4 PLATE, GUIDE
5 CAP COMP., BREATHER CHAMBER
6 FILTER, BREATHER
7 VALVE, BREATHER
8 GASKET, BREATHER CHAMBER
9 PIPE, OIL DEFENSE
10 GAUGE COUP., OIL LEVEL
11 EXTENSION, OIL FILLER
12 GOVERNOR ASSY.
13 WEIGHT, GOVERNOR
14 HOLDER, GOVERNOR WEIGHT
15 PIN, GOVERNOR WEIGHT
16 SHAFT, GOVERNOR HOLDER
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
Q
T
Y
n
E
Q
PART NUMBER
HONDA
CODE
//?/£> -aGf Vtf}
9?2
11300-ZG9-800
4536934
11381-ZG9—TOO
4224259
121G0-IG9-800
4459491
12125-ZG9-000
3307287
12360-ZE6—000
1662535
1236P-ZE6-010
2794402
12372-879-000
0452151
12373-2E6—000
1452622
12385-ZE6-000
1825702
15620-ZE6-810
3337862
15630-ZE6-810
3337870
1651Q-ZE6-000
3337904
16511-ZE1-000
1427228
16512-ZE6-000
1452846
16513-ZE1-000
1427244
16515-ZE6-000
1452853
9 AMERICAN HONQA MOTOR CO, LTD, IBM
-------
CYLINDER BARREL
ZG93C0300
GXV140
TYPE
N
1
N
2
ENGINE
SERIAL NUMBER
o
T
Y
Ref BLOCK NO. E-3
A
1
A
2
R
E
Q
HONDA
No. DESCRIPTION
a
b
c
d
FROM TO
PART NUMBER
CODE ¦
17 PLATE, GOVERNOR SHAFT HOLDER ....
18 SLIDER, GOVERNOR
a
a
b
h
c
f
d
d
1
1
16525-ZE6-010
16531-IE1-0OO
3337912
1427251
19 SHAFT GOVERNOR ARM
b
c
d
d
d
1
16541-ZE7-000
1724»-ZE6-OOD
90014-952-000
2289643
1453000
0803619
Jfi rni 1 SB FUTFtKTflM
b
h
1
21 BOLT, FLANGE, 6X14
a
r
?
22 BOLT, FLANGE, 6X32
a
b
c
rl
1
90017-883-000
0636076
23 BOLT, DRAIN PLUG
a
h
r
d
,, m „m m m Mm m m
1
90131-ZE1-000
1431246
24 WASHER, THRUST, 6HN
a
h
r
d
r | *******
1
90451-ZE1-000
2413862
WASHER. THRUST, 6MH
a
h
c
d
eeewwewe L ,
1
90451-898-000
1106764
25 WASHER. DRAIN PLUG, 10.2RH
a
h
c
d
m ^ M |B , m M a 11 m |
1
90601-ZE1-000
1436S83
26 CLIP GOVERNOR HOLOER
a
h
r.
d
1
90602-ZE1-000
2456697
77 fill ^FAI
b
f
d
d
1
9120Z-ZE6-003
3270246
7fi SF4I fill
a
b
1
91231-891-003
0801043
29 OIL SEAL. 25X38X7 (ARAI) -
a
h
r.
d
m „ ^ w , -
1
91252-868-003
0671628
Tfi n-Aiiuc 77 5*? 7
b
d
1
91301-ZE9-003
22B0006
n-RTMG 7
a
h
d
1
91301-805-000
0065185
1
4 © AMERICAN HONDA MOTOR CO. LTD. 1994
-------
CRANKSHAFT
— 5
ZG93E0700
GXVI40
, BLOCK NO. E-7
. st.
No. DESCRIPTION
1 WING SET, PISTON (STO.)
RING SET, PISTON (0.25)
RING SET, PISTON (0.50)
RING SET, PISTON (0.75)
2 PISTON (STO)
PISTON (0.25)
PISTON (0.50)
PISTON (0.75)
3 PIN, PISTON
4 BOO ASSY., CONNECTING
5 CRANKSHAFT COUP
CRANKSHAFT COMP
6 GEAR, TIMING
7 BOLT, CONNECTING ROD
8 CLIP, PISTON PIN, 13KM
9 BASING, MJIftLEftLL, tlfll
HOT.O* MOTOR 0
-------
CAMSHAFT
ZG93E0900
GXV140
Ret.
Na
BLOCK NQ
DESCRIPTION
E-9
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
Q
T
Y
R
E
a
PART NUMBER
HONDA
CODE
1 CAHSHAFT ASSY
2 ROD, PUSH
3 ARM, VALVE ROCKER
4 LIFTER, VALVE
5 PIVOT, ROCKER ARM .....
6 SPRING, WEIGHT RETURN .
7 VALVE, IN
8 VALVE, EX
9 SPRING, VALVE
10 RETAINER, VALVE SPRING
11 PLATE, PUSH ROD GUIDE .
12 BOLT, PIVOT
13 NUT, PIVOT ADJUSTING ..
14 PIN, WEIGHT CENTER ....
15 COLLAR, WEIGHT CENTER .
1
2
2
2
2
1
1
1
2
2
1
2
2
1
1
100—ZG9-800
14410-ZE0-010
14431-ZEWJ00
14441-ZE1-000
14451-ZE1-013
14568—Z69—800
14711-ZG9-801
14721-ZG9-801
14751-ZF1-000
14771-ZE1-T01
14791—ZE0-010
90012-ZE0-010
90206-ZE1-000
90701—Z69-800
91502-ZG9-800
4327334
3337854
1426824
1426832
4300901
4327342
4428454
4428462
3683489
1929769
1756964
1431287
4327557
4452355
'}
© AMERICAN HONDA MOTOR CO. LTD. 1994
-------
CARBURETOR
ZG93EU00
GXV140
Ref.
Na
BLOCK NO.
DESCRIPTION
E-14
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
Q
T
Y
R
E
Q
PART NUMBER
HONDA
CODE
1 GASKET SET
2 VALVE SET, FLOAT
3 FLOAT SET
4 CHAMBER SET, FLOAT
5 SCREW SET
6 SCREW SET B
7 CHOKE SET
8 CARBURETOR ASSY. (BE53A A)
9 SCREW, THROTTLE STOP
10 NOZZLE, MAIN
11 INSULATOR, CARBURETOR ...
12 PACKING, CARBURETOR (HPE)
13 SPACER COHP., CARBURETOR .
14 GASKET, CARBURETOR-
15 LEVER, VALVE
16 PLATE, LEVER SETTING
16010-
16011-
16013-
16015-
16016-
16028-
16045-
16100-
16124-
16166-
16211-
16212-
16220-
16221-
16953-
16954
ZG9-800
2EQ-005
ZE0-OO5
ZG9-800
ZH7-W01
ZE0-C05
2E7-005
2G9-800
ZE0-005
ZG9-800
ZG9-000
¦ZG9-TOO
¦ZE6-010
¦ZG9-TOO
-ZE6-005
¦ZE1-811
4428827
1441476
1441492
4428835
4219879
14.41518
3352671
4428843
1441559
4428850
3307311
4224267
2455640
4224275
2580116
1807791
9 AMERICAN HONDA MOTOR CO. LTD. 199* "
-------
General Purpose Engine
G100 • G100K1 • G100K2
HONDA
Power
Equipment
Parts Catalog
Second Edition
July, 1996
AMERICAN HONDA MOTOR CO., INC
© American Honda Motor Co., Inc. 1996
14ZG00E2-AH
PRINTED IN USA
-------
CYLINDER BARREL
ZG04E0100
GIOO
GIOOKI
G100K2
G
1
O
O
G
1
O
0
K
1
G
1
O
O
K
2
TYPE
Q
A
a
A
F
Q
A
H
Q
A
2
S
M
D
2
ReJ BLOCK Ntt E-1
Na DESCRIPTION
1 CYLINDER ASSY
•
•
•
•
•
•
•
CYLINDER ASSY
•
•
•
•
•
•
•
CYLINDER ASSY
•
•
•
•
2 CYLINDER C0MP
•
•
CYLINDER C0HP
•
«
•
3 GUIDE, VALVE (OS)
•
•
•
•
•
•
•
•
•
•
•
GUIDE, VALVE
•
•
•
•
•
4 CYLINDER HEAD
•
•
•
CYLINDER HEAD
•
•
CYLINDER HEAD
•
•
ENGINE
SERIAL NUMBER
FROM TO
2143546
2143546
2143546
— 1010983
2376620
2376619
PART NUMBER
HONDA
CODE
— 2376619
2422128
2422129
(2
120A0'
120A0-
120 AO'
120A0'
120 AO
12OA0'
12000'
12100'
12100'
12133
12133'
12133'
12133'
12134'
12134
12221
12221
12221
-ZGO-OOO
-Z60-000
•ZGO-OOO
-ZSO-010
-ZG0-010
¦ZGO-010
-ZG0-O2O
¦896-305
-896-315
-896-306
-896-306
-896-306
-896-306
-896-305
-896-305
-896-000
-ZGO-OOO
-ZGO-010
1794924
1794924
1794924
3210846
3210846
3210846
4481362
0927368
1033026
4457842
4457842
4457842
4457842
0927376
0927376
0927384
1794932
4481404
e AMERICAN HONDA MOTOR CO, INC 1996
B1
-------
G100
G100K1
G100K2
^ BLOCK NO. E-1
No DESCRIPTION
4 CYLINDER HEAD
CYLINDER HEAD
5 GASKET, CYLINDER HEAD ....
GASKET, CYLINDER HEAD
GASKET, CYLINDER HEAD
GASKET, CYLINDER HEAD
6 BED, ENGINE (O-TYPE)
BED, ENGINE (STD.)
7 BED, ENGINE
8 COVER, TAPPET
COVER, TAPPET ROM
9 SEPARATOR (INNER)
SEPARATOR COUP. (INNER)
SEPARATOR COHP. (INNER)
SEPARATOR CONP. (INKER)
10 GASKET, TAPPET COVER
GASKET, TAPPET COVER
GASKET, TAPPET COVER
11 BOLT, FLANGE (5K10)
12 BOLT, STUD C5X80I
13 OIL SEAL (17X30X6) (NOK)
OIL SEAL (17X30X6HARAI)
OK
0 t
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
2422129 —
3056813
3058813
3058814
3058814
1443596
1443595
1014735
1014735
2410563
PARTNIMBER
12221-ZG0-020
12221-ZG0-020
12221-ZG0-020
12221-Z60-030
12221-ZGO-030
12221-ZG0-030
12281-896-000
12281-896-306
12281-ZG0-003
12281-ZC0-003
12351—Z60—810
12351-ZGQ-810
12351-ZG0-810
12351-Z60-Q0Q
12351-896-630
12361-896-000
12361-160-000
12361-ZGO-OOO
12365-896-000
12365-896-700
12370-896-000
12370-ZG0-000
12370—ZGO-OOO
12375-B96-000
12375—ZSO—000
12375—ZSO—010
12375-ZGO-OIO
90002-892-000
90002-892-000
90002-892-000
90041-896-000
90041-896-000
90041-896-000
91202-892-004
91202-892-004
91202-892-004
91202-892-003
HONDA
CODE
4640413
4640413
4640413
4776001
4776001
4776001
0927392
4192910
2084838
2064723
1794965
1794965
1794965
5176177
0927400
0927418
1794973
1794973
0927426
0933291
0942730
1794981
1794981
0927434
1794999
4454534
4454534
0928051
0928051
0928051
0928085
0928085
0928085
0866145
0866145
0866145
1104884
6 AMERICAN HONDA MOTOR CO, INC. 1996
3
-------
CYLINDER BARREL
2G04E0100
Q
T
Y
R
F
HONOA
Q
PART NUMBER
CODE
1
91231-816-000
0158998
1
91231-816-000
0158998
1
91231-816-000
0158998
2
92700-06045-3B
0928119
2
92900-06028-3B
4932208
2
94050-06080
0612689
2
94301-08140
0069310
2
94301-08140
0069310
2
94301-08140
0069310
4
95700-06035-08
0498238
4
95701-06035-08
2170801
4
95718-06035-08
1405232
4
95718-06035-08
1405232
6
95801-06035-00
2569069
6
95801-06035-00
2569069
6
95818-06035-00
1825124
6
95818-06035-00
1825124
4
95700-08018-00
1096791
G100
GI00K1
G100K2
Ret
Na
BLOCK NO.
DESCRIPTION
E-1
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
14 OIL SEAL
15 BOLT/ STUD (6X45) ..
BOLT/ STUD (6X45) ..
16 NUT/ FLANGE (6NN) ..
17 PIN A/ DOWEL (8X14)
18 BOLT, FUNGE (6X35)
BOLT/ FLANGE (6X35)
BOLT/ FLANGE (6X35)
BOLT/ FLANGE (6X35)
BOLT/ FLANGE (6X35)
19 BOLT, FLANGE (8X18)
1001095
1001095
1001096
C AMERICAN HONOA MOTOR CO, INC. 1998
B2
-------
G100
G100K1
G100K2
Ref BLOCK NO. E-1
No DESCRIPTION
19 BOLI, FLANGE (8X18)
20 BOLT, FLANGE (8X18)
BOLT, FLANGE (8X18)
21 SPARK PLUG (BM-4A) (NGK)
SPARK PLUG (BMR-4A) (NGK)
SPARK PLUG (W14M-U) (ND)
SPARK PLUG (W14MR-U) (ND) .......
SPARK PLUG (BPH4A-10) (NGK)
SPARK PLUG (BPNR-4A10)
SPARK PLUG (W14MP-U10) (ND)
SPARK PLUG (BRMR4A)
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
4
4
4
4
1
(1)
1
(1)
(1)
1
(1)
(1)
(1)
1
PART NUMBER
HONDA
CODE
95701-08018-00
95701-08018-00
95700-08018-08
95701-08018-08
98073-54740
98073-54744
98073-54744
98073-54750
98073-54754
98073-54754
98073-54941
98073-54944
98073-54951
98073-54776
2660694
2660694
0928150
2563237
0928168
0940759
0940759
1420603
1668896
1668896
1033539
1202498
1842467
4497996
® AMERICAN HONDA MOTOR CO, tNC. 1996 S
-------
CRANKCASE COVER
ZG04E02008
G100
Q100K1
G100K2
Ret
Na
BLOCK NO.
DESCRIPTION
E-2
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
Q
T
Y
R
E
HONDA
Q
PART NUMBER
CODE
(1)
06165-Z60-000
3313624
(1)
06165-ZGO-000
3313624
1
11300-896-000
0927343
1
11300—Z60—000
1840370
1
11300-ZGO-000
1840370
1
11300-Z60—010
5176110
1
11381-896-000
0927350
1
11381-ZGO—000
1794916
1
11381-Z60—306
4437760
1
11381—Z60—800
4034971
1
11381-Z60—800
4034971
1
15600-ZG4-003
4497921
2
15620-896-000
0927541
2
15620-ZG0-010
1814326
1
15620-ZG0—010
1814326
1
15620-ZG0-003
5164207
1
15620-ZGO-003
5164207
1 GOVERNOR KIT (STD)
2 COVER ASSY., CRANKCASE
COVER ASSY., CRANKCASE
COVER ASSY., CRANKCASE
3 GASKET, CASE COVER ....
GASKET, CASE COVER ....
GASKET, CASE COVER ....
GASKET, CASE COVER ....
4 CAP ASSY., OILFILLER
5 CAP, OIL FILLER
CAP, OIL FILLER
CAP, OIL FILLER
2400550
2400550
3126184
3126185
« AMERICAN HONDA MOTOR CO, INC. 1896
B3
-------
G100
G100KI
G100K2
Ref BLOCK NO. E-2
Wo. DESCRIPTION
6 GASKET, OIL FILLER CAP
GASKET/ OIL FILLER CAP
GASKET, OIL FILLER CAP
7 GASKET, OIL FILLER CAP
8 WEIGHT, GOVERNOR
9 HOLDER/ GOVERNOR WEIGHT
HOLDER, GOVERNOR WEIGHT
10 PIN, GOVERNOR HEIGHT
11 SLIDER, GOVERNOR
SLIDER, GOVERNOR
12 SHAFT, GOVERNOR ARM
13 BOLT/ FLANGE (6X28)
BOLT, FLANGE (6X28)
BOLT, FLANGE (6X28)
14 BOLT, DRAIN PLUG
BOLT/ DRAIN PLUG
BOLT, DRAIN PLUG
15 WASHER/ DRAIN PLUG (12KK)
WASHER/ DRAIN PLUG (10.2MO
16 CLIP/ GOVERNOR HOLDER
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
PART NUMBER
HONDA
CODE
- 1061541
1443596
1443595
1443596
1443596
1443595
2198807
2198806
15621-896-000
15621-896-010
15625-ZG0-000
15625-ZGO-OOO
15625-ZE1-003
16511-896-000
16511-896-000
16511-896-000
16512-ZGO-OOO
16512-ZGO-OOO
16512-ZGO-OOO
16512-896-300
16513-ZE1-000
16513-ZE1-000
16513-ZE1-000
16531-ZG0—000
16531-ZG0-000
16531—ZGO-COO
16531-896-000
16541-896-000
16541-896-000
16541-896-000
95700-06028-08
95701-06028-08
90015-883-000
90015-883-000
90131-883-000
90131-896-650
90131—ZE1—000
9013 WE 1-000
94109-12000
90601—ZE1-000
90601—ZE1-000
90602—ZE1—000
90602—ZE1—000
90602—ZE1-000
90602-ZE1-000
90602-2E1-000
0927558
1033042
1795103
1795103
4497947
0927632
0927632
0927632
1795160
1795160
1795160
0927640
1427244
1427244
1427244
1795178
1795178
1795178
0927657
0927665
0927665
0927665
0252296
2488500
0636852
0636852
0636902
1986231
1431246
1431246
0171868
1436583
1436583
2456697
2456697
2456697
2456697
2456697
e AMERICAN HONDA MOTOR CO, ING 1996
-------
CRANKCASE COVER
U^j,
1u 1
,S
ZGCMEOZOOe
G100
GIOOKI
G100K2
BLOCK NO. E-2
Rel.
No DESCRIPTION
16 CLIP, GOVERNOR HOLDER
17 OIL SEAL (17X30X6) (N0K)
OIL SEAL (17X30X6) (ARAI)
18 WASHER, PLAIN (5MN)
WASHER, PLAIN (5MM)
19 WASHER, PLAIN (6fW)
WASHER, PLAIN (6HM)
WASHER, PLAIN (6MM)
20 PIN, COTTER (2.5X28)
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
PART NUMBER
HONDA
CODE
2198806
2198806
1443595
90602-896-000
90602-896-000
90602-896-000
91202-892-004
91202-892-004
91202-892-004
91202-892-003
94101-05800
94101-05000
94101-05000
94101-06800
94101-06800
94101-06800
94101-06000
94101-06000
94101-06080
94101-06080
94201-25280
0928101
0928101
0928101
0866145
0866145
0866145
1104884
0285791
0059055
0059055
0345900
0345900
0345900
0059071
0059071
3136074
3136074
0928135
6 <3 AMERICAN HONDA MOTOfl CO, INC. 1996
84
-------
GtOO
TYPE
G100K1
G100K2
0
G
1
G
1
ENGINE
SERIAL NUMBER
T
Y
Re) BLOCK NO. E-2
1
A
0
0
K
1
0
0
v
Q
A
Q
A
F
Q
A
H
Q
A
2
S
M
D
2
R
p
HONDA
CODE
No. DESCRIPTION
0
2
FROM TO
Q
PART NUMBER
h PIN, LOCK (8MN)
•
•
•
1
1
1
94251-08000
94251-08000
94251-08000
0115527
0115527
0115527
•
•
•
•
•
•
22 BEARING, RADIAL BALL (6203) ....
•
•
•
1
1
1
96100-62030-00
96100-62030-00
96100-62030-00
0722199
0722199
0722199
•
•
•
•
® AMERICAN HOfOA MOTOR CO, INC 1996 9
-------
CRANKSHAFT
ZG04E0500A
G100
G100K1
G100K2
Ret
Na
BLOCK NO.
DESCRIPTION
E-5
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
Q
T
Y
R
E
HONDA
Q
PART NUMBER
COOE
1
13310-ZGO-600
1795020
1
13310—ZGO—600
1795020
1
13310—Z60—600
1795020
1
13310-ZGO-601
3499704
1
13310—ZGO—601
3499704
1
13310—ZGO—601
3499704
1
13310—ZGO—601
3499704
1
13310-896-630
0927483
1
13310-ZGO-010
5176185
1
90745-ZE1-600
1441062
1
90745—2E1—600
1441062
1
96100-62030-00
0722199
1
96100-62030-00
0722199
1
96100-62030-00
0722199
1 CRANKSHAFT COUP. (Q-TYPE)
CRANKSHAFT COUP. «1-TYPE)
2207846
2207846
2207846
CRANKSHAFT COUP
CRANKSHAFT COUP. CS-TYPE)
2 KEY (4.78X4.78X38)
2207846
3 BEARING, RADIAL BALL (6203)
Q AMERICAN HONDA MOTOR CO, tJC. 1996 1i
-------
CAMSHAFT
ZG04E0600A
G100
G100K1
G100K2
L BLOCK NO. E-6
m DESCRIPTION
1 SEAL, VALVE STEM
2 CAMSHAFT COMP
CAMSHAFT COHP
CAMSHAFT COMP
CAMSHAFT COMP
3 VALVE, IN
VALVE, IN. .
VALVE, IN
VALVE, IN
4 VALVE, EX
VALVE, EX
VALVE, EX
VALVE, EX.
5 LIFTER, VALVE
LIFTER, VALVE
« ® AMERICAN HONDA MOTOH CO, INC. 1996
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
PART NUMBER
HONDA
CODE
1063118
2346140
2346139
1085262
209-Z61-H11
111-896-000
111-896-010
111-ZCO-OOO
111-ZC0-000
111-ZGO-OOO
711-896-000
711-Z60-000
711-ZG1-H10
711-ZG1-000
721-896-000
721-Z60-000
721-ZG1-H10
721-ZG1-000
732-892-000
732-892-010
2821528
0927491
1068337
2064830
2064830
1795038
0927517
1795053
2821536
1817105
0927525
1795061
2821544
1817113
0865048
1068345
BS
-------
G100
G100K1
G100K2
Ref BLOCK NO. E-6
No DESCRIPTION
5 LIFTER, VALVE
LIFTER/ VALVE
6 SPRING, VALVE
7 RETAINER/ VALVE SPRING
RETAINER/ VALVE SPRING
8 ADJUSTER, TAPPET CLEARANCE (3.15)
ADJUSTER, TAPPET CLEARANCE (3.25)
ADJUSTER, TAPPET CLEARANCE (3.34)
ADJUSTER, TAPPET CLEARANCE (3.43)
ADJUSTER, TAPPET CLEARANCE (3.52)
ADJUSTER, TAPPET CLEARANCE (3.61)
ADJUSTER, TAPPET CLEARANCE (3.72)
ADJUSTER, TAPPET CLEARANCE (3.82)
9 WASHER (10MM)
WASHER, THRUST (9.9MM)
WASHER (12MN)
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
PART NUMBER
HONDA
CODE
2063201
1443596
1443595
1000944 1033288
1033289
— 1000943
14732-ZC0-000
14732-ZC0-000
14732-ZGO-OOO
14751-896-000
14751-896-000
14751-896-000
14771-ZGO-OOO
14771-ZG0-000
14771-ZGO-OOO
14771-892-000
14801-892-000
14801-892-000
14801-892-000
14803-892-000
14803-892-000
14803-892-000
14806-892-000
14806-892-000
14806-892-000
14809-892-000
14809-892-000
14809-892-000
14812-892-000
14812-892-000
14812-892-000
14815-892-000
14815-892-000
14815-892-000
14818-892-000
14818-892-000
14818-892-000
14820-892-000
14820-892-000
14820-892-000
90412-329-000
90412-329-000
90412-329-000
9O452-ZG0—000
90452-Z60-000
2271278
2271278
1795079
0927533
0927533
0927533
1795087
1795087
1795087
0865063
0866160
0866160
0866160
0866178
0866178
0866178
0866186
0866186
0866186
0866194
0866194
0866194
0866202
0866202
0866202
0866210
0866210
0866210
0866228
0866228
0866228
0866236
0866236
0866236
0279620
0279620
0279620
90452-892-000 0866129
1795756
1795756
C AMERICAN HONDA MOTOR CO, INC 1996
-------
CAMSHAFT
ZG04E0600A
G100
G100K1
G100K2
sf.
l^Q.
BLOCK NO.
DESCRIPTION
E-6
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
PART NUMBER
HONDA
CODE
10 WASHER, THRUST (9.9MH)
1033289 ~
90452-892-000
90452-892-000
0866129
0866129
® AMERICAN HONDA MOTOR CO. INC. t99fl
-------
PISTON • CONNECTING ROD
*-c
ZG04E0700
G100
G100K1
G^00K2
Ret
No.
BLOCK NO.
DESCRIPTION
E-7
TYPE
ENC3NE
SERIAL NUMBER
FROM
TO
PART NUMBER
HONDA,
COOE
130A1—896-003
1104595
130M-W6-004
W0257
13081-896-003
1104603
13081-896-004
1410265
HOC 1-896-003
1104611
130C1-896-004
1410273
13001-896-003
1104629
130D1-896-004
1410281
13010-896-003
1007384
13011-892-003
0876805
13011-896-003
0965624
13012-892-003
0876813
13Q12-M&-003
W65632
13013-892-003
0876821
13013-896-003
0965640
13010-Z20-003
1796010
1 RING SET, PISTON (STD)
RING SO, PISTON (S7t»
RING SET, PISTON (0.25)
RING SET, PISTON (0.25)
SING SET, PISTON (0.50)
RING SET, PISTON (0.50)
RING SET, PISTON (0.75)
RING SET, PISTON (0.75)
RING SET, PISTON (STD)
MUG SET, PISTOH U.25)
RING SET, PISTON (0.25)
RING SET, PISTON (0.50)
RING SET, PISTON (0.50)
RING SET, PISTON (0.75)
SINS SET, PISTON (0;?5)
RING SET, PISTON (STD)
© AMERICAN HONDA MOTOR CO, NC. 1990 19
-------
PISTON • CONNECTING ROD
4—
ZG04E0700
GfOO
G100K1
G100K2
tel.
.to.
BLOCK NO.
DESCRIPTION
E-7
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
PART NUMBER
HONDA
COOE
1 RING SET, PISTON (STD)
RING SET, PISTON (0.25)
RING SET, PISTON (0.25)
RING SET, PISTON (0.50)
RING SET, PISTON (0.50)
RING SET, PISTON (0.75)
RING SET, PISTON (0.75)
RING SET, PISTON (STD)
RING SET, PISTON (0.25)
RING SET, PISTON (0.50)
R1N6 SET, PISTON (0.75)
2 PISTON
PISTON (STD)
PISTON (0.25)
PISTON (0.25)
PISTON (0.50)
1
(1)
(1)
(1)
(1)
(1)
(1)
1
(1)
(1)
(1)
1
1
(1)
(1)
(1)
13010-
13011-
13011-
13012-
13012-
13013-
13013-
13010-
13011-
13012-
13013-
13101-
13101-
13102-
13102-
13103-
ZG0-004
ZG0-003
2G0-004
ZG0-003
ZG0-004
ZG0-003
ZG0-004
ZC0-003
ZCO-003
ZC0-003
ZCO-003
ZA8-000
892-000
ZA8-000
•892-000
¦ZA8-000
1796028
1796036
1796044
1796051
1796069
1796077
1796085
2064731
2064749
2064756
2064764
1787381
0864959
1819234
0876839
1819259
50 © AMERICAN HONDA MOTOR CO, INC. 1996
BIO
-------
G100
Q100K1
G100K2
Ref BLOCK NO. E-7
No DESCRIPTION
2 PISTON (0.50)
PISTON (0.75)
PISTON (0.75)
PISTON (STD)
PISTON (0.25)
PISTON (0.50)
PISTON (0.75)
PISTON (STD)
PISTON(0.25)
PISTON (0.50)
PISTON (0.75)
3 PIN, PISTON
4 CLIP, PISTON PIN (10M)
5 ROD ASSY., CONNECTING (STD) ....
ROD ASSY., CONNECTING (UNDER
SIZE)
6 ROD ASSY., CONNECTING
ROD ASSY., CONNECTING (U.S. 0.25)
7 WASHER, CONNECTING ROD
3 BOLT, CONNECTING ROD
BOLT, CONNECTING ROD
9 WASHER, LOCK
G G
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
PART NUMBER
HONDA
CODE
1443596
1443596 -
1443595
1443595
1443595
1443596
-- 1443595
-- 1443595
(1)
(1)
(1)
1
(1)
(1)
(1)
1
(1)
(1)
(1)
1
1
1
2
2
2
1
1
1
13103-892-000
13104-ZA8-000
13104-892-000
13101-ZG0-003
13102-260-003
13103-ZG0—003
131C4-ZGO-O03
13101-ZC0-OC3
13102-ZCO-003
13103-ZC0-O03
13104-ZCO-003
13111-892-000
13111-892-000
13111-892-000
13115-147-000
13115-147-000
13115-147-000
13200-Z60-000
13200—Z SO-OOO
13200-ZGO-000
0876847
1819275
0876854
1795004
1796093
1796101
1796119
2064772
2064780
2064798
2064806
0864967
0864967
0864967
0463380
0463380
0463380
1795012
1795012
1795012
(1)
13200-ZGO-305
1796127
(1)
13200—ZGO-305
1796127
(1)
13200—Z60-305
1796127
1
13200-892-000
0864975
(1)
13200-892-305
0933317
1
13213-892-000
0864983
2
90001-IGO-000
1795707
2
90001-ZGO-000
1795707
2
9OO01-ZGO-OOO
1795707
2
90001-892-003
0947390
2
90456-892-000
0866137
e AM5QCAN HONDA MOTOR Oa MC. 1 BOB
-------
G100 - CARBURETOR
13
12
It
ZG04EM00
G100
QIOOKI
G100K2
. BLOCK NO. E-11
el.
a DESCRIPTION
1 GASKET SET
GASKET SET
2 FLOAT SET
3 CHAMBER SET, FLOAT
CHAMBER SET, FLOAT
4 SCREW SET A
5 SCREW SET A
6 SCREW SET B
SCREW SET B
7 SCREW, PLUG
8 CARBURETOR ASSY
CARBURETOR ASSY
9 VALVE COHP., FLOAT
10 NOZZLE, MAIN
11 INSULATOR, CARBURETOR ..........
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
PART NUMBER
HONOA
CODE
16010-896-005
0927574
16010-896-015
4554838
16013-883-005
0636258
16015-891-003
3476744
16015-896-701
2473312
16016-892-005
0897645
16016-896-005
1033075
16028-ZE0-005
1441518
16028-883-005
0636274
16071-881-003
0927582
16100-896-308
4424982
16100-896-661
1033083
16155-883-005
0636282
16166-896-005
0927608
16211-896-000
0927616
32
IS AMERICAN HONDA MOTOR CO, INC 1896
CS
-------
Gio:s
Gi:;ok2
Rel BLOCK NO. E-11
No DESCRIPTION
11 INSULATOR, CARBURETOR
12 GASKET, INSULATOR
GASKET, INSULATOR
13 GASKET, AIR CLEANER
GASKET, AIR CLEANER
14 JET, MAIN (#45)
JET, MAIN (#48)
JET, MAIN (#50)
JET, MAIN (#52)
JET, MAIN (#55)
TYPE
ENGINE
SERIAL NUMBER
FROM
TO
1
(1)
1
1
1
1
(1)
(1)
(1)
(1)
1
PART NUMBER
HONDA
CODE
16211-
16211-
16212-
16212-
16269-
16269-
99101-
99101-
99101-
99101-
99101-
¦896-306
896-306
896-000
896-306
892-000
>892-306
124-0450
124-0480
124-0500
124-0520
124-0550
4026209
4026209
0927624
4593596
0865139
4513404
0947333
0947341
0947358
0897736
0635458
@ AMERICAN HONDA MOTOR CO, WC. 1996
-------
CYLINDER HEAD ASSEMBLY • MODELS gfitegUteSffite,
4^RVtW»lV
-------
CYLINDER & CRANKCASE ASSEMBLY - MODELS 96Qr4>70i$90r
(S«rfal no. 403016296 u4 twite)
bun PirtHs.
ft—eriDilon
Ktm
Part ffff.
DtKrfeffen
1
161000
O-AIng, Push Rod Tii>»
IS
111014
Folowir, Cam
2
161001
CUak*!, Cy Under Head
ie
HI 015
Cam Ge%r
3
161002
Cyflnd4*
17
161016
Seal
4
161009
Sor#w. MS X 16.7mm
16
161017
Cwtleeau W/Powar Shaft
5
161004
GaalnrtiOytndar-
(Includa* ttama 11,12 & 17)
a
161006
Piatcn ftlng Sal
19
r«!016
Gjaka*. OK Pm
7
181006
Pw.Wi^t
20
161010
Pan. Oil
a
181007
Piston
21
131020
Screw. Ms X 1S.6mm fa required)
9
181006
BuIIoa, WrUl Pin
22
191021
O-Ring
1»
181006
Rod, ConMClIno
23
131022
Plug. Oil Fill (Includes tacn £2)
It
181010
Cylinder Stud (83 Simn[
»
131023
Piston ahd RodAuamfcty
T2
181011
Cylinder Stud (1 tSSmmf
faam*o-)D)
13
181012
5cr«w, Cam Bracket
•
181024
Engins Gasket Kit
14
181013
Brack*. Cam
9
not shown
IhuMIW
-------
CARBURETOR & MUFFLER ASSEMBLIES - MODELS 960r-970r.W«,
RVOBI AMERICA CORP. ViM CHAPUAU iuuajl
f O. BOX 1J0?
AN0ER$ON. $C 29622-1207
TELEPHONE: (643) 228-651 I
^ TELEFAX; (6031281 9435
Itam
Part No.
fttttriptlon
1
181043
Screw. Muffler Mounting
2
181044
Screw, Muffler Mounting
3
180890
Scraan, Spaifc Abactor
4
181045
Cover, Scraan
5
181046
Scraw, Screen Covar
6
181047
Mufflar (includes items 1-5 8 7)
7
181048
Gasket, Mufflar
8
181049
Baffle, Mufflar
9
181060
Screw, Air Rter Covar
10
181051
Covar, Air filter
11
180350
Filar, Air
12
181052
Scraw. Air Fitter Base (52.?mm)
13
181053
Screw, M5X 29mm
14
181054
Primer and Una Assembly
15
181055
Base, Air Filter
16
181056
Gasket
17
181057
Lever, Choke
18
181058
Carburetor W/Choke lever
19
181059
Gasket
Item Part No. Description
20 181060 Insulator, Carti Mount
21 181034 Nut, Hex 5M
22 181061 Gaaket, Intake
23 1 81062 Baffla, Intake
24 181003 Screw, M6 X18.7mm
25 181063 Housing,-Pan
26 181064 Nut, Tlnnarman
27 181065 Spacer
28 153624 Flywhaal
29 181068 Scnw, Module
30 611063 Tab, Ground
31 181067 Module. Ignition—
""32 181094 Lead. Wire 18* (2 required)
610676 Kay, FlywfcMl
180142 Flywheel Stailar P«w4 Repair Kk
101068 O.E.M. Carburetor Repair K&
* 181069 Gasket-Diaphragm Rapak Kit
not shown
UlUMlW
-------
CLUTCH, STARTER MODULE & FUEL TANK ASSEMBLIES •
MODELS 960r-970r-990r _
(Serial no. 403026296 and greater)
HUB Part Ho.
[laudation
Him Part No.
Date riot (en
1
612468
Spring, Cotr^fuha
12
161076
Retainer, Startsr Pulley
(970c and W0r only)
13
161077
Screw, M4 X 12.7mm
2
161070
Screw, MS X 32mm
14
161078
Retainer, Rope Quids
3
18l07t
Housing. Clutch
15
611061
Guide, flop*
4
180232
Drum, Clutch
16
161079
Hsndle, Stsitsr
•
161102
Clutch Houaing Asesirfcly WIDiun
17
161080
Screw, Fuel Tank 8/adcat
(l«ni 3 6 4)
IB
161081
Bracket, FuslTsnk
5
161072
Isolator
19
161062
Tank, Fuel
e
161073
Ckilch
(Includes fcams 20,22 k 23)
7
161074
Wsahsr, Clutch
20
161063
Cap, Fuel
•
181£fl7
Starter Module Assembly
21
181064
Pad, Fusl Tank
(lams fc.13. 16 & 16)
22
161066
Fuel Una Assembly W/F#ef
161079
Housing, Start'sr
23
181086
Line. Fuel Return
9
613102
Spring, Slsitsr
10*
160699
Pulsy, Slsrlar
not shown
11
613103
Ropa. Stsitsr
-------
HANDLE & UPPER BOOM ASSEMBLY - MODELS 9rf0r-970r-990r
(Serial oo. 403024294 and greater)
Ham
Piiua. Dneriotton
Item
Part No.
PfKriplteft
1
181020
Screw, MS X 15.8mm
11
181095
Screw, Anti-Rotation
2
laioaa
Cover, Engins
12
610327
Clip, Shoulder Strap
3
181080
8c<$tf. M6 X 18.78mm 8 EMS
13
181096
Trigger
4
181104
Sefcw, Engine Cover
14
610314
Spring
S
181000
Handle, Aaewnbly
15
181097
Swtch
6
181070
Screw, M5 X 32mm
18
181098
Retainer, Switch ft Trigger
7
181081
SOda. Switch
17
6*3295
Handle Bracket Aiwambly
8
181082
Housing, Upper Drva
18
181099
J-Handle Assembly (Nema 19 & 20)
(970r end 990r only)
19
612831
Grip
8
181106
Hooting, Upper Drtve (960r only)
20
612021
Tube Closure
9
181093
Cable, Tlvottta
•
181103
Cecal KM
10
181094
Lead, Wire 18* (2 required)
•
not shown
lMuad»*4
-------
LgWERBOOM & CUTTING HEAD ASSEiyfl^g£n'
WRVCOf AMERICA CORF. SSSS
GARDEN GROVE. CA M«40
TELEPHONE: {?U| W8 3170
TELEFAX: (714I5JS15«0
5*01 peahwxn OAlAY roao
f O. 80* 12or
^OgftaOH. 6C i9622*1207
TELEPHONE: 4803) 226-6511
TELEFAX: (603)261-943;
flam Part Mo.
1 181106
153671
683074
147649
181106
180406
153597
180547
145566
180549
180546
180653
153616
i
11
12
13
neecrioHan
Housing, Upp«r Driwe
Spfit Boom Coupling Set
Screw. Coupling Set
Screw, Wing (qty 1)
Housing, Uwvar Orf*e
Shaft. Rankle Drive
Clamp Aaeembty
Hardware, Guard Mounting
Screw, AnU-Rotation
Gaaibot
Guard, Cutting Head
8lad* Aeeembly
Spool, Outer W/Eyelet
Htm part Mo. n.acHatian
14 145566 Eyelet
15 610660 Retainer
16 610917 Spring
17 153600 Real, Irihar
16 153066 Bunp Head Knob AeeembV
Optional Aeeeaiortea
6)0376 MonoAal Cutting Una (50 It)
153577 Spool and Line (30 ft) Awennbly
68207S Shouldet Strap Assembly
187 J 00 OiJ, SAE 30100ml Bottle
181101 Spout, Oil FV
not shown
-------
LOWER DOOM & CUTTING HEAD ASSEMBLY ^ model 970r
(ScrlaJ bo. 403024296 and jreitcr)
torn Part Mo.
DaftCriotlan
1
181092
Housing, Uppw Dri«
2
083606
SpDl Boom CoupHng 3*
3
063009
Sere*, Costing 34
4
683607
Screw, Wing (qfy 2)
6
180689
Housing, LwmrOrtai
0
683000
Shafl, FUttfcl* Drfcs
7
193607
Clomp AMMitty
B
180647
Hantaan, Quard Mounting
e
146660
So**, Artf-RoMiM
10
180648
Gawtkot
ii
180640
Quant, Cutting Head
12
180653
BledsAMMty-
13
153619
Spooi, Ouiw W/Ey«to
14
14UM
EyaH
15
610660
RaUtar
14
610917
Spring
17
163600
Rm4. Inrwr
IB
153060
Btunp Head Knob Aumbiy
Qpttenil ACfiliIfl/1—
' 610376 Monoikl Cutting Lin* (50 ft)
* 153577 Spool«ndlin»(30ll)AAMfnbty
* 682075 Should** Strap AsMUntty
181100 Oil 8AE 30 100m* BottU
181101 Spool. Oil FBI
not shown
UaufttfM*
-------
m
g*?,HEADASSE^^-^aBfi^O.
RVCWf^lVllBRJiGA COR?. SSSBSKSSi
Garden GROVE. CA 92U0
TELEPHONE: (7t4> $36-3t70
TELEFAX: (71«) S39-3960
5201 °CAftMArt DAIRY ROAD
P.O. 90* HOT
ANDERSON. 6C 29413-1107
TELEPHONE: (603) 22S-6S11-
(803) 2ai-M3e
iFAX:
1
¦181002
Housing, Upper Drive
2
683606
Split Boom Coupling SK
3
663606
Screw, Coupling Set
4
683607
Screw, Wing (qty 2)
S
190604
Housing, Lower Dr*/e
6
613300
Shaft, Bwibl* Drive
7
147530
Hardware. Biush Blade
Guard Mounting
a
147677
Mounting Hardutfrs A Grass*
Plug Assembly
8
147486
Gearbox
(items 8, 14, 17 and 18)
10
663304
Screw, Guard Mounting
VV
100367
5uanil£uMlnff Hetfd
12
68206f
Bbul» Aaeombty
l
147492
Guard Mount
• 4
147489
DrKser
IS
145873
Blade. Brush
(Includes Ham 16)
16
147670
Cower, Blade
17
147490
Washer. Retainer
16
147491
Nut, Lock
19
612483
Shalt, Spool
20
147494
Spool, Outer W/Eyelet
21
145566
Eyelet
22
612026
Retainer
23
610636
Spring
24
147495
Reel. Inner
25
180614
Bump Head Knob Assembly
*
147299
Locking Rod tool
•
682075
Shoulder Strap Assembly
Optional Accessories
•
180120
Monollall Cutting Line (50 ft)
•
147345
Spool and Line Assembly (40 ft)
•
147498
Complete Hoed Assembly
(Items 19>2S)
•
180014
Blade Retaining Kit
(rtems 17 end 18)
•
181100
Oil, SAE 30 IOOit. Some
181101
Spout, Oil Fill
®
&S.
® @
not shown
-------
(S RVOBI AMERICA CORP.
IV
WCCTenM RE
GARDEN PROMENADE
9699 CHAPMAN AVENUE
GARDEN GROVE. CA 92640
TELEPHONE: (714) 539-3170
TELEFAX: (714)539-3560
5201 PEARMAN DAIRY HOAD
P O BOX 1207
ANDERSON. SC 29622-1207
TELEPHONE: {803] 226-6511
TELEFAX: {8031261-9435
Item
Part No.
DaacriDllon
Item
P*1 No.
QatfriBlfeii
1
160349
Carburetor/Air Cleaner Covtr Assembly
33
810300
PuB Handle
(Includes item 2)
34
613103
Rope
2
180350
Air Cleaner Filter
35
180097
Starte/Housing Assembly
3
180351
Carburetor Mounting Screw Assembly
38
153S91
Clutch Rotor Assembly
4
180352
Wavey Washer
37
153593
Clutch Drum Assembly
5
1803S3
Chcka Lavar and Plat*
38
612468
Spring
6
147572
Caibure lor Assembly
39
663601
Clutch Cover Assembly
7
682048
Throttle Adjustment AssemfcY (Walbfo)
40
145888
Clutch .Cover Screw Assembly
7
147640
Throttle Adjustment Assembly (TiBotson)
41
153597
Upper Ctamp Assembly
8
61067S
Carburetor Gasket (10 pack)
42
180036
Wire Lead
9
S03974
Primer and Hom Assembly
43
683390
Module Assembly
10
180354
Carburetor Mount Assembly (includes 11 and 13)
610311
Spark Plug
11
147S73
Read Assembly
45
610672
Exhaust Gasket (10 pack)
12
180022
Power Shaft Assembly
46
180119
Muffler Assembly (includes 46 and 48)
13
812115
Carburetor Mount Gasket (10 pack)
47
1*75M
Muffler Mounting Bolt Assembly
14
180026
Crankcase Service Assembly (item* 12,14-17)
48
180063?
Cylinder Assembly
1S
682041
Inner Bearing Assembly
49
147012
Piston and Rod Assembly
18
610309
Seal
SO
145564
Cylinder Gasket (10 pack)
17
610308
Outer Bearing Assembly
•
180034
Engine Hardware Kit
18
612t34
Rear Mounting Pad
•
180011
Engine Gasket Kit
19
147580
Fuel Tank Assembly (includes item* 20-22)
•
153308
O.E.M. Carburetor Repair Kit (Walbro)
20
180000
Fuel Cap Assembly
•
147170
O.E.M. Carburetor Repair Kit (TUlotson)
21
147290
Return Line Assembly
•
153309
Gasket Diaphrapn Repair Kt (Walbro)
22
682039
Fuel Line Assembly
•
147171
Gasket Diaphragm Repair Kit (TTBoUon)
23
145308
Front Mounting Pad
•
682S07
Piston Ring
24
153520
Shroud Assembly
•
160027
Short Block Assembly (items 12, 14-17,48-50)
25
68307B
Shroud Extension and Stand
•
610678
Flywheel Key (10 pack)
26
153624
Flywheel Assembly
•
147544
Starter Housing Screw Set
27
145918
683856
613102
Spacer
Recoil Pulley Assembly
Recoil Spring
•
not shown
30
153644
Pulley Retainer Assembly
31
611061
Rope Guide
The above part numbers are for serial numbers 203096321 and
32
180035
Switch Assembly
greater.
Issued fl/93
-------
BOOM & TRIMMER PARTS - RYOBI 720<;
53 RYDBI AMERICA CORP.
ESTEnil HEUWJHUL UPfR-ET
GARDEN PROMENADE
9699 CHAPMAN AVENUE
GARDEN GROVE. CA 92640
TELEPHONE: (714) 539-3170
TELEFAX: (714) 539-3560
" tUHfURMIL UMR,e.
5201 P6ARMAN DAIRY ROAD
P.O. BOX 1207
ANDERSON. SC 29622-1207
TELEPHONE: (803) 226-6511
TELEFAX: <803} 261-9435-
^ ^ s-
Item
Part No.
Qcacrinlfen
t
180277
Throttle Housing and Trigger Assembly
2
610314
Throttle Trigger Spring
3
180021
Throttle Cable Housing Assembly
4
180127
Throttle Cable
s
610327
Shoulder Strap Clamp
6
683603
Drive Shalt Housing Assembly
7
683295
Handle Bracket Assembly
a
612021
Tube Closure
9
612831
Grip
10
683015
J-Hande Assembly (Includes item* a and 9)
11
683605
Split Boom Coupling Set
12
683606
Coupling Bolt Assembly
13
683607
Adjustment Knob Set
14
683604
Lower Drive Shaft Housing Assembly
IS
1S3597
Lower Clamp Assembly
16
683600
Lower Flexible Drive Shaft
17
145570
Retaining Ring
18
145567
Washer
19
153312
Bushing Housing Assembly
20
153318
Guard Mounting Screw Assembly
21
683274
Guard and Blade Assembly
22
145569
Anti-Rotation Screw
23
682061
Blade Assembly
24
153313
Spool Shaft
25
153619
Outer Spool and Eyelet Assembly
26
145566
Eyelet
27
610660
Retainer (10 pack)
28
610317
Spring
29
153600
Inner Reel
30
153066
Bump Head Knob Assembly
Optional Acceeioriee
610375
Monoflaii Cutting Line, 50IL
•
153577
Spool and 30 It Line (dual)
•
147823
Complete Cutting Head Assembly
(includes items 15, 17-30)
•
682075
Shoulder Strap Assembly
•
147541
IDC or Ryobi 2-Cycle Oil (4. or. can)
not shown
-------
APPENDIX C:
ADDITIONAL TECHNOLOGIES TO REDUCE
EMISSIONS IN HANDHELD ENGINES
-------
This appendix describes in detail additional technologies to reduce emissions in handheld
engines.
Exhaust Control Valve
Hsieh et al (1992), Tsuchiya et al (1980), and Duret and Moreau (1990) have demonstrated the
potential of exhaust charge control valves in small two-stroke engines. Results of their studies
show that significant reductions in HC emissions and fuel consumption can be achieved, as well
as a reduction in unstable combustion at light load. A study done by Yamagishi et al. (1972)
concluded that misfire is most likely to occur at a delivery ratio less than 0.3. It was also
observed that the scavenging losses were low but the exhaust HC concentration was still high.
At a low delivery ratio, the trapping efficiency was higher and resulted in lower scavenging
losses. However, at very low delivery ratios corresponding to light load and idle, misfire or
irregular combustion were occurring - resulting in high HC emissions even though the
scavenging losses were low.
Tsuchiya et al. identified the delivery ratio at which a rapid increase in irregular combustion
occurs (defined as the critical delivery ratio) as 0.2. This is very similar to the finding of Hsieh
et al that 0.25 was the critical delivery ratio. With exhaust charge control, Hsieh et al. found
that the critical delivery ratio decreases from 0.25 to 0.20 and 0.15 at low and medium engine
speeds (1,500 and 3,000 rpm), respectively. Thus, the exhaust charge control technique
effectively reduced irregular combustion under light-load conditions. Hsieh et al. found that HC
emissions and fuel consumption were reduced by 30% and 6% respectively when the exhaust
charge control technique was used in a test engine. Also, at the same delivery ratio, the engine
with exhaust charge control produced higher power output. Duret and Moreau found that a 60%
reduction in HC emissions and 20% reduction in fuel consumption could be achieved through
the use of an exhaust charge control valve.
Honda has incorporated a "Revolutionary Controlled Exhaust Valve (RC Valve)" in a 150 cc
two-stroke motorcycle model equipped with a capacitive-discharge ignition, computerized
controller and servo motor to attain high power efficiency at low and high speed conditions.
Although the "RC Valve" is intended to improve engine performance, it can also serve as an
emissions control device.
Queen's University of Belfast - At the Queen's University of Belfast (QUB), Magee et al. have
developed an "air head" scavenging system that uses the stratified scavenging concept in a 50
cc two-stroke engine (Magee et al., 1993). In this engine, two charge inlets are used: one for
pure air only, and the other for the regular carburetion intake. Controlled by reed valves, the
pure air is inducted into the top of the transfer passages through an auxiliary air inlet, while a
mixture of air and fuel is inducted into the crankcase. At wide open throttle and maximum
secondary air flow, Magee et al reported a 30% reduction in HC emissions and a 10%
improvement in brake specific fuel consumption throughout the speed range. The fuel trapping
efficiency for the engine with the stratified scavenging system was improved by 10%, and the
performance (power and BMEP) of the engine also improved. However, in another paper on
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the same study (Magee et al., 1993-2), it was reported that the engine experienced some bad
performance characteristics at light and part-load conditions, with BMEP less than 3.5 bar. It
was suspected that this was due to the low delivery ratio, which was around 0.25-0.35 (Magee
et al, 1993-2).
Ricardo - Recently, Ricardo Consulting Engineers PLC published a paper discussing their
stratified charging concept (RSCE) (Glover and Mason, 1995). This system employs quite
similar principles to the QUB's concept. In the Ricardo system, the fuel is initially delivered
to a specially-shaped rear transfer port, which serves as a storage as well as a fuel preparation
area. During the initial of the scavenging process, pure air is driven from the crankcase to the
combustion chamber through two lateral transfer ports. Controlled by the piston, the rear
transfer port is opened almost at the end of the scavenging process. This allows some remaining
pure air to flow through the port and mix with the fuel, carrying the fuel/air mixture into the
combustion chamber. Ricardo has demonstrated this concept in a 50 cc scooter engine.
Emission results indicate that substantial HC emission reduction is achieved only during
medium/high engine speed/load conditions. The stratified charging engine was found to be more
unstable than the baseline engine, and it produced as much HC emissions as well.
Indian Institute of Petroleum - Saxena et al. (1989) of the Indian Institute of Petroleum have
developed a 150 cc engine using the stratified scavenging concept with a dual intake system.
The secondary pure air is induced into the transfer passages through reed valves. The primary
and secondary air supplies were chosen to be 50% each, as Saxena et al's experiment showed
that the HC emission reductions and BSFC level off after the supply of secondary air exceeded
50%. At full load conditions, the results showed 25 to 30% reductions in HC emissions, as well
as about 10% improvement in BSFC throughout the range of air/fuel ratios tested (0.75-1.05).
The performance of the engine was also improved slightly. Saxena et al. also showed the effect
engine load on HC emissions and BSFC. Lower HC emission reductions (13-16%) and BSFC
(2-3%) were found at low-load conditions, while at high load the benefits were a more than 30%
reduction in HC emissions and a 10% improvement in BSFC. Under simulated road-load
conditions (over a range of speeds) at an air/fuel equivalence ratio of 0.85, the HC emission
reductions varied from 20 to 30% and BSFC improvements varied from 5 to 10%, depending
on the engine speeds. Again, lower HC reductions and BSFC improvements were found at
lower road/speed conditions.
To explain the low HC emission reduction and BSFC improvement at low load conditions,
Saxena et al. determined the fuel trapping efficiency and scavenging losses from both engines
for a range of delivery ratios (0.2-0.6). High fuel trapping efficiencies and low scavenging
losses were observed at low delivery ratio (light load conditions), similar to Yamagishi's
findings; and low fuel trapping efficiency and high scavenging losses were found at higher
delivery ratios. Compared with the base engine, the fuel trapping efficiency was improved and
the scavenging losses were decreased for the stratified scavenging engine throughout the range
of delivery ratios. However, minimal improvements in both fuel trapping efficiency and
scavenging losses were achieved at low delivery ratios or light load conditions. With these
results, Saxena et al. concluded that at low delivery ratio the losses due to poor combustion were
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high and the scavenging-through losses were low, and therefore, minimal HC emission reduction
could be achieved with this dual-intake stratified scavenging engine.
India Institute of Technology - Babu et al. (1993), of the Indian Institute of Technology, also
investigated the stratified scavenging approach. Similar to the system investigated by Saxena
et al, Babu et al. used a second intake system to induct pure air through reed valves into the
transfer passages. A difference was that the secondary intake system was set up to be able to
supply compressed air. The system was applied on three engines, with engine displacements
ranging from 55 cc to 250 cc. A control valve was used in the secondary air intake system to
regulate or vary the air flow through the intakes. A compressor was set up to supply a slightly
higher pressure air flow through the reed valves if needed. Also, three openings were selected
to regulate the air flow through the reed valves to determine the effect of the amount of
secondary air induced into the engine. In general, the results showed reductions in HC
emissions of about 25 %, and as much as 17 % improvement in the brake thermal efficiency due
to the reduction in scavenging losses. When an optimum amount of compressed air was supplied
to the secondary air intake, the improvement in brake thermal efficiency and reduction in HC
emission were even higher; especially at the full throttle condition; This was mainly due to the
reduction in secondary air flows during high throttle conditions when the secondary air was
induced at the atmospheric pressure. In this study, it was also concluded that an optimum
secondary air flow rate was necessary in order to obtain maximum performance and emission
benefits.
Catalyst
Graz University of Technology - The Graz researchers focused on reducing exhaust emissions
from two-stroke moped, motorcycle and chainsaw engines by using catalytic converters, as well
as by improving the thermodynamic characteristics of the engine, through changes in gas
exchange and fuel handling systems, cylinder and piston geometry, and exhaust and cooling
systems. Table I shows the effects of catalytic converters on emissions from production, lean-
burn production, and advanced moped engines tested under the ECE-15 driving cycle. As the
table shows, addition of a catalytic converter to the conventional moped reduced HC and CO
emissions by 64 and 61%, respectively. The relatively low efficiency in this case was due to
the rich air-fuel mixture used in the conventional moped, which limited the ability of the catalyst
to oxidize the excess HC.
Comparing baseline emissions between the conventional moped and the lean-burn production
moped, Table I shows that the lean-burn moped produced about 80% less CO and 18% less HC
emissions, without the catalytic converter. The efficiency of the catalytic converter was also in-
creased, due to the higher oxygen concentration in the exhaust. In this case, the CO and HC
reductions were 75% and 89%, respectively. Durability testing on two production lean-burn
Puch mopeds equipped with catalytic converters showed that the HC emissions increased by 42%
while the CO emissions were reduced by 31% after 10,200 km or about 450 hours. At that
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Table I: Emission data for production and advanced moped engines with and without catalyst tested under ECE-R47
driving cycle.
Engine Configuration
Emissions (g/km)
CO
HC
Nox
Production Puch
Without Catalyst
5.6
3.9
n/a
With Catalyst
2.2
1.4
n/a
Production Puch Superm-
axi, Lean-Burn
Without Catalyst
1.1
3.2
n/a
With Catalyst
0.28
0.34
n/a
Advanced 1.2 hp
Without Catalyst
1.311
2.432
0.038
With Catalyst
0.036
0.094
0.031
Advanced 2.7 hp
Without Catalyst
0.771
3.205
0.090
With Catalyst
0.093
0.116
0.065
With Dual Catalyst
0.022
0.037
0.067
point, the emission levels still met the Swiss standards. Since the overall air-fuel mixture was
rich, the catalyst oxidized HC to CO. The increase in HC and reduction in CO are consistent
with a fairly rapid decline in catalyst efficiency with age. This would be expected, given the
high operating temperature of the catalyst.
Table I also shows emission results for two advanced-technology moped engines of 1.2 and 2.7
HP. These engines were designed to operate near or lean of stoichiometric over almost the
entire speed-load range. Addition of a catalytic converter to the 1.2 HP advanced moped engine
reduced HC, CO and Nox emissions by 96, 97 and 18%, respectively. For the advanced 2.7
hp moped engine, the HC, CO, and Nox emissions were reduced by 96, 88 and 29%
respectively when a catalytic converter was used. Data on catalyst temperatures were not
provided in the Graz papers.
The Graz researchers also developed an advanced chainsaw engine equipped with a catalytic
converter (Laimbock, 1991). In addition to the catalytic converter, this engine incorporated a
new cylinder with four transfer ports, better cooling for the cylinder and cylinder head, and an
optimized piston shape. Unlike the mopeds, this engine operated rich of stoichiometric. Engine
maps showing emission results vs. speed and BMEP were presented in the Laimbock paper. For
the chainsaw without catalyst, the engine map showed CO emissions ranging from 0.5 to 4.5%,
HC emissions from 15,000 to 29,000 ppm, and Nox emissions from 30 to 400 ppm, depending
on the load/speed conditions. For the chainsaw with catalyst, the CO, HC, and NOx emissions
CM
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ranged from 0.5 to 4.7%, 7,000 to 17,000 ppm, and 3 to 300 ppm, respectively. These results
translated into changes in CO emissions from about a 40% increase to an 80% reduction; 20 to
80% reduction in HC; and a 20 to 85% reduction for NOx. It should be noted that the NOx
increased by 100% in a spot with high BMEP and air-fuel ratio slightly above stoichiometric.
For chainsaw engine emission development work, Graz University of Technology (G.U.T.) has
developed a special emissions test cycle. This cycle is intended to simulate the main operation
modes of chainsaws used by professional woodcutters, namely cutting and debranching
operations. Laimbock (1993) reported that the typical emission results for standard production
chainsaws, depending on the adjustment of the carburetor, were 3.7-5.9 g/min of HC emissions,
7.7-11.1 g/min of CO emissions, and 0.002-0.009 g/min of NOx emissions based on the GUT
cycle. When the catalyst-equipped chainsaw was tested on GUT cycle, the emission results
were 0.47 g/min for HC, 1.03 g/min for CO, and 0.028 g/min for NOx emissions. Comparing
these results with the standard production chainsaws, average emission reductions for CO and
HC were about 90%, while the NOx emissions slightly increased by 4%. Again, data on
catalyst and tailpipe-out exhaust temperatures were not provided in the Graz papers.
It should be noted that in the work at Graz, catalytic converter efficiencies of 90% for HC and
CO emissions were obtained mainly by the application of metal substrate technology along with
lean air-fuel ratios.
Industrial Technology Research Institute - Researchers at ITRI have successfully retrofitted a
catalytic converter to a 125 cc two-stroke motorcycle engine, and demonstrated both effective
emissions control and durability (Hsien et al, 1992). The ITRI researchers evaluated the effects
of catalyst composition and substrate, the cell density of the substrate, the converter size and
installation location, and the use of secondary air injection on the catalytic effectiveness and
engine performance. Their conclusions were as follows: 1) the use of a metal substrate is
superior to the ceramic substrate of the same converter size in terms of conversion efficiency
and engine performance, since the thin walls of the metal substrate result in a larger effective
area and lower back pressure, 2) exhaust temperature profile, space availability, and the effects
on engine exhaust tuning must be considered when installing the catalytic converter, 3) use of
additional reduction catalyst Rh would improve the CO conversion efficiency in the rich air/fuel
mixture environment typical of motorcycle two-stroke engines, 4) the cell density of the substrate
should be less than 200 cpsi to minimize pressure loss and maintain engine power, 5) HC and
CO conversion efficiencies increase significantly when secondary air is supplied, and 6) exhaust
smoke opacity was also reduced with the use of the catalytic converter. This latter effect was
due to the catalytic oxidation of the lubricating oil vapor in the catalytic converter. This effect
has also been observed in other engines (Pfeifer et al., 1993).
In a more recent study, ITRI retrofitted a catalytic converter to a two-stroke scooter engine,
together with fuel injection and skip-firing at idle. Adding the catalytic converter to the other
emission control techniques improved the overall emissions control efficiency from 58.2% to
92.8% for HC, and from 56.8 to 97.6% for CO emissions. Efficiency improved only slightly
with the use of secondary air. This is because the fuel-injected engine tested was able to operate
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with a lean mixture overall, so that sufficient oxygen was available in the catalytic converter
even without the air injection.
Advanced Fuel Metering Systems
Precise metering of air and fuel can improve engine performance and fuel consumption and
reduce exhaust emissions. Conventional carburetion systems for small two-stroke engines are
designed to provide smooth and stable operation under a variety of speed and load conditions,
but give little consideration to fuel consumption or exhaust emissions. The potential advantages
of fuel injection in two-stroke engines are two-fold: more precise control of the air-fuel ratio
over the entire range of operation, permitting the engine to operate with leaner mixtures; and
the possibility of using timed injection and/or in-cylinder injection to eliminate HC emissions
due to short-circuiting of fresh charge during scavenging.
The electronic fuel injection systems used in modern automobiles provide a precisely metered
amount of fuel, based on a measure of the air flow into the engine. The fuel supply system,
which provides the fuel flow to the injection system, consists of a fuel pump, fuel filter and
pressure regulator. The fuel injector is a high-speed solenoid valve connecting the pressurized
fuel supply to the engine air intake. By opening the valve, the electronic control unit permits
pressurized fuel to spray into the air intake, where it mixes with air, vaporizes, and is inducted
into the engine.
A similar fuel injection system could be applied in advanced small two-stroke engines. This
system could be configured to spray fuel either into the intake port, or into the crankcase, to
provide better mixing and increased time for vaporization. Numerous studies have been
undertaken with two-stroke engines using this approach to reduce exhaust emissions (Sato et al.,
1987; Nuti, M., 1988; Plohberger et al., 1988; Beck et al., 1986; Duret et al., 1988; Huang et
al., 1991; Leighton et al., 1994, Yoon et al., 1995).
By appropriate control of fuel injection timing, it is possible to reduce the hydrocarbon content
of the air that short-circuits the combustion chamber during scavenging. Because of the need
to assure a combustible mixture at the spark plug, however, it would not be possible to eliminate
short-circuiting HC completely in port or crankcase-injected engines. Furthermore, some
ingenuity is required to provide the pumping power necessary to maintain injection pressure
without adding unduly to the size and cost of the engine. In this discussion, we will refer to this
approach as "indirect injection".
An alternative fuel injection approach can eliminate short-circuiting entirely. This is to inject
the fuel directly into the cylinder near or after the time that the exhaust port closes. This
approach is generally referred as direct in-cylinder fuel injection. Because injection directly into
the cylinder provides very little time for fuel mixing and vaporization, direct fuel injection
systems must inject very quickly, and achieve very fine levels of atomization of the fuel. This
type of fuel injection can use high-pressure, liquid-fuel injection systems to inject the fuel
directly into the cylinder (Sato et al., 1987; Nuti, M., 1988; Plohberger et al., 1988; Beck et
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ah, 1986; Yoon et ah, 1995). Direct in-cylinder fuel injection can also be achieved with low-
pressure fuel systems, using air-blast injection (Duret et ah, 1988; Huang et ah, 1991; Leighton
et ah, 1994; Yoon et ah, 1995). For air-assisted direct-injection systems, an air pump or
similar means is required to supply compressed air for the injection system.
The quality of the atomization of a fuel spray is usually measured in terms of the Sauter Mean
Diameter (SMD) of the fuel droplets. In order to quickly vaporize the fuel spray, a fuel droplet
SMD of 10 to 20 microns is usually required for direct (in-cylinder) fuel injection. For indirect
injection, a fuel droplet SMD of 100 microns is quite acceptable, as the fiiel will have time to
vaporize in the intake port and during the compression stroke.
A good fuel-injection system needs to have the ability to deliver extremely small fuel droplet
sizes, to control spray penetration and fuel distribution. It must also mix fuel adequately with
all of the available air in the short time available at the high engine speeds typical of two-stroke
operation. In addition to fine fuel droplet size, the fuel droplet size distribution must remain
much the same throughout the fuel spray to assure minimum coalescence of the droplets towards
the end of the spray plume.
Due to the achievements reported for engines using the air-assisted Orbital Combustion Process
(OCP) and similar direct-injection approaches, two-stroke engines are presently a major area of
automotive research and development. Some prototype two-stroke engines have reached
emission levels comparable to good four-stroke engines. However, only limited studies have
been carried out on the application of the advanced direct fuel-injection systems in small two-
stroke engines such as those in motorcycles and small handheld equipment. A few prototype
injection systems for handheld equipment engines are discussed below.
BKM - The BKM project is partly funded by the New York State Energy Research and
Development Authority. As of today, BKM has demonstrated a "proof of concept" breadboard
prototype chainsaw equipped with its Servojet high pressure, liquid-fuel direct injection system.
In its demonstration, the auxiliary parts that are required to run the fuel injection system, such
as fuel and oil pumps, electric motors, pressure regulators etc., were not integrated with the
chainsaw. The BKM breadboard prototype'has been tested at the University of Michigan, with
the injection system operated from a standard 120 volt electrical supply. The average emission
data with two different injectors and cylinder heads were reported as 30, 1.29, and 94 g/kW-hr
and for HC, NOx, and CO emissions, respectively (EPA, 1995), and no PM emission results
were reported. The PM emissions is expected to be quite similar to uncontrolled levels, since
no special steps were taken to reduce emissions of unburned lubricating oil. The major prob-
lems in incorporating the system into a self-contained, portable chainsaw remain to be resolved.
FMS - The FMS project was funded by the Swiss Department of Forestry. A prototype indirect
(intake port) fuel injection chainsaw, has been developed and tested at the Swiss Federal Na-
tional Test Institute. This system used an FMS electronic control unit and Siemens automotive
fuel injector. It is claimed that on the GUT cycle, 33% and 85% reductions in HC and CO
emissions were achieved, with a 408% increase in Nox emissions. A video provided by the
C-7
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FMS also documents the laboratory and field testing of the prototype chainsaw. However,
similar to the BKM prototype, the system auxiliaries required to run the prr :type chainsaw
were not integrated or built into the chainsaw, but were powered by a separar ^ar battery.
Function of a Pneumatic Fuel Injection
Figure 8: Schematic of the Stihl mechanical direct fuel injection system.
Stihl - Stihl, a major manufacturer of handheld equipment, is developing a prototype mechanical
direct fuel injection chainsaw. A schematic of Stihl's mechanical direct fuel injection system
is shown in the Figure above. For this prototype, all of the components have been integrated
into the chainsaw, without auxiliary components such as an external energy supply. As the fuel
and lubricating oil are supplied to die engine separately, the prototype chainsaw is equipped with
a lubricating oil system, comprising an oil tank, filter, pump, and injection channel. This is
different from the current fuel/oil mixing system used in carbureted chainsaws. Similar to the
Orbital SEFIS system, the Stihl injection system also uses the pressure pulses of the crankcase
to drive the fuel pump. The Stihl fuel injection system does not use any electronic control
system, and the injection timing is controlled by a hole in the piston skirt. The emission results
for this prototype chainsaw were reported as 20 g/hp-hr for HC emissions, and 200 g/hp-hr of
CO emissions. According to a Stihl engineer, a few of these prototype chainsaws have been
evaluated in the field, and the results were encouraging; Because of the additional parts,
especially costly precision parts, required, the cost of these chainsaws would be significantly
higher than for present units. Stihl has estimated that the incremental cost to the customer for
these advanced chainsaws would be $200 per unit, even at high production volume.
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All these data and studies, as well as data from other studies of fuel-injection systems for
automotive two-stroke engines, show that significant reductions in HC and CO emissions can
be achieved through the use of fuel-injection systems. However, innovative design will be
needed to develop a practical, economical, and efficient fuel injection system that can be in-
stalled in a two-stroke engine for handheld equipment.
Skip-firing
Besides precision in fuel metering, another advantage of electronically controlled fuel-injection
systems is the ability to shut off fuel injection in some engine cycles. With this feature, the fuel
supply can be shut off for a definite number of consecutive engine cycles under idle and light
engine load conditions. These are the conditions at which misfire and irregular combustion
usually occur. This allows time for exhaust gas to be purged from the combustion chamber, and
thus providing better combustion conditions for the next designated engine firing cycle. Thus,
irregular combustion under light engine load conditions can be eliminated or minimized.
Researchers at ITRI have successfully applied this skip-injection technique to a scooter engine
to minimize unburned HC emissions due to irregular combustion under idle and light load
conditions (Huang et al, 1992 & 1993). ITRI researchers found that, without skip-firing, the
indicated mean effective pressure (IMEP) varied significantly at idle, and many cycles could
easily be identified as having incomplete combustion cycles or even complete misfire. This
resulted in a very high concentration of unburned HC emissions: of the magnitude of 3,500 to
4,000 ppm of hexane equivalent in the exhaust. Several skip-injection modes were investigated,
including fuel injection every other cycle, and every three, four and five cycles. The results
showed that IMEP variations decreased as the number of skipped injections increased. In an
engine dynamometer test with fuel injected every four cycles, the HC emissions and fuel flow
rate at idle were reduced by 50% and 30% respectively. This skip-injection mode was also
applied and tested in a scooter engine, producing the exhaust emissions and fuel economy results
shown earlier. Reductions of HC and CO emissions of 58% and 57%, respectively, and a 31 %
improvement in fuel economy were demonstrated with this approach.
It has been reported that the BKM high pressure fuel injection system for two-stroke engines also
uses this approach during idle and low load conditions.
Lubricating Oil Technologies
Lubricating oil is the major source of PM emissions from two-stroke engines. Since the
crankcase of a two-stroke engine is used for pumping air or a fuel-air mixture to the combustion
chamber, it cannot also act as a lubricant-oil reservoir. Instead, a fine mist of oil is injected into
the incoming air stream. As this stream passes through the crankcase, lubrication is provided
for cylinder walls, and crankshaft and connecting-rod bearings. Ball or roller bearings are
typically used instead of a four-stroke engine's plain bearings. The oil mist continues to the
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combustion chamber, where some of it is trapped and burned. Oil that is not trapped in the
combustion chamber, or which survives the combustion in the chamber, recondenses in the
exhaust plume to create the blue or white smoke that is the distinguishing characteristic of the
two-stroke engine. Any phosphorus or other deposit-forming additives in the two-stroke oil can
also be expected to poison the catalytic converter, reducing its efficiency. Thus, two-stroke oils
for catalyst-equipped motorcycles or equipment will need to be formulated without these
compounds.
Table II: Comparison of particulate emissions from a two-stroke motorcycle engine lubricated with mineral oil and
a low-smoke PIB oil.
Particulate Emissions (g/600 liter Exhaust Gas)
Fuel Oil Ratio
20 : 1
40 : 1
60 : 1
Conventional Mineral Oil
Solid Component
0.009
0.005
0.006
Oil Component
0.304
0.247
0.204
Total
0.313
0.252
0.210
Low-Smoke Oil With PIB
Solid Component
0.008
0.005
0.004
Oil Component
0.228
0.120
0.061
Total
0.236
0.125
0.065
Source: Sugiura et al (1977).
Lubrication system - Three approaches are commonly used to supply lubricating oil to two-
stroke engines: pre-mixing with the fuel when it is added to the tank; line-mixing in which the
oil is metered into the fuel between the fuel tank and the engine; and oil injection, in which the
lubricating oil is metered directly into the intake manifold or other points using a pump
controlled by engine speed and/or throttle setting. The last two approaches are common in
motorcycle engines, as they have the ability to control the flow rate of the lubricating oil and
provide more reliable lubrication. For cost reasons, however, nearly all hand-held equipment
engines premix the oil with the fuel. Most chainsaws do have an automatic lube oil feeder, but
this is for the chain lubricant, not the engine oil.
The injection-type lubricating oil metering system provides the best control of oil metering.
Orbital has designed an electronic lubrication system for their OCP two-stroke engines to reduce
the amount of oil required by the engine. Several models of Yamaha two-stroke motorcycles
marketed in Asia have also used an electronic lubricating oil metering system to alter the
lubricating oil flow, to the carburetor according to the engine load demand. The Yamaha
Computer-Controlled Lubrication System (YCLS) supplies the required amount of lubricating
oil to the engine according to the engine speed, using an electronic control unit and three-way
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control valve. In a fuel-injected two-stroke engine, this function could be handled by the same
electronic control unit as the fuel injection system.
"Low-smoke" oil - Conventional two-stroke lubricating oils are based on long-chain paraffin or
naphthene molecules that break down slowly under combustion conditions, and are thus resistant
to combustion. The use of synthetic long-chain polyolefin materials instead of naphthenes and
paraffins can significantly reduce smoke opacity and particulate emissions from two-stroke
engines. Because of the periodic occurrence of double carbon bonds in the polyolefin chain,
these chains break down much more rapidly and thus burn more completely in the two-stroke
engine. Studies by Souillard (Souillard et al., 1971), Sugiura (Sugiura et al., 1977), Kagaya
(Kagaya et al., 1988), and Eberan-Eberhorst (Eberan-Eberhorst et al, 1979) have provided ample
evidence that substitution of polyisobutylene (PIB) for bright stock or other heavy lube-oil frac-
tions in two-stroke lubricating oils can reduce engine smoke levels and particulate emissions.
An experiment performed by Broun of Lubrizol further demonstrated the decrease in smoke
levels using such materials (Broun et al, 1989). Results of lubricity tests by independent labo-
ratories using lubricating oil with PIB and bright stock showed that the lubricity performance
for both lubricating oils was essentially the same.
In addition to smoke levels, Sugiura et al.'s study also investigated the effect of PIB on
particulate emissions (Sugiura et al., 1977). A comparison of the particulate emissions with a
conventional oil and oil with PIB is shown in table II. As this table shows, substantial reduc-
tions in particulate emissions were achieved using oil with PIB, ranging from 25 to 70%
depending on the fuel/oil ratio. It also shows that the leaner the fuel/oil ratios, the lesser the
particulate emissions, especially for the oil with PIB. Thus, higher particulate emission
reductions were observed with the oil with PIB at leaner fuel/oil ratio as compared to
conventional oil.
While research is still under way to formulate better lubricating oils for two-stroke engines, a
"low smoke" polyisobutene based lubricating oil is being required to be used for two-stroke
mopeds and motorcycles in some of the countries of Southeast Asia, including Thailand. The
current Japanese standard and a proposed International Standards Organization (ISO) standard
for two-stroke oil include a special category of low-smoke oils.
Although probably helpful, the use of low-smoke lubricating oils alone will not solve the particu-
late problem for two-strokes. The oil contained in the 20-30% of the fresh charge that short-
circuits the cylinder will be unaffected by combustion. In addition, there is a possibility that the
combustion of the polyisobutene lube stock may increase emissions of toxic air contaminants,
especially 1,3 butadiene. Further laboratory research is needed to assess the real effects of these
oils on particulate and other emissions.
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APPENDIX D:
DETERMINING HIGH, INTERMEDIATE, AND LOW VOLUME ENGINE
FAMILIES FOR NON-HANDHELD AND HANDHELD ENGINES
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Determining the High. Intermediate, and Low-Volume Engine Families for Non-HanrihpiH
Engines
We estimated the incremental costs of modifying non-handheld engines for a high, intermediate,
and low volume engine family to provide a possible range of incremental costs estimates. These
estimates per engine for a high, intermediate, and low volume family correspond to case 1,2,
and 3 of the study of non-handheld engines (Part 1). The volumes were selected as a result of
an analysis of the PSR database and were also geared to represent the potential volume size
difference between class I and class II engine lines.
The high-volume engine family was based on the largest class I engine lines by the largest class
I small engine manufacturers (Briggs and Stratton and Tecumseh). Using 1993 sales information
from the PSR database, we identified the models with the largest sales volume for both these
manufacturers. In determining the largest sales volume, we accounted for the use of the engine
in all applications, as loose engines for a distributor and as exports. We assumed the model was
essentially its own engine family. We then averaged the largest model sales for each
manufacturer. Specifically, we counted 1,200,000 units for a Briggs and Stratton model
92900/94900 engine. We counted 1,200,000 units for a Tecumseh model TVS90 engine. The
average was 1,200,000 units.
An intermediate-volume engine family provided a typical mid-range volume. Because engine
family size for the class II market tends to be much smaller than for the class I market, the
intermediate-volume could also be used to account for the possibility of that certain engine
modifications would be used on class II, but not class I engines. Consequently, for this
intermediate-volume number, we examined the high-volume engine families of the largest class
II engine manufacturers (Briggs and Stratton and Tecumseh). We focused our search on side-
valve engine models because these have the potential to undergo any of the possible engine
modifications studied in this report. In determining the largest sales volume, we accounted for
the use of the engine in all applications, as loose engines for a distributor and as exports. We
then averaged the largest model sales for each class II manufacturer. Specifically, we totalled
approximately 300,000 unit for a Briggs and Stratton line and 124,000 units for a Tecumseh
line. The average was roughly 200,000.
To determine the low-volume family, we examined the manufacturers that have a small market
share of the class I or class II engines. We defined small market share as between 0.2 and 4
percent of the combined class I and class II market. The 0.2 threshold was to eliminate the
handful of manufacturers that generated really insignificant market share (e.g., 247 total engines
sold from ACME). We examined the high-volume engine lines for these manufacturers and
came up with 35,000 based on an examination of both class I and class II engines. By averaging
sales data from Kawasaki and Wisc-Teledyn, we determined that the class I and class II models
varied between 25,000 and 45,000 units, respectively. Consequently, for the low-volume
family, we selected the midpoint or 35,000.
D-l
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Determining the High and Low Volume Engine Families for Handheld Engines
For the handheld engines, we elected to provide numbers for only a high and low volume family
because we were not accounting for the possibility of that certain engine modifications would
be used only on certain classes of handheld engines. Also, the range between high and low-
volume is less prominent for handheld than non-handheld engines. The incremental cost
estimates per engine for a high and low volume family correspond to case 1 and 2 of the study
of handheld engines (Part 1).
For the high-volume engine family, we conducted a similar analysis as for the non-handheld
engine market. The handheld engine market is largely composed of four engine manufacturers -
Poulan, Homelite, Ryobi, and Stihl. Using 1993 sale information from the PSR database, we
identified the models with the largest sales volume for all these manufacturers. In determining
the largest sales volume, we accounted for the use of the same engine in all applications, as
loose engines for a distributor and as exports. We then averaged the largest model sales for
each manufacturer. Specifically, we averaged 800,000 units for a Ryobi/Inertia Dynamic modei.
400,000 units for a Homelite model, 350,000 units for a Poulan model, and 160,000 units for
a Stihl model. The average was approximately 400,000 units for a single model from the
manufacturers with the largest market share.
We then conducted a similar analysis of the manufacturers with a small market share. Like for
the non-handheld, we defined that small market share as between 0.2 and 4 percent of the
combined class III, IV, and V market share. The 0.2 threshold was to eliminate the handful of
manufacturers that generated really insignificant market share (e.g., 828 total engines sold from
US Engines). The average number of engines for two manufacturers with small market shares -
Kioritz (95,000 engines) and Tecumseh (88,000) - was approximately 90,000 engine units.
Determining the Special High-Volume Production for Manufacturing an Improved Carburetor
for Non-Handheld Engines (see Section 4.6 of Study)
An improved carburetor, due to an improvement in manufacturing variability, would be used in
many models of relatively similar horsepower. Therefore, the annual production of carburetors
could be higher than the even 1.2 million engines, representing only one high-volume class I
engine line. To determine the special high-volume production number for an improved
carburetor, we selected a manufacturer with a large market share (Briggs and Stratton) and
added the production volumes for any engine models between 3.5 and 5 horsepower. These
models could share the same improved carburetor. The resulting total was 4 million engines
which was used in the study. The analysis was performed using the PSR ENGINDATA
database.
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