76-27 AB
Emission Testing of a 1976 Toyota with the
TTC-L Lean Burn Engine
September 1976
Technology Assessment and Evaluation Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
U.S. Environmental Protection Agency
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Background
Lean Mixture combustion engines are attractive because cf the low emis-
sions and good fuel economy that are possible with a properly designed
lean burn engine. Toyota Motor Company Ltd. has developed several small
displacement (under 2 litres) lean burn engines, and early this year
began selling a lean burn vehicle in Japan.
The Emission Control Technology Division (ECTD), because of its interest
in evaluating developments in automotive technology, has recently tested
several prototype lean burn vehicles. When Toyota offered to provide
EPA a lean burn vehicle for emissions testing, ECTD was pleased to have
the opportunity to evaluate this new technological development.
The Environmental Protection Agency receives information about many
systems which appear to offer potential for emissions reduction or
improvement in fuel economy compared to conventional engines and vehicles.
EPA's Emission Control Technology Division is interested in evaluating
all such systems, because of the obvious benefits to the Nation from the
identification of systems that can reduce emissions, improve economy, or
both. EPA invites developers of such systems to provide to the EPA
complete technical data on the system's principle of operation, together
with available test data on the system. In those cases in which review
by EPA technical staff suggests that the data available show promise for
the system, attempts are made to schedule tests at the EPA Motor Vehicle
Emission Laboratory at Ann Arbor, Michigan. The results of all such
tests are set forth in a series of Technology Assessment and Evaluation
Reports, of which this report is one.
The conclusions drawn from the EPA evaluation tests are of limited
applicability. A complete evaluation of the effectiveness of a system
in achieving improvements on the different types of vehicles that are in
actual use requires a much larger sample of test vehicles than is eco-
nomically feasible in the evaluation test projects conducted by EPA.
For promising systems it is necessary that more extensive test programs
be carried out.
The conclusions from this EPA evaluation test can be considered to be
quantitatively valid only for the specific test car used. However, it
is reasonable to extrapolate the results from the EPA test to other
types of vehicles in a directional or qualitative manner, i.e., to
suggest that similar results are likely to be achieved on other types of
vehicles.
Vehicle Description
The vehicle tested was a 1976 Toyota Corolla Liftback fitted with the
TTC-L (Toyota Total Clean System - Lean Burn) lean burn engine and a
five-speed manual transmission. The engine is an in-line four-cylinder
of about 1600 cc displacement volume. The vehicle is described in
detail on the following page.
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TEST VEHICLE DESCRIPTION
Chassis model year/make - 1976 Toyota Corolla Liftback
Emission control system - Toyota Lean Burn - TTC-L
Engine
type 4 Stroke Otto Cycle, OHV, In Line 4 cyl.
bore x stroke 3.35 x 2.76 in. (85 x 70 mm)
displacement . 96.9 cu. in. (1588 cc)
compression ratio 9.0:1
maximum power @ rpm 68 bhp/51 kW at 5200 rpm
fuel metering single 2-barrel carburetor
fuel requirement regular unleaded; tested with
Indolene HO, Unleaded, with .03 wt. % sulfur
Drive Train
transmission type 5 speed manual
final drive ratio 3.91 to 1
Chassis
type Unitized body, front engine, rear drive
tire size 165 SR 13
curb weight 2250 pounds
inertia weight 2500 pounds
passenger capacity 4
Emission Control System
basic type TTC-L, Lean burn engine with divided
chamber (Turbulence Generating Pot-TGP),
Exhaust Port Liners, and Heat Shielded
Exhaust Manifold
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The engine is a modified version of the Toyota 2T-C engine, with a
turbulence generating pot (TCP) in the main combustion chamber to
promote fast burning of lean mixtures. (See Figure 1).
EXHAUST VALVE
TURBULENCE
GENERATING
POT(TGP)
EXHAUST MANIFOLD CASE
OUTER CORE
INNER
CORE
GROSS-SECTION OF
AND
Figure 1
Toyota TTC-L Lean Burn Engine
A dual-electrode sparkplug is placed at the throat of the TCP to ensure
ignition. According to Toyota, the mixture flow speed and sparkplug
location are critical factors in obtaining good ignition with a homo-
geneous lean mixture.
Exhaust port liners and a heat shielded exhaust manifold are used to
maintain high exhaust gas temperatures. Thus, HC and CO are further
oxidized because the lean combustion process leaves enough oxygen in the
exhaust.
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An improved carburetor is used to reduce flow pulsations and deliver a
homogeneous mixture to the combustion chamber. The principal change was
the use of a sintered metal air bleed tube.
Toyota claims that this improved carburetor and the TCP have improved
vehicle driveability and reduced HC, CO, and NOx emissions. Figure 2
below (furnished by Toyota) shows typical NOx formation characteristics
for Toyota's conventional engines and their TTC-L lean burn engine.
Lean Burn
14 15 16
17 18
A/F
19 20
Figure 2
NOx Formation Characteristics
Test Procedures
Gaseous exhaust emissions tests were conducted according to the 1975
Federal Test Procedure ('75 FTP), described in the Federal Register of
November 15, 1972, except that no evaporative emissions tests were
conducted. Additional tests included the EPA Highway Fuel Economy Test
(HFET), described in the Federal Register, Volume 39, Number 200,
October 15, 1974, and steady state emissions tests.
These tests are conducted on a chassis dynamometer and employ the Con-
stant Volume Sampling (CVS) procedure, which gives exhaust emissions of
HC, CO, NOx and C02 in grams per mile. Fuel economy is calculated by
the carbon balance method. The fuel used was Indolene unleaded 96 RON
gasoline. All tests were conducted using an inertia weight of 2500
pounds (1134 kg) with a road load setting of 9.4 horsepower (7.0 kW) at
50 miles per hour (80.5 km/hr). Three different shift patterns were
employed.
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The vehicle was also tested for sulfate emissions using the EPA sulfate
test procedure, a description of which is given at the end of this
report.
Since Toyota recommended shifting gears at what were considered very low
speeds, tests were also conducted using alternate shift points to
determine the effects on emissions and fuel economy. The shift patterns
used were:
1 Toyota recommended shift pattern for TTC-L vehicle.
2 Toyota recommended shift pattern for U.S. Toyota Corolla.
3 EPA shift pattern for 4-speed vehicles (marked on driver's aid
strip chart) when none is specified by manufacturers.
Shift
Pattern
1
2
3
Shift point
1-2
10 mph
12 mph
15 mph
Shift point
2-3
20 mph
22 mph
25 mph
Shift point
3-4
26 mph
30 mph
40 mph
Shift point
4-5
45 mph
Test Results
Exhaust emissions data, summarized below, showed that the Toyota TTC-L
vehicle was well within the levels required by the 1977 Federal emis-
sions standards of 1.5 gm/mi HC, 15.0 gin/mi CO, 2 gm/mi NOx. However,
the vehicle did r.ot meet the statutory 1978 emission standards of .41
gm/mi HC, 3.4 gm/mi CO, .4 gm/mi NOx. Detailed results appear later in
this report.
The test results for shift pattern 1 are listed below. Results are
listed in Tables 1 and 2 for the other shift patterns.
'75 FTP Composite Mass Emissions
grams per mile .,-..
(grams per kilometre)
HC C() CO2 NOx Fuel Economy
Shift pattern 1
(average of 7
tests)
1977 Federal
Standards 1.5 15 2.0
Values in parentheses denote metric units.
1.14
(.71)
6.43
(4.00)
295
(183)
1.55
(.96)
(fuel consumption)
28.7 miles/gal
(8.2 litres 100/km)
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On the EPA Highway Fuel Economy Cycle the results were:
3 En
(1)
EPA Highway Fuel Economy Test Mass Emissions
grams per mile
Shift pattern 1
(average of 7
tests)
(grams per kilometre)
HC CO C02 NOx
,09 2.40 229 1.35
(.06) (1.49) (142) (.84)
Fuel Economy
(Fuel consumption)
38.2 miles/gal
(6.2 litres/100km)
Steady State fuel economy results were:
Speed mph (mi/hr)
15
30
30
45
45
60
Gear
2
3
4
4
5
5
Fuel economy
miles/gal
29,
35,
46,
40.0
44.2
37.1
(Fuel consumption)
litres/100km
(8.0)
(6.6)
(5.1)
(5.9)
(5.3)
(6.3)
A comparison of the test vehicle's combined city/highway fuel economy
with that of the Toyota Corolla tested for compliance with 1977 standards,
showed that the test car had essentially the same fuel economy. When
compared to all vehicles in the same inertia weight class (2500 Ibs) the
test car showed a 13% fuel economy improvement.
City/Highway Combined
Fuel Economy
miles/gal
Toyota TTC-L
(96.9 CID)
Toyota Corolla (1977 Certification
vehicle) (96.9 CID)
Average of all 2500 Ib 1977
Vehicles (avg. 98.1 CID)
32.3
31.8
28.7
(Fuel consumption)
litres/100km
(7.3)
(7.4)
(8.2)
(1)
Values shown in parentheses denote metric units.
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In calculating city/highway combined fuel economy, the urban fuel economy
is weighted 55% and the highway fuel economy is weighted 45% to account
for the 55/45 ratio of urban to rural mileage accumulation. The following
equation is used:
MPG , . , = 1
combined
.55 + .45
MPG , MPG, . ,
urban highway
The tests using shift pattern 2 (See Tables 1, 2, and 3) showed no
significant differences in emissions from shift pattern 1. However,
using shift pattern 3 resulted in 10% lower fuel economy over the 75
FTP, when compared to shift pattern 1.
In tests conducted by Toyota at their emissions laboratory, the vehicle
achieved approximately 6% better fuel economy than was achieved at the
EPA laboratory in initial testing. Some previous test programs had
shown better correlation between EPA and Toyota test facilities. Normally
ECTD conducts only three tests in its confirmatory evaluation programs.
However, because of the importance of fuel economy, ECTD conducted
additional tests to investigate this 6% difference in fuel economy.
These added tests used an EPA dynamometer test facility that had cor-
related well with Toyota's laboratory, No significant differences
between EPA dynamometers were observed for these additional tests.
Therefore all EPA test results were averaged together.
Sulfate emission test results are summarized in Table 5. Over the
sulfate cycle the vehicle emitted about .4 milligrams of sulfuric acid
per mile.
For comparison, typical vehicle sulfate emission rates (as found in the
EPA sulfate baseline study*) are:
Catalyst vehicles with excess air - about 30 mgm/mile H-SO,
(range 0.3-96)
Catalyst vehicles without excess air - about 17 mgm/mile H7SO,
(range 0.5-83) L *
3-way catalyst vehicles - 1 mgm/mile H_SO,
Non-catalyst vehicles - 1 mgm/mile H_SO,
The large range in sulfate levels is due to the wide variations in
technologies among the many vehicles tested.
* Internal report "Test Report, Automotive Sulfuric Acid Baseline
Program, " EPA, Emission Control Technology Division, January 1976.
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The Toyota TTC-L vehicle had excellent driveability, and the engine ran
quietly and smoothly. With all shift patterns the vehicle accelerated
well enough to follow the prescribed driving schedules. No cold start
problems were encountered. The vehicle performed equally well when it
was driven on the road for a driveability evaluation. However, the
various drivers preferred to shift at much higher speeds when not using
Toyota's shift pattern, in order to maintain what were considered more
normal acceleration rates.
Conclusions
At low mileage this Toyota Corolla equipped with the TTC-L lean burn
system met the emission levels required by the 1977 Federal Standards.
No catalyst aftertreatment was employed.
This system had a significant fuel economy advantage relative to con-
ventional engines tested for 1977 emission standard certification in the
same weight class.
Sulfate emission levels were found to be similar to non-catalyst vehicles.
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Table 1
Bag 1 Cold Transient
Fuel
Economy
HC
77-2497
77-2501
77-2800
77-4289
77-4323
77-4344
77-4348
77-2581
77-2583
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(2)
(3)
1
1
1
1
1
1
1
1
1
.77
.59
.56
.70
.60
.78
.63
.65
.34
CO
11.
10.
8.
9.
10.
10.
10.
10.
10.
43
71
76
45
50
46
OS>
50
52
C02
316
313
299
305
309
311
313
330
340
< NOx
2.
2.
I.
2.
2.
2.
2.
2.
2.
05
15
88
19
17
10,
08
24
12
mpg
26
26
28
27
26
26
26
25
24
.1
.5
.0
.3
.9
.6
.6
.2
.6
75 FTP Mass Emissions
grams per mile
Bag 2 Hot Stabilized
KC
1.02
.95
1.03
.87
.98
1.02
.92
.86
.92
CO
5.95
5.75
5.73
5.57
5.04
5.31
5.87
6.15
6.26
CO 2
313
311
294
298
291
303
308
328
346
NOx
1.22
1.35
1.01
1.21
1.08
1.16
1.26
1.18
1.21
Fuel
Economy
mpg
27.3
27.4
29.0
28.6
29.4
28.2
27.7
26.1
24.7
Bag 3 Hot Transient
HC
1.08
1.07
1.10
1.03
1.08
1.12
1.12
.99
1.10
CO
5.48
5.86
5.13
5.21
4.87
4.68
5.07
5.00
4.65
CO 2
276
278
263
273
265
268
274
276
300
NOx
1.80
1.89
1.68
1.81
1.98
1.83
1.87
1.92
1.61
Fuel
Economy
mpg
30.8
30.6
32.3
31.2
32.2
31.8
31.1
30.9
28.5
Test Number
(1) Shift points
(2) Shift points
(3) Shift points
HC
Table 2
75 FTP Composite Mass Emissions
grams per mile
CO
C02
77-2497 (1)
77-2501 (1)
77-2800 (1)
77-4289 (1)
77-4323 (1)
77-4344 (1)
77-4348 (1)
77-2581 (2)
77-2583 (3)
1-2 at 10 mph,
1-2 at 12 mph,
1-2 at 15 mph,
1.19
1.12
1.16
1.08
1.13
1.20
1.12
1.06
1.06
2-3 at
2-3 at
2-3 at
6.95
6.80
6.19
6.27
6.11
6.20
6.52
6.73
6.69
20 mph,
22 mph,
25 mph,
303
303
286
293
288
295
300
314
332
3-4 at 26 mph,
3-4 at 30 mph,
3-4 at 40 mph,
NOx
1.55
,66
,37
,58
,55
,54
,60
,60
1.51
4-5 at 45 mph
Fuel
Economy
2ES.
27.9
28.0
29.6
29.0
29.5
28.8
28,
27,
25.7
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10
Test Number
Table 3
Highway Fuel Economy Test
Mass Emissions
grams per mile
HC
CO
COo
NOx
77-2496
77-2502
77-2728
77-4325
77-4326
77-4345
77-4349
77-2582
77-2584
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(2)
(3)
.09
.09
.09
.11
.10
.09
.09
.11
.09
2
2
2
2
2
2
2
2
1
.29
.26
.45
.47
.46
.45
.40
.33
.48
232
229
221
228
232
227
236
227
237
1.22
1.37
1.23
1.41
1.43
1.39
1.39
1.31
1.53
Fuel
Economy
MPG
37.6
38,
39.
38,
38,
38,
1
4
4
5
5
36.9
38.4
37.1
(1) Shift points
(2) Shift points
(3) Shift points
1-2 at 10 mph, 2-3 at 20 mph, 3-4 at 26 mph,
4-5 at 45 mph.
1-2 at 12 mph, 2-3 at 22 mph, 3-4 at 30 mph,
4-5 at 40 mph.
1-2 at 15 mph, 2-3 at 25 mph, 3-4 at 40 mph.
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Table 4
Steady State Mass Emissions
grams per mile
Test Number
77-2593
77-2503
77-2503
77-2504
77-2504
77-2505
77-2505
Speed
Idle *
15
30
30
45
45
60
Gear
N
2
3
4
4
5
5
HC
.19
.87
.83
.17
.02
.04
.01
CO
.97
4.43
2.40
2.95
1.95
2.48
1.21
CO
33
291
246
186
219
197
237
NOx
.02
.32
.61
.51
.89
.86
2.13
Fuel Economy, mpg
.23
29.5
35.5
46.5
40
44.2
37.1
* grams per minute/gallons per hour
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Table 5
Mass Emissions from Sulfate Tests
grama per mile
Fuel
Test Number Test Type
77-2516 75 FTP (Composite)
77-2518 HFET
77-2517 SET
HC
1.15
.18
.35
CO
6.36
2.41
3.38
C02
300
233
234
NOx
1.66
1.52
1.24
Economy , mpg
28.3
37.4
36.9
H2S04*
.38
.65
.39
% Conversion
.4
.9
.6
* H So emissions are in milligrams per mile.
** Percent conversion of fuel sulfur to sulfuric acid
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13
Toyota Lean Burn System TTC-L
Procedures used to measure sulfate emissions
1. The fuel was drained from the test vehicle. The vehicle was re-
fueled with unleaded Indolene HO gasoline containing 0.03% sulfur by
weight.
2. The vehicle was prepped by driving the vehicle over one LA-4 cycle
to precondition the vehicle.
3. The following sequence of test cycles was used to measure sulfate
emissions.
a) 75 FTP
b) Sulfate Emissions Test (SET)
c) HFET
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