/!!\ % PRO^ Dec. 1975 FAIRBANKS, ALASKA AUTOMOTIVE RETROFIT EVALUATION STUDY U. S. ENVIRONMENTAL PROTECTION AGENCY CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY ARCTIC ENVIRONMENTAL RESEARCH STATION COLLEGE. ALASKA 99701 CERL-004 ------- FAIRBANKS, ALASKA AUTOMOTIVE RETROFIT EVALUATION STUDY by Ronald K. Turner Harold J. Coutts WORKING PAPER NO. 29 CERL-004 U.S. ENVIRONMENTAL PROTECTION AGENCY CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY ARCTIC ENVIRONMENTAL RESEARCH STATION COLLEGE, ALASKA 99701 December 1975 ------- EPA REVIEW NOTICE This report has been reviewed by the Corvallis Environmental Research Laboratory--Corvallis, and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommenda- tion for use. AERL Working Paper Series presents results of investigations which are, to some extent, limited or incomplete. Therefore, conclusions or recommendations, expressed or implied, are tentative. i i ------- ABSTRACT During the winter of 1974-1975, automotive retrofit pollution control devices were installed on 18 domestic in-service automobiles to evaluate their winter performance for carbon monoxide emission reduction, drive- ability and fuel economy. The retrofit devices were (1) air bleed to intake manifold, (2) exhaust gas recirculation plus air bleed, and (3) catalytic converters. The emissions were measured at idle and at 2500 no-load rpm. The air bleed devices initially functioned on 8 out of 11 installations. For the 8-month study, the overall carbon monoxide reduction was 44 percent. Fuel economy increased 2 to 3 percent. The exhaust gas recirculation plus air bleed devices were successful on 3 out of 4 installations. A 30 percent overall reduction in carbon monoxide was attained. Fuel economy increased about 1 percent. The average carbon monoxide reduction for catalytic con- verters was 62 percent. These devices worked on all four test vehicles. Fuel economy was not expected to be affected. Conclusions indicate that, technically, the retrofits work, but the practicality of a mandatory retrofit program for the Fairbanks area is in question. iii ------- TABLE OF CONTENTS SECTION PAGE I Summary of Findings ] II Introduction 3 III Retrofit Devices 5 Air Bleeds to Intake Manifold 5 Exhaust Gas Recirculation plus Air Bleed 5 Catalytic Converters 3 IV Test Equipment and Methods 11 V Discussion 13 Data Summary 13 Air Bleeds 13 Exhaust Gas Recirculation plus Air Bleed 17 Catalytic Converters 13 Fuel Economy 13 Associated Problems and Considerations is i v ------- LIST OF FIGURES NUMBER PAGE 1 Typical Exhaust Gas Composition vs. Air/Fuel 6 2 Installation of A1r Bleed (STP Corp.) 7 3 Installation of Exhaust Gas Recirculation plus A1r Bleed (DANA Corp.) 9 4 Installation of Exhaust Gas Recirculation plus A1r Bleed (STP Cprp.) 10 LIST OF TABLES NUMBER PAGE 1 Retrofit Evaluation Preliminary Data Summary- Phase I 14 2 Retrofit Evaluation Preliminary Data Summary- Phase II 15 v ------- ACKNOWLEDGEMENTS We acknowledge the following individuals for their invaluable assistance with the project: Mr. John Miller, head of Scientific Services, Geophysical Institute, University of Alaska, Fairbanks, Alaska, for providing test vehicles; The U.S. Environmental Protection Agency, Region X, Seattle, Washington, for financial support; The STP Corporation, Santa Monica, California, and Dana Corporation, Whittier, California, for supplying the retrofit devices and Figures 2, 3 and 4; The U.S. Department of Transportation, Federal Highway Administration, Washington, D.C., for use of fuel meters; The State of Alaska, Department of Highways, Fairbanks, Alaska, for measuring out the mileposts; The Atlantic Richfield Company, Harvey Technical Center, Harvey, Illinois, for use of a lead-in-gasoline analyzer; The cooperative citizens who volunteered the use of their private vehicles during the Automotive Retrofit Evaluation Study. vi ------- SECTION I SUMMARY OF FINDINGS Three types of retrofit devices were evaluated on 18 vehicles from October 1974 to June 1975. Exhaust gas concentrations of carbon monoxide (CO) and hydrocarbons (HC) were measured at normal idle and at 2500 rpm, no-load engine speeds. The effectiveness of each type of retrofit varied from vehicle to vehicle. For the 11 pre-1969 vehicles equipped with air bleed devices, the overall result was a 44 percent CO reduction. This performance rate included 3 devices which failed after several months but excludes 2 vehicles on which the devices would not initially work. Exhaust gas recirculation plus air bleed devices were installed on one 1968, one 1969, and two 1970 vehicles. The 1968 vehicle would not operate with either the exhaust gas recirculation plus air bleed or with the air bleed alone. A 40 percent CO reduction was achieved on the other three vehicles. The air bleeds and some exhaust gas recirculation plus air bleed de- vices included vacuum delay valves on ignition timing as part of the retrofit package. The valves were designed to reduce HC emissions. How- ever, it was found that during cold weather driveability tests, they caused such excessive stumbling on acceleration, especially for the smaller engines, that they were removed. On 1971 to 1974 vehicles equipped with catalytic converters, the re- duction in CO and HC was 62 and 47 percent, respectively. Changes in fuel economy were measured both with and without retrofits. Results were in favor of retrofitting, with an overall increase in mileage of 2 to 3 percent for the air bleed devices and about 1 percent for the exhaust gas recirculation plus air bleed devices. It had not been antic- ipated that fuel economy would be affected by the catalytic converter retrofits. Driveability was affected on some vehicles equipped with air bleed and exhaust gas recirculation plus air bleed devices. Hesitation and/or stumbling on acceleration was noticed on small engine vehicles. No effect on driveability was evident on vehicles equipped with catalytic converters except for some reduction in road clearance. Because of excessive choking, the retrofits did not effectively reduce cold start emissions. Cold starts may be the highest contributor to total CO emissions in the Fairbanks central business district. Knowledgeable engine maintenance is critical in controlling exhaust pollution. The lower emissions levels possible with vehicles equipped with emission control devices cannot be realized in continued service unless a proper inspection/maintenance program is implemented. The effect of such a program in the Fairbanks area will be limited by the 1 ------- interest of the vehicle owner, the competence of the service mechanic and his ability to understand and maintain emission control devices using exhaust gas analyzers. 2 ------- SECTION II INTRODUCTION As part of the 1970 amendments to the Clean Air Act, states where air quality was below Federal standards were required to develop an approved plan to attain these limits. Since none was developed for Alaska, the U.S. Environmental Protection Agency (EPA) formulated a plan (Transporta- tion Control Strategy—Federal Register, November 27, 1973) to reduce ambient carbon monoxide levels in the Fairbanks central business district. This plan required that retrofit devices be installed in all pre-1975 light duty vehicles in the Fairbanks North Star Borough. Fairbanks residents questioned the affect of the devices upon their vehicles during cold weather operation. In response, EPA decided to evaluate retrofit systems perfor- mance in the Fairbanks area during the winter and spring of 1974-1975. Although this report is concerned primarily with the technical aspects of retrofitting automobiles in the Fairbanks basin, many other factors should be considered. The small sample size, 18 test vehicles, represents only 0.04 per- cent of the approximately 45,000 registered vehicles in the Fairbanks North Star Borough. Thus, extrapolating from these data may yield an unfair indication of the effective, realistic reduction of air pollu- tion that would result if a borough-wide program were implemented. This study was performed on warmed-up vehicles only. Three types of retrofit devices were chosen to be evaluated on the following U.S. manu- factured vehicles: 1. Air bleed to intake manifold - through positive crankcase venti- lator (PCV) line on all domestic pre-1968 light duty vehicles, hereafter, simply designated air bleeds. 2. Exhaust gas recirculation plus air bleed - both to intake manifold through the PCV line on 1968 to 1970 domestic light duty vehicles. 3. Catalytic converters - installed in the exhaust lines of 1970 to 1974 domestic light duty vehicles. Initially there were 18 vehicles in the Retrofit Program: (a) 10 with air bleeds supplied by STP Corporation (the 4 pre-1964 vehicles had to first be retrofitted with positive crankcase ventilators). (b) 2 with exhaust gas recirculation plus air bleed supplied by DANA Corporation. (c) 2 with exhaust gas recirculation plus air bleed supplied by STP Corporation. (d) 4 with catalytic converters supplied by U0P Corporation. 3 ------- The authors hope that the technical information provided by this study will stimulate thought and discussions leading to scientifically sound decisions regarding an air pollution abatement program in the Fair- banks, Alaska area. 4 ------- SECTION III RETROFIT DEVICES Air Bleeds to Intake Manifold At idle most pre-1968 carburetors supply air to fuel ratios (A/F) richer than 13 to 1, resulting in exhaust gas CO concentrations of more than 3 percent. Figure 1 shows how the typical exhaust concentrations of CO, 0? and HC vary with respect to input air to fuel ratio (A/F) The stoichiometric ratio is the A/F which, for complete combustion, should produce no CO, 02 or HC in the exhaust. The air bleeds increase the A/F by adding air below the carburetor, resulting in more complete combustion. All of the original air bleeds had thumb screws for regulating the air. When too much air is added, the engine lean-misfires causing increased exhaust hydrocarbons. Therefore, an exhaust gas CO/HC analyzer is needed for proper installation. The installation instructions are shown in Figure 2. Most carburetors installed in 1970 or after were designed to operate so lean that addition of an air bleed would cause them to lean-misfire. Under cold weather operation, improper retrofitting caused some of the pre-1969 vehicles to lean-misflre. Since the vacuum delay valves (Figure 2) reduced hydrocarbon only on accelerations and decelerations, they were removed because, in some cases, they caused the test vehicles to stumble (have a short, sharp reduction in acceleration rate). The air bleed devices are considered (by the authors) to be modified to suit cold climate conditions when the vacuum delay valve is removed. Exhaust Gas Recirculation plus Air Bleed In the exhaust gas recirculation system a valve is connected between the exhaust and intake manifold. This valve allows a small amount of exhaust gas to recirculate back into the intake. The amount of exhaust gas recirculated is controlled by engine speed and load, being least at idle. The exhaust gas recirculation is primarily a nitric oxide (NO) con- trol technique. The function of the recirculated exhaust is to dilute the intake charge which results in lower peak combustion temperatures, thus creating less NO. The air bleed is the only part of this system that reduces CO emissions. In the DANA system, the air bleed is actually an enlarged PCV valve which admits more air into the .intake manifold. In the STP system, fresh air is admitted through the exhaust gas recirculation valve. Typical installations are shown in the manufacturers' installa- tion drawings (Figures 3 and 4). To effectively operate with the two above types of retrofits, auto- motive engines must have carburetors and vacuum plus centrifugal spark 5 ------- FIGURE 1 TYPICAL EXHAUST GAS COMPOSITION VS. AIR/FUEL 15 AIR/FUEL RATIO ------- FIGURE 2 STP MODULATING AIR BLEED Distributor P.C.V. Intake Manifold Carburetor Vacuum Source o ) Red Side Velocity Nozzle Vacuum Delay Valve Modulating A1r Bleed • T-F1tti ng While at engine idle, / adjust this screw for minimum hydrocarbons HOW IT WORKS: The modulating air bleed is designed to allow additional air to enter the intake system during engine modes making a leaner fuel-air ratio possible. This self-modulating control device allows a substantial fuel savings while reducing ex- haust emissions. INSTALLATION: To Install the modulating air bleed, cut the PCV hose and insert the velocity nozzle. Mount the modulating air bleed on tapered nipple using 3/8" I.D. rubber hose. Cut vacuum line leading from carburetor to vacuum diaphragm on ignition distributor. Insert T-f1tting as shown 1n diagram. Install vacuum delay valve between T-f1tt1ng and vacuum diaphragm on ignition distributor. Be sure red side of vacuum delay valve is facing distributor. 7 ------- advance. Many foreign vehicles lack these three features, and therefore cannot be retrofitted. Catalytic Converters The two systems mentioned above reduce the creation of CO by leaning out the A/F mixture to the engine. The catalytic converter does not reduce engine emissions of CO and HC. Instead, it burns them in the exhaust system. A catalyst is a substance which accelerates a chemical reaction. In this case, the oxidation of carbon monoxide to carbon di- oxide is catalyzed. The catalyst is platinum coated alumina pellets approximately 1/8-inch in diameter. The oxygen required for combustion of CO and HC (hexane in this case) can be calculated: Carbon Monoxide CO > + 1/2 02 » CO2 1 percent + 1/2 percent by volume n-Hexane C6H14 + 9_1/2 °2 * 6C02 + 7H2° 100 ppm + 0.095 percent by volume Therefore, it can be seen that for each 1 percent of CO to be oxi- dized, one-half that amount of 02 is required. The 02 required to burn the HC (which is usually less than 200 ppm) is small compared to that necessary for the CO. There are two ways to get the necessary oxygen into the exhaust. One is by retrofitting an air pump to inject air (20 percent 02) into the ex- haust manifold. The other is to adjust the carburetor to operate on or near the lean side of the stoichiometric ratio (Figure 1). Retrofitting air pump systems is difficult and expensive. In attempt- ing a retrofit on a 1971' GMC Sprint, it was found that the dealer-supplied parts would not fit. Experience with this and two other vehicles indicates that the cost of installing air pumps alone can amount to over $300 per vehicle. Since there were considerable air pump retrofit problems, the catalytic converters were installed without air pumps. It was found that the carbure- tors of many newer vehicles can be adjusted lean enough to provide suffi- cient exhaust oxygen. This was done with the catalytic converter retrofit vehicles. The converters are also known as catalytic mufflers because they look like mufflers and are located in the exhaust pipe just before or in lieu of conventional mufflers. Installation was performed by a Fairbanks muffler shop. 8 ------- FIGURE 3 INSTALLATION DRAWING OF DANA CORPORATION EXHAUST GAS RECIRCULATION PLUS AIR BLEED RETROFIT TO CARBURETOR VACUUM ENGINE SPEED SWITCH & SOLENOID VACUUM VALVE POSITIVE CRANKCASE VENTILATION VALVE ifV EXHAUST PIPE OUTLET FITTING STAINLESS STEEL RETURN TUBING I— VACUUM OPERATED EXHAUST GAS RECIRCULATION VALVE -v.! i\ ] v\ m\' i VACUUM SPARK ADVANCE ------- AIR CLEANER* FITTING VELOCITY NOZZLE* PCV VALVE PCV LINE r & $ DISTRIBUTOR* VACUUM DELAY VALVE HEAT RISER RUBBER HOSE* STP/EGR VALVE* HEAT RISER CONVOLUTED* TUBING DISTRIBUTOR VACUUM LINE FIGURE 4 * SUPPLIED IN KIT TYPICAL V8 INSTALLATION EGR PLUS AIR BLEED STP/EGR NOx EMISSION CONTROL SYSTEM ------- SECTION IV TEST EQUIPMENT AND METHODS This emission study was performed on warmed up engines at steady state conditions. The 18 vehicles in the test program are Identified on the Data Summary Tables (Tables 1 and 2). Engine rpm was measured with an electric Kal-Equipment Dwell-Tac Tester, Model #T-111. Exhaust concentrations were measured with a Horiba Mexa 300 CO/HC meter. Oxygen was measured using a portable Teledyne meter. The gas analyzers were placed in a heated garage on the West Ridge of the University of Alaska Fairbanks campus. An insulated and heat traced sample line was run outside to the vehicle being monitored. Before testing, the vehicle was warmed up until hot air was coming from the heating system. Emissions were first measured at 2500 rpm no-load, then at normal idle speed, both with transmission in neutral. The test procedure is similar to that developed by Atlantic Richfield Company for their Clean Air Caravan. A drlveabiHty test was performed by driving east down the University of Alaska hill to the College Road-University Avenue intersection and back via the Nenana Highway—a total trip distance of about 3 miles. The retro- fit device was then defeated and the tests repeated. The air bleed was defeated by disconnecting from the PCV "T" (velocity nozzle--Figure 2) and plugging the open hose end. The air bleed was not always physically removed from the carburetor to distributor vacuum ad- vance tubing since there was no flow (other than signal) on that line. To defeat the STP exhaust gas recirculation device, both the rubber hose from the air cleaner and the convoluted tubing (Figure 4) were disconnected. The open end left at the velocity nozzle was plugged. To defeat the DANA exhaust gas recirculation device, the vacuum line to the valve was disconnected and the air bleed-PCV was replaced with the original (before retrofit) PCV. The catalytic converter could not be easily removed and/or by-passed for testing so 1/8-inch nominal pipe size sample taps were welded into the exhaust pipe above and below each converter. To prevent nonrepresentative sampling, the downstream taps were located at least 5 pipe diameters from the converters. The catalytic converter came with a thermocouple tempera- ture probe installed in the approximate center of the catalyst bed. Gaso- line tank filter neck restrictors were installed on the Plymouth, Vega and Nova. The gasoline in all the catalytic converter retrofit vehicles was routinely tested for lead by use of a diathiazone absorption color comparator (ARCO lead test kit). Constant speed fuel economy tests were performed between the 2-1/2 and 22-1/2 mlleposts on the four-lane Richardson highway, south of Fairbanks. The Alaska Highway Department provided milepost measurements, to an accuracy of 1:1000, for the 20-mile course. The course was rela- tively level with maximum short distance grade less than 1 percent and maximum curvature less than 2 percent. Each test run consisted of a 40- mile round trip with the retrofit operating. The device was then defeated 11 ------- and the run repeated. A stopwatch was used in lieu of a fifth wheel to calculate actual speed. Four fuel odometers were used. Three were manu- factured by Columbia Systems—two of which read to 0.01 gallons and one to 0.05 gallons; one from the Kent Moore Tool Company read 0.001 gallons. The manufacturer stated accuracy varied from + 0.02 percent for the Colum- bia systems to +3 percent for the Kent Moore meter. They were checked and calibrated at Arctic Environmental Research Laboratory using water and a graduated cylinder. 12 ------- SECTION V DISCUSSION Data Summary All significant data have been condensed and are presented In the Retrofit Evaluation Preliminary Data Summary Tables (Tables 1 and 2). Phase I was the Initial testing program that ran from October 1, 1974, to February 23, 1975. Phase II continued from February 24, 1975, to June 1, 1975. The composite test temperatures are listed after the en gine type and displacement (cubic Inches). Before Installation of retrofits, in most cases, the carburetors' Idle mixtures were set to the following specifications: Models Pre-1968 1968-1969 1970-1971 1973-1974 Air Bleeds In the first test phase, air bleeds effectively reduced CO over a 6 to 94 percent range. The idle and 2500 rpm removals averaged 55 and 44 percent, respectively. Prior to the second test phase,three vehicles were removed from the program. The 1964 Chevrolet station wagon and the 1968 Ford station wagon became inoperable when retrofitted. The owner of the third vehicle, a 1974 Ford 1/2-ton pickup, discontinued its use. The air bleeds were effective in reducing CO over a 0 to 82 percent range for the remaining vehicles during Phase II. Combining the results of the idle and 2500 rpm tests for Phase I yielded an overall average CO reduction of 39 percent. Overall reduction from both phases was 44 percent even though only 5 of the original 11 installations were still performing. During Phase II the air bleeds on the 1968 Chevrolet carryall, 1968 Chevrolet 1/2-ton pickup and the 1968 Jeep were found to have failed on the dates noted on Table 2. Even though they were readjusted, they were considered to have failed completely and willbe carried as zero removal until the 1-year anniversary at which time they would be repaired or re- placed. Data were handled in this arbitrary manner because 1t was assumed that the failed device would not have been detected and corrected except during a routine (yearly) Inspection and maintenance program. 2.5-4 percent CO 2-3 percent CO 1 - 2 percent CO To manufacturer's specifications 13 ------- TABLE I RETROFIT EVALUATION PRELIMINARY DATA SUMMARY PHASE I From 10/1/74 to 2/24/75 COMP. AVERAGE % CO AVERAGE % HC REMARKS AND TEMP. REDUCTION REDUCTION ** FUEL CONSUMPTION MI/GAL. VEHICLE MODEL ENGINE °F IDLE 2500 RPM IDLE 2500 RPM AT CONSTANT 50 MPH WITH DEVICE WITHOUT DEVICE AIR BLEEDS '55 Chevy 1/2TPU V8-283 -26 59 56 -39 -49 16.8 @ -20°F 16.5 (3 -20°F Device removed & carb. adjusted as lean as w/device w/less stumble. r60 Olds Sedan V8-394 + 15 94 81 4 45 r60 Ford Sedan V8-352 +8 61 50 36 15 16.0 @ -20°F 15.6 (3 -20°F Slight hesitation. r63 Chevy StnWgn V8-283 + 5 73 26 7 9 Device removed & carb. adjusted as lean as w/device w/less stumble. 64 Ford 1/2TPU 16-223 -5 66 63 14 -220 15.1 @ -2°F (choking required) 14.4 @ -2°F. 66 Ford Sedan V8-352 -2 18 22 2 2 68 GMC Caryal V8-327 -3 59 77 22 30 68 Chevy Caryal 16-250 -14 69 11 -3 3 18.6 (a 0°F 18.4 @ 0°F 68 Chevy 1/2TPU 16-250 -10 21 42 -15 30 68 Jeep CJ5 V1-225 -8 31 6 29 64 Fuel pump failure. EXHAUST GAS RECIRCULATION PLUS AIR BLEED 68 Ford StnWgn 16-200 -4 -640 40 -230 -480 20.4 @ -4°F 19.8 @ -4°F Device removed because of excessive stumble. Carb. A/F swings too lean. 69 GMC 1/2TPU V8-350 -19 56 45 42 23 14.42 @ -6°F 14.46 @ -6°F 70 GMC 3/4TPU V8-350 -25 2 45 -6 -27 15.3 @ 10°F 14.6 (3 +10°F (w/o EGR but w/PCV-AB) 70 AMC Sedan 16-232 +6 78 -n 36 25 23.6 @ -10°F 23.5 G> -10°F CATALYTIC CONVERTER 71 GMC Jimmy 16-250 +23 50 66 51 49 21.3 @ 30°F 16.8 @ -2°F (No air pump) 73 Ply. Sedan V8-318 — — -- Catalyst not in yet. Mo air pump. 73 Chevy Vega 14-140 + 14 80 66 42 28 No air pump. 74 Chevy Nova 16-250 -20 75 83 78 40 No air pump. *A11 pre-1964 vehicles had to first be retrofitted with positive crankcase ventilation (PCV) systems. ** All negative percent reductions mean an actual increase in emissions. ------- TABLE II RETROFIT EVALUATION PRELIMINARY DATA SUMMARY PHASE II From 2/24/75 to 6/1/ COMP. AVERAGE % CO AVERAGE % HC REMARKS AND TEMP. REDUCTION REDUCTION FUEL CONSUMPTION MI/GAL. VEHICLE MODEL ENGINE °F IDLE 2500 RPM IDLE 2500 RPM AT CONSTANT 50 MPH AIR BLEEDS 55 Chevy 1/2TPU V8-283 24 76 37 37 23 Engine stumbles on acceleration w/AB. 60 Olds Sedan V8-394 40 77 72 50 28 No driveability difference with device. 60 Ford Sedan V8-352 35 82 67 20 21 Vehicle out of service; low mileage accumulated. 66 Ford Sedan V8-352 42 24 21 17 21 Engine idles rough w/AB. 68 GMC Caryal V8-327 24 25 75 20 54 Engine tuned up 3-15-75. 68 Chevy Caryal 16-250 26 0 0 * * AB failure 2-24-75. 68 Chevy 1/2TPU 16-250 20 19 45 * * AB failure 3-31-75. 16.3 & 16.7 mi/gal. w/wo AB @ l°l 68 Jeep CJ5 V6-225 30 0 0 * ~ AB failure 2-26-75. 19.6 & 19.5 mi/gal. w/wo AB @ 12' EXHAUST GAS RECIRCULATION PLUS AIR BLEED 69 GMC 1/2TPU V8-350 42 76 57 64 43 _ _ _ 70 GMC 3/4TPU V8-350 18 26 * 32 7 Engine in poor operating condition. 70 AMC Sedan 16-232 29 74 42 28 27 Carburetor jet backed out 1/4 turn, 5-6-75. CATALYTIC CONVERTER 71 GMC Jimmy 16-250 30 31 57 19 51 Engine misfires; unstable idle mixture. 73 Chevy Vega 14-140 32 92 32 49 26 Temperature of CC 900°F @ idle. 73 Ply. Sedan V8-318 43 78 68 67 51 Temperature of CC 1175°F ©idle. 74 Chevy llova 16-250 26 31 61 49 52 CC striking ground, breaking manifold-tailpipe joint. ~Static conditions showed negative HC reduction. Dynamic test revealed no negative HC reduction. Contradictory data deleted. ------- Other problems with individual air bleed devices were encountered. After 5 months, the air bleed on the 1968 1/2-ton pickup failed because vibrations had loosened the adjusting screw. A retaining spring was installed around the screw and the device was readjusted. The owner of the 1968 Jeep encountered a power loss and sluggish engine performance. Thinking he might improve engine response, he screwed down the air bleed adjustment, defeating its function. The initial problem was traced to a faulty carburetor which was repaired and the device readjusted. After 4 months, the device again failed and had to be readjusted. An inspection and maintenance program would be able to detect and correct such failures. The air bleed on the 1968 Chevrolet carryall was installed inside the garage at approximately +50°F. Driveability tests at -30°F revealed stumbling and engine kill at stops caused by a lean A/F mixture. To cure the driveability problem, the air bleed was then readjusted outside at -30°F. Based on this experience, it was determined that all air bleed installation adjustments should be done outside in ambient air during one of the colder winter days. This particular air bleed device failed to modulate after the second month. In general, there were no noted driveability problems with air bleeds on the larger eight cylinder engines. However, the air bleeds so severely affected driveability of the 1955 and 1963 Chevrolets that they had to be removed. The manufacturer felt the problem was lack of ported vacuum sig- nal to the distributor vacuum advance. Their advice was to adjust idle mix jets for 2 percent CO. This was done with some improvement in drive- ablity. However, when the air bleed was removed and the carburetor reset at 2 percent exhaust CO, the driveability improved further. On Feb- ruary 11, 1975, a 2 cfm nonadjustable (vs. the regular 3 cfm adjustable) air bleed with two vacuum delay valves was installed on the 1955 pickup. With this smaller device the owner reported acceptable driveability with minor stumbling. Initially, the 1964 Ford 1/2-ton pickup had an intermittent leak in its induction system. With this problem it took several days to get its air bleed working properly. The operator reported that considerably more choking was required at temperatures of -25°F or colder. Three vehicles with the air bleed had an increased tendency to diesel after the ignition was switched off. The three major causes of dieseling are: [1] too high an idle speed (rpm), [2] too lean a mixture (A/F), and [3] too low octane fuel. The air bleeds lean out the idle mixture and for winter operation Fairbanks drivers usually set the idle speed above the manufacturer's specifications., thus aggravating the problem. The disadvantage of leaning out the engine at low temperatures is the risk of increasing HC emissions (lean-misfire). On some vehicles the HC reduction was less than 10 percent. There were a few vehicles which had negative HC reductions. The retrofit manufacturer indicated there should be no HC increases (negative percent reduction) under loaded tests. Two vehicles, the 1968 1/2-ton pickup and the 1968 Chevrolet carryall, were instrumented and tested under load. Analytical data confirmed the manu- facturer's statement. The Phase II data showed about the same percentages 16 ------- HC reduction. Because the static testing procedure does not apply for HC in air bleed type devices, whenever negative reductions were obtained, the data were deleted from the Phase II Data Summary Table. The Inability of the static test procedure to accurately quantify HC reductions is of little significance since this study was aimed primarily at determining CO reduc- tion performance. As a research effort to investigate a way to reduce CO and HC effec- tively, and determine a more economical retrofitting procedure, a PCV valve designed for a larger engine displacement (307 CID) was installed on the 1968 Chevrolet carryall equipped with a 250 CID engine. Since the exhaust gas recirculation system incorporated its air bleed in the PCV valve, it was felt that this combination would allow more air to bleed into the Intake manifold simply by making the PCV valve larger. For comparison, the STP air bleed device was removed and data were taken using the larger engine PCV valve. Test results upheld this theory. However, in this case the larger PCV was not as effective in reducing air pollution and the air bleed was reinstalled. Exhaust Gas Recirculation Plus Air Bleed It should be noted that the STP air bleeds and the air bleeds in the exhaust gas recirculation plus air bleed devices are different types (Fig- ures 2 and 3). Excluding the 1968 Ford and the 1970 GMC from the Phase I data, the exhaust gas recirculation plus air bleed retrofits would probably have performed as well as the air bleed only group, except that the fuel economy improvement was less. Overall CO reduction for Phase II was approximately 43 percent for the three exhaust gas recirculation plus air bleed devices. The overall average CO reduction for both phases was 40 percent for the 1969 and 1970 vehicles. Some problems were also encountered with these devices. Just after installation, the PCV-air bleed (Figure 3) on the 1970 GMC 3/4-ton pickup was intermittently clogging and sticking open (apparently due to machining lubricants) resulting in poor performance. Cleaning with acetone solved the problem, but the problem caused overall poor performance (Phase I of the Data Summary Tables). Another PCV-air bleed suspected of clogging had been installed on the 1968 Ford station wagon which had a carburetor that independently varied the idle A/F mixture. Without any retrofit device, the exhaust CO would vary from 1 to over 4 percent within two to three minutes during idling. Unsuccessful attempts were made to clean the idle ports. Instead of reducing emissions, the idle CO with the device increased over six times (Phase I of the Data Summary Tables). The DANA retrofit device was removed because it caused excessive stumble and an STP air bleed was attached. The engine would not run with the air bleed so the vehicle was dropped from the test program. The owners of the 1969 GMC 1/2-ton pickup and the 1970 AMC sedan noted sluggishness on acceleration with the exhaust gas recirculation 17 ------- devices. This was probably due to leaness because of the air bleed or flame dilution by the recycled exhaust gas. Catalytic Converters Before the catalytic converters would work properly, the carburetors had to be leaned out to get O2 in the exhaust (Figure 1). These devices were not effective in reducing CO emissions during cold starts because the catalyst bed temperature had to be warmed to above 600°F before it would burn the CO to CO2- The warm-up period appeared to range from 3 to 6 minutes. The overall average reduction of CO and HC for both test phases was 62 and 47 percent, respectively. The catalytic converter performance appeared to have deteriorated between Phase I and II. But analytical caution should be exercised since the data in Phase I are based on only one or two tests. Routine tests for lead in the gasoline have ruled out lead poisoning of the catalyst. The idle A/F on the Nova and Jimmy carburetors dropped during the test period, thus lowering catalytic converter performance. However, the devices had no effect upon driveabi1ity. Fuel Economy The fuel economy effect of the retrofits is listed in the Data Sum- mary Tables. The fuel consumption (miles per gallon) is listed right before the test temperature. All tests were performed at constant speed of 50+2 miles per hour. Each test result is based on a 40-mile run both with and without the retrofit device. Tests were run consecutively except on the vehicles equipped with a Catalytic Converter. In general, the air bleed device varied the mileage from -2 to +5 percent, averaging a 2 to 3 percent increase. The exhaust gas recirculation plus air bleed devices increased the mileage by about 1 percent. The catalytic converter could not be easily removed so the mileage tests had to be performed be- fore and after installation. The catalytic converter was not expected to affect mileage. The 4x4 utility vehicle yielded better mileage at +30°F than at -2°F. Apparently considerable energy (gasoline) is required to overcome the viscous shear of cold lubricants. Associated Problems and Considerations Several problems associated with retrofitting have been noted, but there were many others. The first exhaust gas recirculation plus air bleed was installed on the 1970 AMC. Installation time was 8 hours. Since this was the first device for the program, extensive time was required due to misleading installation instructions provided by STP Corporation. As a result, the device was initially installed on the intake manifold rather than the exhaust manifold. This caused the engine to surge as excessive fresh air was drawn into the intake manifold. The associated vacuum delay valve caused extensive stumble after installation. After removal of the valve, the owner reported no problems with the retrofitted engine during the first three months. During the next three months the owner 18 ------- reported that the exhaust gas recirculation valve Intermittently stuck causing erratic Idle. He could solve the problem by lightly tapping the valve with a mallet. Finally, after six months, the idle surging and dying problem became so severe that the owner requested removal of the device. Upon removal, 1t was found that the hose leading from the carbure- tor to the velocity nozzle was ruptured, apparently causing the problem. Experience with the 1970 AMC and 1968 Ford Indicates that adding a retrofit to any engine increases vulnerability and raises the possibility of partial failure. The 1968 GMC carryall was given a second tune-up midway through Phase II because the owner felt 1t was Idling too rough. He backed out the idle jets approximately one-fourth of a turn to enrich the mixture causing the idle carbon monoxide levels to increase from 0.2 percent to 3.5 percent with the air bleed. The owner requested that the idle be left in this state. In this case, the air bleed device probably enticed the owner to adjust the A/F mixture. This over-riding effect resulted in higher CO emissions than before retrofitting, thus defeating the entire retrofit Idea. The vehicle would have easily idled at less than 3.5 percent CO without the air bleed. The 1968 GMC 1/2-ton pickup required the installation of a new car- buretor due to mechanical linkage wear. The exhaust gas recirculation plus air bleed device had been added to the engine prior to the breakdown and ultimate failure of the carburetor. The owner thought that the retro- fitting was partially responsible for improper carburetor operation. A new carburetor was reinstalled giving an Idle CO of 0.9 percent. Several months later the Idle mix screws were adjusted according to the industry specifications. The Idle CO then increased from 0.9 percent to 2.2 percent with the device again showing that a simple carburetor adjustment can override the objective of retrofitting gasoline engines. The above two examples illustrate what'could happen in a mandatory program if the owner decides to readjust his idle mix to compensate for lack of (or apparent lack of) engine performance due to the retrofit. It should also be realized that the air bleed and exhaust gas recircula- tion plus air bleed devices tested may well be modified or deleted if the manufacturers go into mass production. Therefore, some of the initial failures and problems encountered in these tests may be replaced by others. Within one month after installation, the catalytic converters on the 1973 Plymouth, attached with muffler clamps, were knocked off—presumably due to rough roads. They were welded back into place with no subsequent difficulties. The converters on the Nova and Vega also hung low and bumped high spots in the road, which caused leaks at the exhaust pipe manifold joints. Because it was mounted up between the frame and the transmis- sion, the converter on the Jimmy did not have those problems. Experience with the air bleed and exhaust gas recirculation plus air bleed types of retrofits during this study indicates that they are not effective on vehicles with malfunctioning carburetors. Of the 18 19 ------- test vehicles, the 1963 Chevrolet, the 1968 Ford, and the 1969 GMC 1/2-ton pickup would require new carburetors for effective retrofit performance. Extrapolating these data to all pre-1971 Fairbanks area vehicles indicates that as many as 10 to 20 percent would require new carburetors for retro- fitting. The new carburetors would cost approximately $75 to $200 in- stalled. Since the air bleed and exhaust gas recirculation plus air bleed devices are mass produced, they should cost less than $35 for parts and $20 to $40 for installation. However, the air bleeds require use of an exhaust gas analyzer for installation. The several garages in the Fair- banks area that have these analyzers do not routinely use them. The catalytic converters used in this study cost $115 for the 4 cylinder, $225 for the 6, and $230 for the 8 cylinder vehicles. The installation charges ran from $40 for the 4 cylinder to $100 for the 8 cylinder vehicles. If they were retrofitted for thousands of vehicles, the cost should be substantially less. For instance, earlier this year in Canada, if one were to order a 1975 light duty GM vehicle without a catalytic converter, the total cost would be about $80 less than with the converter. The deterioration factors were not calculated for all the retrofits because they could not be reasonably separated from the deterioration factors of other engine components. The authors feel that for Fairbanks winters, mileage accumulation may not be as significant as the number of cold starts in causing engine component deterioration. For example, one cold start at -50°F may put more wear on the valve train than would 1000 miles of highway driving. The accumulated mileage for the retrofitted vehicles was: 16,000 miles for the air bleed, 8000 miles for the exhaust gas recirculation plus air bleed, and 4000 for the-catalytic converter equipped vehicles. Individually, the accumulations were from 100 miles for the 1960 Ford to 5800 miles for the 1970 AMC. This study was too short to determine any long-term effectiveness of any mandatory retrofit program and, at best, results were only semiqualita- tive. However, it does document some of the initial problems associated with retrofitting. Before a vehicle retrofit program is implemented for the reduction of CO levels in the Fairbanks area, the problems encountered during this Study must be considered. An inspection/maintenance program must be initiated before retrofitting can be effective. Lower levels of exhaust pollution will result only when the need for proper maintenance is under- stood and carried out by vehicle owners and competent service mechanics. Of major concern is the ability to enforce a mandatory retrofit pro- gram. The driving public has a somewhat negative viewpoint concerning automotive air pollution equipment. Individuals are interested in the performance of their vehicles as a means of dependable transportation. Added expenses and vulnerability are viewed as a personal hassle rather than health insurance. 20 ------- Finally, emissions from the vehicles operated during Fairbanks' win- ters can be divided into two parts. First, a cold start which involves 2 to 15 minutes of idling; and second, a warm run. It may be that the cold start portion contributes more CO than the warm run for a typical trip from the central business district. Preliminary cold start data obtained by the authors and the University of Alaska* indicates that, because of excessive choking and catalyst warm-up time, the retrofits are not effective before the engine warms up. * For more information on this subject see the interim report entitled "Cold Start Automotive Emissions in Fairbanks, Alaska," by L.E. Leonard, Univer- sity of Alaska, Geophysical Institute, Fairbanks, Alaska, Report UAGR-239, July 1, 1975. 21 ------- |