72-7 EXHAUST EMISSIONS FROM A 25 - PASSENGER INTERNAL COMBUSTION ENGINE POWERED GASOLINE FUELED BUS October 1971 H. Anthony Ashby, Engineer Test and Evaluation Branch Division of Emission Control Technology Mobile Source Pollution Control Program Environmental Protection Agency ------- Background Under a grant from the U.S. Department of Transportation, LTV Aerospace of Dallas will install a Rankine cycle power system, built by Sundstrand Aviation, in a 25-passenger city bus for use in the Dallas public transit system. The bus chosen for this project is a Twin Coach built by Highway Products, Inc. of Kent, Ohio. The engine usually installed in the bus Is a gasoline fueled V8 internal combustion engine. The Test and Evaluation Branch will test the bus when the Rankine system installation is completed and it was necessary to test the conventionally powered bus in order to establish "baseline" emissions, with which the Rankine system emissions could be compared. Vehicle Tested The vehicle was a Twin Coach 25-passenger city bus powered by a 413 C.I.D. Chrysler V8 engine burning gasoline. The engine was mounted in the rear and drove the rear wheels through an automatic transmission. The engine had positive crankcase ventilation, but no other emission control tech- nique was in evidence. The normal curb weight of the bus is about 10,500 pounds. The bus we tested was somewhat lighter, since none of the passenger seats had been installed. Test Program The bus was delivered to the Willow Run laboratory on Monday, September 13, 1971. Engine trouble delayed testing until Friday, September 17. For these tests a simulated inertia weight of 5500 pounds, the maximum available on the Clayton two-roll dynamometer, was used. All, emissions tests employed the Constant Volume Sampling method. Operating conditions used were the Ann Arbor-1 (AA-1) Urban Bus Cycle, steady state modes, and an approximation of the- CARB-EMA Diesel Emissions Test Procedure. ------- Normal analysis methods were employed: FID for unburned hydrocarbons, NDIR for CO and CO?, and chemiluminescence (C.L.) for NOx. The AA-1 Bus_ Route was developed by EPA for this project and is—an~""a~ctual speed versus time trace generated using a fifth wheel on one of the busses of the Ann Arbor Trans- portation Authority. It can be and was used with either a hot or cold start. The modes used for the steady state tests were idle, 15, 25, and 35 mph cruises, each maintained for two to five minutes to allow time for an adequate sample to be collected. The CARB-EMA Diesel procedure used is described in SAE paper number 700671. It is a steady state procedure for testing a Diesel engine on an engine dynamometer with engine load as the operating variable at each of two engine speeds, "Rated" and "Intermediate." The load is varied from zero to maximum torque available at the particular engine speed, in steps of 25% of maximum torque. Three idle periods are interspersed among these load points, for a total of 13 operating modes. From data supplied by Mr. J.M. Nunez of Chrysler (who was contacted for us by Mr. David Randolph of LTV) it was determined that Rated speed for the 413 engine was 3200 rpm. The Intermediate speed is defined in the Diesel procedure as "Peak torque speed or 60% of rated speed, whichever is higher." On the Chrysler 413, peak torque occurs at 2000- 2100 rpm, so 2000 rpm was used as the Intermediate speed. The engine loads at each speed were based on the estimated output of the Rankine system, which information was acquired -from-Sundstrand. The -Rankine system will deliver to the wheels a maximum of 70 hp at its Rated speed and 50 hp at 60% of its Rated speed. The procedure for our 13-mode tests was to establish the desired engine speed with the transmission engaged and the chassis dynamometer water brake fully unloaded. In this condition the dynamometer still absorbed 7 hp because of internal friction. After sufficient time in this mode for collection of an adequate sample of the diluted exhaust gas, the water brake load was then increased'to 25%, 50%, 75%, and 100% of the maximum power at the chosen engine speed, with bag samples collected at each condition. The idle ------- modes were run with the transmission engaged and the bus brakes on to prevent creeping. Power absorption limitations prevented us from running in the 70 hp @ 3200 rpm mode. In addition to the emissions test a simple exterior noise test was conducted using the SAE Recommended Practice J366, for full throttle acceleration onlyi two ¥Uns wete made in each direction. The closed throttle deceleration test was not run. Results Mass emissions are reported here in grams per minute for the 13-mode tests. Specific mass emissions in grams per rear wheel horsepower-hour have also been calculated. Data from the AA-1 bus route tests is presented in grams per mile. The length of-the bus route was estimated to be eight miles. From the steady state tests the data is pre- sented in both grams per minute and grams per mile. Data from the bus route tests are presented in Table 1. Emissions of CC>2 are included to indicate fuel consumption. The variability of CC>2 emissions was greater than normally experienced, and the variability of HC and NOx emissions was less than expected, considering the apparent condition of the engine. Quite early in our testing a random knocking noise was heard in the engine. Informal diagnosis by our experienced technicians was that the noise was due to problems in the valve train of one of the cylinders. The bus was taken, at the suggestion of Chrysler, to the Continental-Kromis engi-ne repair center, which -specialize in_ Chrysler engines. It was returned two days later with a report that the engine Was okay. The tests and the knocking continued, with an intermittent miss developing soon after. The knock and the miss disappeared when the engine was heavily loaded. Data from the steady state tests are presented in Table 2. On the basis of grams per mile there was little change in emissions when speed was increased, except for the HC emissions. The increase in road load power from 15 mph to 35 mph was apparently not enough to affect NOx emissions greatly. The C02 emissions, in grams per mile, decreased about 101 when cruise speed was increased from 15 mph to 25 or 35 mph. ------- Listed in Tables 3 and 4 are the results from the 13-mode tests. Table 3 presents emissions in terms of grams per minute. The Intermediate speed data are fairly repeatable. Repeatability of the.Rated speed data is poor, except for NOx emissions. The mass emissions in Table 4 are in terms of grams per rear-wheel horsepower-hour. The efficiency of the drive train was not known so it was not possible to calculate brake horsepower. The arithmetic average of four noise tests, two in each direction, was 83 dBA. See Table 5. Runs 1 and 3 were in one direction, with the bus radiator on the opposite side of the bus from the microphone, and were 2 dBA lower than the runs in. the opposite direction with the .radiator on the same side as the microphone. Conclusions These tests of a gasoline-powered bus were of value to the T§E Branch mainly for the experience of testing a large '""' ' ' vehicle at high engine loads. The value of the emissions data is suspect because significant test conditions were not as they should have been. Because the data are probably not suitable even as a rough approximation of baseline for this bus, additional baseline tests are pla-ned when these limitations are overcome. Among the conditions that gave rise to questionable data were the following: 0 The simulated inertia weight was only 5500 pounds, while the actual bus weight is about 10,500 pounds. Thus, CO- and -NOx emissions were -ce-rtainly-lower- than they.should be. 0 Because of power absorption limitations we were not able to test the maximum load at Rated speed. 0 The bus was new, with only about 500 to 600 miles on the odometer. Thus the engine was probably still in a break-in period and the emissions were probably not typical of the same engine when broken in. 0 The intermittent knocking and misfiring condition of the engine should not be considered typical or baseline, and probably had a detrimental effect on emissions. 0 It was not known whether the engine timing and carb- uretion conformed to the manufacturer's specifications. ------- It would be valuable to conduct a similar series of tests in the future, using an adequate chassis dynamometer, on a Diesel-powered bus as well as a properly operating gasoline- powered bus . ------- Table 1 25-Passenger Gasoline Powered Bus Mass Emissions Ann Arbor -1 Bus Route Grams per mile Date 9 9 9 9 9 9 9 -17 -20 -23 -24 -20 -21 -23 HC 22 25 25 23 22 23 25 .09 .77 .31 .75 .63 .85 .09 CO 100 130 97 91 115 101 109 .10 .29 .80 .82 .77 .55 .87 C02 1035 1145 962 1068 1049 1003 1064 NOx .6 .5 .8 .91 .83 .09 .98 10 11 10 11 11 11 11 .23 .52 .73 .57 .66 .58 .54 Comments Cold Cold Cold Cold Hot Hot Hot Start Start Start Start Start Start Start ------- Table 2 Mode Idle Idle 15 mph 15 mph 15 mph 25 mph 25 mph 25 mph 35 mph 35 mph 35 mph Date 9-20 9-21 9-20 9-21 9-23 9-2.0 9-21 9-23 9-20 9-21 9-23 25-Passenger Gasoline Powered Bus Mass Emissions Steady State Modes 'Grams per minute HC CO C09 NOx .12 .11 .65 2.42 2.61 373.3 5.06 365.7 4.87 335.7 4.54 524.7 7.42 510.2 6.44 472.7 5.79 3.70 3.65 9.36 9.00 off scale -9.09 4.35 17.52 15.89 15.5 93.15 103.26 257.5 220.1 243.3 12.83 13.07 off scale 5.48 6.46 7.41 "32.26 25.05 23.71 off scale 46.62 43.99 Grams per mile HC CO Not applicable Not applicable 37.44 36.00 off scale 30.79 31.37 off scale 9.39 11.07 12.70 70.08 63.56 62.0 77.42 60.12 56.90 off scale 79 .'92 75.41 CO- NOx 1030.0 2.60 880.4 9.68 973.2 10.44 895.9 12.14 877.7 11.69 805.7 10.90 899.5 12.72 874.6 11.04 810.3 9.93 ------- Table 3 Mode Idle Idle Idle 7 hp@2000 rpm T, hp§2000 rpm 7 hp@2000 rpm 13 hp@2000 rpm 13 hp@2000 rpm 25 hp@2000 rpm 25 hp@2000 rpm 25 hp@2000 rpm 38 hp@2000 rpm 38 hp@2000 rpm hp@2000 rpm 50 hp@2000 rpm Idle Idle Idle 7 hp@3200 rpm 7 hp@3200 rpm 18 hp@3200 rpm 18 hp@3200 rpm 35 hp@3200 rpm 35 hp@3200 rpm 53 hp@3200 rpm Idle Idle 25-Passenger Gasoline Powered Bus Mass Emissions CARB-EMA 13-Mode Diesel Engine Test Procedure Date HC Grams per minute CO C02 NOx 9-23' 9-23 9-24 9-23 9-23 9-24 9-23 9-23 9-23 9-23 9-24 9-23 9-23 9-23 9-24 9-23 9-23 9-24 9-23 9-24 9-23 9-24 9-23 9-24 9-23 9-23 9-24 2.91 3.58 3.40 8.91 9.16 3.36 6.38 6.15 2.73 3.04 2.47 6.59 2.42 2.34 2.56 . 3.13 2.76 2.18 3.65 2.79 3.11 2.18 3.33 1.78 3.70 2.22 1.84 10.61 4.36 4.10 35.20 34.41 31.90 39.76 38.41 off scale off scale 47.12 48.15 off scale 45.49 off scale 5.70 9.27 5.95 off scale 49.53 off scale 47.09 off scale 35.88 off scale 10.93 4.48 109.95 91.97 92.85 457.94 428.20 446.63 464.30 436.41 562.05 550.49 530.16 off scale 588.21 686.40 674.93 92.63 130.0 107.16 714.69 619.55 752.74 591.72 867.07 574.07 off scale 110.33 80.48 .15 no data .16 6.24 5.28 6.89 7.06 5.99 9.66 9.02 10.47 off scale 11.20 off scale 12.78 .07 .23 .39 12.45 12.18 14.48 12.76 off scale 13.94 off scale .23 .28 ------- Table 4 continued Mode Date 18 hp @ 3200 rpm 9-23 18 hp @ 3200 rpm 9-24 35 hp @ 3200 rpm 9-23 35 hp @ 3200 rpm 9-24 53 hp @ 3200 rpm 9-23 HC CO CO, NOx 9 9 9 9 9 -23 -24 -23 -24 -23 10 7 5 3 4 .37 .27 .71 .05 .19 off scale 157.0 off scale 61.51 off scale 2509. 1972. 1486. 984. off scale 1 4 4 1 48.27 42.53 off scale 23.90 off scale ------- Table 4 25 - Passenger Gasoline Powered Bus Mass Emissions CARB-EMA 13-Mode • Diesel Engine Test Procedure Grams per rear wheel horsepower-hour Mode 7 7 7 13 13 25 25 25 38 38 50 50 7 7 hp hp hp hp hp hp hp hp hp hp hp hp hp hp @ @ @ @ •@ e 6 @ e. @ '@ @ e @ 2000 2000 2000 2000 2000 2000 2000 2000 - 2000 2000 200.0 2000 3200 3200 rpm rpm rpm rpm rpm rpm rpm <• rpm rpm rpm rpm rpm rpm rpm Date 9 9 9 9 9 9 9 9 9 9 9 9 9 9 -23 -23 -24 -23 -23 -23 -23 -24 -23 -23 -23 -24 -23 -24 HC_ 76 78 28 29 28 6 7 5 10 3 2 3 31 23 .4 .5 .80 .45 .38 .55 .30 .93 - .41 .82 .81 .07 .29 .91 C^ 301.7 294.9 273.4 183.5 177.3 off scale off scale 113.1 76.03 off scale 54.59 off scale off scale 424.5 CO- L 3925.2 3670.3 3828.3 2142.9 2014.2 1348.9 1321.2 1272.4 off scale 928.7 823.7 809.9 6125.9 5310.4 NOx 53.49 45.26 59.06 32.58 27.65 23.18 21.65 25.13 off scale 17.68 off scale 15.34 106.7 104.4 ------- Table 5 25 - Passenger Gasoline Powered Bus Noise Tests per SAE RP J366 Full Throttle Acceleration Run No. Noise Level 1 82 dBA 2 84 dBA 3 82 dBA 4 84 dBA ------- |