Environ. Sci. Techno/

. 2003

, 37

, 630-637



# Quantifying the Emission Benefits of Opacity Testing and Repair of Heavy-Duty Diesel Vehicles

ROBERT L. MCCORMICK,* MICHAELS. GRABOSKI

, TERESA L. ALLEMAN.t AND JAVIER R. ALVAREZ Colorado Institute for Fuels and Engine Research. Colorado School of Mines. Golden. Colorado 80401-1887



### K. G. DULEEP Energy and Environmental Analysis, Inc., Arlington. Virginia 22209



### The objective of this study was to begin to quantify the benefits of a smoke opacity-based (SAE J1667 test) inspection and maintenance program. Twenty-six vehicles exhibiting visible smoke emissions were recruited: 14 pre-1991 vehicles and 12 1991 and later model year vehicles. Smoke opacity and regulated pollutant emissions via chassis dynamometer were measured, with testing conducted at 1609 m above sea level. Twenty of the vehicles were then repaired with the goal of lowering visible smoke emission, and the smoke opacity testing and pollutant emissions
measurements were repeated

. For the pre-1991 vehicles actually repaired, pre-repair smoke opacity averaged 39% and PM averaged 5.6 g/mi. NO x emissions averaged 22.1 g/mi. After repair, the average smoke opacity had declined
to 26% and PM declined to 3.3 g/mi, while NOx emissions increased to 30.9 g/mi. For the 1991 and newer vehicles repaired, pre-repair smoke opacity averaged 59% and PM averaged 2.2 g/mi. NO x emissions averaged 12

. 1 g/mi. After repair, the average opacity had declined to 30% and PM declined to 1.3 g/mi, while NOx increased slightly to 14

. 4 g/mi. For vehicles failing the California opacity test at >55% for pre-1991 and > 40% for 1991 and later model
years, the changes in emissions exhibited a high degree of statistical significance. The average cost of repairs was $1088, and the average is very similar for both the pre1991 and 1991 

## + model year groups. Smoke opacity was shown to be a relatively poor predictor of driving cycle PM emissions. Peak CO or peak CO and THC as measured during a snap-acceleration were much better predictors of driving cycle PM emissions.



### Introduct i on A number of states have been concerned about the contribution of heavy-duty diesel vehicle (HDDV) emissions to emission inventories. This is because HDDVs are important

sources of fine particulate matter (PM) and nitrogen oxide

• Co rr espond ing author present address: Nat ional Renewable Energy Laboratory

, 1 617 Cole Blvd., MS 1633, Golden, CO 80401; phone: (303)275-4432; fax: (303)275

- 4415; e-mail: robert_mccormick @ nrel.gov.
1 Present address: National Renewable Energy Laboratory, Golden, 

## co 80401.

6 3 0 • ENVIRONMENTAL SCIENCE & TECHNOLOGY I VOL

. 37

, NO .3, 2003 (NOx) 

### air pollutants (1, 2). 

### Fine carbon or primary PM can lead to reduced visibility (3, 4), 

### and potentially mutagenic and carcinogenic polycyclic aromatic hydrocarbons (PAH)

are associated (1, 5) 

### with these respirable particles (6-9). 

### Gas-phase taxies such as formaldehyde are also emitted. The U.S. Environmental Protection Agency (U.S. EPA) has proposed new national ambient air quality standards for PM z.s. Nitrogen oxides contribute to the formation of visibilityreducing and respirable secondary PM (J {}J 

### as well as groundl eve l ozone (J 1)

. 

### Furthermore, a broad spectrum of other organic compounds can also be found in the gaseous fraction of diesel exhaust (1, 12)

. 

### To limit or reduce pollutant emissions from diesel vehicles, th e U.S. EPA regulates both the quality of on-road di ese l fu e l and the pollutant emission levels from engines under the authority of the Clean Air Act. Additionally, smoke opacity
tests are used by many states as part of inspection programs for control of PM em issions

. Opacity is defined as the percentage 

### a flight transmitted from a source that is prevented from r eaching a light detector. In smoke opacity measurements from a diesel vehicle, a beam of light is transmitt ed

across the exhaust plume to a light d etector. High opacity may indicate engine malfunction and increased emissions of air pollutants

, primarily unburned fu e l hydrocarbons (emitted as an aerosol) or soot particles (13). 

### It is well-known that diesel engine malfunction or maladjustment can result in increased emissions of pollutants (J 4), 

### and repair of high opacity emitters may therefore result in a decr ease in the contribution of diesel vehicles to the pollutant inventory. The measured value of smoke opacity is highly dependent upon the test procedures

, including ambient conditions, engine operating mode, measurement configuration, and instrumentation. In recent years, the SAEJ1667 test proc edure has been suggested as a standard test (J 5). 

### This test was developed specifically to id ent ify gross emitting h eavy-duty trucks and buses. To date, no study has quantified the actual emission benefits of smoke opacity testing. The objective of this study is to begin to quantify the benefits of a smoke opacity-based inspection and maintenance (I / M) program. To that end, a number of vehicles exhibiting visible smoke emiss ions were recruited

. Smoke opacity and r eg ulated pollutant emissions

were measured. The vehicles were then repaired with the goal of lowering visible smoke emissions, and the smoke opacity testing and pollutant em issions measurements were repeated. Because of cost and time limitations and because relatively few vehicles exhibit high opacity, no effort was made to test a representative sample of the in-us e heavyduty vehicle n eet in Colorado. Instead, all vehicles emitting visible smoke that could be obtained during the time p eriod of the study were tested. The study was conducted in Denver, CO, at 1609 m above

sea l eve l. At this altitude, the barometric pressure is typically 82.6 kPa versus 98.9 kPa at sea l eve l. This change in altitude has been estimated to increase engine transient test PM emissions by from 50 to more than I 00 % in several studies (16

- 18). 

### During short duration accelerations, e ngine mechanisms that sense air pressure may not adequately compensate for the reduced air density at altitude, leading to a de crease in air / fu e l ratio and increased emissions of PM. Maximum speed in the snap-acceleration test cycle is reached in 1 -1.5 s,leading to similarly low air / fuel ratio and incr eased smoke opacity at altitude. The SAE has recommended that

a correction factor be app lied to smoke opacity measured on theJ1667 test cond ucted at high altitude (15). 

### Th e calculated correction is quite larg e for typical values of dry air density

10 .1021/es0 256919 CCC: S25.00

### TABLE 

### 1. Properti e s of Vehicles Tested

ve h icle n o

. m i l e ag e (mi) GVW(Ib) t est w ei ght mod e l y e ar engine mod e l e ng i n e fa m i ly engi n e h p v e h ic l e u se
1999-1 86 671 25 000 20 000 1995 Navistar X4L SNV466D6DARA 190 rental 1999-2 • 33 649 34 000 28 000 1988 DOC 6V-92 JDD0552FZG8 350 bus 1999

- 3 112 436 50 000 35 000 1986 Caterpi liar 3208 GCT0636DAA2 210 delivery 1999-4 • 129 345 50 000 39 000 1987 Caterpillar 3208 E6HT -6007 -FH 215 delivery 1999

- 5 160 817 80 000 39 000 1989 Cummins NTC315 G93E 315 class 8 1999-5 b 160 817 80 000 39 000 1989 Cummins NTC315 G93E 315 class 8 1999

- 6 99 024 50 000 39 000 1986 Caterpi liar 3208 GCT0636DAA2 210 delivery 1999-7 116 004 50 000 39 000 1986 Caterpi liar 3208 GCT0636DAA2 210 delivery 1999-8 122 360 80 000 52 000 1990 Cummins NTC315 093E 315 class 8 1999-9 23 519 32 000 26 000 1989 I nternational DT466 unknown 210 school bus 1999-10 191 525 80 000 52 000 1989 Cummins NTC315 093E 315 class 8 1999-10 < 191 525 80 000 52 000 1989 Cummins NTC315 093E 315 class 8 1999-11 128 292 50 000 39 000 1987 Ford 8000 HFM07-8FPA3-01 210 delivery 1999-12 119 280 54 000 43 000 1987 I nternational DT466 unknown 210 delivery 1999-13 • 52 031 42 000 30 000 1994 International DT466 unknown 250 delivery 1999-14 83 000 54 000 39 000 1990 Cummins LTA10 unknown 240 delivery 1999-15• 47 511 50 000 39 000 1993 Cummins C8

. 3 413C 210 delivery 1999-16 131 349 50 000 39 000 1989 Ford KEM708FPD1 210 delivery 1999-17 125 127 50 000 39 000 1989 Ford KFM078FD1 210 delivery 2000-1 108 490 30 000 22 244 1995 Cummins 85.9 SCE35906DAAA 210 box truck 2000-2 43 151 15 000 12 500 1994 GMC 6.2L RGM6.5C6DAA 190 f l at bed 2000-3 36 872 16 000 13 715 1998 Cummins 85

. 9 WCEXH0359 175 step van 2000-4 50 319 16 000 13715 1999 Cummins 85.9 unknown 175 step van 2000-5 84 039 16 000 13 715 1997 Cummins 85

. 9 TCE35906DARW 160 step van 2000-6 189 155 11 050 11 625 1991 lsuzu 4BD2TC NSZ0235FAAX 135 box truck 2000-7 d 145 596 15 000 12 500 1995 GMC TSA6

. 5L RGM6.5C6DAA 190 box truck 2000-8 162 005 62 000 52 000 1992 Cummins L 10 unknown 250 garbage 2000-9 8 106 567 60 000 37 310 1996 Cummins M11 TCE661 EJ DARB 280 c l ass 8

• Vehicles rejected after initial tests because of low smoke opacity. b Vehicle 5 was repaired and tested twice . ' Vehicle 10 was repaired and te s ted twice

. " Vehicle not te s ted after repair because the owner could not make i t available

.

e n co untered at Denver. A vehicle whose measured smoke opacity at Denv er exceeds 70 % points would hav e an ""a djusted " smoke opacity at reference conditions (0.0755 lb /ft 3 air density) of around 40 %. R

ece ntly the U.S. EPA has recomm e nded that the states

use smoke opacity failure points dev e loped by the State of California (55 % for pre-1991 and 40 % for 1991 and newer engines) to ensure uniformity across state lines {19). In a 1997 analysis performed for the Ca l ifornia Air Resources Board (CARB), EEA and CARB reviewed the diesel liM
programs currently in place in the United States (20). Many other states were using or planning to use the 55 / 40 % points. In some states there are random roadside smoke inspections while others require the opacity test annually as a part of vehicle registration. Additionally

, some states merely require vehicles that fail to be r e paired while others issue a fine in addition to r e quiring repair. Very little information is available on the performance of HDDV liM programs other than failure rates. For the California program in place before 1997 (a snap-acceleration with smoke opacity measurement by SAE 1243 procedure), the failure rate was 34% from spring of 1989 through autumn of 1991 but declined to 18.5 % in 1993 (20). This decline was presumably caused by vehicle owners repairing their vehicles
to avoid being cited and fined. The current California opacity program experiences a failure rate of about 8% (for the HDVIP in March 2000; 21). NESCAUM (Northeast States for Coordinat e d Air Use Managem e nt) performed a pilot study of SAE 11667 during 1996 (22). On the basis of a sample of 781 heavy

- duty vehicles, the failure rates (at 40 /55% ) were 4 % for 1991 and later model years and 25% for pre-1991 model
years. There appear to be no studies of the impact of 1 / M programs on actual pollutant emissions from HDDVs. However
, in the 1980s Ragazzi and co-workers conducted a study of the impact of an 1/M program on emissions from light

- duty diesel vehicles (LDDVs; 23). R e pair of thes e vehicles produced, on average, a 37% decrease in PM, a 50 % decrease in CO, a 34 % decrease in HC, and a 21% increase in emissions of NOx

. Several of the vehicles actually exceeded the NOx standard after repair. While the NO x increase was not discussed in depth, this is apparently a manifestation of the well-known NOxiPM tradeoff where factors (such as injection timing) that decrease PM cause an increase in combustion temperature and hence emissions ofNO x. At least two studies oflight-duty IM240 programs have also shown NOxincreases following repair of high CO-emitting gasoline automobiles (24

, 25). A number of different engine malfunctions can cause retarded or delayed injection timing

, which would increase PM emissions while decreasing NOx (26). These include fuel pump and injector wear as well as tampering with pump settings and smoke

- limiting throttle controls. Other malfunctions and maladjustments can apparently have the same result, as was demonstrated by Ullman and co-workers {1 4). In their study, two 1979 model year engines were tested with various ma l adjustments including increased intake air restriction

, intake air leak, improperly set injector lash

, disabling of throttle delay, and injection timing retard

. One engine was tested new and with a set of fuel injectors that had accumulated 50 000 mi of service in a city bus

. 

### All maladjustment configurations produced a doubling in PM emissions and a decrease in NOx emissions of roughly 25- 30%. In a second study, Ullman and Human examined maladjustment of a 1986 transit bus engine (27). Retarded fuel injection timing

, increased intake air restriction

, and reduced throttle delay all resulted in a decrease in NOx emissions. All of these studies taken together indicate that diesel engines deteriorate with use to have higher PM emissions but generally lower NOx emissions.



### Methods

Ve h icles Tested. Table !lists Lhe properties of the 26 vehicles recruited : 14 pre-1991 and 12 of 1991 and later model year.

VOL. 37, NO .3, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY • 631

### The only criterion for vehicle selection was the emission of visible levels of smoke during acceleration; no attempt was made to test a fleet representative of in-use smoking vehicles. Thus, the study results cannot be directly applied to inventory calculations of the impact of smoke opacity testing and repair. Five vehicles were rejected for repair after initial testing

as not being acceptable candidates (smoke opacity too low and reasonably low emissions), but emissions results are included for comparison. Two vehicles, nos. 1999-5 and 1999- 10

, were repaired twice with emissions testing after each repair. These vehicles both had high smoke opacity and PM emissions, and initial repairs were not successful at reducing emissions. Vehicle no. 2000-7 could not be made available for final testing in a timely manner and so was not tested following repair. Decisions regarding what repairs to perform were largely left to shop technicians. However, repair shops were requested to use the following sequence of checks in order to determine the cause of smoke: (i) Intake air restriction or malfunctioning turbocharger. (ii) Malfunctioning or maladjusted throttle controls. (iii) Fuel pump or fuel injector malfunction or maladjustment. No fixed limit to repair costs was used. Reduction of the smoke opacity for many of the vehicles required replacement of all fuel injectors, which typically cost in excess of $1500

. Smoke Opacity Testing. 

### Snap-idle tests were performed with the warmed-up vehicle in neutral using a Wager Digital Smoke Meter, model6500. The accelerator is rapidly pushed
to the floor held there for 5 s or until the engine reaches maximum (governed) speed, while smoke opacity is measured. The maximum opacity observed is reported

. For the SAE ]1667 test, three practice tests are first performed. This is followed by three real tests, which are averaged to obtain the reported value. The three tests must meet an allowable spread criterion, and the percentage of smoke opacity is corrected for stack diameter using an extinction coefficient specific to the instrument. The correction factor for ambient temperature, humidity, and barometric pressure specified in the ]1667 

### procedure was applied. Chassis Dynamometer Testing. 

### The chassis dynamometer system employed in this work has been described in detail in previous publications (28, 2f!). 

### The system is suitable for operating at vehicle speeds up to 60 mph (97 km/h) at up to 52 000 lb (23 586 kg) vehicle inertial weight. Inertia is simulated mechanically using flywheels, while wind and road friction are simulated electrically. The vehicle is driven on twin 40-in

. rolls. The driver manages the vehicle speed. The cycle is displayed for the driver using a driver's aid prompt that shows the driver his current speed and approximately 30 s into the future so he can anticipate shifting. For quality control purposes, ±2 mph error bands are displayed for the heavy-duty driver. This study used the Urban Dynamometer Driving Schedule for Heavy-Duty Vehicles (30), 

### except for vehicle 1999-2 (a transit bus), which was tested using the Central Business District Cycle (31). 

### All testing was performed using certification diesel fuel obtained from Phillips Chemical Company. While five different lots of certification diesel were used over the course of the study, every vehicle was tested before and after repair

on fuel from the same lot. The fuel lots employed were W-642, D434

, 9CP05201, 9HP5202, and OKP05202. Emissions Measurement. 

### The system for emissions
measurement includes supply of conditioned intake and dilution air, exhaust dilution system. and capability for sampling of particulate and analysis of gaseous emissions. All components of the emissions measurement system meet the requirements for heavy-duty engine emissions certification testing as specified in Code of Federal Regulations 40, Part 86

, Subpart N.

632 • ENVIRONMENTAL SCIENCE & TECHNOLOGY I VOL

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. 2003 

### Engine and Dilution Air. Engine intake and dilution air

are supplied to the chassis test cell through a conditioning system at 77 ± 9 ° F at 0 ± 0.5 in. of water column. The air is filtered to ASHRAE 80% minimum. Humidity is controlled
to produce a NOx humidity correction factor of I ± 0.03. Humidity is measured continuously in the conditioned air inlet by two independently calibrated methods: a dew point
meter and a polymer membrane sensor. The relative humidity obtained is converted to absolute humidity using the intake air temperature. The emissions measurement system includes an 18-in. dilution tunnel for exhaust conditioning. Engine exhaust and dilution air are mixed at the tunnel inlet with a typical dilution ratio of 20 (dilution ratio varies in a narrow range with the size of the engine being tested). Exhaust emission samples

are removed through a secondary sampler to the emission bench 10 tunnel diameters downstream. The total flow is controlled with a critical flow venturi (CFV) system. A centrifugal blower provides suction. Gaseous Emissions Measurement. A Pierburg emissions bench provides total hydrocarbon from a heated FID, NOx from a chemiluminescence analyzer (CLA), and CO and C02 from infrared detectors. All instruments meet or exceed CFR (Title 40

, Part 86

, Subpart N) 

### requirements for response and accuracy. The gas analysis bench is calibrated against U.S. EPA protocol gases. NOx and hydrocarbon analyses are performed on wet gas while the CO and C02 analysis is for

a dried gas sample

. Gas samples are also collected in an automated bag sampler through a small sampling CFV rated at about 5 Lim in and maintained at the same temperature and pressure as the main exhaust CFV to ensure proportionality. The sample line is equipped with a Balston filter to remove particulate
matter and most of the water in the sampled gas. The bag sampler gives an integral average emission directly. Dilution air is also collected in the bag sampler system. Correction for background emissions is performed using the dilution air analysis. Particulate Matter Sampling. Particulate matter is sampled in a Pierburg secondary dilution tunnel with sampling temperature maintained below 52 ° C. Particulate is proportionally collected in filtering units equipped with two filter coupons in series. The particulate weighing is conducted in

a temperature and humidity controlled room meeting CFR specifications. The weighing room is kept at a temperature of71 ±I ° F, a nominal relative humidity of 50%, and a dew point of 48 ± 3 ° F. Weighing is accomplished on a Sartorius R200D semimicro-balance meeting CFR specifications. The loading of particulate on the filter coupons ranged from I to 8 mg. depending upon vehicle and test cycle.



### Results and Discussion
Smoke Opacity. 

### The study was performed in two phases during 1999 (phase 1) and 2000 (phase 2). Smoke opacity (via SAE ]1667) 

### test results are reported in Tables 2 and 3, respectively, for each phase. Also noted are visual observations regarding smoke (i.e., if the vehicle was a white smoker) and a very brief description of repairs made to the engine. Nine of the 26 vehicles emitted white smoke. Of the pre-1991 vehicles

, four would have failed the California IIM test level of 55 %

. Other pre-1991 vehicles that were repaired exhibited visible smoke at lower opacity levels. Of the 1991 

### + model year vehicles. five failed the opacity cutpoint of 40% used in California. In most cases repair resulted in an apparent reduction in opacity. although not always to a passing level. For several of the vehicles, additional repairs were probably needed in order to pass the opacity test. but this could not be done because of cost and demands of the vehicle owners for return of their vehicles.

### TABLE 2. Averag e Emissions and Fuel Economy for Phase 1 Vehicles before and after Repa i r (g/m i )

s m o k e vehicle p re/post o paci t y 

### THC N O, 

## co PM

no. repair (%) (g/mi) ( g / m i) (g/ m i) (g / m i) mp g c omm ents

1999-1 pre 72 43 .6 15 .3 28.9 5.29 5 .32 black and white smoke 1999-1 po s t 11 2.4 15.4 12 .3 1.18 6.11 replace one injector 1999-2 nr 6 1 .0 44 .3 24

. 4 1

. 59 3.61 1999 -3 pre 21 2.2 41.7 26 .8 3.61 5.56 black smoke 1999 -3 post 8 2.8 35.1 54 .5 4

. 58 5.37 broken throttle pedal

, r ese t pump timing 1999

- 4 nr 8 1 .5 29.8 14.8 2.33 5

. 09 1999 -5 pr e 82 2.7 20.4 58.8 6.99 4 .3 9 black and white smoke 1999 -5 post 77 2.2 21

. 5 44.5 5.84 4 .5 4 6 new injectors, black smoke 1999 -5 2nd post 29 2.2 26.1 22.4 3

. 25 4.49 new fuel pump 1999

- 6 pre 13 1 .3 25.3 42 .3 5

. 14 5.40 low level of black smoke 1999-6 post 7 1 .2 32.9 54.6 4.43 5 .3 6 major tune up , pump timing 1999-7 pre 13 0 .8 15

. 8 37.5 6

. 82 4 .8 4 low level of black smoke 1999-7 post 13 1 .2 29.8 55.6 5.00 5.09 major tune up 1999-8 pr e 76 2

. 4 19.1 73.7 9.98 4

. 19 bl ac k and white smoke 1999

- 8 post 34 2.8 24

. 3 15.3 2.64 4

. 00 reset tampered fuel pump 1999 -9 pre 19 1

. 6 16

. 6 17.0 2

. 32 6

. 70 low level s of black smoke 1999 -9 post 23 2

. 1 36.8 21.3 2.01 5

. 57 new i njectors

, rebuild fuel pump 1999

- 10 pre 59 60 .2 28.2 79

. 4 16.4 3.95 black and white smoke 1999

- 10 post 36 58.9 26.2 79

. 2 15

. 5 3.97 replace fuel pump 1999-10 2nd post 33 2

. 8 25

. 4 20.2 5 .39 4

. 04 replace one fuel injector 1999-11 pre 31 1

. 1 25.7 17

. 6 2.56 5.18 low level of black smoke 1999-11 post 35 1 .6 54.1 26.2 1

. 86 5.21 fuel pump , overhead

, governor control 1999-12 pre 31 1.8 26.6 41

. 2 4

. 69 4.48 black and white smoke 1999-12 post 30 1

. 3 29

. 7 38.9 3

. 98 5

. 05 replace ir]jectors 1999-13 nr 11 0

. 36 13

. 6 8

. 1 1

. 08 5.77 1999

- 14 pre 76 7 .5 14

. 3 18.6 3.62 5

. 11 black and white smoke 1999-14 post 49 4.4 21

. 4 17.2 2.32 5.05 new injectors and camshaft 1999-15 nr 4 0 .9 6 14

. 5 3.2 0

. 89 5.58 1999-16 pre 30 1

. 4 16

. 6 15

. 3 2.68 4

. 90 black smoke 1999-16 post 25 1

. 4 26.3 14

. 7 1.75 5.48 rebuilt throttle linkage 1999-17 pre 21 1

. 4 15 .2 13

. 1 2.00 5.10 black smoke 1999-17 post 24 1 .1 29.2 18 .3 2.03 4

. 88 set pump timing

, repair throttle linkage

• nr ,= not rep ai r ed

.



### TABLE 3

. Average Emissions and Fuel Economy for Phase 2 Vehicles before and after Repair (glmi)

s mok e vehicle pre / po s t op acit y 

### TH C NO

, 

## co PM

no

. r e p air (% ) (g / m i) (g / mi) (g/ m i ) ( g/ mi) m pg c omment s

2000-1 pre 31 0

. 33 13

. 81 8

. 94 1

. 59 7

. 04 very large volume of white smoke 2000-1 po s t 31 0 .22 14.27 6 .1 0 1.06 7.04 replace fuel injectors and thermostat 2000-2 pr e 82 0

. 98 6 .62 24

. 44 2

. 78 9

. 99 very heavy black smoker 2000-2 po s t 40 0

. 08 5

. 88 3

. 66 0

. 77 10

. 76 replace fuel injectors 2000-3 pre 37 0 .2 7 13.34 6

. 46 0

. 52 9.50 black and white smoke 2000-3 post 8 0

. 23 13 .3 6 5.46 0.44 9 .5 8 replace cracked intercool er 2000-4 pr e 41 0

. 32 11.72 5

. 64 0

. 70 9.54 moderate black smoke 2000-4 po s t 12 0

. 35 11

. 65 4

. 79 0

. 44 9 .5 4 moderate adjustment to fuel pump 2000-5 pr e 33 0

. 31 11.39 5.41 0

. 35 10

. 25 black and whit e smoke 2000-5 post 10 0 .2 7 11.05 6

. 27 0

. 50 10

. 32 replace fuel injectors, pressure release valve 2000-6 pr e 70 0

. 23 4

. 94 10 .1 5 1

. 46 11

. 42 very he a vy black smoke 2000-6 post 57 0.13 4.84 6

. 21 0

. 96 11

. 62 replace fuel injectors

, recalibrate fuel pump 2000-7 pre 38 0

. 19 5

. 35 6

. 50 0

. 95 10.65 moderate black smoke 2000-8 pre 80 3.52 26

. 45 61 .9 3 6

. 17 3.38 heavy bl ac k smoke 2000-8 post 69 2 .2 4 38.56 73

. 72 4

. 76 3

. 32 replaced fuel injectors 2000-9 nr • 11 0

. 28 14

. 13 27

. 26 2

. 71 5

. 08 low smoke, veh ic le rejected

• nr, = not repair ed.

R egu l ated Emissions. Table 2 r eports average regulated data for on the order of 100 trucks. Both of the studies are emissions and fu e l economy for each phase I vehicle before believed to include almost entirely data for properly fun cand after r epai r , and the same r es ults are reported in Tabl e tioning vehicles, although this cannot be proven

. 3 for phase 2 vehicles. Raw data can be obtained from the The vehicles in both model year groups have PM

, THC, study final r e port (32). T ab l e 4 reports average emission values and CO emissions well above the averages from the ear li e r for all of the vehicles in this study by the two opacity cutpoint studies. The pr e- 1991 vehicles exa min ed in this study are on model year ranges, both before and after repair. For average lik e l y to be high PM e mitters with an average of

com parison, average emission values from the Northern more than 5 g/mi as compared to 2.8 g/mi for NFRAQS and Front Range Air Quality Study (NFRAQS; 28) and average 2.0 g/mi for v e hicles covered in the review. Av e rage PM emissio n values from a r ecen t revi ew of all h eavy-duty vehicle e missions from the 1991 and l ater vehicles are also more emissions data (33) are includ ed. This lat er study included than two times high er than the average values from the

VOL. 37, NO.3, 2003/ ENVIRONMENTAL SC IEN CE & TECHNOLOGY • 633..---, Opacrty c:::::J THC -NO

, r:s:s! 

### co

- PM 1991+ (>40%) 

### c=::::::::::::::::::::::::::::::: ==1-



## --

Pre-1991 (>55%)

· 80

- 60

· 40

- 20 0 20 40

Percent Change in Emission

FIGURE 1. Average percent change in opacity and g/mi emissions after repair for failure points of 55% (pre-1991) and 40% (1991 and later)

. Failing vehicles only

.



### TABLE 4. Average Emissions Levels from This Study Compared with Other Stuc1ies

repaired vehicles (pre) repaired vehicles (post)

repaired vehicles (pre) repaired vehicles (post) smoke opacity

(%)

Pre

- 1991

39 26 THC NO

, CO PM (g/mi) (g/mi) (g/mi) (g/mi)

7

. 0 22

. 1 36.8 5 .6 2.1 30.9 29.9 3.3
1991 and Later 59 5.5 12.1 17 .6 2

. 2 30 0.74 14.4 14 .8 1.3 NFRAQS Study (211) pre-1991 36 2.3 23.2 30.1 2.8 1991 and later 22 0.77 18

. 4 9.4 1 .0
Review Study (33) pre-1991 2.6 28.1 15 .1 2.0 1991 and later 1.2 25.9 9.0 1.0

previous studies. Emissions from the 1991 and l ater model
year vehicles are on average much low er than for the older vehicles. In part this is because the vehicles are newer. However, these vehicles are on average much l ower gross vehicle weight and hence lower horsepower, which also l eads
to lower grams per mile emissions. Four of the pre-1991 vehicles failed the 55% f ailure point used in California and recommended by the U

. S. EPA

. The
average change in emissions for this group of opacity test failing vehicles is shown in Figure I. Apparent benefits in
terms of reduced smoke opacity. PM, CO, and hydrocarbon emissions are observed. 

### NOx emissions appear to have increased by more than 20 %

. Additionally, five of the 1991 

## + model year vehicles exhibited greater than 40% opacity before repair, the failure point used in Cali fornia and recommended by the U

. S

. EPA

. The average change in emissions is shown in Figure I, and this group also shows appare nt benefits in reduced opacity, PM
, CO, and hydrocarbon emissions. 

### NOx appeared to increase by about 6 % for this group. A statistical analysis of the data was performed to allow

a determination as to whether observed differences in emissions after repair were significant. This analysis employed a two-sample 

### t-test comparing mean emission before and after repair. The t-test tool in Microsoft Excel was used under the assumptions o f equa l variance

, two tailed 

### tdistribution, and hypothesized mean difference of zero.

634 • ENVIRONMENTAL SCIENCE & TECHNOLOGY I VOL. 37, NO

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### TABLE 5. Significance of Emissions Changes after Repair Reported as 

### p Value

fa iling vehicle vehicles

no. 

### HC NO

, 

## co PM (%)

1999 -1 0 .0003 0.926 < 0.0001 0.0001 > 40 1999-3 0

. 015 0.0002 O.Q18 0.065 1999 -5 0.0200 0

. 0002 0.0420 0.0065 > 55 1999 -6 0.757 < 0.0001 0

. 003 0.932 1999 -7 < 0.0001 < 0.0001 0 .00063 0.075 1999 -8 0

. 018 0

. 267 0.051 0.076 > 55 1999 -9 0.085 0.0007 0

. 027 0 .06 1999-10 < 0.0001 0

. 012 < 0.0001 0 .0067 > 55 1999

- 11 0.012 < 0.0001 0.0026 0.0087 1999-12 0.06 0

. 0003 0.21 0.202 1999-14 < 0.0001 < 0

. 0001 0.042 0.032 > 55 1999-16 0.854 0.0006 0.482 0.0022 1999-17 0.0069 < 0

. 0001 0.024 0.845 2000-1 0.089 0.051 0.138 0.316 2000-2 0.018 0.044 0.0039 0.0045 > 40 2000-3 0

. 119 0.683 0.274 0.545 2000-4 0

. 121 0.775 0.28 0.134 > 40 2000-5 0.013 0.41 0.202 0

. 022 2000-6 0

. 0194 0

. 342 0.027 0.032 > 40 2000-8 0

. 0057 < 0.0001 0.178 0.094 > 40

no. < 1 16/20• 14/20 13/20 14/20

no

. < 1, > 55 4/4 3/4 4/4 4/4

no. < 1

, > 40 4/5 2/5 3/5 4/5 avg 0.11 0

. 18 0.10 0.17 avg failing > 55 0.0095 0

. 070 0

. 034 0.030 avg failing > 40 0.0323 0

. 42 0.098 0.053

• Numbers of vehicles for which p < 0.1 are noted as a fraction of the total number of vehicles in each group

.

Results of this analysis are reported in terms of p value in Table 5

. A low p va l ue indicates a higher probability that the change in emissions was significant. For examp l e. a p value of 0.01 corresponds to a significant change with 99 % confidence. If we arbitrarily select 90 % confidence as the significance level. about 75 % of the repaired vehicles showed

a significant change in emissions of all four criteria pollutants. All of the pre-199 !-vehicles failing the opacity test exhibited significant reductions in emissions of HC, CO. and PM following repair. Two out of four of these vehicles exhibited

a s i gnificant increase in emissions ofNOxwhile one exhibited

a significant decrease

. For the 1991 

## + vehicles, 4 out of 5 exhibited significant reductions in HC and PM, and 3 out of 5 exhibited a significant reduction in CO. 

### NOx emissions

### increased significantly for one and decreased s i gnificant l y for a second one out of these 5 vehicles

. Exam i nation of the average p 

### va l ues for all 20 repaired vehicles indicates that

, on average, changes in emissions after repair are significant with 80-90 % confidence. However
, this increases to greater than 90 % confidence when the average is taken on l y for pre1991 vehicles w i th greater t h an 55 % opacity before repair, including a significant increase in NO x emissions. For those vehicles failing the 1991 and later mod e l year opac i ty cutpoint of 40 %
, changes in HC

, CO, and PM were on average significant with greater than 90 % confidence w hil e the change in NO x is 

### not on average significant for this group as a whole. It 

### would be desirable to estimate the magnitude of the changes associated with a diese l I/M program

. However
, since

a distribution function for j-1667 smoke opacity based on a large samp l e does not exist for the Co l orado fleet, it is not possible to estimate how many vehicles an IIM program would impact. Typ es of R e p a ir s a nd R e p a ir C o s t s. Excessive smoke is caused by operation at a fuel/air ratio above the smoke lim i t, and thus repairs typical l y invo l ve components that affect fuel / air ratio. Virtually all repairs were to the injectors

, fuel pumps, fuel pump calibration, and injection timing. Injection pump work was performed on 10 out of 20 engines. E l even outof20 engines had injectors replaced

, of which 9 required replacement of all injectors. Injection timing and governor adjustment was the most common repair for pre-1991 vehicl e s , and injector replacement was the most common repair for 1991 and l ater vehicles. Three vehicles exhibited

a maladjusted throttle linkage. There was a l so one replacement of a cracked intercooler. Repair costs ranged from $85
to $2053 with an average of $1088, including both repairs as
a single cost for the vehicles that were repaired twice

. Average repair cost for the pre-1991 opacity test failing group was $1202 and for the 1991 +opacity test failing group was $991

. C ompari so n to NO

. Em iss ion Stand ar d s. NO x emissions

were observed to increase for 12 of the 20 repaired vehicles. To understand the cause of this increase, it is usefu l to compare the observed NO

. emissions to the NO x standard in effect for each model y e ar. Engine certification testing is performed on an engine dynamometer, and emissions are reported in units of grams of po ll utant emitted per unit work (g / bhp-h). To compare vehic l e emissions with the emissions standards

, which are likewise in g / bhp

- h

, a method for converting the g / mi emissions to g / bhp

- h is needed. The conversion of vehicle emissions in grams per mile to engin e emissions in units of grams per bhp-h can be performed on
a fu e l consumption basis using eq I:



### I . 

### __g__ bhp

- h g

- fuel 

### g m 1 = X X

, 

### bhp

- h g

- fuel m1 (l)



### The term g-fuel / bhp-h is the engine brake-specific fuel consumption (BSFC). The BSFC for new engines over the engine transient cycle is avai l ab l e from the manufacturers,

as measured from the certification test. In genera l

, the presence or absence of mal performances alters the BSFC by less than ±5% unless the ma l performance is very severe

. A comparison o f measured NO x emissions, converted to g / bhp

- h using eq 1, with the emissions standards is shown in Figure 2

. For the pre-1991 vehicles, all but one was below th e NO x standard before repair

, and all but one vehicle (a different one) was below after repair. Vehic l e 1999-3 had high NO x emissions (above the standard) before repair

, and th e injection timing may have been set incorrectly for the vehicle as received. Adjustment of timing resu l ted in decreased NOx and increased PM emissions. Vehicle 1999-11 ' s repairs a l so i nvolved changing or resetting injection timing and it is possib l e that timing was set inaccurate l y resulting in the high g / bhp

- h NO

. emissions. NO x emissions were 54**~** 16 

# c.**~** .Q 0,12 

## r:: .Q
(/) 8 0 (/) 

# ·e

w

>< 4 

# • 0 

## z Q Vthlcle11tV

· 11 • Pr e- Rep ai r 0 P ost .R epalr

e vehic

.. 1!iiH..J - NO x S ta n da r d

0 0 0 

# • • • 

# : l

0 

# i

. • 0 CL- _..;....

__ 

# _, e 1-...,L_ o**~** 

# i

. 0**+- --~--** **--~--~--~--~--~~ ~**  1984 1986 1988 1990 1992 1994 1996 1998 2000 

### Model Year

FIGURE 2. Brake-specific NO

. emissions before and after repair

as compared to the NO

. emission standards.



### g / mi (28 1 g / gal) after repair for this veh i cle. These va l ues are very high in comparison to other heavy-duty vehicles of this vintage (33). 

### For the 1991 and later mode l year vehicles on average, pre and post repair NO. emissions are near the standard

, a l though the 1998 and 1999 mode l year vehicles fa ll s l ightly farther above the l ine

. The increase in NOx emissions for these newer vehicles is smaller and not evident in every case. Since BSFC is a function of speed and load, using an average value to estimate emissions is only an approximation. Additiona ll y, it is not known i f the emissions certification for any of these engines included any allowance for emissions banking or trading. Even with these considerations, the resu l ts suggest that in many cases repair resu l ts in an increase i n NO x

. but to leve l s that are still near or be l ow the standards for the engine's model year. The po l icy and regulatory implications of the observed NOxincrease are not clear at this time. The U.S. EPA pollutant inventory mode l s do not cons i der emissions deterioration for heavy-duty d i ese l s, so these models are already counting the increased NO x emissions that would result from a widespread opacity based IIM program. However, in some urban areas the i ncrease in actua l NOx. as opposed to modelpredicted NOx. cou l d have a significant impact on air quality and l ead to vio l ation of the National Ambient Air Quality Standards for ozone and fine particles. Both the U.S. EPA ' s guidance document and all current diesel IIM programs are based on the belief that repair of high opacity vehicles will have on l y air quality benefits. Given data that this is not the

case , it is recommended that deterioration be incorporated into inventory models and that these mode l s be used to determine the overall air qua l ity i mpact of diese l I/M. A great deal of additional data will clearly be required to model deterioration accurately. Pr e diction of High PM Emi tte r s. Early work on smoke opacity found some corre l ation between smoke and PM emissions. McGuckin and Rykowski (34) 

### observed good correlation when comparing smoke opacity with steady-state emissions of PM. Alkidas (35) 

### found that Bosch smoke number corre l ated reasonab l y we ll with total PM but that the corre l ation was better with the nonvolati l e (soot) fraction of PM. A compar i son of smoke opacity and PM emissions is presented in Figure 3. The data from this study has been combined with results from two previous studies (28, 36) 

### of proper l y funct i oning vehicles in order to examine the correlation between smoke opacity and PM emiss i ons and
to examine the potential for using other measurements to predict what vehicles are high PM emitters. Note that these previous studies used uncorrected opacity (not corrected f or ambient temperature, humidity, or barometric pressure), and thus Figure 3 includes uncorrected opacity resu l ts from this study as well.

VOL. 31

, NO

. 3

, 2003/ ENVIRONMENTAL SCIENCE & TECHNOLOGY • 63518 

# • 19 99 li M Study , Pre-rep ai r 0 1999 l/ M Study ,**ost-n~pair** 

## • 16



# .. 2000 li M Stu d y , P re- re p a i r 0
'V 2 0 00 li M Study , Post-t'8pair
14 

## • Refer ence 3 6
0 R e f e r ence 2 8

- Linear Regression



# · e 1 2 lntercept=O

. 79 Slope=0

. 052 c;, r 2 =0

. 23 vi 10 

# •
c: 0 'iii 8 Ill



# · e • • w ::!! 6 0..

4

2

0

0 20 40 60 80 100
J1667 Smoke Opacity (uncorrected)

FIGURE 3. PM emissions as a funct i on of smoke opacity for this study and two previous studies

.

18 

# • Phase 1 1 / M Study, P re-repai r 0 Phase 1 1 / M S tu dy, P ost-re p air 

## • 16 

# .. Phase 2 1/ M Study, P re-repai r
'V Phase 21/ M S tud y, Po s t-rep a i r 0 

## • Re f erence 36 14 0 Re f erence 28

- Linear Regression lntercept=-0

. 006 1 2 Slope=0

. 115
r 2 =0

. 67 

## .E 10 

# • c, ::i 8 Q, 

# •
6 0 

# .. 0 0 

## • 

# • 0 

## e 

## " 4 

## • • 0 0 0

2 

## •

0 0 20 40 60 80 100


### CO

, g/mi

FIGURE 4. Correlation of PM and CO em i ss i ons

.


### Clearly there is a relationship between PM and smoke opacity, although smoke opacity is not a particu l arly good predictor of PM emissions (f! = 

### 0.23

, note that remova l of the two > 

### 14 g / mi PM points increases f! 

### to 0.40). For the results of this study on l y, f! 

### values are about 0.1 for both uncorrected and corrected opacity. Exam i ning pre-repair data from this study only, smoke opacity is still a poor predictor of PM emissions with an f! 

### of 0.21. The fact that severa l vehicles with re l atively high PM emissions exhibit l ow smoke opacity indicates that smoke opacity measurements may fail
to identify all high emitters. One reason for t h is is probab l y emission of white smoke. which is primarily unburned fuel. White smoke is typically caused by fue l pump or fuel injector

ma l functions but can also be caused by disab l ed or ma l

functioning throttle contro l s. Figure 4 compares CO and PM resu l ts from th i s study along with results from the previo u s studies. For all of the data taken together (pre- and post-repair), there is a reasonably good correlation (f! = 

### 0.67. pva l ue on s l ope much

636 • ENVIRONMENTAL SCIENCE & TECHNOLOGY I VOL. 37

, NO.3

, 2003 

### l ess than 0.01). However, considering on l y the pre-repair data from this study, f! 

### improves to 0.85 and the coefficient for CO is significant at we ll above the 99% confidence l evel (p 

### value much l ess than 0.0 1 ). H ydrocarbon em i ssions are

a slightly better predictor of PM emissions than smoke opacity (f! = 

### 0.48, p < 

### 0.01); however, corre l ation of PM emissions with both CO and hydrocarbon produces an f! 

### o f 0.94 with high l y s i gnificant coefficients for both independent variab l es. Thus, CO and hydrocarbon emissions for driving u nder l oad

can be an exce ll ent predictor of PM emissions. For diese l inspection and maintenance purposes, CO and hydrocarbon emissions while driving a cycle under l oad may not be obtainab l e because of h igh testing equipment capital and operating costs. Measurement of CO and h ydrocarbon during the snap-acce l eration (as performed for smoke opacity measurement) wou l d be a much easier measurement to make in the fie l d. During the phase 2 study, concent r ations of gaseous po ll utants were monitored during snap-accelerations. To accomp l ish this, the snap-acce l erations were performed repeated l y while the veh i cle exhaust was connected to the dil u tion tunnel. Results for regression ofUDDS cycle PM emissions as a function of snap-acce l eration peak THC and CO emissions indicate that peak CO is a reasonable predictor of PM emissions (f! = 

### 0

. 74, p 

### va l ue < 

### 0.01) and multiple regression of both snap-CO and

- THC is even better (f! = 

### 0.86, p 

### va l ue < 

### 0.01)

. Use of either CO or CO and THC from a snap-acceleration test has sig n ificant l y better predictive capability for high PM em i tters than does smoke opacity for the vehicles examined in this study.


### Acknowledgments
This work was supported by the United States Environmental Protection Agency through a State and Triba l Agency Grant
to the Co l orado Department of Pub l ic Hea l th and Env i ronment. This work was a l so supported direct l y by t h e Co l orado Department of Public Health and Environment. Air Po ll ution Contro l Division.



### Literature Cited

(I) Sawyer

, R. F. ; johnson

, ]

. H. Diesel Exhaust: A Critical Analysis of Emissions

, Exposure. and Health Effects; Health Effects Institut e: Cambridge

, MA, 1995; pp 67-81. (2) U

. S

. EPA. National Air Pollutant Emission Trends Update

. 1970

- 1997; EPA

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. Government Printing Office : Washington

, DC

, 1998. (3) Larson
, S

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. R. ; Gray

, H. A. Aerosol Sci. Techno]. 1 9 8 9
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, S

. M.; Cass. G. R. Environ. Sci. Techno]. 198 9, 23, 281- 289. (5) Nauss, K. M. Diesel Exhaust: A Critical Analysis of Emissions. Exposure

, and Health Effects; Health Effects Institute: Cambridge. MA. 1995; pp 1 1-61. (6) Miguel

, A

. H

. ; Fri e dlander, S. K

. Atmos. Environ. 1978

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, 2407- 2413

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, C .; Lyons
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. Environ. Sci

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, 28, 555-562. (8) Venkataraman, C

. ; Friedlander, S. K. Environ. Sci. Technol. 1994, 28, 563

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. 0 .; Dookeran

, N

. M

. ; Smith, K. A

. ; Sarofim. A. F. ; Taghizadeh, K .; Lafleur

, A

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, 1023-1031. (10) Atkinson

, R. Air Pollution, the Automobile, and Public Health ; National Academy of Sciences Press : Washington, DC

. 1988

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, ]. H

. }. Air Waste Manage

. Assoc

. 1 9 88

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- 645. (12) Winer. A

. M .: Busby

. W. F

. Diesel Exhaust : A Critical Analysis of Emissions

, Exposure. and H e alth Effects; Health Effects Institute: Cambridge, MA, 1 995 ; pp 83

- 105. (I 3) Williams, G.; Hartman
, F

. W

. , 

### Jr. : Mack e y. G

. R. SA£ Tech. Pap. Ser. 19 73

, No. 730660

. (14) Ullman

, T

. L. ; Hare, C

. T .; Bain e s, T. M. SA£ Tech. Pap

. Ser. 1 9 8 4

, No. 8404/6

. (IS) SAE. Surface Vehicl e R e commended Practice }1667

, SnapAcc e leration Smoke Test Procedure for Heavy

- Duly Diesel Powered Vehicles; 1 996.(16) Human, D. M.; Ullman, T. L.; Baines, T. M. SA£ Tech. Pap. Ser. 1990, No. 900883

. (17) Chaffin

, C. A

. ; Ullman, T

. L. SAETech. Pap

. Ser.1994

, No. 940669. (18) Graboski, M.S .; McCormick

, R. L. SA£ Tech. Pap. Ser. 1996 , No

. 961947. (19) Oge, M. T. Guidance to States on Smoke Opacity Cutpoints to be used with the SAE} 1667 In- Use Smoke Opacity Test Procedure; U.S. Environmental Protection Ag e ncy: Washington, DC

, February 1999. (20) California Air Resources Board and Energy and Environmental Analysis, Inc. Regulatory Amendments to California's HeavyDuty Vehicle Inspection Program (HDVIP) and Peroidic Smoke Inspection Program (PSIP); August 1997. (21) jacobs

, P. E.; et al. March 2000 Mobile Source Enforcem e nt Branch Monthly Status Report, April 10, 2000. (22) NESCAUM. Final Report: Northeast Diesel Smoke Testing Pilot Program; May 1997. (23) Ragazzi

, R.; Gallagher

, G. L.; Barrett
, R. A. SAE Tech. Pap

. Ser. 1986 , No. 860297

. (24} McClintock

, P.M. The Denver Remote Sensing Clean Screening Pilot, Final Report prepared for Colorado Department of Public H e alth and Environment

, December

, 1999. (25) Wenzel, T. Human Behavior in liM Programs; Presented at the 15th Annual Mobile Sources/Clean Air Conference, Snowmass, CO

, September 1999 (as cited In ref 23). (26) Weaver
, C. S.; Balam

, M.A

. ; Broderick

, C. j. Modeling Deterioration in Heavy

- Duty Diesel Particulate Emissions; Final Report submitted to U

. S. Environmental Protection Agency

, Contract 8C-SI12-NTSX ; September 30, 1998. (27) Ullman

, T. L.; Human, D. M. SA£ Tech. Pap. Ser. 1991 , No. 910735. (28) Yanowitz, j. ; Graboski, M. S.; Ryan, L. B. A.; Daniels

, T. L.; McCormick

, R. L. Environ. Sci. Techno/. 1999 , 33, 209-216. (29) Clark, N. N. M.; Gautam

, B. L. ; Rapp, D. W. ; Lyons, M.S.; Graboski, R. L.; McCormick, T

. L. ; Alleman, P. Norton SAE Tech. Pap

. Ser. 1999, No. 1999-01

- 1469

. (30) Code of Federal Regulations, Vol. 40, Subpart M. (31) SAE Recommended Pra c tice}1376

, Fuel Economy Measurement Test for Trucks and Buses; 1982

. (32) McCormick, R. L.; Graboski, M.S.; Alleman

, T. L.; Alvarez,]. R. ; Kado

, N. Y.; Kuzmicky

, P. A.; Kobayashi

, R.; Duleep, K

. G

. Quantifying the Emission Benefit of Opacit y Testing and Repair of

Heavy-Duty Diesel Vehicles; Final Report to Colorado Depart

ment of Public Health and Environment, july 200 I (this report

can be obtained from the author). (33) Yanowitz, ].; McCormick, R. L.; Graboski, M

. S. Environ. Sci. Techno!

. 2 00 0, 34, 729

- 740. (34) McGuckin, j.; Rykowski, R. Correlation between Smoke and Particulate Emissions from Heavy

- Duty Diesel Engines; U.S. EPA

, Office of Mobile Sources Technical Report : Washington

, DC

, 1981. (3Sj Alkidas, A. C. SAE Tech. Pap. Ser

. 1984. No

. 840412

. (36) McCormick, R. L. ; Alleman, T. L.; Graboski

, M. S

. Emissions TesUngofHeavy

- Duty Vehicles: Phase I ; Final Report to Colorado Department of Public Health and Environment and Regional Air Quality Council; Colorado Institute for Fuels and High Altitude Engine Research : june 1999

.



### Received for review April 1

, 2002. Revised manuscript received October 23, 2002

. Accepted December 2, 2002.



### ES0256919

VOL

. 37

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. 3, 2003 I ENVIRONMENTAL SCIENCE & TECHNOLOGY • 637QUANTIFYINGTHEEMISSIONSBENEFITOFOPACITYTESTINGANDREPAIROFHEAVY-DUTYDIESELVEHICLESRobertL.McCormick,MichaelS.Graboski,TeresaL.Alleman,JavierR.AlvarezColoradoInstituteforFuelsandEngineResearchColoradoSchoolofMinesGolden,CO80401-1887K.G.DuleepEnergyandEnvironmentalAnalysis,Inc.Arlington,VA22209Acknowledgetnents:ThisstudywassponsoredbytheAirPollutionControlDivisionoftheColoradoDepartmentofPublicHealthandEnvironment.ThisstudywasalsosponsoredbytheOfficeofTransportationandAirQualityoftheU.S.EnvironmentalProtectionAgency.Theauthorswishtothanktheseentitiesfortheirsupport.Theauthorsalsowishtothankthemanytruckowners,largeandsmall,thatallowedtheirvehiclestobeusedinthisstudy.StudyObjectives:•Begintoquantifythebenefitsofasmokeopacity(SAEJ1667test)basedinspectionandmaintenanceprogram.•Providedatausefulforselectionofopacityfailurepoints.Approach:•Identifysmokingtrucksbyvariousmeans(callingfleets,smokingvehiclehotline,Coloradosnaptest,......Obtainpermissiontotest.•TestthesevehiclesonHDchassisdynamometerviaUDDSdrivingcyclewithmeasurementofTHC,CO,NOx,PM.•Repairvehiclestohavereducedopacity.RepairsperformedatOEMlocalrepsorotherauthorizedfacilities.•Repeatchassisdynamometertests.•BestpossibleI/Mscenario-closemonitoringoftechnicianstoinsurethatrealrepairswereperformed.ScopeandLintitations:•Twentysixvehiclestestedbeforerepair•Seventeenpre-1991,fourexhibitedlowopacityandwerenotrepaired,twowererepairedtwice.•Nine1991andlater,oneexhibitedlowopacityandwasnotrepaired,asecondwasnotmadeavailablebytheownerforfinaltesting.•Twentyvehiclesintotalrepairedandtestedasecondtime.•Pre-repairopacityrangedfrom23to99%.•Enginemodelyearsrangedfrom1986-1999.•GVWfrom11,000to80,000lb.•EnginesmanufacturedbyDDC,Caterpillar,Cummins,Isuzu,Ford,International,GMC.SummaryResults:RangeSmokeTHC,NOX,co,Opacity,0/og/mig/mig/miPM,g/miPM,g/miPre-1991:Repairedvehicles(pre)547.022.136.85.62.0-16.4Repairedvehicles(post)*392.130.929.93.30.89-5.41991andLater:Repairedvehicles(pre)665.512.117.62.20.35-6.2Repairedvehicles(post)390.7414.414.81.30.44-4.8NFRAQSStudyi241.321.016.81.7ReviewofDiesel--2.224.411.01.6Emissions11Afterallrepairsforvehiclesundergoingtworoundsofrepair.iYanowitz,J.,Graboski,M.S.,Ryan,L.B.A.,Daniels,T.L.,McCormick,R.L.Environ.Sci.Techno/.1999,33,209-216.iiYanowitz,J.,McCormick,R.L.,Graboski,M.S.Environ.Sci.Techno/.2000,34,729-740.BrakespecificNOxemissionsbeforeandafterrepaircomparedtotheNOxemissionstandards:.c16Ic..c.c........Cl12""s::::0-8·-Ew><40z-Exceptforthenewestengines,NOxgoesupafterrepair-buttolevelsthatareclosetotheemissionstandards0•000Q•••Ii0••00••Pre-RepairoPost-Repair-NOxStandard.ai.0£.._0lMechanicallygovernedenginesdeterioratetohavehigherPMandlowerNOx?198419861988199019921994199619982000ModelYear(Thewell-known)NOx/PMTrade-Off:EngineoperatingstrategiesthatlowerNOxcausealoweringofcombustiontemperatureandincreaseinPM-deteriorationofinjectors,pumps,etclowerscombustiontemperature,reducingengineefficiencyandloweringNOx130120110NaturallyAspirated01000...90I80ITurbochargedlntercooled6065707580859095100105110115120NOx0/oOpacityTesting/RepairObservations:•Mostrepairsinvolvedfuelinjectors,fuelpumps,fuelpumpcalibration,throttlecontrolsandinjectiontiming.•Averagerepaircostwas$1,088(range$699-$2053)andwassimilarforbothpre-1991and1991+engines.Oneoutliercost$85toreduceopacityfrom50to17%andreducePMby35%.•Mostvehicleswereoutofservicefor2daysduetorepair,butsomerequiredaslongastwoweeks-usuallyformultiplerepairs.•Repairofpre-1991vehiclesexceeding45%opacityreducedPMemissionsby45-50%.APMbenefitwasobservedforeveryvehiclerepaired.NOxincreasedbyabout35%onaverage.•of1991+vehiclesexceeding40%opacityreducedPMemissionsby25-30%.ForonevehicletherewasnoPMbenefit.NOxincreasedby7%onaverage.RelationshipBetweenPMandOpacityorCO:1818•19991/MStudy,Pre-repair•19991/MStudy,Pre-repair16-l019991/MStudy,Post-repair•019991/MStudy,Post-repair•20001/MStudy,Pre-repair016..20001/MStudy,Pre-repair'V20001/MStudy,Post-repair'V20001/MStudy,Post-repair014-1•McCormick,etal.,1999•McCormick,etal.,19990NFRAQS140NFRAQS--LinearRegression--LinearRegression12lnt=0.79Int=-6.Oe-3ESlope=0.05212Slope=0.115-r2=0.23r2=0.67C)Ill10•Es::::10-1•0-IllC)8E:!!8w••a.:2:60_____;-n6•a...0004-l------0••00nI:j•n•/6'V2uI0n0oO0•0yv'I0020406080100020406080100J1776SmokeOpacity(uncorrected)CO,g/mi(variouscycles)PredictingPMwithSnapAccelerationPeakCO:-COiswellcorrelatedwithPM.-OpacityandidleemissionsofCOarepoorlycorrelatedwithPM.-Thissuggestsasimpletail-pipeCOmeasurementtoidentifyhighPMemitters.-gaseousemissionsmeasuredduringsnap-testidenticaltoJ1667-1991+vehiclesonly(7vehicles)-peakCOduringsnappredictsPMwithr2==0.74-peakCOisamuchbetterpredictorofPMthanopacityConclusions:•RepairofhighopacityvehiclessignificantlyreducedPMemissionsinessentiallyeveryinstance.•OpacityisapoorpredictorofPM.WhileconsiderableR&Dwouldberequired,asimpletail-pipemeasurementofCOduringasnapaccelerationmightbeamoreaccuratepredictor.•Ingeneral,repairofhighopacityvehiclesalsocausesNOxemissionstoincrease.DrivingCycleandChassisDynaDloDleter:706050"E.40E"030Q)Q)c..en20100Heavy-DutyTransientTruckCycle02004006008001000SAEJ1667OpacityTest:•Vehiclewarmedupandinneutral.•Acceleratorisrapidlypushedtothefloorheldfor5secondsoruntiltheenginereachesmaximum(governed)speed,whilesmokeopacityismeasured.•Themaximumopacityobservedisreportedandtheaverageofthreetestsisreported.•Opacityiscorrectedforstackdiameter.Altitudecorrectionisapartoftheprocedurebutwasnotusedinthisstudyasitisnotbelievedaccurateormeaningful.•EPArecommendsthatstatesuseopacityfailurepointsdevelopedbytheStateofCalifornia(55%forpre-1991and40%or1991andnewerengines)toinsureuniformityacrossstatelines.110ge,M.T.,GuidancetoStatesonSmokeOpacityCutpointstobeusedwiththeSAEJl667In-UseSmokeOpacityTestProcedureU.S.EnvironmentalProtectionAgency,February,1999.Averagepercentchangeing/miemissionswithrepair,pre-1991:.-c'(5<45%a.::snJLL45%0nJa.0C1)55%(J)!:SS.:S1corzzzlNOX-THCc::=JSmokeOpacityV////////////////////////......1///////////////A"'''''"'''-'''''''////////.11-60-40-200204060PercentChangeAfterRepair(Average)55°/oasrecommendedbyEPAand45°/oasrecommendedinthestudybyEEA,Inc.performedforStateofColorado.Averagepercentchangeing/rniemissionswithrepair,1991+:rs;s:ssJco....c:NOX-THC0a.c:::=:::JSmokeOpacityQ)...::::sLXn:sL1.""'""'""""'""""'"'-.'\..........40%tzzJC)n:sa.0IQ)0Een..so-40..JO-20-1001020PercentChangeAfterRepair(Average)40°/oasrecommendedbyEPA.Allvehiclesalsofailed33°/oasrecommendedinthestudybyEEA,Inc.performedforStateofColorado.