Assessing Auto Emissions under Utah-Specific Conditions

Dr. Randy Martin USU/UWRL

Civil & Env. Eng.

Logan, UT

randy.martin@usu.edu

(435) 797-1585

Joe Thomas WSU/NCAST/UDAQ

Nat’l Center for Automotive

Science & Technology

Ogden, UT

joethomas@utah.gov

(801) 536-4175

Study Problem Statement

• Utah has focused on reducing automobile emissions as a core component of the plan to improve the state’s air quality – Emissions inspection & maintenance programs – Anti-idling programs – Driving modification & outreach programs

• 25 driving-related suggestions at UDAQ’s “Choose Clean Air”, http://www.cleanair.utah.gov/winter/50wintersuggs.htm

• However, little literature and data exist identifying the benefits or atmospheric penalties involved with these issues, particularly under Utah-specific conditions in relation to vehicle fleet, temperature regimes, etc.

Past Research • Second-by-Second Characterization of Cold Start

Gas-Phase and Air Toxic Emissions from a Light Duty Vehicle (Sentoff et al., 2009; U. of VT) – repeated measurements on a single 1999 Toyota

Sienna (mini-van)

– summary findings: 1) time to optimal catalytic function varied among

pollutants

2) idle after cold starts produced higher emissions than after warm up driving

3) peak cold start concentrations varied with ambient temperature (9.5 to 38.4°C) • 2-3x increase as temperature decreased from ≈25 to 10°C

Past Research • Transportation Air Quality Facts and Figures January

2006 – U.S. Department of Transportation, Federal Highway Administration

(https://www.fhwa.dot.gov/environment/air_quality/publications/fact_book/page15.cfm)

Source: U.S. Environmental Protection Agency. MOBILE6.2 Model run assumed IDLE Test, National Low Emission Vehicle Standards, summer temperature 64-92 degrees, and United States average vehicle operations. 20 April 2004.

• Typical 7 trips/day, 29 VMT

• Cold Start • 7.7 g VOCs (25% daily) • 88 g CO (26% daily) • 5.0 g NOx (19% daily)

• Running cycle • 7.8 g VOCs ( 25% daily) • 251 g CO (74 % daily) • 20.2 g NOx (81 % daily)

Study Objectives

Study Tasks: 1) Measure the differences in emissions between cold

starts, hot starts, and continuous idling,

2) Verify whether emissions are different under different weather (temperature) conditions, and

3) Determine how long catalytic converters can remain at optimal temperatures in Utah’s seasonal conditions

• To accomplish these tasks, researchers at Utah State University (USU) and the National Center for Automotive Science and Technology (NCAST) at Weber State University (WSU) will test a group of vehicles (n ≥ 50) representative of the vehicle fleets typical of the Cache Valley and Wasatch Front Counties

Target Vehicle Breakdown • Light-Duty (LD), with Gross Vehicle Weight

Ratings (GVWR) ≤ 8,500 lbs.

• Representative of the Wasatch Front counties – Box Elder, Cache, Davis, Salt Lake, Tooele, Utah, and

Weber Counties

– separated by EPA “Tier Level” • surrogate for vehicle age (average of target counties = 8.91 yrs)

• specifies emission requirements

Tier Level Pre-Tier 0 Tier 0 Tier I NLEV Tier II Tier III

Model Year ≤ 1980 1981 - 1993

1994 - 2000

2001 - 2003

2004 - 2016

2017 - 2025

# of vehicles

22,447 (1.4%)

92,827 (5.9%)

372,927 (23.7%)

271,522 (17.3%)

811,802 (51.7%)

NLEV = National Low Emission Vehicle

Methodologies • Measure tailpipe concentrations of hydrocarbons

(VOCs or HCs), oxides of nitrogen (NOx), and carbon monoxide (CO) – Autologic Applus 5-Gas Analyzer

• reports concentrations or mixing ratios (volume % or ppm)

• also measures carbon dioxide (CO2) and oxygen (O2)

– Measure “Cold Start” emissions • vehicle off, outside, for ≥ 12 hours prior to testing

– Measure “Hot Start” emissions (5, 10, 20 min) • after on-road drive cycle, shut off motor and start after

specified period of time

– Measure “Idle” emissions • Continued measurement for ≥ 5 min after start equilibrium

reached

Methodologies • Additional supporting measurements

– Tailpipe velocity (flow rate) • to convert concentrations to emissions (e.g. g/s)

• developed algorithms to relate engine RPM and exhaust gas temperature to tailpipe velocity – velocities measured with a high temperature propeller

anemometer

– Engine operating conditions • as available through the OBD II sensor, if available

– RPM, catalyst temperature, engine coolant temperature, oxygen sensor data

– If OBD sensor unavailable, at a minimum RPMs were manually recorded

– System external (surface) temperatures • engine block, cat skin temperature, exhaust gas, ambient

Methodologies (cont.) • Testing a vehicle at USU’s Utah Water

Research Laboratory (UWRL)

Methodologies (cont.)

• Testing a vehicle at WSU’s National Center for Automotive Science and Technology (NCAST) – on NCAST’s computer-controlled dynamometer

Vehicle Selection & tested-to-date

Preliminary Results

• Example OBD sensor readout showing calculated catalyst temperature (blue), engine RPM (orange), and engine coolant temperature (grey)

Preliminary Results • Start & idle emissions for 2007 Dodge Ram 1500

“Start” period Note differing equil. times

“Idle” period

Preliminary Results • Not all vehicles “equilibrate” quickly after a cold start

– 2001 Dodge Durango (NLEV, pre Tier II vehicle)

Preliminary Results

Cold Start vs. Hot Start Emissions

• Cold starts resulted in higher emissions across vehicle types and pollutants − Avg EHC = 1.02 g (DOT: 7.7 g)

− Avg ENOx = 0.048 g (DOT: 5.0 g)

− Avg ECO = 38.5 g (DOT: 88 g)

Hot Start Emissions vs. Idle (HC)

• Hot Starts almost always resulted in lower HC emissions as compared to an equivalent idle − esp. true as time increases (e.g.

hot start emissions after 20 min, lower than if idled for 20 min

Hot Start Emissions vs. Idle (NOx)

• Similar to HCs, greatest NOx emissions observed during idle periods − Dodge RAM 5-min apparent

exception

Idle Emissions Following Cold and Hot Starts

• NLEV Cold Start idle much higher than “Hot Start” idle − Similar to Sentoff et al

(2009) – 1999 vehicle (Tier 1)

• Tier II vehicles more consistent across idles

Tailpipe Drive Cycle Emissions

• 1-8-15 2007 Dodge Ram 1500 drive around emissions

Summary • Able to quantify pollutant emission difference between cold

starts, hot starts, and idles – similar behavior, but different magnitudes as past research not

specific to local vehicle fleet – anti-idling strategies appear effective

• Continue cold start/hot start/idle across fleet • Effect of ambient temperature on cold starts • Catalyst temperature behavior & efficiency • Drive cycle tests – road/dyno emissions tests

• Test effectiveness of catalyst replacement on previously tested vehicles – CA-certified catalyst vs. “normal” catalysts

• Other issues??

Continuing/Future Research

Questions?

Acknowledgements: Utah State Legislature & Utah Division of Air Quality USU’S Utah Water Research Laboratory (UWRL) WSU’S National Center for Automotive Science & Technology (NCAST) Numerous friends & colleagues for use of their automobiles

Clay Woods (USU) Chris Woodhave (NCAST) Alan Walker (NCAST)

Supplementary Slides

Methodologies (cont.)

Autologic Applus 5-Gas Emissions Analyzer

Methodologies (cont.)

External temperature

measurements and datalogger

Preliminary Results • Comparison of internal (OBD) and external

(surface/skin) temperature measurements

Note: During hot start/idle tests catalyst external surface temperatures approached 60°C

Hot Start Emissions vs. Idle (CO)

• Unlike NOx and HCs, highest CO emissions often observed from “Starts” as opposed to “Idles” − Fuel-rich?