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The LEV IV FTP PM limit in the recently approved CARB ACC II regulations for passenger cars and light duty trucks will be 1 mg/mile starting in 2025. Gravimetric PM measurement at these levels is very challenging as the net mass of PM on the filter in full flow tunnel testing ranges between 8 to 32 micrograms depending on amount of dilution. This is approaching tunnel background levels which, in combination with filter handling, static charge removal and microbalance instability, compounds the uncertainty. One major source of the uncertainty at these low levels is the tunnel contamination resulting in high variability from test to test and cell to cell. This tunnel background is mostly HC artifact which cannot be easily controlled and can be significantly higher than the 5-μg CFR allowable correction limit in some test cells.

Chrysler, Ford, General Motors, the U.S. Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) have collaborated over the past two years to develop an efficiency test for mobile air conditioner (MAC) systems. Because the effect of efficiency differences between different MAC systems and different technologies is relatively small compared to overall vehicle fuel consumption, quantifying these differences has been challenging. The objective of this program was to develop a single dynamic test procedure that is capable of discerning small efficiency differences, and is generally representative of mobile air conditioner usage in the United States. The test was designed to be conducted in existing test facilities, using existing equipment, and within a sufficiently short time to fit standard test facility scheduling. Representative ambient climate conditions for the U.S. were chosen, as well as other test parameters, and a solar load was included.

Flame ionization detector (FID) analyzers used in emission testing to measure total hydrocarbon emissions have been operating for the last forty years on a fuel mixture of 40% H₂ and 60% helium. These mixtures were selected based on research studies reported in the literature indicating that this particular mixed fuel combination gave the best sensitivity and relative response of the different hydrocarbons present in vehicle exhaust with respect to propane, the calibration gas. During the past few years, it was announced that there is a worldwide shortage of helium which triggered the automotive industry to look for alternatives for helium to be used in FID fuels. Helium which is produced as a byproduct from natural gas fields is non-renewable, expensive, and extremely rare on the earth. Current supply cannot keep up with demand. There are only few natural gas fields producing helium and unless new natural gas fields are found, current helium amounts will continue to dwindle.

Flexible fuel vehicle production has been steadily increasing in the US over the past fifteen years. Ethanol is considered a renewable fuel additive to gasoline which helps the US efforts in minimizing the dependency on foreign oil. As a result, it is becoming very hard to find pure gasoline which does not contain some ethanol content at the pump in the US. The fuel currently available at the pump contains close to 10% ethanol. The fuel and evaporative systems components and materials on newer flexible fuel vehicles are being designed to be tolerant of the 10% ethanol content. There is a strong desire from ethanol producers to increase the ethanol content up to a 20% level. This is still being debated by the Environmental Protection Agency and a final decision has not been made yet but will be announced by the upcoming Tier 3 Notice of Public Rule Making (NPRM) in December of 2011.

Ethanol fuel is a sustainable energy resource intended to provide a more environmentally and economically friendly alternative to fossil fuels. Ethanol fuel for automotive applications is becoming increasingly widespread and its market is continuing to grow. Measurement of ethanol was traditionally done with an impinger and a gas chromatograph (GC) system but this method is not a direct measurement, usually requires manual handling and takes a long time for post processing of data. The Innova photoacoustic analyzer can directly measure the ethanol emissions in vehicle exhaust without using the impinger/GC system. For the past eight years at Chrysler, the Innova has been used as a stand alone analyzer and the emission sample bags were physically transported to the chemistry lab for ethanol measurement. The data had to be manually entered and post processed for the final results.

It is becoming increasingly difficult to obtain good repeatability from running lab vehicle correlation testing, since vehicle variability is so significant at the Low ULEV and SULEV emissions levels. These new emission standards are becoming so stringent that it makes it very difficult to distinguish whether a problem is a result of vehicle variability, test cell sampling or the analytical system. A vehicle exhaust emission simulator (VEES) developed by Horiba, can simulate emissions from low emitting gasoline vehicles by producing tailpipe flow rates containing emissions constituents ( HC, CH4, CO, NOx, CO2 ) injected at the tailpipe flow stream via mass flow controllers.

Measuring vehicle exhaust volumetric flow rate accurately and precisely is critical in calculating the correct vehicle modal and bag mini-diluter exhaust emission constituent masses. It is also instrumental in engine calibration practices. Currently, DaimlerChrysler's Emission and Certification Lab in Auburn Hills, Michigan utilizes constant volume sampling bag systems to certify vehicles but the automotive technological trend is heading toward the bag mini-diluter for greater precision at low emission levels. The bag mini-diluters, as well as the modal sampling system, used extensively in vehicle development testing, rely on exhaust flow rate measurement by means of a direct vehicle exhaust flow meter named E-Flow. The E-Flow has few limitations such as flow profile instability at low idle flow rates and reaction to resonating pressure waves in the exhaust system.

Vehicle exhaust flow is difficult to measure accurately and with high precision due to the highly transient nature of the cyclic events which are dependent on engine combustion parameters, varying exhaust gas compositions, pulsation effects, temperature and pressure. Bag mini-diluter (BMD) is becoming one of the few technologies chosen for SULEV and PZEV exhaust emission measurement and certification. A central part of the BMD system is an accurate and reliable exhaust flow measurement which is essential for proportional bag fill. A new device has been developed to accurately and reliably calibrate exhaust flow measurement equipments such as the E-Flow. The calibration device uses two different size laminar flow elements (LFE), a 40 CFM (1.13 m3/min) LFE for low end calibration and a 400 CFM (11.32 m3/min) LFE for higher flows. A blower is used to push flow through a main flow path, which then divides into two flow pathways, one for each of the two LFE's.

Automakers in the United States have started using bag mini-diluters (BMD) for developing, testing and certifying vehicles, to meet PZEV and SULEV regulation requirements. The BMD system which is a new technology developed by AIGER, is being used as an alternative to the traditional CFV/CVS system for accurate ultra low-level emission measurement. BMD system has shown to have considerable advantage over CFV/CVS system, especially at ULEV/SULEV emission levels. This paper details modifications and diagnostic checks conducted with the existing BMD system at the DaimlerChrysler Tech Center emissions facility, Auburn Hills, Michigan. This paper also discusses possible scenarios where the BMD system at DaimlerChrysler could give erroneous results due to system setup, optimization issues and equipment limitations.

As SULEV emission regulations approach, the bag mini-diluter (BMD) technology is gaining acceptance as a replacement for the existing constant volume sampler (CVS) for SULEV exhaust emission measurement and certification. The heart of the BMD system is the direct vehicle exhaust (DVE) flow measurement system. Due to the transient nature of vehicle exhaust during a standard FTP emission test cycle, the DVE must be capable of rapid and accurate response in order to track these varying exhaust flow rates. The DVE must also be robust enough to accurately measure flow rate despite variations in exhaust gas composition, pulsation effects, and rapid changes in both exhaust temperature and pressure. One of the primary DVE systems used on BMDs is the E-Flow, an ultrasonic flow meter manufactured by Flow Technologies, Inc.

As the standards for exhaust emissions have become more stringent, the quality control tools used to evaluate the performance of low level samplers and analyzers has become more important. The Vehicle Exhaust Emissions Simulator (VEES) was developed to evaluate the performance of vehicle or engine exhaust emissions sampling and analytical systems. The simulator emulates emissions from low-emitting gasoline vehicles by producing a simulated exhaust stream containing emission constituents (HC, CO, CO2, and NOx) injected via Mass Flow Controllers (MFCs). This paper discusses various applications of the VEES as a quality control tool for ULEV and SULEV testing. A comparison is made between the injected amount of exhaust species by the VEES and the amounts recovered by the different sampling systems. Different root cause scenarios are discussed as to the source of discrepancies between the results on the CVS and BMD for different driving cycles.