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The US Code of Federal Regulations (CFR) Title 40 Part 1065 and 1066 require gravimetric determination of automobile Particulate Matter (PM) collected onto filter media from the diluted exhaust. PM is traditionally collected under simulated driving conditions in a laboratory from a full flow Constant Volume Sampler (CVS) system, where the total engine exhaust is diluted by HEPA filtered air. This conventional sampling and measurement practice is facing challenges in accurately quantifying PM at the upcoming 2025-2028 CARB LEVIII 1 mg/mi PM emissions standards. On the other hand, sampling a large amount of PM emitted from large size high power engines introduces additional challenges. Applying flow weighting, adjusting the Dilution Ratio (DR) and Filter Face Velocity (FFV) are proposed options to overcome these challenges.

Automobile Particulate Matter (PM) Emission regulation requires gravimetric determination of PM collected on filter media under simulated driving conditions in the laboratory traditionally in a full flow Constant Volume Sampling (CVS) dilution tunnel. There have been discussions about whether current sampling and measurement practices are sufficiently accurate in quantifying PM at the upcoming 1mg/mi PM emissions standards of CARB LEV III. Sampling technique alternative to a CVS such as a Partial Flow Dilution (PFD) system has already been developed and is acceptable for certification testing. Lower dilution ratios and higher filter face velocity (FFV) are options to load traceable amount of PM on filter in case of light duty vehicle (LDV) testing. On the other hand higher dilution ratios and lower FFV are required for heavy duty engine (HDE) testing to keep the PM loaded on filter <400μg.

In the engine and vehicle test procedures described in Parts 1065/1066 of Title 40 of the Code of Federal Regulations (CFR), the United States Environmental Protection Agency (US-EPA) allows for the measurement of N2O emissions from sample storage bags, from a continuous dilute stream or a raw exhaust stream. Typically, batch (Bag) sampling has better accuracy and repeatability, but continuous sampling is more efficient in terms of test cell running time and provides test-mode emissions with good correlation to bag measurements. In this study, correlations between bag sampling and continuous dilute exhaust sampling were investigated using a fleet of vehicles with a wide range of N2O emission levels. Very good correlation between these two sampling methods was observed for the majority of tests conducted. In the best cases, differences in average N2O concentration levels measured by these two methods were less than +/− 1%.

Measurement of exhaust emissions emitted from Plug-in Hybrid Electric Vehicles (PHEV) presents numerous difficulties for conventional emissions measurement equipment. Significant measurement errors are introduced during the measurement of PHEV emissions using conventional emissions equipment, methods, and test cycles due to the combined operation of the Internal Combustion Engine (ICE) and electrical power sources. While previous work has identified possible sources of measurement errors using conventional Constant Volume Sampling (CVS) and Bag Mini-Diluter (BMD) techniques, this paper focuses on quantifying the measurement errors and offers suggestions for improvement. In addition, new sampling strategies are offered to improve measurement accuracy of criteria emissions such as Hydrocarbons (HC), Carbon Monoxide (CO), Oxides of Nitrogen (NOx) and fuel economy.

A 2.5-liter light-duty diesel van certified to Euro 4 emission standards was tested in a chassis dynamometer test cell, which included a modal FTIR exhaust gas analyzer with the capability of measuring 22 separate gas species. The engine was equipped with a cooled Exhaust Gas Recirculation (EGR) system, which controls the nitrogen oxide emissions (NOx) to less than the 390 mg/km limit required by Euro 4 regulations. The vehicle was tested by dynamometer with the New European Drive Cycle (NEDC) sequence, and found to exceed the 390 mg/km NOx limit. The FTIR was applied as a diagnostic tool for the engine EGR function. The FTIR monitored N₂O, NO, NO₂, and NH₃ over the NEDC test cycles. The linear-control EGR valve failed abruptly during a subsequent test, and the relative concentration of the reduced and oxidized nitrogen species showed significant changes.

A Constant Volume Sampler (CVS) over dilutes the exhaust gas sample when testing Plug-In Hybrid Electric Vehicles (PHEV). This is because the CVS continues to fill the sample bag when the engine is shutdown. With a PHEV, it is possible to complete an FTP test with the engine running less than 20% of the time, resulting in a CVS bag dilution ratio in the range of 100 to 300. The CVS dilution ratio should be in the range of 5-25 for accurate results. At higher dilution ratios, the gas concentrations of CO, NOx and THC approach the ambient background level in the test cell. At a dilution of 100, the CO₂ concentration in the sample bag is about 0.13%, which is only 3 times the air background concentration. The measurement errors caused by over dilution create errors of 10% to 30% in the calculated mass of CO₂, CO, and NOx. Estimated errors for THC are in the range of 200%.

On-board Particulate Matter (PM) mass calibration (OB-PMMC) is an approach to calibrate a real-time PM sensor with the gravimetric PM mass being collected on a conventional filter. The real-time PM sensor is integrated in a PM sample system and takes sample upstream of the sample filter. The PM mass collected on the filter is determined either by weighing the filter or by using analytical approaches. A unique calibration coefficient for each sample filter is generated for converting the PM real-time signal to the real-time PM mass emission. This calibration approach can be used to modify Constant Volume Samplers (CVS) and laboratory Partial Flow Sample Systems (PFSS), etc., into real-time PM mass measurement instruments for engine or vehicle exhaust PM measurement. The same technique may also be used to measure real-time PM concentration in the atmosphere under some circumstance.

Engine testing in the United States has been updated with the new centralized testing procedure in 40 CFR 1065. This regulation introduces a variety of new checks and tests required for certification testing. Upgrading existing equipment to run these tests in some cases introduces error or does not follow the spirit of the regulation. The term “good engineering practice” is used within the regulation to insure users make decisions on differences or unclear implementation. This paper addresses some of the recommended modifications and evaluates the differences in the results with and without the modifications.

A partial-flow sampling system, namely a Bag Mini-Diluter (BMD) is an accepted alternative to Constant Volume Sampling (CVS) for obtaining mass emissions in a chassis test cell. Our equipment delivers equivalent CVS and BMD emission results with gasoline engines of 2.0 to 5.6 liter displacement. However, while testing a vehicle with a 1.3 liter engine, CVS and BMD CO2 mass differences greater than 9% were observed during cold-start tests. This paper describes the modifications made to obtain BMD and CVS mass emissions that match within 2% during cold-start tests with a 1.3 liter vehicle.

The accuracy of low-level emission measurements has become increasingly important, due to the development and implementation of ULEV, SULEV, and PZEV vehicles. Measurement of these decreasing levels of automotive emissions requires new sampling and measuring techniques. Several alternative emission sampling techniques have been investigated to minimize measurement variability and maximize system repeatability. An alternative technique to obtain accurate low-level emissions measurement from SULEV vehicles is the Bag Mini-Diluter, which uses a proportional signal from an Exhaust Volume Measurement Device to sample vehicle exhaust. Crucial to successful proportional sampling of vehicle exhaust flow is the performance of the Exhaust Flow Measurement Device. This study evaluates an Exhaust Volume Measurement Device commonly used with a Bag Mini-Diluter.

A single vehicle (3.8L V6) underwent FTP75, HWFE, and US06 emission tests over a 6-month period. A bag mini-diluter and exhaust flowmeter sample system was installed in series with a CVS, so that mass emission results from an individual test could be directly compared between the bag mini-diluter and CVS. At one-month intervals, the bag mini-diluter and exhaust flowmeter sampling system was replaced with new units, while the vehicle and CVS remained unchanged. Assuming that the vehicle and CVS produce constant results, the variability of emissions over the test period are highly correlated with the variability of the bag mini-diluters and exhaust flowmeters. The average CO2 mass comparison between the bag mini-diluter and CVS shows the separate sample systems match within 0.5% for an individual test. The established baseline determined from the CVS has a standard deviation of about 2%, which we believe is predominantly due to vehicle variability.

For the past several years, manufacturers have been developing emission measurement systems for Super Ultra Low Emission (SULEV) measurements. The Bag Mini-Diluter (BMD) with an advanced exhaust flow measurement device is designed as an alternative to the traditional method for sampling vehicle exhaust, the constant volume sampler (CVS). Exhaust sampling instruments require system verification tests. The system verification test described and mandated for the CVS in the Code of Federal Regulations (CFR) §86.119-90(c) is a simulated test with propane. The very low concentration measurements required for SULEV regulations demand a more enhanced and accurate verification technique and procedure than the method described in the CFR. This investigation focuses on the technique and necessary equipment for verifying system integrity of the entire emission sampling system, including the Bag Mini-Diluter and the exhaust flow measurement device in the test cell.

As automakers begin to develop and certify vehicles that meet the California Air Resources Board LEV II and Environmental Protection Agency Tier II Regulations, emissions test cells must be designed and implemented that are capable of accurate low-level measurements. A new test cell has been installed at Ford Motor Company for use in testing vehicles that meet the stringent Partial Zero Emission Vehicle tailpipe requirements (NMOG = 10 mg/mile, NOx = 20 mg/mile). This test cell includes a redesigned Bag Mini-Diluter (BMD), improved analytical benches, an ultrasonic exhaust flow meter with an integrated tailpipe pressure control system, a conventional constant volume sampler (CVS), and a moveable electric dynamometer. The Bag Mini-Diluter will be used as the primary sampling system for the tailpipe measurements. The moveable electric dynamometer enables the test cell to be configured so that the vehicle is moved to the test equipment rather than moving the test equipment to the vehicle.