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FTP emissions tests on a passenger vehicle equipped with a 1.8 L IDI turbo-charged diesel engine show that the mass emissions of particles decrease by (36±8)% when 16.6% dimethoxymethane (DMM) by volume is added to a diesel fuel. Particle size measurements reveal log-normal accumulation mode distributions with number weighted geometric mean diameters in the 80 - 100 nm range. The number density is comparable for both base fuel and the DMM/diesel blend; however, the distributions shift to smaller particle diameter for the blend. This shift to smaller size is consistent with the observed reduction in particulate mass. No change is observed in NOx emissions. Formaldehyde emissions increase by (50±25)%, while emissions of other hydrocarbons are unchanged to within the estimated experimental error.

Currently most automotive manufacturers calibrate for rich air/fuel ratios at wide open throttle which produces lower exhaust gas temperatures. Future federal emissions regulations may require less enrichment under these conditions. This study was undertaken to address the question of what happens to engine-out hydrocarbon emissions with different air/fuel ratios at wide open throttle. Tests were run on a single cylinder research engine with a two valve combustion chamber at a compression ratio of 9:1. The test matrix included three air/fuel ratios (10.5, 12.5 and 14.5) and two speeds (1500 and 3000 rpm) at wide open throttle as well as three air/fuel ratios (12.5, 14.6 and 16.5) at a part load condition (1500 rpm, 3.8 bar IMEP). The exhaust was sampled and analyzed for both total and speciated hydrocarbons. The speciation analysis provided concentration data for hydrocarbons present in the exhaust containing twelve or fewer carbon atoms.

The effect of engine operating parameters (speed, spark timing, and fuel-air equivalence ratio [Φ]) on hydrocarbon (HC) oxidation within the cylinder and exhaust system is examined using propane or isooctane fuel. Quench gas (CO2) is introduced at two locations in the exhaust system (exhaust valve or port exit) to stop the oxidation process. Increasing the speed from 1500 to 2500 RPM at MBT spark timing decreases the total, cylinder-exit HC emissions by ∼50% while oxidation in the exhaust system remains at 40% for both fuels. For propane fuel at 1500 rpm, increasing Φ from 0.9 (fuel lean) to 1.1 (fuel rich) reduces oxidation in the exhaust system from 42% to 26%; at 2500 RPM, exhaust system oxidation decreases from 40% to approximately 0% for Φ = 0.9 and 1.1, respectively. Retarded spark increases oxidation in the cylinder and exhaust system for both fuels. Decreases in total HC emissions are accompanied by increased olefinic content and atmospheric reactivity.

Modern four-valve engines are running at ever higher compression ratios in order to improve fuel efficiency. Hotter cylinder bores also can produce increased fuel economy by decreasing friction due to less viscous oil layers. In this study changes in compression ratio and coolant temperature were investigated to quantify their effect on exhaust emissions. Tests were run on a single cylinder research engine with a port-deactivated 4-valve combustion chamber. Two compression ratios (9.15:1 and 10.0:1) were studied at three air/fuel ratios (12.5, 14.6 and 16.5) at a part load condition (1500 rpm, 3.8 bar IMEP). The effect of coolant temperature (66 °C and 108°C) was studied at the higher compression ratio. The exhaust was sampled and analyzed for both total and speciated hydrocarbons. The speciation analysis provided concentration data for hydrocarbons present in the exhaust containing twelve or fewer carbon atoms.

Absorption of fuel in engine oil layers has been shown to be a possible source of hydrocarbon (HC) emissions from spark-ignited engines. However, the magnitude of this source in a normally operating engine has not been determined unambiguously. In these experiments, a series of n-alkanes of widely different solubility (n-hexane through undecane) was added (1.5 wt % each) to a Base gasoline (CA Phase 2). Steady-state experiments were carried out at two coolant temperatures (339 and 380 K) using a single-cylinder engine with the combustion chamber of a production V-8. Both total and speciated engine-out HC emissions were measured. The emissions indices of the heavier dopants did not increase relative to hexane at either coolant temperature.

In 1992, a Round Robin was sponsored by the CRC's Emissions Analysis Round Robin Subcommittee, to provide an opportunity for automotive emissions laboratories to compare their analytical methodologies with those used in other laboratories. Compressed gas samples were provided to participants to test hydrocarbon methodologies, while liquid samples were used for alcohol and carbonyl analyses. The results of this study were published in SAE 950780 and SAE 941944. A second Round Robin study was conducted in 1995, using the same basic structure as the first study. The results of the carbonyl analyses have been published separately (SAE 971609). The purpose of this paper is to compare methods used for hydrocarbon speciation of emissions by gas chromatography. As in the 1992 study, cylinders of a synthetic exhaust were prepared by using a fuel base, and adding components that would be expected as typical combustion products.

Previous research into Particulate Matter (PM) emissions from a spark-ignition engine has shown that the main factor determining the how PM emissions respond to transient engine operating conditions is the effect of those conditions on intake port processes such as fuel evaporation. The current research extends the PM emissions data base by examining the effect of transient load and speed operating conditions, as well as engine start-up and shut-down. In addition, PM emissions are examined during “real-world” driving conditions - specifically, the Federal Test Procedure. Unlike the previous work, which was performed on an engine test stand with no exhaust gas recirculation and with a non-production engine controller, the current tests are performed on a fully-functional, production vehicle operated on a chassis dynamometer to better examine real world emissions.

The numbers, sizes, and derived mass emissions of particles from a production DISI engine are examined over a range of engine operating conditions. Particles are sampled directly from the exhaust pipe using heated ejector pump diluters. The size distributions are measured using a scanning mobility particle sizer. The numbers and sizes of the emitted particles are reported for stratified versus homogeneous operation and as a function of fuel injection timing, spark timing, engine speed, and engine load. The principal finding is that particle number emissions increase by about a factor of 10 - 40 going from homogeneous to stratified charge operation. The particulate emissions exhibit a strong sensitivity to injection timing; generally particle number and volume concentrations increase steeply as the injection timing is retarded, except over a narrow portion of the range where the trend reverses.

This paper explores the extent to which standard dilution tunnel measurements of motor vehicle exhaust particulate matter modify particle number and size. Steady state size distributions made directly at the tailpipe, using an ejector pump, are compared to dilution tunnel measurements for three configurations of transfer hose used to transport exhaust from the vehicle tailpipe to the dilution tunnel. For gasoline vehicles run at a steady 50 - 70 mph, ejector pump and dilution tunnel measurements give consistent results of particle size and number when using an uninsulated stainless steel transfer hose. Both methods show particles in the 10 - 100 nm range at tailpipe concentrations of the order of 104 particles/cm3.