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High-speed diagnostics capable of accurately resolving emission transients are required to provide the most detailed understanding and optimization of active exhaust-emissions-treatment processes, such as NOX adsorbers. A portable, mass-spectrometry-based instrument with high temporal resolution, linear response and broad dynamic range is described. This instrument provides transient-concentration measurement capability for many relevant exhaust species including total NOX. In applications for evaluation of NOX-adsorber systems using heavy-duty diesel engines, the instrument revealed relevant emission transients not previously resolved with conventional analyzers. Specifically, the instrument resolved transient emissions associated with the competition between desorption and reduction rates. The temporal resolution of the instruments is sufficient to resolve kinetic rates of the NOX-adsorber system.

A laboratory-based fuel mixture system capable of delivering a range of fuel/air mixtures has been used to observe the effects of differing mixture characteristics on engine combustion through measurement and analysis of incylinder pressure and exhaust emissions. Fuel air mixtures studied can be classified into four different types: 1) Completely homogeneous fuel/air mixtures, where the fuel has been vaporized and mixed with the air prior to entrance into the normal engine induction system, 2) liquid fuel that is atomized and introduced with the air to the normal engine induction system, 3) liquid fuel that is atomized, and partially prevaporized but the air/fuel charge remains stratified up to introduction to the induction system, and 4) the standard fuel metering system. All tests reported here were conducted under wide open throttle conditions. A four-stroke, spark-ignited, single-cylinder, overhead valve-type engine was used for all tests.

A laboratory-based fuel mixture preparation system has been developed that is capable of generating a wide range of fuel/air mixtures, including production of a premixed, prevaporized homogeneous charge, beginning with liquid gasoline fuel. This system has been developed to allow the study of the effects of fuel/air mixture preparation characteristics on engine combustion, in-cylinder pressure, and exhaust emissions. For the study to be described here, engine combustion behavior and emissions measurements were obtained for a wide range of A/F's with the fuel mixture preparation being produced in one case, by the stock carburetor operating with fixed throttle position, and the other case, with the custom-built system producing a homogeneous mixture (HM.) A four-stroke, spark-ignited, single-cylinder, overhead valve-type utility engine was used for all tests.