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Particle number measurements during different real world and legislative driving cycles show that catalyst heating, cold and transient engine operation cause increased particle number emissions. In this context the quality of mixture formation as a result of injector characteristics, in-cylinder flow, operation & engine parameters and fuel composition is a major factor. The goal of this paper is to evaluate the influence of different biogenic and alkylate fuels on the gaseous and particle number emission behavior during catalyst heating operation on a single-cylinder DISI engine. The engine is operated with a late ignition timing causing a high exhaust enthalpy flow to heat up the catalyst, a slightly lean global air fuel ratio to avoid high hydrocarbon emissions and a late injection right before the ignition to reduce the coefficient of variance of the indicated mean effective pressure.

The trend of higher specific power and increased volumetric efficiency leads to unwanted combustion phenomenon such as knocking, pre-ignition and self-ignition. For four-stroke engines, the literature reports that knocking depends, to a large extent, on the ignition angle, the degree of enrichment and the volumetric efficiency. In recent research, knock investigations in two-stroke engines have only been carried out to a limited extent. This paper discusses an investigation of the influence of various parameters on the knock characteristics of a small, high-speed, two-stroke SI engine. In particular, the degree of enrichment, the volumetric efficiency and the ignition timing serve as the parameters.