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Analysis of non-legislated engine-emission components, with different exhaust-gas after-treatment techniques, is an important air quality objective. This paper reports the results for various nitrogen oxides, ammonia and differentiated hydrocarbons emitted at part load from a small 4-S SI engine. It was operated with gasoline, with CNG and with two different three-way catalytic converters. CNG produces less HC and less aromatics. But the HC conversion rate is insufficient. This is due to the lower exhaust gas temperatures, at part load with CNG, and due to the higher stability of light HCs. CNG affects the λ-regulation window, of the investigated system, such that the NOx conversion rate is lowered. In the rich domain of the λ-regulation window, the NO & NOx emissions after catalyst were lowest, while the NH₃ formation was most intense, and vice versa.

A modern HD-Diesel engine for construction machines, Liebherr D 934L (120kW) was set-up for a monofuel operation with crude, cold pressed rapeseed oil (ROR)*). The engine was equipped with a supplementary fuel filtration, supplementary engine & fuel heating for cold start and an appropriate fuel temperature control for the engine operation. A special lube oil was applied. After an extensive basic research of emissions including nanoparticles and energy consumption some adaptations of engine setting were performed: modification of the camshaft to eliminate the internal EGR (same valve timing and lift), earlier start of injection (SOI) at high- and full load, application of a combined exhaust gas aftertreatment system DPF+SCR, testing of DPF+SCR according to the VERT quality verification procedure.

NO₂ is much more toxic than NO. The average proportion of NO₂ in exhaust gases of vehicles increases significantly due to the use of oxidation catalysts and catalytic coatings in the exhaust gas systems during the last decades combined with generalization of using low sulfur fuels. Diesel oxidation catalysts (DOC) and Pt-containing DPF coatings are widely used to support the regeneration of particle filters, being a source of strongly increased production of NO₂. The present work shows some examples and summarizes the experiences in this matter performed at the Laboratories for IC-Engines & Exhaust Emissions Control (AFHB) of the University of Applied Sciences Biel-Bienne, Switzerland, during some research activities on engine dynamometers in the years 2010-2012.