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Particulate traps reduce particle emissions through the physical filtration of solid, predominantly carbonaceous particles and decreasing particle-bound hydrocarbon emissions. Catalyst coated and uncoated traps were examined for their ability to reduce particle-bound hydrocarbons. At low exhaust temperatures some volatile hydrocarbons are particle-bound in the trap and are physically retained. These components become gaseous and are purged from the trap with sharp exhaust temperature rises. Oxidation catalysts considerably improve the ability of traps to decrease particle-bound hydrocarbon emissions, particularly PAH at low exhaust temperatures. Precious metal coated traps generate sulfate particles so that especially at high exhaust temperatures the overall filter efficiency can be reduced.

Particulate emissions from diesel engines mainly consist of soot and high-boiling hydrocarbons (volatile fraction). To reduce the volatile fraction different precious metals and their combinations are tested in traps and supports especially at low loads. A sufficient catalyst's efficiency at low exhaust-gas temperatures (low load) requires a large active catalyst surface. Due to the soot in the diesel exhaust-gas, the catalyst can be covered by a soot layer reducing the catalyst's efficiency. The accumulated soot in the trap must be oxidized. Nonprecious metal catalysts are able to lower the soot ignition temperature. The reduction in ignition temperature depends on the catalyst material used. The influence of the catalyst's concentration and the use of an additional washcoat are also investigated.

The deposits on intake valve tulips of spark ignition and diesel engines can produce an increase in fuel consumption and exhaust gas emission, a deterioration of the driving behavior as well as mechanical defects. The formation of these deposits is investigated with respect to different engine parameters and by using a commercially available leaded fuel without additives. The valve deposits are formed by composing and decomposing phenomena which occur in parallel. The composing elements are oil, particles coming from the combustion chamber via the internal exhaust gas recirculation and, partially, fuel components. The deposits are reduced by the liquid fuel coming in contact with the valve tulips and by a high rate of oil flow. To the end of a shorter test duration and less test efforts a short-time simulation to investigate the deposit formation on inlet valves will be described.

A vehicle investigation programme was initiated to evaluate the influence of diesel fuel sulfur content on the performance of a DeNOx catalyst for NOx control. The programme was conducted with a passive DeNOx catalyst, selected for its good NOx reduction performance and two specially prepared fuels with different sulfur contents. Regulated emissions were measured and analysed during the course of the programme. The NOx conversion efficiency of the DeNOx catalyst increased from 14 to 26% over the new European test cycle when the sulfur content of the diesel fuel was reduced from 49 to 6 wt.-ppm. In addition the number and size of particles produced using 6 wt.-ppm sulfur fuel were measured by two different techniques: mobility diameter by SMPS and aerodynamic diameter by impactor. The influence of the assumed density of the particulate on the apparent diameters measured by the two techniques is discussed.