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A modular particulate trap system for buses, trucks and other applications consiting of honeycomb traps and an electrical regeneration system has been designed and tested on a test bench and in a city bus. For regeneration, the soot is ignited at the entrance of the trap channel by electric heaters. After ignition, the soot burns self-supporting without further energy supply. Regeneration is possible over the whole engine map. The electrical energy consumption of the heaters for a city bus is in average below 100 W. The filtration efficiency of the system including regeneration is about 80 % during transient city driving. During regeneration, appr. 98 % of the accumulated hydrocarbons adsobed to the soot in the trap are burned off the initiated combustion front. Additionally, the odor of the diesel engine exhaust gas behind the trap is lowered at low engine load even during regeneration.

The development of future passenger car diesel engines has to be pointed in many directions. Present diesel techniques already set high standards on fuel economy, as the gasoline engines with catalytic converters did in passenger car application on performance, exhaust emissions, noise and vibrational emissions. Unit Injectors for airborne mixing direct injection diesel combustion offer the flexibility necessary to form injection rate patterns and associated injection pressures for the sake of combustion tuning. The development steps of a small pilot injection of high cyclical precision which is load independend at lower speeds and which disappears into a high-rated injection at the upper speed range are discussed. Recent test results of a prototype engine indicate the high potential of HSDI engines with such Unit Injectors to meet standards on fuel economy in combination with performance and emissions far beyond today's serial diesel engines for passenger cars.