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In diesel engines, pilot injections and injections at a reduced initial injection rate with high-pressure fuel injection have a potential to reduce particulate, NOx and noise emissions simultaneously. For this reason, various shaping methods of injection rate waveform have been proposed. The present authors also propose such a high-pressure injection system with variable injection rate that relies on spool acceleration and oil-hammering in the injection pipeline. This paper first describes the injection rate shaping, including injections with pilot and reduced initial injection rate, and elucidates their effects on reducing exhaust and noise emissions. A pilot injection can be achieved by either installing a fuel spill path in a plunger body or elongating prelift of the spool. Computer simulations and bench tests of such injection systems show that pilot injection quantity is small enough and the pilot injection pressure is much lower than that of the main part of the injection.

The paper describes the designing points and the research results obtained during the development of 2 liter and 3 liter capacity diesel engines, and also reviews the development of small diesel engines. It comoares the diesel engine with the same bore and stroke gasoline engine, simultaneously developed, on the bases of their performances and structures.