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Gasoline engines have the trace-knock phenomena induced by the fast combustion which happens a few times during 100 cycles. And that constrains the thermal efficiency improvement due to limiting the ignition timing advance. So the authors have been dedicating a trace-knock simulation so that we could obtain any pieces of information associated with trace-knock characteristics. This simulation consists of a turbulent combustion model, a cycle-by-cycle variation model and a chemical calculation subprogram. In the combustion model, a combustion zone is considered in order to obtain proper turbulent combustion speed through wide range of engine speed. From a cycle-by-cycle variation analysis of an actual gasoline engine, some trace-knock features were detected, and they were involved in the cycle-by-cycle variation model. And a reduced elementary reaction model of gasoline PRF (primary reference fuel) was customized to the knocking prediction, and it was used in the chemical calculation.

Compression ratio of newly developed gasoline engines has been increased in order to improve fuel efficiency. But in-cylinder pressure around top dead center (TDC) before spark ignition timing is higher than expectation, because the low temperature oxidization (LTO) generates some heat. The overview of introduced calculation method taking account of the LTO heat of unburned gas, how in-cylinder pressure is revised and some knowledge of knocking prediction using chemical kinetics are shown in this paper.