Based on systematical engine performance bench marking tests on a few gasoline engines

as well as on further development and regression analysis of the experimental data

combustion characteristics

such as combustion efficiency

combustion duration

influence factor of heat release rate curve

were summarized as the functions of engine operational parameters

such as speed

load

excess air/fuel ratio

spark timing. Results show that the combustion efficiency is almost only relevant to the excess air coefficient with a good linear relation. Moreover

the value of combustion quality parameter m is mainly related to engine load and has a weaker relationship with other engine design and operational parameters. When engine load is very low

the value m increases slightly with load. However

when the load is up to a certain value

the value m is stable at the constant of 2.0 and the heat release rate curve is symmetric. The combustion duration decreases with the increase of engine load at low load

but it is almost stable and constant when the load (BMEP) is higher than 0.8 MPa. The trend of combustion duration change with other engine operational parameters can be illustrated by a simple linear relation with good prediction accuracy. The research results provide a relatively accurate simplified numerical model for the simulation of the performances of turbocharged direct injection gasoline engines.