In 4-stroke SI engine research the pressure data in cylinder is the base of analysis calculating efficiency and performance. It is therefore necessary to obtain accurate pressure data and yet it is often impossible to install a flush-mounted pressure transducer in a cylinder of a small 4-stroke SI engine. When flush mounting the transducer is not possible, the spark-plug pressure transducer is commonly used. In this case the transmission tube of spark-plug pressure transducer introducs the pressure signal distortion.
Efforts were made to understand the dynamic characteristics of spark-plug pressure transducer by 1-D flow analysis, shock tube tests and real engine experiments. In engine experiment the cyinder pressure data were simutaniouslly obtained both flush mounted and spark-plug pressure transducers with various transmission tube geometry.
Those pressure data collected by spark-plug pressure transducer were tried to be corrected to flush mounted ones by using transfer function. As a result of calibration the IMEP difference between F/M data and improved S/P data was corrected about 75∼98% compared with original ones.
