Gasoline Engine Knock Analysis using Cylinder Pressure Data

This paper addresses issues associated with the measurement and analysis of crank angle based cylinder pressure to obtain accurate knock data. Issues examined include knock model features, the effect of sample size, the impact of sampling frequency, optimum knock windowing and the influence of transducer in-cylinder location and mounting arrangement.

The study has demonstrated that a very large sample size is required to obtain good repeatability and at least 1000 engine cycles is recommended for knock intensity determination. A knock window of TDC to TDC+40 degrees has been shown to be appropriate whilst a 0.2 degree crank angle resolution is considered to be adequate for the knock algorithm employed. This work has also confirmed that transducers should have high natural frequency, be flush mounted to avoid cavity resonance and that knock signals can be significantly influenced by transducer location.