The effect of crank angle (CA) resolution on the analysed cylinder pressure data has been investigated using both simulated and experimental engine cylinder pressure data. This revealed that the noise levels in some of the derived parameter data can be greatly increased by low ADC and high CA resolutions. A method for reducing the noise spikes by dynamically adjusting the calculation CA resolution at each point in the engine cycle is proposed and shown to be very effective.
The accuracy of the calculated imeps has also been studied using experimental pressure data. The sensitivity to both CA resolution and integration period phasing was found to be small.
Overall, this work has shown that the best CA resolution to use depends on the application. A CA resolution of 0.5° to 1.0° should be most suitable for a compression ignition engine increasing to 1.0° to 2.0° for most spark ignition engine studies. For real time imep calculation, a CA resolution of 10° could probably be used with only a small loss in accuracy.