  Using a continuous wavelet transform we have analyzed the cycle-to-cycle
variations of pressure in an internal combustion engine. The time series of
maximum pressure variations are examined for different loading and their
wavelet power spectrum is calculated for each load. From the wavelet power
spectrum we detected the presence of long, intermediate and short-term
periodicities in the pressure signal. It is found that depending on the load,
the long and intermediate-term periodicities may span several cycles, whereas
the short-period oscillations tend to appear intermittently. Knowledge of these
periodicities may be useful to develop effective control strategies for
efficient combustion.
