Accurate resampling technology allows us to analyze not just the first cycle - we show even the first movement of the piston. The example shows the result of the pressure signal based on the 60-2 angle information. This technique can be used for any angle sensor.

Most calculations are done for the high pressure area only, typical defined from -30 to 90 degree TDC. For all calculations it is important that the combustion analyzer is prepared to correct the thermodynamic drift of the sensor for each cycle.

Thermodynamic zero correction:

• Calculated from the defined area
• Known reference value
• Measured with an additional input channel

Based on the perfect setup many online calculations are done as:

• Basic statistics channels (max pressure, max pressure position…)
• Derivation of pressure and position of maximum derivative
• Mean effective pressures
• Overall cycle calculations are the values: cycle count, missed triggers, frequency…
• Overall sum calculations have two modes:
  • Averages: All maximum pressures for one cycle are averaged together:
    ((P0 MAX + P1 MAX + PN MAX) / N)
  • Aligned: All maximum pressures are put into one channel corresponding to the ignition misalignment

What is the energy generated by each cycle? The online heat release gives you the precise figures. At which angle we achieve 5, 10, 50 or 90 % of the heat release, when is the SOC (start of combustion), the EOC (end of combustion).
All these values are based on the heat release algorithm. The DEWETRON combustion analyzer shows all these values as well as the important IMEPg , PMEP and IMEPn values, in graph or numerical values.

The display below shows the typical KNOCKING of a gasoline engine. The high frequency bouncing after the TDC in the frequency range between 10 to 15 kHz is a typical indicator of engine knocking.

Knocking detection is based on the pressure signal by an area (typical 30 degrees) before and after TDC. The integrated signals of these two areas are compared in real time, and the result is shown as the KF (knocking factor). The height of the accepted knocking event value is user-definable, by setting a threshold value. If the knocking signal is above this threshold an alarm output can be generated.