6. Measures related to combustion

These are the most important measurements for the development of all parts of the engine related to thermodynamics, combustion, and fluid flows upstream and downstream of the cylinder. These measurements must be accurate and phased in angle rather than time. This is because the kinematics of the connecting rod-crank system require angular rather than temporal analyses. Based on measurements of pressure changes in the engine cylinder, it is possible to calculate various criteria:

• the cycle PMI (mean indicated pressure), both in the high and low loops of the cycle;

• the value of the maximum combustion pressure;

• the law of heat release and the fraction burned;

• knock detection;

• the sound of combustion;

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