6. Combustion-related measures

These are the most important measurements for fine-tuning all parts of the engine linked to thermodynamics, combustion and fluid flows downstream and upstream of the cylinder. These measurements must be precise and phased in angle, not time. Indeed, the kinematics of the connecting rod-crank system require angular rather than temporal analyses. By measuring the evolution of pressure in the engine cylinder, it is possible to calculate various criteria:

• Pmi of the cycle (Mean Indicated Pressure), in both the high and low loops of the cycle;

• the value of the maximum combustion pressure ;

• the law of heat release and the fraction burned ;

• click detection ;

• combustion noise ;

• acyclisms...