Method of calibrating a crank angle of a combustion engine

A calibrateable combustion engine comprising:

• a crank shaft, which is rotatable about a crank shaft axis;
• a cylinder connected to the crank shaft, for driving the crank shaft;
• a trigger wheel connected to the crank shaft and arranged to rotate with the crank shaft;
• a trigger wheel sensor arranged near the trigger wheel, configured to generate a trigger wheel signal in response to rotation of the trigger wheel;
• a trigger wheel signal evaluation unit having an input connected to the trigger wheel sensor and configured to determine a trigger wheel angle, which is a measure of the instantaneous angle of rotation of the trigger wheel, by evaluating the trigger wheel signal;
• an offset memory unit configured to store a trigger wheel angle offset;
• and
• a fuel and spark scheduling unit configured to determine a crank angle, which is a measure of the instantaneous angle of rotation of the crank shaft, by correcting the measured trigger wheel angle on the basis of the trigger wheel angle offset,
• wherein the trigger wheel angle offset is determined from an in-cylinder pressure profile, which is a representation of trigger angle values and in-cylinder pressure values, which are sensed at the same time while the combustion engine is driven combustionless.

A method of calibrating a crank angle of a combustion engine, wherein the combustion engine comprises:

• a crank shaft which is rotatable about a crank shaft axis;
• a cylinder connected to the crank shaft, for driving the crank shaft;
• a trigger wheel connected to the crank shaft and arranged to rotate with the crank shaft;
• a trigger wheel sensor arranged near the trigger wheel for generating a trigger wheel signal in response to rotation of the trigger wheel;
• a trigger wheel signal evaluation unit having an input connected to the trigger wheel sensor and configured to determine a trigger wheel angle, which is a measure of the instantaneous angle of rotation of the trigger wheel, by evaluating the trigger wheel signal;
• an offset memory unit configured to store a trigger wheel angle offset;
• and
• a fuel and spark scheduling unit configured to for determine a crank angle, which is a measure of the instantaneous angle of rotation of the crank shaft, by correcting the measured trigger wheel angle on the basis of the trigger wheel angle offset;
• wherein the method comprises:
• while the crank shaft is driven combustionless, recording trigger angle values received from the trigger wheel evaluation unit, and, at the same time, and recording in-cylinder pressure values received from a pressure sensor, which is configured to measure a pressure in the cylinder of the combustion engine and to generate the in-cylinder pressure values, wherein the recorded trigger angle values and the recorded in-cylinder pressure values represent an in-cylinder pressure profile;
• determining, on the basis of the in-cylinder pressure profile, a trigger wheel angle which coincides with a maximum of the in-cylinder pressure;
• and
• providing the determined trigger wheel angle as the trigger wheel angle offset to be stored in the offset memory unit.