Method for determining the progress of internal pressure of a cylinder in an internal combustion engine

Method for controlling an internal combustion engine having a shaft, an intake manifold, a fuel supply device, an ignition device and at least one cylinder, the method comprising:

• defining an plurality of operating points of the engine, wherein an average angular speed of the engine shaft and an average internal pressure at the intake manifold define a plane of possible operating points of the engine;
• each of the operating points of the engine being represented by a respective point of the plane;
• the reference operating points of the engine defining a grid on the plane;
• recording an instantaneous angular speed of the shaft;
• defining, in relation to each operating point of the engine, a transfer function relating the instantaneous angular speed of the shaft to an internal pressure to the cylinder;
• determining the internal pressure to the cylinder based on the instantaneous angular speed of the shaft and at least one of the transfer functions;
• and
• controlling the fuel supply device and the ignition device based on the internal pressure to the cylinder.

A control unit for an internal combustion engine having a shaft, an intake manifold, a fuel supply device, an ignition device and a plurality of cylinders, the control unit comprising:

• a sensor to be attached to the engine;
• and
• a processing unit in cooperation with the sensor, the processing unit configured:
• to receive from the sensor a signal reflecting an angular speed of the shaft;
• to store a plurality of predefined transfer functions relating to operating points of the engine, each said operating point based on an average angular speed of the engine shaft and an average pressure at the intake manifold;
• to determine, for each cylinder, an internal pressure to the cylinder based in part on the angular speed signal and at least one of the predefined transfer functions;
• and
• to control the fuel supply device and the ignition device based on the internal pressure to the cylinder.

A control unit for an engine having a shaft, an intake manifold, a fuel supply device, an ignition device and a plurality of cylinders, the control unit comprising:

• a sensor to be attached to the engine;
• means for receiving from the sensor an angular speed of the shaft signal;
• means for storing a plurality of predefined transfer functions relating to operating points of the engine, each said operating point based on an average angular speed of the engine shaft and an average pressure at the intake manifold;
• means for determining, for each cylinder, an internal pressure to the cylinder based in part on the angular speed and at least one of the predefined transfer functions;
• and
• means for controlling the fuel supply device and the ignition device based on the internal pressure to the cylinder.