Electronic Power Control (EPC) System, Function

Electronic Power Control (EPC) System, Function

With the Electronic Power Control system (EPC) the throttle valve is not operated by a cable. There is no mechanical connection between accelerator pedal and throttle valve.

The position of the accelerator pedal is transmitted to the engine control module by two accelerator pedal position sensors (variable resistors together in one housing) connected to the accelerator pedal.

The position of the accelerator pedal (driver's requirement) is a main input value for the engine control module.

The throttle valve is operated over the complete engine speed and load range by an electric motor (throttle valve positioner) in the throttle valve module.

The throttle valve is operated by the throttle valve positioner which is controlled by the engine control module.

When the engine is not running and the ignition is switched on, the engine control module moves the throttle valve exactly as prescribed by the accelerator pedal position sensor. That is, when the accelerator is depressed halfway, the throttle valve positioner opens the throttle valve by the same amount. The throttle is then approximately half open.

When the engine is running (under load), the engine control module can open or close the throttle valve independently of the accelerator pedal position sensor.

This means that the throttle valve can already be completely open even though the accelerator pedal is depressed only half way. This has the advantage of preventing throttling losses at the throttle valve.

After evaluating the torque requirements of various components (e.g. air conditioning system, automatic transmission, ABS/ESP and so on), the engine control module calculates the optimal throttle valve opening angle for the respective situation.

This also results in significantly improved consumption and exhaust emission values at certain load conditions.

"EPC" is a system comprising all components which contribute to determining, controlling or monitoring the position of the throttle valve, e.g. accelerator pedal position sensor, the throttle valve control module, the EPC warning lamp, the engine control module and so on.