| With the EPC system, the throttle valve is not operated by a cable from the accelerator pedal. There is no mechanical connection between the accelerator pedal and the throttle valve. |
| The position of the accelerator pedal is transmitted to the engine control unit by two accelerator pedal position senders (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 unit. |
| 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 unit. |
| When the engine is not running and the ignition is switched on, the engine control unit moves the throttle valve exactly as dictated by the accelerator pedal position sender. That is, when the accelerator is depressed halfway, the throttle valve positioner opens the throttle valve by the same amount. The throttle valve is then approximately half open. |
| When the engine is running (under load), the engine control unit can open or close the throttle valve independently of the accelerator pedal position sender. |
| This means that the throttle valve can already be completely open even though the accelerator pedal is only depressed 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 gearbox, ABS/ESP and so on), the engine control unit calculates the optimal throttle valve opening angle for the particular situation. |
| This also results in significantly improved fuel consumption and exhaust emissions under 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 position sender, throttle valve control module -J338-, EPC warning lamp, engine control unit and so on. |
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