| Checking electronic power control (EPC) |
| With the EPC system, the throttle valve is not operated by a cable. 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 actuated by a servomotor (throttle valve positioner) in the throttle valve control part over the full range of engine speeds and load conditions. |
| 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 depressed half way. This has the advantage of preventing throttling losses at the throttle valve. |
| This also results in significantly improved fuel consumption and exhaust emissions under certain load conditions. |
| The torque required by the engine can be produced by the engine control unit by optimising the combination of throttle valve cross-section and charge pressure. |
| EPC is a system comprising of several components which contribute to determining, controlling or monitoring the position of the throttle valve, e.g. accelerator position sender, throttle valve control part, EPC warning lamp, engine control unit and so on. |
|
|
|
