| Functioning of the electronic accelerator system |
| On the electronic accelerator, the throttle valve is not activated by a control cable from the accelerator. There is no mechanical connection between the accelerator and the throttle valve. |
| The accelerator position is transmitted to the engine control unit via two accelerator position senders (variable resistors; located in a housing) connected to the accelerator. |
| The accelerator position (driver intentions) is a basic quantity input for the engine control unit. |
| The throttle valve is activated by an electric motor (throttle valve activator) incorporated in the throttle valve control unit, throughout the whole range of revs and loads. |
| The throttle valve is activated by the throttle valve activator in function of the data from the engine control unit. |
| With the engine off and the ignition on, the engine control unit activates the throttle valve activator in function of the data from the accelerator position sender. This means that if the accelerator is at the middle position, the throttle valve activator opens the throttle valve proportionally; the throttle valve is in this case open half way. |
| With the engine in running (with load), the engine control unit can open or close the throttle valve, independently of the accelerator position sender. |
| This allows the throttle valve to be, for example, completely open although the accelerator only depressed half way. The advantage of this is that it avoids loss in output caused by choking of the throttle valve. |
| At the same time, at certain load states, much better values for emissions and consumption are attained. |
| The necessary engine torque can be generated by the engine control unit through an optimum combination of throttle valve opening and supercharging pressure. |
| It would be wrong to think of the “electronic accelerator” as being made up of only of one or two components. The electronic accelerator is in reality a system containing all those components that take part in determining, controlling and monitoring the position of the throttle valve (e.g. the accelerator position sender, the throttle valve control unit, the EPC warning lamp, the engine control unit, etc.). |
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