Electronic Accelerator Pedal
E-Gas means that the throttle valve in a petrol engine or the injection equipment in a diesel engine is no longer mechanically
operated, but electrically through the accelerator pedal. Thus, engines with more than one throttle valve (e.g., those having two cylinder banks) are easier to synchronise. Likewise a cruise-control can be more simply
integrated. E-Gas thus replaces the idling filling-regulator or the throttle valve actuator. In co-operation with the ABS- control
device the engine torque can be more easily reduced through the engaging of the electronic differential locking.
The damping of the accelerator retraction, which is also pollutant-reducing, is now more easily possible. There used to be diesel engines, which, under certain running conditions (e.g., when straining, just above the
idling RPMs), made ugly noises or were inclined to be jerky. With the suitable accelerator pedal position, the throttle valve is simply opened a little more by the control device. The required RPMs are simply skipped
over, the accompanying speed-range must be achieved by gear changing. Through the application of E-gas, the engine can also be more smoothly regulated down from maximum RPMs.
For safety reasons, the accelerator pedal sensor is equipped with at leasttwo2 resistors (potentiometers) with varying operating ranges (1 - 4 V and 0,5 - 2 V and separate circuits. The throttle valve is operated by a
servo-motor, and in addition, is monitored by two, mostly counter rotating, potentiometers. The engine control device evaluates these and many other signals and controls the servo-motor on the throttle valve
accordingly. It ought to be quite clear that the processing in a system which is relevant for the safety has an identical back-up operation.
With the introduction of E-Gas, the emergency running
function sometimes provided the grounds for discussions. If only one accelerator pedal sensor fails, an error would probably be noted and the car would carry on functioning. Should both fail to give a signal, it cannot
react otherwise, than to distinctly raise the RPMs, either in certain situations or constantly, thus making it possible to reach the workshop. Modern E-Gas regulating takes into consideration the inlet manifold pressure
or the air-mass, the clutch- and brakelight switch and the wheel RPMs or the driving speed. Then, at the traffic lights, with the brake pedal pressed, the RPMs can be reduced and when pulling off or on an uphill stretch
accordingly increased. However, it is important to know that a defective accelertor pedal transmitter cannot be effectively replaced, even by the most skillfully programmed emergency running feature. How then, should
the control device know what the driver wants? The actuating of more than 50% of the load when emergency running, is neither possible nor does it make sense.
By the way, the servo-motor for the RPMs can also
fail. In this case the emergency running
function is simpler, through a spring it takes on the exact position necessary for increased idling RPMs.
With all the individual reasons for the introduction of E-Gas, one can easily loose sight of it's principal reason. It's all about the regulation of the engine torque independent of the accelerator pedal position. The control
device gathers all the information together, then considering torque, consumption and emission, determines the throttle-valve position. Thereby, a greater opening, despite the accelerator not being depressed, or the
closing, although the pedal is depressed, is even possible, e.g., when the automatic shifts during an acceleration process. Of course there are also other possibilities for influencing the engine torque, e.g., the very
fast reacting ignition adjustment and the slower charging-pressure adjustment. As far as the programming of the control device goes, the constructor can choose freely between these two possibilities.
not simply a replacing of the throttle cable but has, e.g., in modern petrol engine management, a more important significance. At the time when the throttle-valve of the carburetor/injection engine was still activated by
pressing the accelerator pedal the mixture, when accelerating, at first became leaner. It had thus, in addition, to be enriched through the Lambda value of more than 1, to increase the engine RPMs. With E-Gas this
process can be more precisely regulated. In theory, an almost constant addition of air and fuel would be possible. Presumably, in this case, the mixture is still being made richer, however, compared with e.g.,
carburetor engines, not nearly as strongly. The results are, lower toxic exhaust emission and lower fuel consumption. The disadvantage however, is that modern petrol engines no longer have the 'snappy' reaction of
the earlier injection engines or the multi-carburetor engines.
Through the electrically operated throttle valve, it will become possible to control the engine performance, not only through opening the throttle-valve,
but also through the inter-action of several parameters. Thus, even with a slight pedal deflection, the throttle-valve can be opened wide and nonetheless, the engine performance still be kept low, e.g., through a leaner
mixture (layer charge). E-Gas would aslo seem to make sense for high-powered motorcycles, where the control device could bring the enormous power, in a well measured
manner, onto the road surface. However, because a failure in the electronics could be fatal, a pure E-Gas solution is difficult to realise. Apart from that, the brutal and immediate throttle reaction, highly valued by
motorcyclists, would suffer.
Still in the experimental stage, there are combinations of E-Gas and systems which can recognise, e.g., speed regulations. This could take place through scanning the environment or through GPS. Thereby, the
position of the vehicle is compared with a speed-limit road map. Should one exceed the speed limit, an excess-proportional opposing force in the accelerator pedal is developed. Hoewever the requirement would be,
that all speed restrictions are properly entered into the the road map and also correctly deleted at the right time again, which can quite realistically be doubted. Perhaps there could also be a stern warning voice
installed in the vehicle...
Even more "Big-Brother" supervision is a system, where the driver commits him/herself voluntarily, to have all the vehicle data, (e.g., accelerator pedal pressure) constantly transmitted to
their own insurance company. As a reward, a reduced premium is offered, which is especially attractive for young people. 09/06