The new Bosch ME-Motronic system takes a radically different approach to engine management systems. There is no accelerator cable. While it initially appears to have all the usual ingredients of a modern electronic management system – fuel injectors, input sensors, an electronic control unit (ECU) and so on – the use of accelerator position sensing and an electronic throttle actuator makes this system very different.

Fig.1: the torque curve of this twin turbo Audi 2.67 litre V6 shows the very rapid rise that occurs as the turbos start to boost at low engine speeds. Electronic throttle control by the Bosch ME-Motronic 7.1 engine management system allows good driveability, even with this massive torque change. [Audi]

In effect, the direct link between the driver’s foot and the throttle is broken. What the driver demands may not be what the driver gets. This situation has existed on some large trucks for some time now. However, it’s only now that the engine management system has be able to adjust the relationship between the car’s accelerator pedal and throttle opening. Not only can this system control fuel injection and ignition but also the cylinder charge.

Making the advent of the ME-Motronic even more of a sea change is the underlying operating logic. Unlike other engine management systems, ME-Motronic determines how much engine torque is required in any given situation and then opens the throttle sufficiently to allow the engine to develop that much torque.

The accelerator pedal travel becomes just the driver’s "torque request", to be weighed up against other torque requests generated by the traction control system, speed limiter, engine braking torque control and others. Furthermore, at all times the engine management ECU models the engine’s instantaneous torque development, adjusting the throttle opening according to the relationship between the requested and developed torque.

A quick example makes this easier to understand. In some situations, the driver may have only depressed the accelerator pedal halfway – but under the bonnet, the throttle butterfly valve can have snapped wide open! But why would this be an advantage?