Drive By Wire

'Throttle Cable' was a very straightforward name of a car or truck part until recent years; it ran from your gas pedal directly to the throttle lever on your carburettor. Input from driver to engine is becoming ever more mediated by electronic processing. Many vehicles now take your right foot's input as 'demand' input (electromechanical) into a computer, where it is one of several values that are processed, then an electromechanical output (via rod or cable linkage) operates the throttle in a housing or body on the intake side of your engine. Similarly, timing of the ignition spark (and in some cases now, valve operation) is modulated by this processor; each used to be adjusted mechanically and in isolation from the other variables, maximized for at most a few different engine operation regimes.

Those who have driven relatively low powered vehicle might remember being able to 'feel' when additional throttle application gained no additional performance and wasted fuel, or even inhibited performance gains, or when they wanted to be at a certain speed with the throttle already 'packed' to that point of diminishing returns, in order to crest the coming hill without losing a gear. Today's driver, for two reasons, will not generally have such learning opportunities. The vehicles are almost all powered, for their weight, in what we used to call 'sports car' category (1 horsepower or more per 14 lbs of weight) so 'feel' for differences in grade and wind is very subtle. And the sensors and brains are mediating between what we want (demand, via our right foot or the speed control) and the engine components and functions which will deliver.

I will not rail against anti-lock brakes, but point out that the instruction one can get from learning how to feel for the modulation point, where you are at the limits of adhesion between your tires and the road, also instructs about when steering will get squirmy too. Directional control, braking and acceleration all depend on the instantaneous condition of adhesion between four points of contact between tires and earth surface... and 'progress' is taking from us some of the direct ways skilled drivers used to make that very sensible.

Back to our sophisticated throttles: the main downside here is that the connection many of us felt with the primary mover, which told us lots about its capabilities, limits and needs, was also telling us a lot about efficiencies (if we were paying attention). Lots of this is generalizable knowledge, and will prove very useful to us as we figure how to manage fewer resources for more people. The related secondary loss is that engineer/inventor types, and their appreciators, have been put at a remove from the lessons that driving a car could teach about power generation and use.

For now, I hope that lots of Prius drivers are digesting the interesting computer graphics and learning how to get even better mileage by letting up on the 'gas pedal.' Our lives abound in very relevant physics lessons, although we seem to be getting more protected from them all the time!