Yup, forgot to moan the arse off about BE and the commercial backdrop. Haven't forgotten
about it or missed it though.
I like everything about
cider_and_toast's plan apart from one technical hitch. An engine of a given capacity but with fewer cylinders than another of the same capacity but more cylinders will require more fuel per cylinder per cycle. The cylinders and therefore the combustion chambers will be bigger in, say a four as opposed to an eight cylinder engine. Also, as a general rule, an engine with more smaller cylinders can be run at higher rpm than one with fewer, larger cylinders. In simple terms (although it's a bit more complicated, obviously) preference for more cylinders is to do with spreading the resultant loads from the combustion process over a greater surface area of crankshaft and bearings, and greater number of stressed components (pistons, con-rods, valves, bearings, etc).
The answer to that of course is simply to set the limit on the amount of fuel a car can carry full stop. That restriction is already in place and the limit could be reduced year on year if engine suppliers are allowed to continue engine development year on year with economy and efficiency in mind.
Other than that, a very nice plan.
Edit: Re. "surface area of crankshaft "- that's not quite the right way of putting it. I'm trying to rephrase it but I need another cup of coffee ....
Edit 2: ... sometime later ...
"surface area of crankshaft"
that's bollocks
For example: the bore and stroke of an eight-cylinder engine are smaller than those of a four cylinder engine. The size and mass of each piston and con-rod will be smaller, therefore with a shorter stroke. At the same rpm the inertial forces on the reciprocating parts of the engine will be less in the eight cylinder engine allowing it to run at higher rpm than the four cylinder engine. Yet it will produce more power over a wider rpm range as well as allow wider tolerance with regard to wear and durability of the parts.
Conversely the reciprocating parts of the four cylinder engine will have more mass leading to greater inertial forces and thus greater stress. At the same time the larger cylinders will want to gulp more fuel to move all that heavy metal around.