How much could internal combustion efficiency be improved by eliminating pollution controls?

[FarCenter]

Polution controls were put on cars beginning in the '60s to control a variety of pollutants in tailpipe emissions.

Prior to that, in the '50s, cars got relatively good gas mileage, even though they were heavy and the engines were relatively primitive.

Detroit adapted at first by detuning the engines and increasing displacement so that more complete combustion was achieved. This was done at the expense of mileage, leading the the gas guzzlers of the '70s, which also had lousy performance.

The catalytic converter, an expensive device containing platinum and similarly pricy metals, was introduced so that incompletely burned hydrocarbons could be burned in the converter before going out the tailpipe. Obviously, this disapates energy as heat in the converter, instead of propelling the car.

All this was done before the realization that carbon dioxide, a product of the complete combustion of gasoline, was itself a pollutant and would cause climate change.

It is now clear that the tradeoff of producing more carbon dioxide as a means to produce less carbon monoxide, nitrogen oxides, partially burned hydrocarbons, etc is not a particularly good one.

So the question is, can you now design a gasoline engine which is highly efficient?

All the modern technologies of a multitude of sensors, computer controlled ignition, precise electronic fuel injection directly into the cylinders, turbocharging and heating of incoming air, 6-speed automatic transmissions allowing operation in a more optimal rpm band, etc, could be applied to the engine.

To be efficient, it would have to pretty completely burn the fuel-air mixture, and hence would necesarily have limited emissions.

Besides which, not importing platinum from Russia and South Africa would help our balance of trade.