French car gets 8,923 miles per gallon.

Almost all of that gas would evaporate before I got around to using it up. cuhulin

Here is the problem:

In an internal combustion engine, MOST of the heat from the fuel is not transmitted to the powertrain, but rather leaves the engine through radiation and conduction/convection. When braking, your kinetic energy is dissipated by the brakes/rotors in the form of friction/heat.

So...If you get 50% efficiency, IOW, if 50% of the fuel's potential energy IS transmitted to the powertrain, you're doing good.

Next there are the issues of inertia and friction. It takes X amount of energy to push Y amount of tonnage around, and there are the internal resistances to overcome as no machine is 100% friction free.

So, for example, to raise 3,800 pounds of automobile 100 feet (going up a hill) there is no way to get around the fact that some amazing amount of energy is going to need to be expended in order to do so.

If you have a 1:1 ration gear, or a 30:1 block and tackle, it is STILL going to require the SAME amount of energy to overcome gravity and move that poundage up the hill (or into the air) a vertical distance of 100 feet.

Do you reclaim some of that energy when turning around and coming back down the hill. Yes...SOME, but not all, because of the heat dissipation by the engine's cooling system and the other factors already mentioned.

So, the way to economize is to lighten the weight of the vehicle, thus lowering the inertia and size of engine requirements. This is WHY compact cars get better mileage that full-sized vehicles.

So it is a question of How Small do you want to go? Put a lawnmower engine into a paper mache car? Fine. Just don't take it out on the highway in the rain.

Nick

Smokey Yunick, The Best Damn Garage In Town, he was developing a ceramic car engine.I don't know if he gave up, or whatever happened about that.He passed away years ago. He once built a windmill generator for his shop, the City of Daytona/Daytona Beach made him take it down. He was a Bomber Pilot in World War Two.So was Mr.Dillon, James Arness, Gunsmoke. cuhulin

Might have something to do with the fact that it is harder to machine ceramic to tight specifications than it is to machine metals to tight specifications. I don't really know...that's just a wild a$$ guess.

Ceramic might be more brittle than most metals, which could raise a problem in manufacturing parts that get HAMMERED all day long when the engine is running. Don't really know. My guess is that ceramic as we know it is too fragile.

Nick

A bunch of folks have demonstrated one-off ceramic engines, and the advantage of the thing is that you can run them at higher operating temperatures for more efficiencies. Nobody's been able to do real production, though.

Yes, also the coefficient of expansion is really different than that of metal so if you mix it with metal parts you need to build in some slack.

--scott

He was trying to develop what he called an adiabatic engine, to minimize heat losses. He was somewhat successful, but I think his grant ran out and he put the engine in the corner of his garage, hoping to revive it some day.

Ceramics are not easy to machine but they can be formed to reasonable limits of tolerance.

Heat loss is the biggest reason for lack of efficiency in IC engines. If you could run them hot as hell, no cooling, you might get a lot more mileage.