[longshadow]

It then turned out that the secret additive was acetylene - the stuff used in acetylene torches.

Just to clarify what you're saying, the "additive" is actually calcium carbide, which, when mixed with water, produces acetylene gas, which, when combined with oxygen (in the air), forms an explosive mixture.

One of its properties is that it detonates spontaneously at 2 atmospheres pressure, which would have done a number on the pistons in any engine trying to use it. The detonation problem is overcome in welding tanks (which are pressurized to far more than 2 atmospheres) by desolving the acetylene in a liquid (AFAIK).

[finnigan2]

"...calcium carbide, which, when mixed with water, produces acetylene gas, which, when combined with oxygen (in the air), forms an explosive mixture."

- Thanks for the clarification. It was many years ago that I heard this story so parts of it must be hazy. Anyway, I wonder what with the new products now available and on the market such as carbon fiber, heat absorbing ceramics and new alloys, if it might be possible to design an engine which could run on this fuel without suffering the damage that would otherwise be caused by corrosion.

[VadeRetro]

Calcium carbide is also the fuel of the "carbide cannon" long sold in comic books alongside the Charles Atlas dynamic tension bodybuilding program, the whoopee cushion, and the naughty glasses that supposedly let you see through clothing.