Acetylene can burn like hell because its enthalpy of formation is actually positive. It's inherently unstable, and defining a stoichiometric air/fuel ratio for it isn't exactly telling the whole story since it'll burn in an inert environment in the right temperature and pressure.
(Correct me if I'm wrong on this.)
Anyway, all this leads to me to wonder whether acetylene can be used as an injected additive in a very high performance engine. Water could perhaps be used to get the temperatures down to what modern metals can handle. Pressures would be insane, and mechanical failure would truly be the only limit to how much torque you could make at any particular rpm. I'm willing to bet that you'd actually want to make the torque up high just to keep the engine from blowing up. The accelerative forces would cancel some of the compressive forces to keep the rod from buckling in compression. With the same torque, you make more horsepower up top anyway, and average horsepower is what really matters.
(By the way, for the torque-vs-horsepower debate, read this first:
http://kevinthenerd.googlepages.com/torque_vs_hp.html )
I'm thinking this could be used in bracket racing where the rules are damn-near open.