Torsion Powered Vehicle

[the Langolier]

I think I'd be less inclined to worry about picking up springs so much as fishing them out of the various bodies they'd impale.

Springs with the energy necessary to emulate the amount of chemical energy in a gas tank would have huge potential for massive carnage.

Agreed. Considering fatigue, springs are virtually guaranteed to fail in the lifetime of the car. Fatigue is a decrease in the yield strength of a material under a load over a given period of time. As the springs are held in torsion or twisted the metal will just keep getting weaker until the thing will eventually explode into twisted shrapnel. Of course increasing the number of springs will decrease the amount of energy stored in each one so failure won't be so catastrophic and replacing broken springs would be more practical.

Also keep in mind that the spring constant is not constant with deflection so this system is non-linear. A simple power calculation from 1/2*k*d^2 is not likely to be very accurate.