I know that this topic has already been covered (kind of) in a separate forum post, but it became rather confused and there were many differing and contradicting opinions/supposed facts, so I just want to clarify a few things. Firstly, are gas turbines more or less efficient (useful mechanical energy yield per unit mass of fuel) than conventional piston engines? (Assuming that both were allowed to run at their optimum speeds, which I know are very different.) Incidentally, does anyone know the approximate rpm speeds at which gas turbines and piston engines are most efficient? Secondly, do gas turbines have a high or lower power to weight/size ratio? What effect would the addition of a regeneration device for recapturing heat energy from the exhaust gasses to the turbine have upon this ratio? (For clarification of roughly how this works see: http://www.turbinecar.com/mags/R-T1972.htm) Thirdly, do gas turbine engines have faster or slower throttle response than an equivalent piston engine? Most arguments seem to suggest it is slower but this (http://www.bladonjets.com/applications/automotive/) website seems to suggest otherwise in its penultimate paragraph. By how much would the two engine types differ? Finally, are gas turbine engines simpler and smoother when in action compared with piston engines? Are they easier or harder (as well as cheaper or more expensive) to build, maintain and fix? I know the man who set up and runs MadMax Race Team, and who built their "Streetfighter" jet bike (which uses direct drive from a turbofan jet engine that originally came out of a helicopter to turn its wheel). By all accounts it is as smooth to drive as any electric bike, but with a world record holding top speed and literally spine crushing acceleration. (see https://en-gb.facebook.com/Turbinebike/) Also, would noise from the gas turbine engine be a concern, or can they be silenced enough to make them street legal? If you have any other information regarding the advantages or disadvantages of gas turbines in cars please share it. It would be helpful (but by no account necessary) if you could support any statements with facts or references. Any insight you have to offer would be most helpful, and thank you for your time!