Even thinking of using 2 X 1 prop would be a bit whacked. Spinning at 40k RPM still only gives one a pitch speed of around 40 MPH.
These engines are a viable alternative that I have been looking into. At the local track vehicles powered by them have an unforgettable acceleration and top speed. They all use a tuned pipe that gets curled 'round and 'round to fit into the confines of whatever body they choose to use. I can only imagine how much better that engine would run with a nice straight expansion chamber attached to the port.
I believe that the horsepower numbers that they're throwing out aren't too far off. However, you won't see a one of these using direct drive to the wheels. [sm=lol.gif] One guess how they get that horsepower to the workload. [sm=idea.gif] That's all I'm gonna say.......