Jett FIRE 50 (with a question for you engine gurus)
Dusflyer,
I will answer these questions again since I've answered similar question's in previous post.
The answer is NO for a .50 size engine's that would turn a 9x10 prop at 20,000 RPM (especially if the engine was tuned with a quiet pipe). Jett engines are the Most Powerful, period, and it won't even do that. I don't mean to discourage you, but I think you better give it up cause you're asking too much. On the alternative side, if you insist on running a 9x10 at high RPM then I would recommend you to call Dub Jett and ask him to modify the timing on his .60L (same casing as a .40) and tuned the engine with a MAC straight pipe (not quiet pipe) for the maximum RPM, and with this, you should be able to get close to the RPM you were looking for.
One other thing is...
The small props (7.4-7.5 inches) you were using to get over 20,000 RPM are not the right prop for the .50 Jett. That engine was not timed for high RPM and will not give you the speed you're looking for because RPM is not high enough for that little prop within that RPM range. If it was timed for high RPM like his Q-40 engine, then you would see 25,000 + RPM on the ground with that little prop. I believe your engine timing is approximately 165 degree exhaust duration vs. a Q-40 engine at 192 degree. Get my point?
My recommendation for you to run your Jett .50 with a MAC straight open pipe and tuned the engine with an 8.8x9.5 and squeeze out as much RPM as you can out of it. With it, you should be able to push your Diamond Dust in the 180+ if not closer to 190 MPH.
Don't waste your time running around in circle. Call Dub Jett, the Master and ask him yourself for all the answer's.
Sam