RE: Mystery Speed Engine Break In
I'll answer what I can, although I'm shooting in the dark with this thing also.
1) What is a reasonable prop to start with, APC 11x6, 11x7, 10x9? Something with lower load than that, or more load?
I've always believed that it is best to break in a high performance motor at a rich setting and at a higher rpm. I was going to use a 11x6 APC for break in on mine.
2) I have never run a full length tuned pipe before, where can I find info on setting the initial pipe length? I am looking for the formula(s) that will give a ballpark length given a target rpm range and exhaust timing. Or should I look at a Jett short pipe, if they will make one for me? Bob, any thoughts? I realize it's not perfect, but how about an MCP? Simple, light, easy to make. Maybe not full power potential, but decent (in my mind, anyway).
There is a lot of great info on the MACS website, I'm still undecided on a pipe also at this point.
3) To run in, do I just use the typical ABC engine technique of: open needle valve 3 turns, start, peak and then back off 500rpm, let run through several tanks?
With a standard .61 sized prop, that would make sense. Running a smaller prop like I intend, I will be closer to 800 off peak, and pinch the line every 10-15 seconds to warm things up.
4) If I can't find a pipe, is it OK to run it on open exhaust if I elevate my test stand tank a few inches to ensure adequate fuel flow? My neighbors might be pissed, though...
It will be loud, but it is ok to run them that way. I will do all of my initial runs without a pipe to get some baseline numbers that you can compare to afterwards when you add the pipe. Try to find a remote location.