tuning a pipe
Trying to use a Macs pipe on a Mecoa 45.
This is my first pipe experience and I'm learning alot about lean, hot and burning up glow plugs. I was told at one time that the average length of the pipe should be about 9 inches from glow plug to the first hump in the pipe for a 40 size engine.
When trying this measurement the engine seems to respond nice but getting less rpm than the stock muffler. Have a 10 x 5 prop and with the stock muffler at full throttle I was getting 12000rpm. With the pipe I am getting about 9-10k.
The tuning info on the Mac's website states to start at 4" length on the header pipe for most 45 size engines.
I also notied that with the stock muffler the needle valve is open about 1.5 turns, with the pipe I opened it up about 3 turns.
Any suggestions?
Larry Barnes