Oldbob

Darock, Thanks for the reply. I don’t know anything about CL, by engines are on RC planes where the throttle goes up and down. Here is what I see happening. First, I do not see raw fuel coming out the muffler on idle. After WOT, when muffler pressure is high, I then cut the throttle to idle, and then I see fuel backing up the muffler pressure line and into the muffler. Then when I advance the throttle again to or near WOT is when I see large amounts of raw fuel blowing out the muffler. While at idle the raw fuel just collects and stays in the muffler and the engine continues to idle nicely. I think there is too much muffler pressure from my engines. I have now used the uniflow system on three different plane/engine setups with this same problem of blowing a lot of raw fuel out the muffler. Also when I ran these engines on my test stand, with a clear see-through tank and fuel lines, I can see this phenomenon happening very clearly. The more muffler pressure I see at WOT the more fuel I see blowing back into the muffler when I reduce the throttle to idle.

I have a fairly accurate monometer (reads muffler pressure to within .01psi) and my engine /muffler combos are producing between .3 and .6psi at WOT and .03 and .05 at idle. Is this too much muffler pressure differential for the uniflow system? Should I just forget about using the uniflow system or try to reduce my WOT muffler pressure so I do not get this fuel blowback into the muffler?

Bob P.