Originally Posted by
Raleighcopter
a little more scavenging happening with the tubing on or is it just breathing better?
I am inclined to think it breathes better... Most likely, since a Wankel operates at a kinda-sorta fourstroke principle, I think the added inertia in the enclosed column of exhaust gas pulls out more spent gas from the combustion chamber, so scavenging efficiency increases.
Originally Posted by
Glowgeek
Odd, it acts as if leaned out a bit. Higher rpm and won't hold peak.
It actually does hold peak. Not visible in the video, but it does hold that higher peak...
When I noticed the effect, I did not have my camera at hand, and it was peaking out at 12950-ish without, and 13440 with tubing, repeatable and it held RPM for at least 10 seconds (I don't want to hold it WOT too long, given the poor cooling on the teststand). This is a difference of approx 10% in power output, from 0,46 to 0,52 hp.
When I went to get my camera, I left the engine to idle while getting the camera. Probably it pooled a bit of oil, because it peaked at 12500-ish without tubing, but I did not touch the settings.
This set-up is not the most stable (lot of play in the throttle rod, and the carb is a pretty crappy design for something made by OS...)