ORIGINAL: cmoulder
Matt,
Is the 7500 rpm number with your CF-lam Xoar 18-5/8 x 13?
I don't think mine needs a nose ring, but if it adds to the quietness and efficiency I will give it a shot. Although this plane is the quietest gasser I've seen, there are still a few bumping and knocking things I have to track down, and the 18x10PN prop is pretty noisy when the tips start ripping over 8k rpm.
There is also something I noted the other day, the engine permormance dropped significantly when doing an outside loop. I don't believe it was a fuel delivery issue (i.e. fuel clunk not following fuel), but rather the change in air pressure on the little static plate (or whatever it is you call it... the plate on the carb with the small hole in it). I know this is sometimes solved by soldering a nipple on that plate and running a piece of fuel tube back into the fuse. But first I will make absolutely sure it isn't a problem with the clunk. It was cold, and Tygon does stiffen up quite a bit.
Bob,
Not that prop....that prop turns around 7200 give or take. I will probably chop it down to around 17 3/4 to get the prop in a happier zone. The 17x13 turn around 7500 which is about as low as I want to run. The 18x12 will be the prop I use in comps most likely and I expect it to turn around 7500 give or take. We have to see how the engine does in the summer.
I had noticed some dropped off in output at certain times too, when the engine only had a few runs on it, maybe a dozen or so. That has seemed to go away after some running. I think it's a matter of lack of break in but not certain. I do know that now that engine has a gallon through it, it doesn't sag at those same locations in flight as it once did. I suspect this will get even better after a few more gallons.
We are still steep on the learning curve with this engine
Matt