Danno- Good to see ya in here! (We are working on Revvers Bros. t-shirts ans stuff-
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The MA in my experience give higher numbers compared to APC I guess because they are thinner... Having said that, 19K is AMAZING on any 10x6 [X(] Once again I can't remember what that plane looks like but for speed try a 9x8 or 9x9- I would say 9x7 but..... I always ran a 10x7 on 10x8 on my YS-45SE because it was in a CBM F-16N, and it needed some diameter-
Robert- Looks like you have something going on with your YS, my YS-45 on a stock muffler (waste of time-compared to the Macs tuned-pipe) was at 15.1K with same 20/20, APC 9x8, OS-8, 75 Deg. 1,500 ASL...
Have you messed with the header/pipe? If not, there are some really great threads on exactly how to do that! (I say cut 1/4 inch off the header until you quit gaining rpm's then stop there [X(])
Havinfun is always pretty dialed in and his numbers look right to me--- 17K on a 9x8 is NOT easy for a sport engine!
My stock Webra-50GT hit 16.2K on 5% and some old idlebar plug, 9x8 APC, need to try a Jettstream muffler on there!
Take care guys-
James