ORIGINAL: MTK
Having said that, there was a primary baffle approximately 2" aft of the high point, if memory serves. That placed the baffle approximately 17" aft of the plug. Are you measuring to the high point or to the baffle?
The high point was just a convenient way to measure. The baffle is the real desired measure. It's the reflector that causes resonance and hence the power boost.
Bryan, one simple way to check if your pipe is too long, put the model in a shallow 5 degree dive to unload it. If the engine goes fat, pipe is too long
MattK
Gotcha...So actually I'm about 19.8" to the first baffle...I measured to the high point to get the 16.7 dimension...The First weld you see in the pipe is the first baffle which is 3.1" aft of the High Point...
I read your post earlier...Actually while I was running the engine I tried to go shorter...I could go a little...I know I'm a tiny bit conservative where I'm at...But I got a good needle adjustment...about 5 or 6 clicks between rich and lean...When I went more than .5" shorter...The needle began to get pretty sensitive...I don't really like that...I could pick up 100 or so RPM....But I just don't like that hypersensitive needle which is my first little indicator...I did cut the header down to 15.5 (to the high point) and that was too much for me...
I'm sure there will be some more fine tuning when I get these things airborne...All this was on the test stand...
But that is actually pretty consistent with what I had read in previous posts...I went back and re-read some of those comments...They were actually saying 20" to the first baffle rather than the "high point"...
And I'm sure My set-up will be different than Bryan's...But since I was right in the middle of the process as this came up...I thought I'd chime in...
Have Fun...
Chuck