ORIGINAL: Ed_Moorman
I found an old, .91, Ultra Thrust tuned muffler in my muffler box. It happens to be the long chamber one that I bought 4-5 years back to run larger props on an OS .91FX that never ran well so I sold it. I thought I'd give it a try since I still have SK 90 #2 on the test stand.
At this point I am running a big, black, heavy, Master Airscrew 15-6 and turning 9500-9800 rpm on Omega 10%. This is about what my #1 engine turned, too. I installed the Ultra Thrust and cranked it up. I leaned out for a peak of 10,650 and a nice easy 10,400 rpm. That's a good 800-900 rpm. I think that is pretty good on a big prop and at lower rpm.
For this weekend, I'll install it on engine #1 on the Ultra Stick and give it a try in the air. The needle seemed fairly insensitive so I don't think it will lean out in the air or in maneuvers, although you can't tell in advance. I have had engines just scream on a pipe on the ground, but lean out when I pull g's in the air. I'll report later.
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Do you do any 3D flying, Ed?
I have a Hanger9 (I think) Harrier 90 ARF NIB. While I originally intended to put a four-stroke in the nose, I'm wondering how the SK 90 would pull it around? Any engine that can pull a 15x6 or 8 well and throttles good is running right up there with some of the four-strokes I have.
Was your old long pipe Ultrathrust made for the G90 Tigre? I have one that is made for the Tigre G90 and was wondering how close the bolt pattern is between the SK90 and the G90. If you happen to know. TIA
Oh, which Ultra Stick ARF are you using? A .40, .60 or 1.20? I'll bet the .60. Pardon me if I asked this question before.
Ed Cregger