bob27s
Posts: 4833
Joined: 4/9/2002 From: Cleveland,
OH, USA Status: offline
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quote:
ORIGINAL: msweeten I took a look at the mufler port and sure enough the sleve had moved. I loosened the head and moved it back. sinched the head back and now she runs again. I don't know why the 90 would get hot(run lean) that way. I am very carfull not to run too lean. Infact when I started the flight It might have been a little rich, Lots of smoke. I had been trying different props to get the noise down. I wonder if that was enough to over heat it? The head must have been loose before my last filight with the sleve turning in flight? Any way I am going to stick to 12 x 6 and 12 x 7 props and check the head bolts from time to time. The engine now has a 12x7 turning about 13,400 rpm on the ground. That should be Ok. Thanks for the help Dub. Msweeten, Put a smaller prop on it for a bit (break-in size prop - 11x6 or similar). Put a full tank of fuel through it that way, and get the rpm up over 14.5K with it still a tad rich. It will help it get the fit back. Then put your 12x6 or 12x7 back on. In general, you want to set the engine about 500 rpm down below ground peak rpm for flight. In the air, as the engine unloads, it needs the fuel. Do not confuse exhaust smoke for a 'rich' condition - just means there is a lot of oil, and some unburnt fuel - the engine can still get hot if overloaded. Never run the engine at peak rpm for an extend period on the ground. Find peak, quickly back off a bit. Once set, you should only require tiny tweeks to the needle from day to day. The only way you can hurt the engine is to run it lean for a while. The engine and muffler are somewhat RPM dependant. If you have the standard Jett-Stream 90 muffler, it is tuned for 'above' 12,800 rpm. If you find a peak rpm at 13,000 or under with any prop you try, you have too much prop. Noise abatement can be a tricky thing, but there is a balance needed with the engine. Just as a suggestion, try an 11x9 prop on the F-16. Will extend the take-off roll a bit, but the lower tip speed may help you. Bob
< Message edited by bob27s -- 7/5/2005 9:41:50 PM >
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