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Trekkor |
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I do things... ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 7,809 Joined: 2-December 03 From: Napa, Ca Member No.: 1,413 Region Association: Northern California ![]() |
Bought a five gallon jug of leaded 110 octane "VP" brand racing fuel. (IMG:http://www.914world.com/bbs2/html/emoticons/ohmy.gif)
My motor seems to have higher than stock compression. Lowest is 160 PSI. My speed shop guy says the valves will like the lead. (IMG:http://www.914world.com/bbs2/html/emoticons/chowtime.gif) Maybe I just like throwing money out my open windows at speed... (IMG:http://www.914world.com/bbs2/html/emoticons/huh.gif) KT |
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Dave_Darling |
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914 Idiot ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 15,000 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California ![]() ![]() |
Anecdote, from my grandfather, retired A&P mechanic and retired FAA inspector:
Quite a while back, 80-octane AvGas was available. But then the refineries stopped making it. So the owners of the aircraft spec'ed for that stuff had two choices. They could either dump 100 (110?) in, or they could pay the $$$ to get the engines recertified for "MoGas"--that's automotive fuel to you and me. The cheapskates just ran 100 octane. And guess what? They started burning exhaust valves left and right! It's not a good thing when you burn a valve at 120 feet on takeoff, BTW. Evidently the mixture was still burning on its way out of the combustion chamber, thus overheating the exhaust valves significantly. The FAA came down pretty hard on folks who were doing that... Next point: Compression pressure is not compression ratio. They are related, but rather indirectly. Lots of other stuff comes into play, far too many for us to really calculate the ratio if we know the pressures. So 160 PSI compression doesn't necessarily mean that you have a "high-compression" engine that will benefit from high octane fuel. In general, if your engine is not pre-igniting (pinging, detonating) then high-octane fuel won't give you any more power. --DD |
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