huston marlowe
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- Joined
- Apr 10, 2005
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Forgive me for bringing up a subject well known to earlier Cub generations..but I'm just getting around to this stuff. When I joined Cub Club some years ago my membership came with a package of info on how to increase "carb heat". Recently replaced all the heat muff parts so I incorporated some of those features. Running level at WOT and 2400 rpm the heated air system drops me to 2350 or so. ( it was cool at altitude so the more heated air was still at a safe temp to be at full throttle) .That drop on my C-85 takes the HP from about 79.5 to 76.5 per the chart. Using an on-line hp calculator that hp reduction would happen with a 37 F rise in ambient temp. A Skyranch article says you lose about 1% hp per 10 F so that sort of checks. What I intend now is to actually measure the difference between the ambient at altitude and the temp in the carb heat duct at the airbox to see if it all checks. I can then conclude that there is no flow restriction level of the carb heat ducting that is costing me thrust.
