Excessive Fuel Consumption

lwickterlwickter
in General Discussion
I have a Cherokee 140 with the 160 mod and Powerflo exhaust. The airplane has always seemed to have high fuel consumption, even before the mods. I am getting over 11 gph at 70% power, leaning to 380 CHT if not a little higher. Full power consumption is 14 gph give or take. My claims are generally met by disbelief from mechanics, but these measurements are being made based on full tanks. Appreciate any thoughts. BTW, no blue stains anywhere on the airplane!

Comments

  • datorresdatorres
    14GPH at full power for a 160HP engine seems perfect. As a general rule the engine should pull a FF level equal to 9% of rated HP during a full power operation at sea level. All of our carbureted engines have an enrichment valve (also called an economizer valve) that make the mixture richer than normal at full throttle operations. I would not worry about your engine, things seem to be about right. As for your 11 GPH at 70% power, I suspect you are either setting power incorrectly or leaning incorrectly. Remember that the book power settings are based on DA and assumed that you are leaning to best economy which is leaning to the onset of roughness, then richen just until roughness goes away AND NO MORE! (Too many pilots think pushing the mixture a little further "for good measure" helps the engine run better, but doing so puts you in the worst mixture range you can be which is 50dF ROP.) You want to run slightly lean of peak, about 25dF LOP (best economy) or very rich of peak (best power). Best power is usually found at max RPM and is usually found at 100 to 125 dF ROP.
  • lwickterlwickter
    Thanks for your comments. I thought LOP was just for fuel injected engines. If I leaned to engine roughness, then ROP or LOP, my CHT's would be running over 400 dF easily. I've read that 380 is the max to shoot for. Won't that shorten the life of the engine?
  • Mike HartzMike Hartz
    I have had a 1962 Cherokee 160 since 2009 and have kept track of every cent Iv'e put into it. After 300 hours of flying it (including the flying needed for my Inst Rating) I average 7 3/4 GPH. I don't run at full power, but also don't loaf along. I generally cruise at 2500 rpm and lean as I go higher. 11GPH at cruise seems a lot to me.
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