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kevin lane wrote:
thank you for the reply. I will start looking into my fuel supply. I do have a flow meter but haven't been watching it too much since I was so concerned with the very high CHT's that I've been hitting. the mesh filter in the carb is good, brand new in fact. I have two auto mesh fuel filters ahead of the facet pump. they look clean thru the glass, but I will remove them and look more closely. I have been reluctant to remove the wing tanks in order to check the pick-up tubes since it is so much work, plus my tanks are quite full. I suppose I could try to back flush them first with an air hose if I am VERY careful. now that I think about it I don't think I have tried switching tanks yet. that would certainly be an easy task.
I believe that my fuel flow meter was showing 8.5+ gals/hr at full throttle. now that I think about it that may be low, and 10.5 more typical.
thanks for your help. we are having absolutely beautiful weather here and I was so anxious to do some flying, but....at least I can hang out at the airport some more. it's nice to find someone who doesn't immediately say "I'd get rid of that electronic ignition to begin with"!
to answer Tracy, yes I have EGT's, shows low 1100's since I am running full rich, I have manifold pressure but never looked at it(I'd make a hell of an experimental test pilot-wait, I am one, oops). in my defense, I have been nervous running my CHT's up past 400 degrees in order to replicate this problem, since I just had three cylinders welded because of who knows what? I've been thinking about attaching my leaf blower to my plenum to help cool things on the ground runups. it produces 220mph wind, or so the box says.
Kevin Lane Portland, OR
e-mail-> n3773@comcast.net <mailto:n3773@comcast.net>
Catching up.
If you only show 8.5 gph, that's probably only about 100hp at full rich mixture.
In another message, you mentioned checking fuel filters & that fuel pressure was too high. Did the low rpm issue start before or after you put the regulator in the fuel line? Have you disconnected the line *at the carb* & checked for 150% of full power flow into a bucket? I'm wondering if you could have a partially blocked line between the pressure sensor & the carb. Regulating pressure down to 2 psi might keep your pumps from filling the carb bowl at high power settings. Have you tried running at high power until you get the rpm drop, then pulling to idle for maybe 30 seconds & go back to high power to see if you still have the low rpm or it goes up to 2200 & then takes a few seconds to drop back to 1700? If it goes through the complete cycle repeatedly, that might be an indicator that you are sucking the bowl down to a low level & reducing flow due to the low level in the bowl. 30 seconds at idle should let the level in the bowl recover without changing engine temps noticeably.
BTW, have you checked the actual Lyc data on max cht? IIRC, it's a lot higher than 420. I'm not saying it's good to run there, but there may not be any real danger of it going that high during the takeoff cycle. A tight engine is going to run hotter until it wears in & gets comfortable with itself.
Charlie
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