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Date: Sat, 23 Jul 2005 23:01:15 -0500
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: FUEL FLOW was Re: [FlyRotary] Lycoming debugging
 test - -HELP!
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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