X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from sccrmhc12.comcast.net ([63.240.76.22] verified) by logan.com (CommuniGate Pro SMTP 4.3.6) with ESMTP id 624262 for flyrotary@lancaironline.net; Wed, 03 Aug 2005 21:58:57 -0400 Received-SPF: none receiver=logan.com; client-ip=63.240.76.22; envelope-from=kenpowell@comcast.net Received: from 204.127.205.147 ([204.127.205.147]) by comcast.net (sccrmhc12) with SMTP id <2005080401581401200phj5be>; Thu, 4 Aug 2005 01:58:14 +0000 Received: from [68.51.45.41] by 204.127.205.147; Thu, 04 Aug 2005 01:58:12 +0000 From: kenpowell@comcast.net To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] further testing - -lycoming O-320 Date: Thu, 04 Aug 2005 01:58:12 +0000 Message-Id: <080420050158.3072.42F176340007442A00000C00220076219404040A99019F020A05@comcast.net> X-Mailer: AT&T Message Center Version 1 (Dec 17 2004) X-Authenticated-Sender: a2VucG93ZWxsQGNvbWNhc3QubmV0 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="NextPart_Webmail_9m3u9jl4l_3072_1123120692_0" --NextPart_Webmail_9m3u9jl4l_3072_1123120692_0 Content-Type: text/plain Content-Transfer-Encoding: 8bit Hi Kevin, This is a tough one! I would pull the carb apart and verify that the float level is not set too low (note Low, not high). This is a classic case of fuel starvation when all other systems seem to check out. What happens is that the float gradually fills with gas when the engine is at idle but when the fuel flow increases the float does not open the needle /fuel valve enough to replenish the fuel in the float bowl as fast as the fuel is being burned. I have seen this problem with motorcycles but I have never had an airplane carb apart so I can't be any help on the specs. I feel that you have to rule this out before proceeding. I know that the carb is new but this wouldn't be the first time that a carb wasn't setup properly. Ken Powell Bryant, Arkansas 501-847-4721 C150 / RV-4 -------------- Original message -------------- my engine continues to baffle me and everyone else on the airport. I would send it to a mechanic, but I've spoken with all of them and they have no ideas either. it continues to look like fuel starvation, but no gauges support this theory. it runs at 2150rpm, burning 11.5-12.3 gals per hr, 3 lbs fuel pressure, for about 2 minutes then stumbles(and will die unless I reduce the throttle to 1500rpm. )the stumbling occurs when cht's are hitting 375 - 410. continued running at 1500 allows the cht's to climb, so I have to shut things down. the same behavior occurred when I flew the plane the first two times (until I realized I could duplicate the problem on the ground) I have a new carb(ma4spa) and 4 rebuilt cyls (on which I am attempting to set the rings, unfortunately) if I run the engine at less than full rich the engine won't stumble before temps hit 400+ and I have to pull power. I bypassed my fuel filters with no difference. I installed new filters that have a core of little brass balls stuck together and seemingly much better flow than the other filter(no angles either, just straight flow) I cleaned and backflushed the fuel pickups and vents, ran with the gas caps off(no diff). my fuel flow is not changing(until it sputters back to 1500rpm), so my idea that the carb bowl was slowly not being refilled doesn't show up. the same problem existed before I had the cyls rebuilt and welded, so I doubt that stuck valves/weak springs are to blame. also, that would show problems from the start, not a few minutes later. everyone wants to blame the electronic ig. switching between mag and elec. during the first minute shows no diff. switching after it starts to falter shows no diff. pulling back to 1500rpm after falter shows no diff. I can't believe I have a spark or timing problem because there are no times when one works and the other doesn't. my slick mag is brand new also. I haven't tried new plugs yet, the current ones are new, although I've heard many stories of bad new plugs (hey, what do you want for $20?) my 1" dia. cheapy van's fuel pressure meter is now showing 3 lbs. I removed the pressure regulator. in the past it used to show 8lbs pressure (hence I installed the regulator)and my carb showed signs of leakage which is one reason I replaced it. I have no idea why it shows only 3 lbs now. I tried plumbing the carb directly from a gas can. I forgot to switch the fuel line off and shot fuel clear out on the wing when the engine started. I would guess that the mech. fuel pump is working correctly. the facet elec pump will pump about 1 gallon in 2 minutes when pumping into a gas can thru the mechanical pump. it makes no diff. if I run the facet or not. I have bypassed the mech. pump and run just with the facet, no diff., in fact, when I shut off the facet the engine still runs until the bowl burns down, maybe 30 sec.? it is hard to believe that both the auto plugs and aero plugs are simultaneously failing due to heat. I could fly the plane at less than full rich to see how long it would fly I suppose, but that seems unnecessarily risky. I've had two "lucky" flights so far. I checked for induction leaks(pressurized and soap solution) and found nothing. I am out of ideas. this problem is just kicking my butt. hopefully one of you guys will spark an new idea or theory for me. Kevin Lane Portland, OR e-mail-> n3773@comcast.net --NextPart_Webmail_9m3u9jl4l_3072_1123120692_0 Content-Type: text/html Content-Transfer-Encoding: 8bit
Hi Kevin,
This is a tough one!  I would pull the carb apart and verify that the float level is not set too low (note Low, not high).  This is a classic case of fuel starvation when all other systems seem to check out.  What happens is that the float gradually fills with gas when the engine is at idle but when the fuel flow increases the float does not open the needle /fuel valve enough to replenish the fuel in the float bowl as fast as the fuel is being burned.  I have seen this problem with motorcycles but I have never had an airplane carb apart so I can't be any help on the specs.  I feel that you have to rule this out before proceeding.  I know that the carb is new but this wouldn't be the first time that a carb wasn't setup properly. 

Ken Powell
Bryant, Arkansas
501-847-4721
C150 / RV-4
 
-------------- Original message --------------
my engine continues to baffle me and everyone else on the airport.  I would send it to a mechanic, but I've spoken with all of them and they have no ideas either.  it continues to look like fuel starvation, but no gauges support this theory.  it runs at 2150rpm, burning 11.5-12.3 gals per hr, 3 lbs fuel pressure, for about 2 minutes then stumbles(and will die unless I reduce the throttle to 1500rpm.  )the stumbling  occurs when cht's are hitting 375 - 410.  continued running at 1500 allows the cht's to climb, so I have to shut things down.  the same behavior occurred when I flew the plane the first two times (until I realized I could duplicate the problem on the ground)  I have a new carb(ma4spa) and 4 rebuilt cyls (on which I am attempting to set the rings, unfortunately)  if I run the engine at less than full rich the engine won't stumble before temps hit 400+ and I have to pull power.
I bypassed my fuel filters with no difference.  I installed new filters that have a core of little brass balls stuck together and seemingly much better flow than the other filter(no angles either, just straight flow)
I cleaned and backflushed the fuel pickups and vents, ran with the gas caps off(no diff).  my fuel flow is not changing(until it sputters back to 1500rpm), so my idea that the carb bowl was slowly not being refilled doesn't show up.  the same problem existed before I had the cyls rebuilt and welded, so I doubt that stuck valves/weak springs are to blame.  also, that would show problems from the start, not a few minutes later.
everyone wants to blame the electronic ig.  switching between mag and elec.  during the first minute shows no diff.  switching after it starts to falter shows no diff.  pulling back to 1500rpm after falter shows no diff.  I can't believe I have a spark or timing problem because there are no times when one works and the other doesn't.  my slick mag is brand new also.  I haven't tried new plugs yet, the current ones are new, although I've heard many stories of bad new plugs (hey, what do you want for $20?)
my 1" dia. cheapy van's fuel pressure meter is now showing 3 lbs.  I removed the pressure regulator.  in the past it used to show 8lbs pressure (hence I installed the regulator)and my carb showed signs of leakage which is one reason I replaced it.  I have no idea why it shows only 3 lbs now.  I tried plumbing the carb directly from a gas can.  I forgot to switch the fuel line off and shot fuel clear out on the wing when the engine started.  I would guess that the mech. fuel pump is working correctly.  the facet elec pump will pump about 1 gallon in 2 minutes when pumping into a gas can thru the mechanical pump.  it makes no diff. if I run the facet or not.  I have bypassed the mech. pump and run just with the facet, no diff., in fact, when I shut off the facet the engine still runs until the bowl burns down, maybe 30 sec.?
it is hard to believe that both the auto plugs and aero plugs are simultaneously failing due to heat.  I could fly the plane at less than full rich to see how long it would fly I suppose, but that seems unnecessarily risky.  I've had two "lucky" flights so far.
I checked for induction leaks(pressurized and soap solution) and found nothing.
    I am out of ideas.  this problem is just kicking my butt.  hopefully one of you guys will spark an new idea or theory for me.
Kevin Lane  Portland, OR
e-mail-> n3773@comcast.net
 
--NextPart_Webmail_9m3u9jl4l_3072_1123120692_0--