X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.103] (HELO ms-smtp-04-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.3.6) with ESMTP id 624214 for flyrotary@lancaironline.net; Wed, 03 Aug 2005 20:58:07 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.103; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-065-188-083-049.carolina.res.rr.com [65.188.83.49]) by ms-smtp-04-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j740vJL5001260 for ; Wed, 3 Aug 2005 20:57:21 -0400 (EDT) Message-ID: <005f01c58033$5c4f3770$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Float Bowl?? - -lycoming O-320 Date: Sun, 3 Jul 2005 20:57:32 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_005C_01C58011.D4F14C30" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_005C_01C58011.D4F14C30 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Kevin, The fact is the engine does run at 2150 rpm for about 2 minutes before = it stumbles. If burning say 12 GPH. Then that is 0.2 gal/minute = (12/60). So you engine apparently burns from 0.2 to 0.4 gallons before = it starts to stumble. It runs at 1500 rpm (you do not give a fuel = flow) - so assuming the fuel flow is linear then at 1500 rpm your fuel = flow is 1500/2150 *12 =3D 8.37 GPH, which is sustainable. Now since your fuel system (what ever the problem ) can sustain 1500 rpm = or 8.37 GPH (0.139 GPM) that is approx 70% of the fuel flow you need at = 2150 rpm. So lets say your carb's flow bowl volume is 1/2 pint. That = is 0.0625 gallon. =20 So consider the flow bowl simply a part of your fuel flow. At 12 GPH = (0.2 gpm), the bowl would empty (or get too low to sustain 2150 rpm) in = .0625/0.2 =3D 0.3125 minutes or 18.75 seconds. So at first glance that = would not seem to be the problem. However - that is provided there were = no fuel flowing into the bowl at all. But of course there is - at least = at the rate of 0.139 gph (8.37 GPH). So the draw down would actually be = the difference between the demand (12 gph) and the supply (8.37 gph). = That turns out to be 12-8.37 =3D 3.36 GPH (or .056 gpm).=20 So taking our 1/2 pint float bowl at 0.0625 gallons and a draw down rate = of .056 gpm we have .0625/.056 =3D 1.11 minutes in which it would take = a full carb fuel bowl to be drawn down to where it could no longer = sustain the 12 gph flow rate. Now that is not quite your 2 minutes, = but getting close to it . So unless I screwed up the math(or my = assumption about your fuel flow at 1500 rpm is off or your float bowl is = not 1/2 pint), your symptoms sure look like a fuel flow problem to me. =20 Based on everthing you checked and found OK, I would start to suspect = the carburator myself. I know nothing about aircraft carburetors, but = assume they have a float which regulates how open a valve is that = regulates flow into the carburator and therefore can determine the max = rate at which the flow bowl will fill. Its possible that the there is = something wrong in that area (since your check appears to have = eliminated everything else in the fuel system as a possible cause).=20 Also, I would disconnect the fuel feed to the carb stick it into a = container and run the pump (electric in this case) for one minute and = the measure and calculate the max fuel flow your system gives you. This = won't prove anything is wrong with the carb but will at least show you = are getting more than 8.7 gph fuel flow to the carb. If you are not = getting at least 18-20 GPH fuel flow I think you have something in your = system that needs fixing. =20 About all I can think of. Ed A ----- Original Message -----=20 From: kevin lane=20 To: Rotary motors in aircraft=20 Sent: Wednesday, August 03, 2005 7:15 PM Subject: [FlyRotary] further testing - -lycoming O-320 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_000_005C_01C58011.D4F14C30 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Kevin,
 
The fact is  the engine does run at = 2150 rpm for=20 about 2 minutes before it stumbles.   If burning say 12 = GPH. =20 Then that is 0.2 gal/minute (12/60).  So you engine apparently = burns from=20 0.2 to 0.4 gallons before it starts to stumble.    It = runs at=20 1500 rpm (you do not give a fuel flow) - so assuming the fuel = flow is=20 linear then at 1500 rpm your fuel flow is 1500/2150 *12 =3D 8.37 GPH, = which is=20 sustainable.
 
Now since your fuel system (what ever the = problem ) can=20 sustain 1500 rpm or 8.37 GPH (0.139 GPM) that is approx 70% of the fuel = flow you=20 need at 2150 rpm.  So lets say your carb's flow bowl volume is 1/2=20 pint.  That is 0.0625 gallon. 
 
So consider the flow bowl simply a part of your = fuel=20 flow.  At 12 GPH (0.2 gpm), the bowl would empty (or get too low to = sustain=20 2150 rpm) in .0625/0.2 =3D 0.3125 minutes or 18.75 seconds.  So at=20 first glance that would not seem to be the problem.  = However -=20 that is provided there were no fuel flowing into the bowl at all.  = But of=20 course there is - at least at the rate of 0.139 gph (8.37 GPH).  So = the=20 draw down would actually be the difference between the demand (12 gph) = and the=20 supply (8.37 gph).  That turns out to be 12-8.37 =3D 3.36 GPH (or = .056 gpm).=20
 
So taking our 1/2 pint float bowl at 0.0625 = gallons and a=20 draw down rate of .056 gpm we have  .0625/.056 =3D 1.11 = minutes in which=20 it would take a full carb fuel bowl to be drawn down to where it could = no longer=20 sustain  the 12 gph flow rate.  Now that is not quite your 2 = minutes,=20 but getting close to it .  So unless I screwed up the math(or my = assumption=20 about your fuel flow at 1500 rpm is off or your float bowl is not 1/2 = pint),=20 your symptoms sure look like a fuel flow problem to me.  =
 
Based on everthing you checked and found OK, I = would start=20 to suspect the carburator myself.  I know nothing about aircraft=20 carburetors, but assume they have a float which regulates how open a = valve is=20 that regulates flow into the carburator and therefore can determine the = max rate=20 at which the flow bowl will fill. Its possible that the there is = something wrong=20 in that area (since your check appears to have eliminated everything = else in the=20 fuel system as a possible cause).
 
Also, I would disconnect the fuel feed to the = carb stick=20 it into a container and run the pump (electric in this case) for one = minute and=20 the measure and calculate the max fuel flow your system gives you.  = This=20 won't prove anything is wrong with the carb but will at least show you = are=20 getting more than 8.7 gph fuel flow to the carb.  If you are not = getting at=20 least 18-20 GPH fuel flow I think you have something  in your = system that=20 needs fixing. 
 
About all I can think of.
 
Ed A
 
 ----- Original Message -----
From:=20 kevin = lane=20
Sent: Wednesday, August 03, = 2005 7:15=20 PM
Subject: [FlyRotary] further = testing -=20 -lycoming O-320

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