X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from outbound-mail.vgs.untd.com ([64.136.55.15] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with SMTP id 5097782 for flyrotary@lancaironline.net; Fri, 19 Aug 2011 15:14:09 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.136.55.15; envelope-from=alwick@juno.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=juno.com; s=alpha; t=1313781215; bh=47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=; l=0; h=Message-ID:From:To:Subject:Date:Content-Type; b=YGz2naHdW2Se3pfgYVD3cqvpYWorre5KfU8u4b7wLlAS1h6e/8rtB1Ma0NsemQnk2 2UGGKuUrRAHKJTcZ3/zqlDiECZhfxV5ZyOO7J2AWBuRkq/86Q1ag0SeqC//BR1GJqF 0vP02/4tjnQNqAc0N6KRMnK2HfQHG6ZR5UHONlqo= Received: from Penny (50-39-161-17.bvtn.or.frontiernet.net [50.39.161.17]) by smtpout02.vgs.untd.com with SMTP id AABHE7PQ7AQQ87E2 for (sender ); Fri, 19 Aug 2011 12:13:33 -0700 (PDT) Message-ID: From: "Al Wick" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: Dennis Haverlah Fuel System...or any others, for that matter. Date: Fri, 19 Aug 2011 12:13:31 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_01B5_01CC5E69.69468CB0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18197 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18463 X-UNTD-BodySize: 21563 X-ContentStamp: 56:28:283893226 X-MAIL-INFO: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 5a2eafaefb132a6a7e3faa X-UNTD-OriginStamp: L941HVjjYzDhN3itp//mkN1QWH362F0WDoUjq9dLVyk+hnH8/PRH3g== X-UNTD-Peer-Info: 10.181.42.32|smtpout02.vgs.untd.com|smtpout02.vgs.untd.com|alwick@juno.com This is a multi-part message in MIME format. ------=_NextPart_000_01B5_01CC5E69.69468CB0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Mark said: wrote: wrote: Al Wick wrote: I'm really concerned for some of these fuel designs. The fuel = bleed has nothing to do with vapor lock. Virtually no effect at all. =20 I don't know why others are doing it, but for me, the bleed has = nothing at all to do with vapor lock. Some conversations have been = mixed together, so I can see how that could be the impression. The = point of the pressure bleed is to bleed off the pressure after shutdown. I have a strong, positive head pressure going into my pumps. = They, and the regulator, are about 8" directly below the tank. Excess = fuel goes back to the opposite side of the tank from the pickup, and a = single line goes forward to feed the injectors. The fuel lines are = arranged such that heat soaking the lines to the point of boiling the = gas will push liquid fuel down hill and behind the firewall, isolating = the gaseous gas with its heat at the top of the line. Turning the pumps = on will pressurize the line to 55psi, returning most of the gaseous fuel = back to a liquid state. The ECM is programmed for a longer clearing = pulse on hot start. The point of the bleed is to allow fuel to move back to the = tank. I had the issue of a the pressurized lines being perfectly = sealed. The pressurized fuel was finding the path of least resistance = out, which just happened to be out the injector and into the intake = manifold where it sat as a little puddle. Heat soaking the lines would = not push liquid fuel downhill and back behind the firewall. It would = push more fuel into the manifold. A puddle of gas sitting in a = composite manifold, just above a hot exhaust stack is just bad mojo. A = poorly sealed regulator allows the pressure to bleed off in about 5 = seconds (give or take), isolating the hot fuel in front of the firewall, = and keeping the rest cool and out of the intake manifold. Got nuthin' to do with vapor lock. -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html -------------------------------------------------------------------------= ----- -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_01B5_01CC5E69.69468CB0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Mark said:
<Yes, the test led to the search for a solution
Way to be. Glad you went to the effort to test it. Others might = have been=20 tempted to respond just by cracking the fitting on fuel rail. Fuel = starts to=20 flow: "Took care that problem". You pursued further so that running one = tank dry=20 is not catastrophic.
 
Top view of your diagram looks good. = It's the fine=20 details that make a difference. Some plumbing oversight prevented your = pumps=20 from getting wet.
I do hope those two inlet filters are = coarse ones=20 with low pressure drop and high surface area. You can't beat the oem = inlet=20 filter bags.
 
-al wick
----- Original Message -----
From:=20 Mark = Steitle=20
Sent: Wednesday, August 17, = 2011 11:46=20 AM
Subject: [FlyRotary] Re: Dennis = Haverlah=20 Fuel System...or any others, for that matter.

Al,
 
You wrote, "You also test it without the bleed=20 line?" 
 
Yes, the test led to the search for a solution.  You can see = the=20 "bypass circuit" on Egg's fuel system schematic at http://www.eggenfellneraircraft.com/Manual-Updates/EarlyManualFue= l.html. =20 This is what I incorporated into my fuel system, and it = solved=20 the problem.  Its been quite a few years now, but I may = still=20 have some of the posts on the Eggenfellner list that = occurred=20 in search for this as the final solution.
 
You wrote,=20 "FWIW, everything you describe is not vapor lock, has nothing = to do=20 with vapor lock." 
 
As I said, I'm not sure if my condition fits the definition of = "vapor=20 lock", but that's what someone labeled it, and it stuck.  The = problem is=20 that EFI pumps don't draw or push air very well.  So, if the = flowing=20 fuel is replaced by air due to an empty tank, the pump keeps running, = but=20 essentially stops pumping fuel.  With a 40# spring in the = downstream=20 circuit, it is virtually impossible for the pump to pass the = air even=20 though the selector valve has been swiched to the full = tank.  I=20 would agree that the fuel injectors should be able to pass the air, = provided=20 the prop is still turning.  (This was not the case with my ground = test.)=20 The bypass circuit ensures that flow will be restored as soon as = the=20 bubble passes through the pump and the fuel pump regains its = prime. 
 
Mark S.

On Wed, Aug 17, 2011 at 12:06 PM, Al Wick = <alwick@juno.com>=20 wrote:
<I would think that a well-designed fuel system with the = pumps=20 located as low as possible
 
Instead of speculations, you can = actually=20 measure how good it is. A pump, clear fuel lines, and water instead = of fuel.=20 Pinch fuel line with pliers to increase pressure drop.  Watch = bubbles=20 come out of solution. Hear the rattle from pump due to it's = inability to=20 flow air.
If you also put a pressure gage on = pump inlet,=20 you can see how fine fuel filter increases risk. You can see how = small=20 diameter tubing increases risk, heat, head pressure, etc etc. =
 
<the result of a forced landing
Egg had one forced landing. It was caused by vapor lock. = Absolutely=20 NOTHING to do with the lack of bleed line. A day later, Jan made it = to the=20 crash site. Pump would not flow fuel until he cracked the line = loose. This=20 is simply because the inlet to pumps was not wet. He did not = understand=20 this. He just reacted to symptoms. Nothing to do with vapor lock. = Remember,=20 this was crash site. Who knows what attitude plane was at. As I = described,=20 if you screwed up your plumbing from tank to pump, then pump is not = self=20 priming.
 
<tested this system on the ground and it works as=20 advertized
You also test it without the bleed line?
 
FWIW, everything you describe is = not vapor=20 lock, has nothing to do with vapor lock.
 
-al wick
 
----- Original Message ----- =
From: = Mark Steitle
To: Rotary = motors in=20 aircraft
Sent: Wednesday, August 17, = 2011 9:19=20 AM
Subject: [FlyRotary] Re: = Dennis=20 Haverlah Fuel System...or any others, for that matter.

Al,
 
I would think that a well-designed fuel system with = the=20 pumps located as low as possible, in a cool = area, and a=20 return system should not be troubled with vapor=20 locking.  Although I guess it could happen in Death = Valley=20 in August if the a/c is left out in the sun for 8 hours, and = running=20 auto gas.  So far, I haven't had any problem here in Texas = (temps=20 105* today).   
 
My purpose for installing the bypass circuit was more = critical to=20 safe flight.  (The solution was the result of a forced = landing,=20 or two, in an Eggenfellner Subaru installation.)  During = ground=20 runs, using a 5-gallon can, I found that the efi fuel pumps could = not=20 restore pressure once the tank had been allowed to run=20 dry.  When this occurred, the EFI pump would suck a = big=20 slug of air into the inlet side of the pump, loose = pressure, and=20 being unable to build psi equal to the pressure regulator setting, = it=20 would stop pumping fuel (vapor lock).  The only way to = restore=20 operation was to crack open the system downstream of the pump = until the=20 slug of air could be passed on through the fuel = pump.  Not sure=20 this meets your definiton of "vapor lock", but I think it does, = but for a=20 different reason than fuel vapor pressure.
 
I have tested this system on the ground and it works as=20 advertized.  If the tank runs dry, switched to a full tank, = the efi=20 pump will restore pressure to the system within a few = seconds.  I=20 urge all builders to run this test on their fuel system to = determine=20 whether or not their pumps are able to restore pressure after = running a=20 tank dry.  Or, just don't ever run a tank dry.
 
Mark S.


 
On Wed, Aug 17, 2011 at 10:22 AM, Ernest = Christley=20 <echristley@att.net> wrote:
Al Wick wrote:
I'm really concerned for some of these fuel = designs.=20 The fuel bleed has nothing to do with vapor lock. Virtually no = effect=20 at all.
 

I don't know why = others are=20 doing it, but for me, the bleed has nothing at all to do with = vapor=20 lock.  Some conversations have been mixed together, so I = can see=20 how that could be the impression.  The point of the = pressure bleed=20 is to bleed off the pressure after shutdown.

I have a = strong,=20 positive head pressure going into my pumps.  They, and the=20 regulator, are about 8" directly below the tank.  Excess = fuel goes=20 back to the opposite side of the tank from the pickup, and a = single line=20 goes forward to feed the injectors.  The fuel lines are = arranged=20 such that heat soaking the lines to the point of boiling the gas = will=20 push liquid fuel down hill and behind the firewall, isolating = the=20 gaseous gas with its heat at the top of the line.  Turning = the=20 pumps on will pressurize the line to 55psi, returning most of = the=20 gaseous fuel back to a liquid state.  The ECM is programmed = for a=20 longer clearing pulse on hot start.

The point of the = bleed is to=20 allow fuel to move back to the tank.  I had the issue of a = the=20 pressurized lines being perfectly sealed.  The pressurized = fuel was=20 finding the path of least resistance out, which just happened to = be out=20 the injector and into the intake manifold where it sat as a = little=20 puddle.  Heat soaking the lines would not push liquid fuel = downhill=20 and back behind the firewall.  It would push more fuel into = the=20 manifold.  A puddle of gas sitting in a composite manifold, = just=20 above a hot exhaust stack is just bad mojo.  A poorly = sealed=20 regulator allows the pressure to bleed off in about 5 seconds = (give or=20 take), isolating the hot fuel in front of the firewall, and = keeping the=20 rest cool and out of the intake manifold.

Got nuthin' to = do with=20 vapor lock.

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