X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.123] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with ESMTP id 5091022 for flyrotary@lancaironline.net; Sat, 13 Aug 2011 09:18:38 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.123; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.1 cv=SOlsIBN44tkg4MqIq+y2aLZdhoA3kHpmiRsLue6rfnM= c=1 sm=0 a=4GHctdUWtu8A:10 a=SC71y0a/4S6V9vjVxUojGA==:17 a=SkLy3MW7nlD5xqZ0ZnEA:9 a=eFy3rzXLUxGZ2jCgVJgA:7 a=wPNLvfGTeEIA:10 a=mylpmfEa6tDd9mf1:21 a=A44TVjxkz7Bscj6f:21 a=pedpZTtsAAAA:8 a=Ia-xEzejAAAA:8 a=4PR2P7QzAAAA:8 a=ayC55rCoAAAA:8 a=o1OHuDzbAAAA:8 a=r9gIGsyZahTkYzeXaC8A:9 a=H0PVrBFzB6OztKNZtkoA:7 a=eJojReuL3h0A:10 a=EzXvWhQp4_cA:10 a=djSSOgbfo6cA:10 a=ILCZio5HsAgA:10 a=SC71y0a/4S6V9vjVxUojGA==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.175.135 Received: from [174.110.175.135] ([174.110.175.135:55244] helo=EdPC) by cdptpa-oedge01.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 01/94-15242-A89764E4; Sat, 13 Aug 2011 13:18:02 +0000 Message-ID: From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: vapor lock Date: Sat, 13 Aug 2011 09:16:43 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0021_01CC5999.B7A9D210" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 This is a multi-part message in MIME format. ------=_NextPart_000_0021_01CC5999.B7A9D210 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable No question, Charlie - the more of your fuel line kept under EFI pump = level pressures , the less chance for vapor lock. In tank pumps = certainly do that - but, as you point out there are other = considerations. Wing root sounds like a pretty good compromise in luie = of in-tank pumps. I considered that but in the end decided against it = as it would have high pressure fuel lines inside my cockpit - which I = personally do not favor {:>) Don't know for certain (and may never) the cause of the latest = sputtering engine event - but, in absence of in-tank pumps and/or return = to tank - I still believe that pressure applied by a boost pump can = prevent vapor lock (based on my own personal experience with my unique = installation) Ed From: Charlie England=20 Sent: Saturday, August 13, 2011 9:06 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: vapor lock The really frustrating thing about all this is that every installation = is different (not to mention that it's only speculation as to what = caused this particular power loss). Sixties-era cars (carb, engine mounted fuel pump) had vapor lock = problems all the time in hot weather. Modern cars, almost never (in-tank = high pressure pump). Keeping the pumps as low & as close to the tank(s) = as practical would seem to be the best path. Van recommends mounting = pumps on the floor in the cabin. That means that the max lift would be = maybe 3-4 inches, through a -6 line, and nowhere near the high = under-cowl temps. There's a guy flying an injected Lyc on ethanol-laced = mogas who never has a problem with vapor lock. He removed the mech pump = and uses wingroot mounted electric pumps. If it weren't for the maintenance related inconveniences, I'd seriously = consider in-tank pumps, as others have done. But we still don't know whether this is what caused the recent power = loss.... Charlie =20 On 08/13/2011 06:20 AM, Ed Anderson wrote:=20 I should have added - the best overall approach - returning hot fuel = to the heat-sink tanks and drawing new cooler fuel into the lines. Ed From: Ed Anderson=20 Sent: Saturday, August 13, 2011 6:47 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: vapor lock Ok, Finn, that was my guess as well.=20 That then brings up a question - my understanding of "vapor lock" is = that it is caused by a low pressure area/combined with hot fuel on the = EFI pump intake which cause the gasoline to flash to vapor - naturally = the EFI pumps can not pump vapor - therefore as fuel is injected from = the high pressure side of the pump (reducing pressure on that side), = vapor can form there as well. In any case, insufficient fuel is = injected into the engine. Since the injectors are still clicking open, it would seem that any = vapor on that side of the pump already has a chance to vacate the line = (through the injector) - so my assessment is that it is not the relief = of vapor/gas from the high pressure side that remedies the problem, it's = removing the gas from the low pressure side (pump inlet) and thereby = permitting liquid fuel to be pumped that "cures" a vapor lock situation. = =20 So I am puzzled why a gas vent on the high pressure side would have = much (if any) effect on vapor lock. IF there is pressure on the = injector side - I question whether it would be as high as pump pressure = - and even if it were, the injector opening would provide a path for it = to be release - not to mention the pressure regulator. So as I said = -I'm a bit puzzled as to the mechanism that a vent in the high pressure = side prevents vapor lock. In my opinion, there are two ways to reduce/eliminate the vapor in the = low pressure side - either cool the fuel sufficiently (somewhat = difficult to do) or to increase the pressure in the low pressure line = forcing the vapor back into the liquid - ergo - use a boost pump. FWIW Ed From: Finn Lassen=20 Sent: Saturday, August 13, 2011 2:53 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: vapor lock Hi Ed, I believe it's simply a return to the tank from the high-pressure side = via a very small orifice. How small I do not know. Finn On 8/10/2011 9:28 AM, Ed Anderson wrote:=20 The one I potential preventive measure/fix I have not looked into is = the vapor by-pass/dump that I know a few folks are using. I search the = archive but could not find a description of this method - anyone care to = provide one? ------=_NextPart_000_0021_01CC5999.B7A9D210 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
No question, Charlie - the more of = your fuel=20 line kept under EFI pump level pressures , the less chance for vapor = lock. =20 In tank pumps certainly do that - but, as you point out there are other=20 considerations.  Wing root sounds like a pretty good compromise in=20 luie  of in-tank pumps.  I considered that but in the end = decided=20 against it as it would have high pressure fuel lines inside my cockpit - = which I=20 personally do not favor {:>)
 
Don't know for certain (and may never) the cause = of the=20 latest sputtering engine event - but, in absence of in-tank pumps and/or = return=20 to tank - I still believe that pressure applied by a boost pump can = prevent=20 vapor lock (based on my own personal experience with my unique=20 installation)
 
Ed

From: Charlie England
Sent: Saturday, August 13, 2011 9:06 AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: vapor lock

The really frustrating thing about all this is that every = installation is different (not to mention that it's only speculation as = to what=20 caused this particular power loss).

Sixties-era cars (carb, = engine=20 mounted fuel pump) had vapor lock problems all the time in hot weather. = Modern=20 cars, almost never (in-tank high pressure pump). Keeping the pumps as = low &=20 as close to the tank(s) as practical would seem to be the best path. Van = recommends mounting pumps on the floor in the cabin. That means that the = max=20 lift would be maybe 3-4 inches, through a -6 line, and nowhere near the = high=20 under-cowl temps. There's a guy flying an injected Lyc on ethanol-laced = mogas=20 who never has a problem with vapor lock. He removed the mech pump and = uses=20 wingroot mounted electric pumps.

If it weren't for the = maintenance=20 related inconveniences, I'd seriously consider in-tank pumps, as others = have=20 done.

But we still don't know whether this is what caused the = recent=20 power loss....

Charlie
 
On 08/13/2011 06:20 AM, Ed = Anderson=20 wrote:=20
I should have added - the best overall = approach -=20 returning hot fuel to the heat-sink tanks and drawing new cooler fuel = into the=20 lines.
 
Ed

From: Ed = Anderson=20
Sent: Saturday, August 13, 2011 6:47 AM
Subject: [FlyRotary] Re: vapor lock

Ok, Finn,  that was my guess as=20 well. 
 
 That then brings up a question - my = understanding=20 of "vapor lock" is that it is caused by a low pressure area/combined = with hot=20 fuel on the EFI pump intake which cause the gasoline to flash to vapor = -=20 naturally the EFI pumps can not pump vapor - therefore as fuel is = injected=20 from the high pressure side of the pump (reducing pressure on that = side),=20 vapor can form there as well.  In any case, insufficient fuel is = injected=20 into the engine.
 
Since the injectors are still clicking open, = it would=20 seem that any vapor on that side of the pump already has a chance to = vacate=20 the line (through the injector) - so my assessment is that it is = not the=20 relief of vapor/gas from the high pressure side that remedies the = problem,=20 it's removing the gas from the low pressure side (pump inlet) and = thereby=20 permitting liquid fuel to be pumped that "cures" a vapor lock = situation. =20
 
So I am puzzled why a gas vent on the high = pressure side=20 would have much (if any) effect on vapor lock.  IF there is = pressure on=20 the injector side - I question whether it would be as high as pump = pressure -=20 and even if it were, the injector opening would provide a path for it = to be=20 release - not to mention the pressure regulator.  So as I said = -I'm a bit=20 puzzled as to the mechanism that a vent in the high pressure side = prevents=20 vapor lock.
 
In my opinion, there are two ways to = reduce/eliminate=20 the vapor in the low pressure side - either cool the fuel sufficiently = (somewhat difficult to do) or to increase the pressure in the low = pressure=20 line forcing the vapor back into the liquid - ergo - use  a boost = pump.
 
FWIW
 
Ed
 

From: Finn = Lassen=20
Sent: Saturday, August 13, 2011 2:53 AM
To: Rotary motors=20 in aircraft
Subject: [FlyRotary] Re: vapor lock

Hi Ed,

I believe it's simply a return to the = tank from=20 the high-pressure side via a very small orifice. How small I do not=20 know.

Finn

On 8/10/2011 9:28 AM, Ed Anderson wrote:
 
The one I potential preventive measure/fix I = have not=20 looked into is the vapor by-pass/dump that I know a few folks are=20 using.  I search the archive but could not find a description = of this=20 method - anyone care to provide=20 one?


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