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 5091018 for flyrotary@lancaironline.net; Sat, 13 Aug 2011 09:13:12 -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=ayC55rCoAAAA:8 a=7g1VtSJxAAAA:8 a=Ia-xEzejAAAA:8 a=u9GX8GPkTaJzzvSwxUEA:9 a=YKsFxDXwoS9HD0yw8j8A:7 a=wPNLvfGTeEIA:10 a=Qa1je4BO31QA:10 a=pGLkceISAAAA:8 a=o1OHuDzbAAAA:8 a=MQafE411KMLU4_YgJ_sA:9 a=goyYhGDcMNpiVazYmrsA:7 a=tXsnliwV7b4A:10 a=MSl-tDqOz04A:10 a=EzXvWhQp4_cA: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] ([174.110.175.135:55229] helo=EdPC) by cdptpa-oedge01.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id F8/AE-15242-448764E4; Sat, 13 Aug 2011 13:12:36 +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 09:11:17 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0019_01CC5998.F553E980" 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_0019_01CC5998.F553E980 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Thanks for the clarification, Mark. Agree! more fuel passing through = will likely mean cooler fuel and less chance of vapor lock Ed From: Mark Steitle=20 Sent: Saturday, August 13, 2011 8:41 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: vapor lock Ed, =20 My fuel system includes a bypass circuit (see picture). But it wasn't = done to resolve or prevent vapor lock due to heat. It was installed to = prevent vapor locking due to running a tank dry. These are two = different scenarios. However, the bypass circuit may help with = resolving a vapor lock due to heat by allowing a bit more fuel to pass = through the fuel rail and return it to the tank, taking heat with it. = But that wasn't its original purpose. =20 The orifice size is approx .020" and serves as a bypass around the = pressure regulator. Mark On Sat, Aug 13, 2011 at 6:20 AM, Ed Anderson = wrote: 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? -------------------------------------------------------------------------= ------- -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_0019_01CC5998.F553E980 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Thanks for the clarification, Mark.  Agree! = more fuel=20 passing through will likely mean cooler fuel and less chance of vapor=20 lock
 
Ed

From: Mark Steitle
Sent: Saturday, August 13, 2011 8:41 AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: vapor lock

Ed, =20

My fuel system includes a bypass circuit (see picture).  But = it wasn't=20 done to resolve or prevent vapor lock due to heat.  It was = installed to=20 prevent vapor locking due to running a tank dry.  These are two = different=20 scenarios.  However, the bypass circuit may help with resolving a = vapor=20 lock due to heat by allowing a bit more fuel to pass through the fuel = rail and=20 return it to the tank, taking heat with it.  But that wasn't its = original=20 purpose.  

The orifice size is approx .020" and serves as a bypass around the = pressure=20 regulator.

Mark


On Sat, Aug 13, 2011 at 6:20 AM, Ed Anderson = <eanderson@carolina.rr.com&g= t;=20 wrote:
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
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
Sent: Saturday, August 13, 2011 2:53 AM
To: Rotary = motors in=20 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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Homepage:  http://www.flyrotary.com/
Archive and=20 UnSub:  =20 http://mail.lancaironline.net:81/lists/flyrotary/List.html
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