X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.122] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with ESMTP id 5090910 for flyrotary@lancaironline.net; Sat, 13 Aug 2011 06:48:59 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.122; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.1 cv=8mDY8c80ZOa76EOwICuS+E2YRQjxDgO9xqUnRMONc7w= c=1 sm=0 a=4GHctdUWtu8A:10 a=SC71y0a/4S6V9vjVxUojGA==:17 a=XXrHF1es7ruspy53DaQA:9 a=Zh-6P0jdIzf2SYhgUwsA:7 a=wPNLvfGTeEIA:10 a=o1OHuDzbAAAA:8 a=Ia-xEzejAAAA:8 a=4PR2P7QzAAAA:8 a=x9wWBtiLEDgo-I-Z_JkA:9 a=K0LtXLxoJH_yI2H6K5QA:7 a=ILCZio5HsAgA:10 a=EzXvWhQp4_cA:10 a=djSSOgbfo6cA:10 a=SC71y0a/4S6V9vjVxUojGA==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.175.135 Received: from [174.110.175.135] ([174.110.175.135:53395] helo=EdPC) by cdptpa-oedge03.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 5E/A9-00666-876564E4; Sat, 13 Aug 2011 10:48:24 +0000 Message-ID: <9CF1D84B009140E28A816663E5101153@EdPC> From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: vapor lock Date: Sat, 13 Aug 2011 06:47:05 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_002F_01CC5984.D04527D0" 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_002F_01CC5984.D04527D0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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_002F_01CC5984.D04527D0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Ok, Finn,  that was my guess as=20 well. 
 
 That then brings up a question - my = understanding of=20 "vapor lock" is that it is caused by a low pressure area/combined with = hot fuel=20 on the EFI pump intake which cause the gasoline to flash to vapor - = naturally=20 the EFI pumps can not pump vapor - therefore as fuel is injected from = the high=20 pressure side of the pump (reducing pressure on that side), vapor can = form there=20 as well.  In any case, insufficient fuel is injected into the=20 engine.
 
Since the injectors are still clicking open, it = would seem=20 that any vapor on that side of the pump already has a chance to vacate = the line=20 (through the injector) - so my assessment is that it is not the = relief of=20 vapor/gas from the high pressure side that remedies the problem, it's = removing=20 the gas from the low pressure side (pump inlet) and thereby permitting = liquid=20 fuel to be pumped that "cures" a vapor lock situation.  =
 
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 the=20 injector side - I question whether it would be as high as pump pressure = - and=20 even if it were, the injector opening would provide a path for it to be = release=20 - not to mention the pressure regulator.  So as I said -I'm a bit = puzzled=20 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=20 vapor in the low pressure side - either cool the fuel sufficiently = (somewhat=20 difficult to do) or to increase the pressure in the low pressure line = forcing=20 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 = aircraft
Subject: [FlyRotary] Re: vapor lock

Hi Ed,

I believe it's simply a return to the tank = from the=20 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 = using. =20 I search the archive but could not find a description of this method - = anyone=20 care to provide one?

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