X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from nm14.access.bullet.mail.mud.yahoo.com ([66.94.237.215] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with SMTP id 5091013 for flyrotary@lancaironline.net; Sat, 13 Aug 2011 09:06:54 -0400 Received-SPF: none receiver=logan.com; client-ip=66.94.237.215; envelope-from=ceengland@bellsouth.net Received: from [66.94.237.126] by nm14.access.bullet.mail.mud.yahoo.com with NNFMP; 13 Aug 2011 13:06:19 -0000 Received: from [66.94.237.118] by tm1.access.bullet.mail.mud.yahoo.com with NNFMP; 13 Aug 2011 13:06:19 -0000 Received: from [127.0.0.1] by omp1023.access.mail.mud.yahoo.com with NNFMP; 13 Aug 2011 13:06:19 -0000 X-Yahoo-Newman-Id: 466051.30946.bm@omp1023.access.mail.mud.yahoo.com Received: (qmail 8930 invoked from network); 13 Aug 2011 13:06:19 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bellsouth.net; s=s1024; t=1313240779; bh=NN9D3Ay/aO7DSnkz/R8Qtb7PAKoma31Qy9JC0Rhcnrs=; h=X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:Date:From:User-Agent:MIME-Version:To:Subject:References:In-Reply-To:Content-Type; b=v480Uc2ZIR3v33tC31PgGlU54dxEx7C3LcUG0MZjz4zypExsMLpoSANl/4QFsg+qRlLHR+tYbGLa546niQJK3D8e1+PhRKuJE7LYkLD2KuyaZp+h324ngCStD5ZdOoosu411WtrQ8aZ7GQNByLmGPwuNQXfXS+MmUQXqcYY+JE4= X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: d_8cSfIVM1lW17bu4ZonJv_d1ixafaRomT3yTeASnaGwN79 d4KCev6AHVERuSwMsI.VisLTmkVwEKHhOFu7fp_cGK98HUhwjngVAvN7ibOj vPyEaExkDiO91IcyEua0.rL1wfQYsBgvQBf39krhJUsyrvNO0iuLC7HQ.nAg YDDKOs6ATWrUvz3891AqPMntRJt0cqh2pyqNS9Iz0Wr.viwkBrmKfdYJuTzF KqebJPkaMQiwIkJHVeibBwCQujKjMFKzs01a7ov9oNgSVdKfbLL_qWe_aMs4 Tdkw5mKD.TGRSJ6XlSfoaypvcXKLVF4zEoWjHtdjF9bpi.oyGpLe2OdNCScn wjPqsM9txQcsQd39L3EvsEdFsTAMGtspvMLitkYTOnZ4octKoPtN8vVAhjoH oBfgSEmXpUNUrttuW6smSxu1Y1F8TnuQ818U- X-Yahoo-SMTP: uXJ_6LOswBCr8InijhYErvjWlJuRkoKPGNeiuu7PA.5wcGoy Received: from [192.168.10.8] (ceengland@98.95.239.168 with plain) by smtp103.sbc.mail.ne1.yahoo.com with SMTP; 13 Aug 2011 06:06:18 -0700 PDT Message-ID: <4E4676C9.3020906@bellsouth.net> Date: Sat, 13 Aug 2011 08:06:17 -0500 From: Charlie England User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.18) Gecko/20110617 Thunderbird/3.1.11 MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: vapor lock References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------090009030401070806000907" This is a multi-part message in MIME format. --------------090009030401070806000907 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit 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 On 08/13/2011 06:20 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 > *Sent:* Saturday, August 13, 2011 6:47 AM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Re: vapor lock > > Ok, Finn, that was my guess as well. > 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. > 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 > *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 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: >> 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? > --------------090009030401070806000907 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit 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
 
On 08/13/2011 06:20 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

Sent: Saturday, August 13, 2011 6:47 AM
Subject: [FlyRotary] Re: vapor lock

Ok, Finn,  that was my guess as well. 
 
 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. 
 
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
 

Sent: Saturday, August 13, 2011 2:53 AM
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:
 
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?


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