X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-fx0-f52.google.com ([209.85.161.52] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with ESMTPS id 5091016 for flyrotary@lancaironline.net; Sat, 13 Aug 2011 09:13:24 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.161.52; envelope-from=msteitle@gmail.com Received: by fxd18 with SMTP id 18so2745922fxd.25 for ; Sat, 13 Aug 2011 06:12:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=idMr1/CS2CsDNw63gfKWqrJ2AFOK6yzSq76cI4pUxps=; b=v1aK0/1p3b9g6C6bWIyV7ZX178DL6SKXnfSb3LRwbQdYBOxN4DZQzSdctjyhtj6G0X nU/vIuwDZIXuYoMhhIJ0ArJa28fWeS0FijKrwjP4CGb1/J/KgKzu7mxb2ZfqfLBxNDqg iDYrNhfziafnMrT275TX2NpO/hYe3/zSd2GCU= MIME-Version: 1.0 Received: by 10.223.98.83 with SMTP id p19mr2798916fan.2.1313241168074; Sat, 13 Aug 2011 06:12:48 -0700 (PDT) Received: by 10.223.74.129 with HTTP; Sat, 13 Aug 2011 06:12:48 -0700 (PDT) In-Reply-To: References: Date: Sat, 13 Aug 2011 08:12:48 -0500 Message-ID: Subject: Re: [FlyRotary] Re: vapor lock From: Mark Steitle To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=0015174bef4653d99404aa62c938 --0015174bef4653d99404aa62c938 Content-Type: text/plain; charset=ISO-8859-1 Charlie, Good points. I mounted my pumps on the floor as low as I could get them, just downstream of the Andair valve. With the dihedral built into my wings, they are below the fuel level. I've never had any problems with vapor lock, and I fly in some pretty hot air. I like the idea of mounting the pumps in the tanks, except for the maintenance issues it creates. Mark On Sat, Aug 13, 2011 at 8:06 AM, Charlie England wrote: > ** > 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? > > > > --0015174bef4653d99404aa62c938 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Charlie,=A0

Good points. =A0I mounted my pumps on the fl= oor as low as I could get them, just downstream of the Andair valve. =A0Wit= h the dihedral built into my wings, they are below the fuel level. =A0I'= ;ve never had any problems with vapor lock, and I fly in some pretty hot ai= r. =A0I like the idea of mounting the pumps in the tanks, except for the ma= intenance issues it creates.

Mark

On Sat, Aug 13, = 2011 at 8:06 AM, Charlie England <ceengland@bellsouth.net> wrote:
=20 =20 =20
The really frustrating thing about all this is that every installation is different (not to mention that it's only speculatio= n 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 powe= r loss....

Charlie

=A0
On 08/13/2011 06:20 AM, Ed Anderson wrote:
=20 =20 =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.
=A0
Ed

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

Ok, Finn, =A0that was my guess as well.=A0<= /font>
=A0
=A0That 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.=A0 In any case, insufficient fuel is injected into the engine.
=A0
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)=A0- 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.=A0
=A0
So I am puzzled why a gas vent on the high pressure side would have much (if any) effect on vapor lock.=A0 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.=A0 So as I said -I'm= a bit puzzled as to the mechanism that a vent in the high pressure side prevents vapor lock.
=A0
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=A0 a boost pump.
=A0
FWIW
=A0
Ed
=A0

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:
=A0
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.=A0 I search the archive but could not find a description of this method - anyone care to provide one?



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