X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-iy0-f176.google.com ([209.85.210.176] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with ESMTPS id 5091124 for flyrotary@lancaironline.net; Sat, 13 Aug 2011 14:01:14 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.210.176; envelope-from=fluffysheap@gmail.com Received: by iyn35 with SMTP id 35so4292738iyn.7 for ; Sat, 13 Aug 2011 11:00:39 -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=INYfup/4K7KfWMtUOET+2bR+/O33D079aZILzGyUZvk=; b=na/bOagV/bxTraVAXuYsaWvnFzT9hOanDhKTjuv/a3TE3O9BfQ+xzHwQSCVbboueIQ MDSW+fK6zAIm9sgZmVt5dtPOhYaYFPZiKm3DpXv14Hmq0B4GXvApuZvRhbOw/XlRxSy4 NRaJiSFyq1NFqets+JDA5AmyI7WoRteJ10kpk= MIME-Version: 1.0 Received: by 10.231.68.16 with SMTP id t16mr1707014ibi.13.1313258439720; Sat, 13 Aug 2011 11:00:39 -0700 (PDT) Received: by 10.231.162.67 with HTTP; Sat, 13 Aug 2011 11:00:39 -0700 (PDT) In-Reply-To: References: Date: Sat, 13 Aug 2011 12:00:39 -0600 Message-ID: Subject: Re: [FlyRotary] Re: vapor lock From: William Wilson To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=000e0cd3e812cc403904aa66ce4c --000e0cd3e812cc403904aa66ce4c Content-Type: text/plain; charset=ISO-8859-1 It is not really the high pressure of the pumps that makes a difference in modern cars, but the fact that the pumps are submersible in the tank. Even if there is negative pressure in the fuel tank the pump can still do its job because the pressure at the bottom of the tank where the pump inlet is is still positive because of the weight of the liquid fuel. I would not worry about running high pressure fuel through the plane unless there is a part that is not rated for the pressure. Modern cars all do this and none of them leak fuel. The pumps are not positive-displacement pumps and so once they build up their maximum pressure, that's all you get, even if you have the fuel selector turned off. You can easily check the system any time you like by by doing exactly that and sniffing around. If you really don't want high pressure fuel (or can't install a submersible pump) your best bet is to mount a low-pressure fuel pump as low and close to the tank as possible, and then have a header tank somewhere else with a high pressure submersible pump in it. This system can still vapor lock, depending on how far the first stage pump has to suck fuel. If the header tank is below the regular tank gravity will keep the fuel flowing to it even without the first-stage pump and this system will also be resistant to vapor lock (but you would need to make sure the gravity feed is able to supply enough fuel flow). Because of the extra risks and complexity of these types of systems I think the in-tank high pressure pump is the best way to go but it will still work. On Sat, Aug 13, 2011 at 8:22 AM, Kelly Troyer wrote: > Guys, > > I vote for keeping high pressure pumps as close to the tanks and as low > as possible to fuel level...............I would not locate pumps and/or > suppy > hoses firewall forward unless totally encapulated, insulated and cooled > by ram air...........And by all means use the bypass > oriface...........Besides > helping to reprime pumps (as Mark says) it will relieve pressure on leaky > injectors to prevent flooding (if you have experienced this with the 13B > you know what I mean and the Renesis is even worse to clear) and to > allow a vapor lock to clear the high pressure supply lines from pump to > the regulator............One more thing I would install the regulator after > the > fuel rails/injectors to allow any vapor to pass through the rails on their way > > to the bypass oriface...........I have seen some fuel > regulator installations > with the fuel rails "Dead Ended" after the regulator leaving vapor trapped > in the rail.................When flying vapor might clear with only an apparent > > misfire to the pilot but after shutdown and after heat soak it could cause > > "Hot Start" problems (has anyone tryed to hot-start an fuel injected > "Lyc" > lately............IMHO > > Kelly Troyer > *"DYKE DELTA JD2" (Eventually)* > "13B ROTARY"_ Engine > "RWS"_RD1C/EC2/EM2 > "MISTRAL"_Backplate/Oil Manifold > "TURBONETICS"_TO4E50 Turbo > > *From:* Ed Anderson > *To:* Rotary motors in aircraft > *Sent:* Saturday, August 13, 2011 8:16 AM > > *Subject:* [FlyRotary] Re: vapor lock > > 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 > *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 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? > > > > > > --000e0cd3e812cc403904aa66ce4c Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable It is not really the high pressure of the pumps that makes a difference in = modern cars, but the fact that the pumps are submersible in the tank.=A0 Ev= en if there is negative pressure in the fuel tank the pump can still do its= job because the pressure at the bottom of the tank where the pump inlet is= is still positive because of the weight of the liquid fuel.

I would not worry about running high pressure fuel through the plane un= less there is a part that is not rated for the pressure.=A0 Modern cars all= do this and none of them leak fuel.=A0 The pumps are not positive-displace= ment pumps and so once they build up their maximum pressure, that's all= you get, even if you have the fuel selector turned off.=A0 You can easily = check the system any time you like by by doing exactly that and sniffing ar= ound.

If you really don't want high pressure fuel (or can't install a= submersible pump) your best bet is to mount a low-pressure fuel pump as lo= w and close to the tank as possible, and then have a header tank somewhere = else with a high pressure submersible pump in it.=A0 This system can still = vapor lock, depending on how far the first stage pump has to suck fuel.=A0 = If the header tank is below the regular tank gravity will keep the fuel flo= wing to it even without the first-stage pump and this system will also be r= esistant to vapor lock (but you would need to make sure the gravity feed is= able to supply enough fuel flow).=A0 Because of the extra risks and comple= xity of these types of systems I think the in-tank high pressure pump is th= e best way to go but it will still work.

On Sat, Aug 13, 2011 at 8:22 AM, Kelly Troye= r <keltro@att.net> wrote:
Guys,
=A0
I vote for keeping high pressure pumps as close to the tanks and= as low
as possible to fuel level...............I would not locate pumps= and/or suppy
hoses=A0firewall forward unless totally encapulated= ,=A0insulated and cooled
by ram air...........And by all means use the bypass oriface....= .......Besides
helping to reprime pumps (as Mark says) it will relieve pressure= on leaky
injectors to prevent flooding (if you have experienced this with= the 13B
you know what I mean and the Renesis is even worse to clear) and= to
allow a vapor lock to clear the high pressure supply lines=A0fro= m=A0pump to
the regulator............One more thing I would install the regu= lator after the
fuel rails/injectors to allow any vapor to pass through the rail= s on their way
to the bypass oriface...........I have seen some fuel regulator= =A0installations
with the fuel rails "Dead Ended" after the regulator l= eaving vapor trapped
in the rail.................When flying vapor might clear with o= nly an apparent
misfire to the pilot but=A0after shutdown and after heat soak it= could cause
"Hot Start" problems (has anyone tryed to hot-start an= fuel=A0injected=A0 "Lyc"
lately............IMHO=A0
=A0
Kelly Troyer
"DYKE DELTA JD2" = (Eventually)
"13B ROTARY"_ Engine
"RWS"_RD1C/EC2/EM2
&quo= t;MISTRAL"_Backplate/Oil Manifold
"TURBONETICS"_TO4E50 Turbo

From: Ed Anderson <= eanderson@ca= rolina.rr.com>
To:= Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Saturday, August 13, 2= 011 8:16 AM

Subject: [FlyRotary] Re: vapor lock

No question, Charlie=A0-=A0the more of your fuel = line kept under EFI pump level pressures , the less chance for vapor lock.= =A0 In tank pumps certainly do that - but, as you point out there are other= considerations.=A0 Wing root sounds like a pretty good compromise in luie= =A0 of in-tank pumps.=A0 I considered that but in the end decided against i= t as it would have high pressure fuel lines inside my cockpit - which I per= sonally do not favor {:>)
=A0
Don't know for certain (and may never) the ca= use of the latest sputtering engine event - but, in absence of in-tank pump= s 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 un= ique installation)
=A0
Ed

Sent: Saturday, August 13, 2011 9:06 AM
Subject: [FlyRotary] Re: vapor lock

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

Sixties-era cars (carb, e= ngine mounted fuel pump) had vapor lock problems all the time in hot weathe= r. Modern cars, almost never (in-tank high pressure pump). Keeping the pump= s as low & as close to the tank(s) as practical would seem to be the be= st path. Van recommends mounting pumps on the floor in the cabin. That mean= s that the max lift would be maybe 3-4 inches, through a -6 line, and nowhe= re 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 s= eriously consider in-tank pumps, as others have done.

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

Charlie
=A0
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.
=A0
Ed

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

Ok, Finn, =A0that was my guess as well.=A0=
=A0
=A0That then brings up a question - my understand= ing of "vapor lock" is that it is caused by a low pressure area/c= ombined with hot fuel on the EFI pump intake which cause the gasoline to fl= ash to vapor - naturally the EFI pumps can not pump vapor - therefore as fu= el is injected from the high pressure side of the pump (reducing pressure o= n that side), vapor can form there as well.=A0 In any case, insufficient fu= el is injected into the engine.
=A0
Since the injectors are still clicking open, it w= ould seem that any vapor on that side of the pump already has a chance to v= acate the line (through the injector)=A0- so my assessment is that it is no= t the relief of vapor/gas from the high pressure side that remedies the pro= blem, 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 pressu= re side would have much (if any) effect on vapor lock.=A0 IF there is press= ure on the injector side - I question whether it would be as high as pump p= ressure - and even if it were, the injector opening would provide a path fo= r 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 pressur= e side prevents vapor lock.
=A0
In my opinion, there are two ways to reduce/elimi= nate 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.<= /font>
=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 k= now.

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





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