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 5113661 for flyrotary@lancaironline.net; Sun, 04 Sep 2011 18:57:03 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.161.52; envelope-from=msteitle@gmail.com Received: by fxd18 with SMTP id 18so2814684fxd.25 for ; Sun, 04 Sep 2011 15:56:26 -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=Mp0dyHG02ihNTfxOFZl3UdU5z45XykzgNR2ilDtyRzo=; b=buPKzMo4HPIW09OaEiGiUCBhqIR3CfUjG2HxJGK/cEHFEkCBPhT/tgg8Ps3PbZULdF GJNTvESE9EA6D0dpIZeWa7ZejPqAdJtsgdgW8cfvOYZS+2dTH1DjR0Bbwh/sNjoLEsFV gggCrzpsvymTCAmZGtdEWP543Rw5tr22iXK/w= MIME-Version: 1.0 Received: by 10.223.48.208 with SMTP id s16mr1829500faf.75.1315176984935; Sun, 04 Sep 2011 15:56:24 -0700 (PDT) Received: by 10.223.101.133 with HTTP; Sun, 4 Sep 2011 15:56:24 -0700 (PDT) In-Reply-To: References: Date: Sun, 4 Sep 2011 17:56:24 -0500 Message-ID: Subject: Re: [FlyRotary] Re: vapor lock From: Mark Steitle To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=00151747c34400fe9e04ac258189 --00151747c34400fe9e04ac258189 Content-Type: text/plain; charset=ISO-8859-1 Take a look at the Holley HP series pumps. They look to be about the same length as the Walbro, but the inlet and outlet come in the sides instead of the ends, effectively making the install more compact. Also, they are a gerotor type pump, so should be quieter and more robust. They're also twice the price of the Walbro. http://www.summitracing.com/parts/HLY-12-125/ Mark S. On Sun, Sep 4, 2011 at 3:46 PM, wrote: > ** > We currently have a pair of new Walbro GSL393 EFI pumps, is there something > comparable that is not so long? > > Chrissi & Randi > www.CozyGirrrl.com > CG Products, Custom Aircraft Hardware > Chairwomen, Sun-N-Fun Engine Workshop > > In a message dated 9/4/2011 2:26:53 P.M. Central Daylight Time, > ceengland@bellsouth.net writes: > > On a low wing plane (at least the RV's), it will usually be impossible to > gravity-feed all fuel to a sump tank, since the lowest point on the a/c will > likely be only an inch or so below the low point in the tank. (I never said > 'pump to a pump'; was that a typo?) While Ed A's vacuum-fed sump is > obviously successful, I can't get comfortable with using that technique > unless I exactly duplicate everything in his system. My personal preference > is to keep as much of the fuel system as possible out of the engine > compartment, to minimize heating of the fuel until it will actually be going > through the injectors. > > I think you make my point on life risk vs design decisions. Life risk > should obviously carry more weight, but if it's the only criteria, we'd find > a way to never leave home. Van could have found a way to pull fuel directly > from the bottom skin of his tanks, and feed it directly to the carb with the > lines & shutoff valve hanging under the fuselage, and there might be a > slight reduction in 'life risk'. But the system he chose has had zero > problems in unmodified installations, meaning to me that the choice to keep > the design cleaner was justifiable. Furthermore, difficulty in maintenance > can actually *drive up* life risk. I consider it safer to make everything > except a single mechanical joint (fuel pickup to bulkhead fitting) the only > thing that I can't conveniently inspect. > > I tried to keep my primary fuel delivery path to the pump(s) as close as > possible to the 'stock' configuration from the designer. At least in my > feeble mind, this is the best I can do to minimize life risk, since it's > been successful in at least 7,000 flying a/c. > > Are we closer to being on the same page? > > Charlie > > > On 09/04/2011 11:34 AM, Al Wick wrote: > > Charlie wrote: > you're willing to risk pumping fuel overboard > > Yeah. It seems so. It's a bit strange to think someone MUST pump to the > pump. I'd be quick to question that assumption. > > < removing several dozen screws, the vent line and fuel line, and then > removing the tank before I could remove the 6 or 8 screws that access plate to the tank > > So, once every twenty years you might have to access the pump. And the > number of screws is your reason to have higher risk fuel design? I try my > best not to let anything get in the way of improving safety. That's why I > changed my fuel design even though I'd never had a problem. I want that > extra safety margin from sump tank with two wet pumps, self cleaning filter. > It's real. It's significant. > > *every* decision makes that choice > > Of course not. I'd never agree with a sweeping assumption like that. Life > risk SHOULD always carry more weight in a decision. > > -al wick > > > ----- Original Message ----- > > *From:* Charlie England > *To:* Rotary motors in aircraft > *Sent:* Friday, September 02, 2011 12:21 PM > *Subject:* [FlyRotary] Re: vapor lock > > I'd have to differ on a couple of points. > > If you must pump to the sump, then the vent can't 'go anywhere' unless > you're willing to risk pumping fuel overboard. > > On a typical RV, it would require removing several dozen screws, the vent > line and fuel line, and then removing the tank before I could remove the 6 > or 8 screws that hold on the access plate to the tank. So, there is a bit of > a maintenance issue for us. If not for that, I'd use in-tank pumps. For my > application, the external sump would add more weight/complexity. > > To the implication that we would choose maintenance ease vs life risk: you > have to be honest; *every* decision makes that choice. The safest G/a > factory plane in the world uses bolt-on wings instead of a one-piece wing; a > one-piece would be both lighter and safer. > > Charlie > > > > On 09/02/2011 01:04 PM, Al Wick wrote: > > What fine work Steve. I love it when someone converts theory to facts. You > measured that all at sea level. Now just subtract 5.35 from all your > pressure numbers if you fly at 12k ft. You've now measured all of the > variables that affect vapor lock. Only remaining item is measuring pressure > at your pump inlet. You then can predict exactly how safe your plane is > without ever flying! How cool is that? > > I use a submerged fuel pump for added safety. Two actually. Easy to > maintain, just remove the 6 screws that hold the pumps in place. So there is > zero significance to the argument of maintenance. Can't imagine how anyone > could claim maintenance is more important than life risk anyway. I return > all fuel to my 3 gallon sump. Vent can go anywhere, you don't have to tie > vent into main fuel vents. > > Once again, nice work Steve. > > -al wick > > > > ----- Original Message ----- > *From:* Steven W. Boese > *To:* Rotary motors in aircraft > *Sent:* Friday, September 02, 2011 12:04 AM > *Subject:* [FlyRotary] vapor lock > > For those concerned about the formation of vapor in a pressurized fuel > rail, I've attached a plot of data collected from local samples of 100 LL > avgas, 87 octane auto fuel with no ethanol, 91 octane auto fuel with 10% > ethanol, and tap water. The water was measured just as a check on the > method. > > > > The data would be considered more of a true vapor pressure rather than > a Reid vapor pressure due to the method used. > > > > The data indicates to me that if the fuel pressure in the fuel rail is 35 > psi as measured with a regular gauge referenced to the atmosphere at sea > level, the temperature of 100 LL or 91 octane 10% ethanol in the rail would > have to be in the neighborhood of 240 deg F for it to form bubbles of vapor > (boil). The sample of 87 octane would require a temperature of about 215 > deg F to form a vapor phase. > > > > My take on this is it may be more productive to be concerned about the fuel > supply to the high pressure pumps rather than worrying about "vapor > lock" downstream of those pumps. This seems to be the conclusion reached by > the recent thread on this subject, possibly now supported by actual data. > Of course the data only applies to the samples I obtained. > > > > The higher temperature tolerance of the auto fuel with ethanol compared to > the auto fuel without ethanol was surprising to me. > > > > But I only collect data --- it is up to an engineer to make sense of it ;>) > > > Steve Boese > RV6A, 1986 13B NA, RD1A, EC2 > ------------------------------ > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: > http://mail.lancaironline.net:81/lists/flyrotary/List.html > > > > --00151747c34400fe9e04ac258189 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Take a look at the Holley HP series pumps. =A0They look to be about the sam= e length as the Walbro, but the inlet and outlet come in the sides instead = of the ends, effectively making the install more compact. =A0Also, they are= a gerotor type pump, so should be quieter and more robust. =A0They're = also twice the price of the Walbro. =A0


Ma= rk S.

On Sun, Sep 4, 2011 at 3:46 PM, <CozyGirrrl@aol.co= m> wrote:
We currently have a pair of new Walbro GSL393 EFI pumps, is there some= thing=20 comparable that is not so long?
=A0
Chrissi &=20 Randi
www.CozyG= irrrl.com
CG=20 Products, Custom Aircraft Hardware
Chairwomen, Sun-N-Fun Engine Workshop=
=A0
In a message dated 9/4/2011 2:26:53 P.M. Central Daylight Time,=20 ceengland@bell= south.net writes:
On a low=20 wing plane (at least the RV's), it will usually be impossible to grav= ity-feed=20 all fuel to a sump tank, since the lowest point on the a/c will likely be= only=20 an inch or so below the low point in the tank. (I never said 'pump to= a pump';=20 was that a typo?) While Ed A's vacuum-fed sump is obviously successfu= l, I=20 can't get comfortable with using that technique unless I exactly dupl= icate=20 everything in his system. My personal preference is to keep as much of th= e=20 fuel system as possible out of the engine compartment, to minimize heatin= g of=20 the fuel until it will actually be going through the injectors.

I = think=20 you make my point on life risk vs design decisions. Life risk should obvi= ously=20 carry more weight, but if it's the only criteria, we'd find a way= to never=20 leave home. Van could have found a way to pull fuel directly from the bot= tom=20 skin of his tanks, and feed it directly to the carb with the lines &= =20 shutoff valve hanging under the fuselage, and there might be a slight=20 reduction in 'life risk'. But the system he chose has had zero pr= oblems in=20 unmodified installations, meaning to me that the choice to keep the desig= n=20 cleaner was justifiable. Furthermore, difficulty in maintenance can actua= lly=20 *drive up* life risk. I consider it safer to make everything except a sin= gle=20 mechanical joint (fuel pickup to bulkhead fitting) the only thing that I = can't=20 conveniently inspect.

I tried to keep my primary fuel delivery pat= h to=20 the pump(s) as close as possible to the 'stock' configuration fro= m the=20 designer. At least in my feeble mind, this is the best I can do to minimi= ze=20 life risk, since it's been successful in at least 7,000 flying a/c.
Are=20 we closer to being on the same page?

Charlie


On 09/04/2= 011=20 11:34 AM, Al Wick wrote:=20
=20
Charlie wrote:
<If you must pump to the sump, then the vent can't 'go = anywhere'=20 unless you're willing to risk pumping fuel overboard
=A0
Yeah. It seems so. It's a bit strange to think someone=A0MUST = pump=20 to the pump. I'd be quick to question that assumption.
=A0
<=A0removing several dozen screws, the vent line and fuel line,= =20 and then removing the tank before I could remove the 6 or 8 screws that= =20 <hold on the access plate to the tank
=A0
So, once every twenty years you mi= ght have to=20 access the pump. And the number of screws is your=A0reason to have high= er=20 risk fuel design?=A0I try my best not to let anything get in the way of= =20 improving safety. That's why I changed my fuel design even though I= 'd never=20 had a problem. I want that extra safety margin from sump tank with two = wet=20 pumps, self cleaning filter. It's real. It's significant.
=A0
<we would choose maintenance ease vs life risk: you have to be= =20 honest; *every* decision makes that choice
=A0
Of course not. I'd never agree= with a sweeping=20 assumption like that. Life risk=A0SHOULD always carry more weight in a= =20 decision.
=A0
-al wick
=A0
=A0
----- Original Message -----
Sent: Friday, September 02, 201= 1=20 12:21 PM
Subject: [FlyRotary] Re: vapor= =20 lock

I'd have to differ on a couple of points.

I= f you=20 must pump to the sump, then the vent can't 'go anywhere' = unless you're=20 willing to risk pumping fuel overboard.

On a typical RV, it wo= uld=20 require removing several dozen screws, the vent line and fuel line, a= nd=20 then removing the tank before I could remove the 6 or 8 screws that h= old=20 on the access plate to the tank. So, there is a bit of a maintenance = issue=20 for us. If not for that, I'd use in-tank pumps. For my applicatio= n, the=20 external sump would add more weight/complexity.

To the implica= tion=20 that we would choose maintenance ease vs life risk: you have to be ho= nest;=20 *every* decision makes that choice. The safest G/a factory plane in t= he=20 world uses bolt-on wings instead of a one-piece wing; a one-piece wou= ld be=20 both lighter and safer.

Charlie



On 09/02/2011 0= 1:04=20 PM, Al Wick wrote:=20
=20 =20
What fine work Steve. I love i= t when=20 someone converts theory to facts. You measured that all at sea leve= l.=20 Now just subtract 5.35 from all your pressure numbers if you fly at= 12k=20 ft. You've now measured all of the variables that affect vapor = lock.=20 Only remaining item is measuring pressure at your pump inlet. You t= hen=20 can predict exactly how safe your plane is without ever flying! How= cool=20 is that?
=A0
I use a submerged fuel pump fo= r added=20 safety. Two actually. Easy to maintain, just remove the 6 screws th= at=20 hold the pumps in place. So there is zero significance to the argum= ent=20 of maintenance. Can't imagine how anyone could claim maintenanc= e is more=20 important than life risk anyway. I return all fuel to my 3 gallon s= ump.=20 Vent can go anywhere, you don't have to tie vent into main fuel= vents.=20
=A0
Once again, nice work Steve. <= /font>
=A0
-al wick
=A0
=A0
----- Original Message -----
Sent: Friday, September 02,= 2011=20 12:04 AM
Subject: [FlyRotary] vapor= =20 lock

For those concerned about the formation of va= por in a=20 pressurized fuel rail, I've attached a plot of data collected= from=20 local samples of 100 LL avgas, 87 octane auto fuel with no ethano= l, 91=20 octane auto fuel with 10% ethanol, and tap water.=A0 The water wa= s=20 measured just as a check on the method.

=A0

The data would be considered more of a true v= apor=20 pressure rather than a=A0Reid vapor pressure due to the method=20 used.

=A0

The data indicates to me that if the fuel pre= ssure in=20 the fuel rail is 35 psi as measured with a regular gauge referenc= ed to=20 the atmosphere at sea level, the temperature of=A0100 LL or 91=20 octane 10% ethanol=A0in the rail would have to be in the=20 neighborhood of 240 deg F for it to=A0form bubbles of vapor=20 (boil).=A0 The sample of 87 octane would require=A0a temperature= =20 of about 215 deg F to form a vapor phase.

=A0

My take on this is it may be more productive = to be=20 concerned about the fuel supply to the high pressure pumps rather= than=20 worrying about=A0"vapor lock"=A0downstream of those pum= ps.=A0=20 This seems to be the conclusion reached by the recent thread on t= his=20 subject, possibly now supported by actual data.=A0 Of course the= =20 data only applies to the samples I obtained.

=A0

The higher temperature tolerance of the auto = fuel with=20 ethanol compared to the auto fuel without ethanol was surprising = to=20 me.

=A0

But I only collect data --- it is up to an en= gineer to=20 make sense of it ;>)

=A0

Steve Boese
RV6A, 1986 13B NA, RD1A,=20 EC2
--
Homepage:=A0 http://www.flyrotary.com/=
Archive and=20 UnSub:=A0=A0 http://mail.lancaironline.net:81/lists/flyro= tary/List.html



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