X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imr-ma03.mx.aol.com ([64.12.206.41] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with ESMTP id 5113628 for flyrotary@lancaironline.net; Sun, 04 Sep 2011 16:46:54 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.206.41; envelope-from=CozyGirrrl@aol.com Received: from mtaomg-db01.r1000.mx.aol.com (mtaomg-db01.r1000.mx.aol.com [172.29.51.199]) by imr-ma03.mx.aol.com (8.14.1/8.14.1) with ESMTP id p84KkEab029929 for ; Sun, 4 Sep 2011 16:46:14 -0400 Received: from core-dsd001c.r1000.mail.aol.com (core-dsd001.r1000.mail.aol.com [172.29.253.129]) by mtaomg-db01.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 6414FE000085 for ; Sun, 4 Sep 2011 16:46:14 -0400 (EDT) From: CozyGirrrl@aol.com Message-ID: <66c46.4bad28ae.3b953d96@aol.com> Date: Sun, 4 Sep 2011 16:46:14 -0400 (EDT) Subject: Re: [FlyRotary] Re: vapor lock To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_66c46.4bad28ae.3b953d96_boundary" X-Mailer: AOL 9.6 sub 5004 X-Originating-IP: [69.154.218.212] x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:456130304:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d33c74e63e39647a1 --part1_66c46.4bad28ae.3b953d96_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit 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_ (http://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: ) Steve Boese RV6A, 1986 13B NA, RD1A, EC2 ____________________________________ -- Homepage: _http://www.flyrotary.com/_ (http://www.flyrotary.com/) Archive and UnSub: _http://mail.lancaironline.net:81/lists/flyrotary/List.html_ (http://mail.lancaironline.net:81/lists/flyrotary/List.html) --part1_66c46.4bad28ae.3b953d96_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
We currently have a pair of new Walbro GSL393 EFI pumps, is there some= thing=20 comparable that is not so long?
 
Chrissi &=20 Randi
www.CozyGirrrl.com
C= G=20 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,=20 ceengland@bellsouth.net writes:
= On a low=20 wing plane (at least the RV's), it will usually be impossible to gravity-= 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 p= ump';=20 was that a typo?) While Ed A's vacuum-fed sump is obviously successful, I= =20 can't get comfortable with using that technique unless I exactly duplicat= e=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 neve= r=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 problems i= n=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 from 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
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
 
Yeah. It seems so. It's a bit strange to think someone MUST p= ump=20 to the pump. I'd be quick to question that assumption.
 
< removing several dozen screws, the vent line and fuel li= ne,=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
 
So, once every twenty years you might = have to=20 access the pump. And the number of screws is your reason to have h= igher=20 risk fuel design? I 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 n= ever=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.
 
<we would choose maintenance ease vs life risk: you have to be= =20 honest; *every* decision makes that choice
 
Of course not. I'd never agree with a = sweeping=20 assumption like that. Life risk SHOULD always carry more weight in= a=20 decision.
 
-al wick
 
 
----- Original Message -----
To: = Rotary=20 motors in aircraft
Sent: Friday, September 02, 20= 11=20 12:21 PM
Subject: [FlyRotary] Re: vapor= =20 lock

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

If yo= u=20 must pump to the sump, then the vent can't 'go anywhere' unless you'r= e=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 application, t= he=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
What fine work Steve. I love it wh= en=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?
 
I use a submerged fuel pump for ad= ded=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 maintenance 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 ven= ts.=20
 
Once again, nice work Steve.
 
-al wick
 
 
----- Original Message ----- From:= Steven W. Boese
To: Rotary motors in aircraft
Sent: Friday, September 02= , 2011=20 12:04 AM
Subject: [FlyRotary] vapor= =20 lock

For those concerned about the formation of vapo= r in a=20 pressurized fuel rail, I've attached a plot of data collected fro= m=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.  The water= was=20 measured just as a check on the method.

 

The data would be considered more of a true vap= or=20 pressure rather than a Reid vapor pressure due to the method= =20 used.

 

The data indicates to me that if the fuel press= ure 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 100 LL or 91= =20 octane 10% ethanol in the rail would have to be in the=20 neighborhood of 240 deg F for it to form bubbles of vapor=20 (boil).  The sample of 87 octane would require a temper= ature=20 of about 215 deg F to form a vapor phase.

 

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 "vapor lock" downstream of those pumps.&= nbsp;=20 This seems to be the conclusion reached by the recent thread on t= his=20 subject, possibly now supported by actual data.  Of course t= he=20 data only applies to the samples I obtained.

 

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

 

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

 

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


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