Return-Path: Received: from [65.54.168.110] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.3c1) with ESMTP id 742457 for flyrotary@lancaironline.net; Thu, 17 Feb 2005 00:59:45 -0500 Received-SPF: pass receiver=logan.com; client-ip=65.54.168.110; envelope-from=lors01@msn.com Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Wed, 16 Feb 2005 21:59:00 -0800 Message-ID: Received: from 4.171.174.137 by BAY3-DAV6.phx.gbl with DAV; Thu, 17 Feb 2005 05:58:15 +0000 X-Originating-IP: [4.171.174.137] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Vapor Lock Date: Thu, 17 Feb 2005 00:58:13 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00B9_01C5148B.C1ADCE10" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MimeOLE: Produced By MSN MimeOLE V9.10.0011.1703 Seal-Send-Time: Thu, 17 Feb 2005 00:58:13 -0500 X-OriginalArrivalTime: 17 Feb 2005 05:59:00.0247 (UTC) FILETIME=[C6899A70:01C514B5] This is a multi-part message in MIME format. ------=_NextPart_000_00B9_01C5148B.C1ADCE10 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable The Facet pump in this position is a two edged sword. It can help = eliminate a vapor lock when on but it is a restriction that can create a = vapor lock when off. A properly laid out fuel system should not = require another pump to prime the main EFI pump. It is a bandaid IMO. = Again, any restriction other than a strainer to stop the 'big chunks' = before the EFI pumps is not a good thing. Tracy Without a Facet pump between the tank and the HP and you have a vapor = lock at the HP pump you will have no flow. With the Facet at the tank = it will prime the HP pump by pushing liquid fuel into the HP pump. = Once the vapor lock is gone, the HP can suck through the Facet even when = it is running. How much flow is really coming out of an HP pump with a = normal FI system with a return to the tank. I doubt is it 30 + gph. I = guess I's saying the HP pump will be operating at much less than its = max. rated capacity and the system with the Facet between the tank and = the HP pump should work fine. I'm considering this system for my RV 7A. Dennis H. Jim Sower wrote:=20 <... HP pumps are capable of moving LOTS more fuel than a Facet pump = .. HP pumps would be drawing fuel through the Facet pump ... because = the Facet can't keep up ...>=20 You're right. I hadn't thought of that. Facet pumps deliver 30 = gph. I'll check how much my HP pumps are putting out. Wonder if Facet = delivers more at lower head pressure, objective being to push fuel = through filter and plumbing so there's less chance of pressure drop that = could cause the fuel to vaporize.=20 Back to the drawing board ... maybe ... Jim S.=20 Marvin Kaye wrote:=20 Jim Sower = wrote:=20 """=20 I have a canard, but I will have a Facet pump near (and below) = the wing tanks=20 to PUSH the fuel through the filter and fuel flow transducer. I = don't want=20 the HP pumps to SUCK through the filters and etc. for fear of = vaporizing the=20 fuel.=20 """=20 This doesn't make any sense to me, but perhaps I'm missing = something. The HP pumps are capable of moving LOTS more fuel than a = Facet pump. Consequently, it seems to me that the HP pumps would = actually be drawing fuel through the Facet pump when they're switched = on, simply because the Facet can't keep up with what's being drawn out = of the sump tank by them. Additionally, a return system needs 2 flow = transducers, one for the feed line and one for the return... then the = display instrument's electronics deduct the return flow from the feed = flow to properly calculate actual through-the-injectors instantaneous = flow data. (The EI fuel flow instrument uses an FFDM-1 (fuel flow = differential module) to do the job, GRT EIS does it itself, as do other = flow instruments with both feed and return inputs.)=20 As long as the filters are rated to flow as much fuel as the HP = pumps are capable of pushing I don't see that (vapoization) as an issue. = The filter elements do need to be kept clean, and are a = replace-at-annual item.=20 =20 Homepage: = http://www.flyrotary.com/=20 Archive: = http://lancaironline.net/lists/flyrotary/List.html=20 Homepage: http://www.flyrotary.com/ = Archive: = http://lancaironline.net/lists/flyrotary/List.html=20 ------=_NextPart_000_00B9_01C5148B.C1ADCE10 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
The Facet pump in this position is a two edged sword.  It can = help=20 eliminate a vapor lock when on but it is a restriction that can create a = vapor=20 lock when off.   A properly laid out fuel system should not = require=20 another pump to prime the main EFI pump.  It is a bandaid = IMO.  Again,=20 any restriction other than a strainer to stop the 'big chunks' before = the EFI=20 pumps is not a good thing.
 
Tracy
Without=20 a Facet pump between the tank and the HP and you have a vapor lock = at the=20 HP pump you will have no flow.  With the Facet at the tank it = will=20 prime the HP pump by pushing  liquid fuel into the HP pump.  = Once=20 the vapor lock is gone, the HP can suck through the Facet even when it = is=20 running.  How much flow is really coming out of an HP pump with a = normal=20 FI system with a return to the tank.  I doubt is it 30 + = gph.  I=20 guess I's saying the HP pump will be operating at much less than its = max.=20 rated capacity and the system with the Facet between the tank and the = HP pump=20 should work fine.  I'm considering this system for my RV=20 7A.

Dennis H.

Jim Sower wrote:=20
<... HP = pumps are=20 capable of moving LOTS more fuel than a Facet pump ... HP pumps = would be=20 drawing fuel through the Facet pump ... because the Facet can't keep = up=20 ...>

You're right.  I hadn't thought of that.  = Facet=20 pumps deliver 30 gph.  I'll check how much my HP pumps are = putting=20 out.  Wonder if Facet delivers more at lower head pressure, = objective=20 being to push fuel through filter and plumbing so there's less = chance of=20 pressure drop that could cause the fuel to vaporize.

Back to = the=20 drawing board ... maybe ... Jim S.

Marvin Kaye wrote: =

Jim Sower <canarder@frontiernet.net>= =20 wrote:

"""
 I have a canard, but I will have a = Facet pump=20 near (and below) the wing tanks
to PUSH the fuel through the = filter=20 and fuel flow transducer.  I don't want
the HP pumps to = SUCK=20 through the filters and etc. for fear of vaporizing the
fuel. =
"""=20

This doesn't make any sense to me, but perhaps I'm missing = something.  The HP pumps are capable of moving LOTS more fuel = than a=20 Facet pump.  Consequently, it seems to me that the HP pumps = would=20 actually be drawing fuel through the Facet pump when they're = switched on,=20 simply because the Facet can't keep up with what's being drawn out = of the=20 sump tank by them.  Additionally, a return system needs 2 = flow=20 transducers, one for the feed line and one for the return... then = the=20 display instrument's electronics deduct the return flow from the = feed flow=20 to properly calculate actual through-the-injectors instantaneous = flow=20 data.  (The EI fuel flow instrument uses an FFDM-1 (fuel flow = differential module) to do the job, GRT EIS does it itself, as do = other=20 flow instruments with both feed and return inputs.)

As = long as the=20 filters are rated to flow as much fuel as the HP pumps are capable = of=20 pushing I don't see that (vapoization) as an issue.  The = filter=20 elements do need to be kept clean, and are a replace-at-annual = item.=20

   <Marv>

 Homepage:  http://www.flyrotary.com/=20
 Archive:   http://lancai= ronline.net/lists/flyrotary/List.html=20




 Homepage:  http://www.flyrotary.com/ =
 Archive:   http://lancai= ronline.net/lists/flyrotary/List.html=20 =

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