Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2.8) with ESMTP id 617397 for flyrotary@lancaironline.net; Sat, 22 Jan 2005 11:07:21 -0500 Received-SPF: none receiver=logan.com; client-ip=24.25.9.100; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-185-127.carolina.rr.com [24.74.185.127]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j0MG6mKk025544 for ; Sat, 22 Jan 2005 11:06:49 -0500 (EST) Message-ID: <001201c5009c$ae451bb0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Manifold-Reference Fuel Pressure was [FlyRotary]Re: Fuel Injector Sizing Date: Sat, 22 Jan 2005 11:08:58 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000F_01C50072.C5384C40" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_000F_01C50072.C5384C40 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Re: [FlyRotary] Re: Fuel Injector SizingDepends on the type of pressure = regulator. The concept of a manifold-referenced pressure regulator is = to keep the pressure differential between the pressure of the fuel and = the pressure of the manifold a constant. That way the injectors see the = same pressure differential at all times and inject the same amount of = fuel for the same duration open time. If the pressure regulator does not compensate for the difference, then = when the fuel pressure is 40 psi and the throttle wide open the = difference would be (approx) 40 - 14.7 (at sea level standard day) =3D = 25.3 psi. Then if you close the throttle and manifold pressure drops to = - say 7.7 psi then the difference would be 40 - 7.7 =3D 32.3 psi. So = there would be a 7.7 psi increase in pressure across the injectors and = more fuel would be injected for the same duration signal. So in this = example the manifold-referenced fuel pressure regulator should sense the = manifold pressure and reduce the fuel pressure by 7 psi down to 32.3 = psi. Then the difference 32.3 - 7 =3D 25.3 psi and the injectors see = the same pressure differential at both throttle settings and injects the = same amount of fuel for the same duration in both cases for steadier = performance.=20 If that understanding is correct then it would seem to imply you should = see the fuel pressure gauge reacting to major changes in manifold = pressure (say from WOT to idle) without a problem. If the pressure = regulator was not manifold-referenced then, the fuel pressure would be = maintain at some constant pressure without regard to maintaining the = pressure differential across the injectors and you would see a steady = fuel gauge needle. At least, that is my understanding of it. =20 Ed A=20 ----- Original Message -----=20 From: jesse farr=20 To: Rotary motors in aircraft=20 Sent: Saturday, January 22, 2005 10:21 AM Subject: [FlyRotary] Re: Manifold-Reference Fuel Pressure was = [FlyRotary]Re: Fuel Injector Sizing Ain't that what they are supposed to do ? Keep it steady as outside = pressure diminishes ? Doesn't your gauge suffer from the same = diminishing outside pressure as altitude increases; therefore, wouldn't = they stay constant, if working properly ? 'Splain to us simple minded, = of which I may be the only one. jofarr ----- Original Message ----- From: Ed Anderson=20 I agree with your statement, Buly. Ideally if the pressure = differential between fuel rail and manifold is kept constant by use of a = manifold reference then that would imply that the fuel pressure should = vary to compensate for different manifold pressure. However, my fuel = pressure is rock steady and this is the second manifold-referenced fuel = pressure regulator I have used with no difference. So either my = manifold-reference fuel pressure regulator isn't or I am = misunderstanding what they are suppose to do. But, that is my experience. How about others of you flying what is = your experience with fuel pressure??? Does it vary? The variance = corresponds to what?? ------=_NextPart_000_000F_01C50072.C5384C40 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Re: [FlyRotary] Re: Fuel Injector Sizing
Depends on the type of pressure = regulator. =20 The concept of a manifold-referenced pressure regulator is to keep the = pressure=20 differential between the pressure of the fuel and the pressure of the = manifold a=20 constant.  That way the injectors see the same pressure = differential at all=20 times and inject the same amount of fuel for the same duration open=20 time.
 
  If the pressure regulator does = not=20 compensate for the difference, then when the fuel pressure is 40 psi and = the=20 throttle wide open the difference would be (approx) 40 - 14.7  (at = sea=20 level standard day) =3D 25.3 psi.  Then if you close the = throttle and=20 manifold pressure drops to - say 7.7 psi then the difference would be 40 = - 7.7 =3D=20 32.3 psi.  So there would be a 7.7  psi increase =  in=20 pressure across the injectors and more fuel would be injected for the = same=20 duration signal.  So in this example the manifold-referenced fuel = pressure=20 regulator should sense the manifold pressure and=20 reduce the fuel pressure  by 7 psi down = to 32.3=20 psi.  Then the difference 32.3 - 7 =3D 25.3  psi and the = injectors see=20 the same pressure differential at both throttle settings and injects the = same=20 amount of fuel for the same duration in both cases for steadier=20 performance. 
 
If that understanding is correct then = it would seem=20 to imply you should see the fuel pressure gauge reacting to major = changes in=20 manifold pressure (say from WOT to idle) without a problem.  If the = pressure regulator was not manifold-referenced then, the fuel pressure = would be=20 maintain at some constant pressure without regard to maintaining the = pressure=20 differential across the injectors and you would see a steady fuel gauge=20 needle.
 
 At least, that is my = understanding of=20 it. 
 
Ed A
----- Original Message -----
From:=20 jesse = farr=20
Sent: Saturday, January 22, = 2005 10:21=20 AM
Subject: [FlyRotary] Re:=20 Manifold-Reference Fuel Pressure was [FlyRotary]Re: Fuel Injector = Sizing

Ain't that what they are supposed to = do ? =20 Keep it steady as outside pressure diminishes ? Doesn't your gauge = suffer from=20 the same diminishing outside pressure as altitude increases; = therefore,=20 wouldn't they stay constant, if working properly ? 'Splain to us = simple=20 minded, of which I may be the only one.
jofarr
----- Original Message ----- = From: Ed=20 Anderson
 
I agree with your statement, = Buly. =20 Ideally if the pressure differential between fuel rail and = manifold is=20 kept constant by use of a manifold reference then that would imply = that the=20 fuel pressure should vary to compensate for different manifold=20 pressure.  However, my fuel pressure is rock steady and this is = the=20 second manifold-referenced fuel pressure regulator I have used with = no=20 difference.  So either my manifold-reference fuel pressure = regulator=20 isn't or I am misunderstanding what they are suppose to = do.
 
But, that is my experience.  = How about=20 others of you flying what is your experience with fuel = pressure??? =20 Does it vary? The variance corresponds to what??
 
 
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