Return-Path: Received: from [24.25.9.102] (HELO ms-smtp-03-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2.8) with ESMTP id 617429 for flyrotary@lancaironline.net; Sat, 22 Jan 2005 11:55:11 -0500 Received-SPF: none receiver=logan.com; client-ip=24.25.9.102; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-185-127.carolina.rr.com [24.74.185.127]) by ms-smtp-03-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j0MGsckd019032 for ; Sat, 22 Jan 2005 11:54:39 -0500 (EST) Message-ID: <003701c500a3$5ceecbb0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Manifold-Reference Fuel Pressure Date: Sat, 22 Jan 2005 11:56:48 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0034_01C50079.73E69020" 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_0034_01C50079.73E69020 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Re: [FlyRotary] Re: Fuel Injector SizingI agree, Al. With the NA engine = its not a major concern - with a turbo, it would be a different story. = Early on I wondered about it, but after it did the same thing when I = changed the pressure regulator, I just stopped viewing it as a problem - = since it did not appear to affect the reliable running of the engine. My manifold pressure gauge and fuel pressure regulator are off the same = manifold line and the manifold gauge shows that there is vacuum in the = line. I suspect that this fuel pressure regulator may be too small to = effectively handle manifold pressure fluctuations. I recall reading = somewhere that it had a maximum return rate of something like 9-10 GPH = which with our higher pressure/volume pumps may be simply causing the = return flow to choke and stop the regulating process. =20 Guess I'll have to change make of pressure regulator and see what that = shows. That's what's great about this list - always something to learn = and someone (or many) will have a rational and sensible suggestion about = the solution. Ed A ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Saturday, January 22, 2005 11:36 AM Subject: [FlyRotary] Re: Manifold-Reference Fuel Pressure Subject: [FlyRotary] Manifold-Reference Fuel Pressure was [FlyRotary] = Re: Fuel Injector Sizing 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. Ed; I'd say it is clear that your FPR is not functioning properly; = although the problem may not be in the pressure regulator. You may want = to check to make sure the manifold pressure (vacuum) is really being = seen at the regulator. The fact that the fuel pressure does not change with MP is not a big = issue for NA engine. The idea of MP referencing of the fuel pressure = came with super/turbo charging; the purpose is to keep the pressure = differential across the injector nozzle from getting too low as the = boost went up. It is an issue with the EC2 because the default mixture = mapping is set up for MAP referenced fuel pressure. =20 I did all the dyno runs with my engine without MAP reference; fixed = at 40 psi. This was before I knew that the EC2 was set up for MAP = referenced FP for NA application. It worked fine except it was = difficult to get things lean enough at idle. With my current MAP referenced FPR and one fuel pump running, I have = about 41 psi fuel pressure with a MAP of 30", and about 31-32 psi at a = MAP of 11-12". So that's about a 9 psi change in MAP resulting in about = 9 psi change in fuel pressure. Keeps the pressure differential that the = injector sees constant. With both FPs running, the fuel pressure is a = couple psi higher. It was interesting yesterday; I ran the engine until the fuel tank = was empty. I watched the FP as the pump started to suck air. I turned = the mixture knob up as the FP started to drop. The engine continued to = run at low power until pressure got down to about 9 psi. Al ------=_NextPart_000_0034_01C50079.73E69020 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Re: [FlyRotary] Re: Fuel Injector Sizing
I agree, Al.  With the NA engine = its not a=20 major concern - with a turbo, it would be a different story.  Early = on I=20 wondered about it, but after it did the same thing when I changed the = pressure=20 regulator, I just stopped viewing it as a problem - since it did not = appear to=20 affect the reliable running of the engine.
 
My manifold pressure gauge and fuel = pressure=20 regulator are off the same manifold line and the manifold gauge shows = that there=20 is vacuum in the line.  I suspect that this fuel pressure regulator = may be=20 too small to effectively handle manifold pressure fluctuations.  I = recall=20 reading somewhere that it had a maximum return rate of something like = 9-10 GPH=20 which with our higher pressure/volume pumps may be simply causing the = return=20 flow to choke and stop the regulating process. 
 
Guess I'll have to change make of = pressure=20 regulator and see what that shows.  That's what's great about this = list -=20 always something to learn and someone (or many) will have a rational and = sensible suggestion about the solution.
 
Ed A
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Saturday, January 22, = 2005 11:36=20 AM
Subject: [FlyRotary] Re:=20 Manifold-Reference Fuel Pressure

Subject:=20 [FlyRotary] Manifold-Reference Fuel Pressure was [FlyRotary] Re: Fuel = Injector=20 Sizing

 

I agree with your = statement,=20 Buly.  Ideally if the pressure differential between fuel rail = and=20 manifold is kept constant by use of a manifold reference then = that=20 would imply that the fuel pressure should vary to compensate for = different=20 manifold pressure.  However, my fuel pressure is rock steady = and this=20 is the second manifold-referenced fuel pressure regulator I have = used with=20 no difference.

 

Ed;

 

I=92d=20 say it is clear that your FPR is not functioning properly; although = the=20 problem may not be in the pressure regulator.  You may want to = check to=20 make sure the manifold pressure (vacuum) is really being seen at the = regulator.

 

The=20 fact that the fuel pressure does not change with MP is not a big = issue for=20 NA engine. The idea of MP referencing of the fuel pressure came with = super/turbo charging; the purpose is to keep the pressure = differential=20 across the injector nozzle from getting too low as the boost went = up. =20 It is an issue with the EC2 because the default mixture mapping is = set up=20 for MAP referenced fuel pressure. 

 

I=20 did all the dyno runs with my engine without MAP reference; fixed at = 40=20 psi.  This was before I knew that the EC2 was set up for MAP = referenced=20 FP for NA application.  It worked fine except it was difficult = to get=20 things lean enough at idle.

 

With=20 my current MAP referenced FPR and one fuel pump running, I have = about 41 psi=20 fuel pressure with a MAP of 30=94, and about 31-32 psi at a MAP of=20 11-12=94.  So that=92s about a 9 psi change in MAP resulting in = about 9 psi=20 change in fuel pressure.  Keeps the pressure differential that = the=20 injector sees constant.  With both FPs running, the fuel = pressure is a=20 couple psi higher.

 

It=20 was interesting yesterday; I ran the engine until the fuel tank was=20 empty.  I watched the FP as the pump started to suck air. =  I=20 turned the mixture knob up as the FP started to drop. The engine = continued=20 to run at low power until pressure got down to about 9=20 psi.

 

Al

 

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