Return-Path: <13brv3@bellsouth.net> Received: from imf21aec.mail.bellsouth.net ([205.152.59.69] verified) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP id 2621596 for flyrotary@lancaironline.net; Thu, 02 Oct 2003 13:45:40 -0400 Received: from rad ([68.212.15.208]) by imf21aec.mail.bellsouth.net (InterMail vM.5.01.05.27 201-253-122-126-127-20021220) with ESMTP id <20031002174513.QFRI1847.imf21aec.mail.bellsouth.net@rad> for ; Thu, 2 Oct 2003 13:45:13 -0400 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Fuel Pressure Regulators Date: Thu, 2 Oct 2003 12:45:14 -0500 Message-ID: <00c101c3890c$ef4ab790$0201a8c0@rad> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00C2_01C388E3.0674AF90" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4510 Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_00C2_01C388E3.0674AF90 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable I understand that the vacuum port causes a change in fuel pressure as the manifold pressure changes, but I don't understand why we want the pressure to change. This seems like it would make it more difficult to tune the EC-2. What am I missing here? As I understand it... =20 I'm guessing that it makes it a little easier to program, because it = takes away a variable. Think about it this way, when you open the injector, = fuel sprays out. It sprays at a rate that's not just related to the fuel pressure, but to the difference between the fuel pressure, and the = intake pressure. In an extreme case, if you had 10 psi of boost with a turbo, = and only had 10 psi of fuel pressure, opening the injector wouldn't spray = any fuel at all. =20 =20 Now think of the real situations. At idle, where there's the least need = for fuel, you have the most vacuum. This gives you the greatest fuel flow = rate (appears to have a larger injector), when you need it the least. Just = the opposite happens at full throttle. The pressure referenced regulators = keep the fuel pressure differential the same across the board, so your = injector flow remains constant. =20 Also, what is the preferred fuel pressure for a n/a injected rotary? (I recall Ed Anderson stating he runs 45psi... Is this correct Ed). Mark S. =20 I'm not sure there is a "preferred" pressure. Higher pressure will = allow more fuel flow, and perhaps a better spray pattern, but promotes leaks = if you get carried away. The only real standard is the one that's used = when testing injector flow rates, and that's 3 bar, or 43.5 psi. For lack = of any better setting, I adjusted mine for standard 43.5 psi. =20 Cheers, Rusty (gotta go finish my brake repair now) =20 ------=_NextPart_000_00C2_01C388E3.0674AF90 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Message

I understand that the vacuum port
causes a change = in fuel=20 pressure as the manifold pressure changes, but I
don't understand why = we want=20 the pressure to change.  This seems like it
would make it more = difficult=20 to tune the EC-2.  What am I missing here?

As I = understand=20 it...
 
I'm = guessing that it=20 makes it a little easier to program, because it takes away a = variable. =20 Think about it this way, when you open the injector, fuel sprays = out.  It=20 sprays at a rate that's not just related to the fuel pressure, but = to the=20 difference between the fuel pressure, and the intake = pressure.  In an=20 extreme case, if you had 10 psi of boost with a turbo, and only had 10 = psi of=20 fuel pressure, opening the injector wouldn't spray any fuel at = all. =20
 
Now = think of the real=20 situations.  At idle, where there's the least need for fuel, you = have the=20 most vacuum.  This gives you the greatest fuel flow rate (appears = to have a=20 larger injector), when you need it the least.  Just the opposite = happens at=20 full throttle.  The pressure referenced regulators keep the fuel = pressure=20 differential the same across the board, so your injector flow remains=20 constant.
 
Also, what is the preferred fuel pressure for a n/a = injected=20 rotary?  (I
recall Ed Anderson stating he runs 45psi... Is this = correct=20 Ed). Mark S.
 
I'm not = sure there is a=20 "preferred" pressure.  Higher pressure will allow more fuel flow, = and=20 perhaps a better spray pattern, but promotes leaks if you get carried=20 away.  The only real standard is the one that's used when testing = injector=20 flow rates, and that's 3 bar, or 43.5 psi.   For lack of = any=20 better setting, I adjusted mine for standard 43.5 = psi.
 
Cheers,
Rusty = (gotta=20 go finish my brake repair now)
  
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