Return-Path: Sender: (Marvin Kaye) To: flyrotary Date: Thu, 02 Oct 2003 21:16:28 -0400 Message-ID: X-Original-Return-Path: Received: from [128.83.126.136] (HELO mail.utexas.edu) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP-TLS id 2621739 for flyrotary@lancaironline.net; Thu, 02 Oct 2003 15:25:46 -0400 Received: (qmail 82049 invoked from network); 2 Oct 2003 19:25:44 -0000 Received: from dhcp-191-101.per.utexas.edu (HELO benefits3.mail.utexas.edu) (146.6.191.101) by wb2.mail.utexas.edu with SMTP; 2 Oct 2003 19:25:44 -0000 X-Original-Message-Id: <5.1.1.5.2.20031002141215.012d2618@localhost> X-Sender: msteitle@mail.utexas.edu@localhost X-Mailer: QUALCOMM Windows Eudora Version 5.1.1 X-Original-Date: Thu, 02 Oct 2003 14:25:36 -0500 X-Original-To: "Rotary motors in aircraft" From: Mark Steitle Subject: Re: [FlyRotary] Re: Fuel Pressure Regulators In-Reply-To: Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="=====================_1689780765==.ALT" --=====================_1689780765==.ALT Content-Type: text/plain; charset="us-ascii"; format=flowed At 12:45 PM 10/2/2003 -0500, you wrote: >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... > >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. Well, that makes sense... >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. > > The pressure referenced regulators keep the fuel pressure differential > the same across the board, so your injector flow remains constant. I can see where that would be good, as long as the EC-2 fuel map knows how to adjust for the variations in fuel pressure. So, then the EC-2 will automatically adjust for my "poor man's turbo (ram air system)? > > > For lack of any better setting, I adjusted mine for standard 43.5 psi. > Sounds reasonable. I initially set mine for 45psi, but there's an adjustment screw and know how to use it! However, my guage is really an oil pressure guage and probably isn't sensitive enough for the accuracy needed here. I'll wait for my EIS to set it more precisely. Thanks for the lesson in fuel pressure regulators, Mark S. --=====================_1689780765==.ALT Content-Type: text/html; charset="us-ascii" At 12:45 PM 10/2/2003 -0500, you wrote:

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...

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.

Well, that makes sense...

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.

The pressure referenced regulators keep the fuel pressure differential the same across the board, so your injector flow remains constant.

I can see where that would be good, as long as the EC-2 fuel map knows how to adjust for the variations in fuel pressure. So, then the EC-2 will automatically adjust for my "poor man's turbo (ram air system)?

For lack of any better setting, I adjusted mine for standard 43.5 psi.

Sounds reasonable. I initially set mine for 45psi, but there's an adjustment screw and know how to use it! However, my guage is really an oil pressure guage and probably isn't sensitive enough for the accuracy needed here. I'll wait for my EIS to set it more precisely.

Thanks for the lesson in fuel pressure regulators,
Mark S.
--=====================_1689780765==.ALT--