Return-Path: Received: from mtiwmhc12.worldnet.att.net ([204.127.131.116] verified) by logan.com (CommuniGate Pro SMTP 4.2b5) with ESMTP id 165969 for flyrotary@lancaironline.net; Thu, 17 Jun 2004 09:37:21 -0400 Received: from 204.127.135.59 ([204.127.135.59]) by worldnet.att.net (mtiwmhc12) with SMTP id <2004061713364511200sv73he>; Thu, 17 Jun 2004 13:36:46 +0000 Received: from [209.247.222.115] by 204.127.135.59; Thu, 17 Jun 2004 13:36:48 +0000 From: keltro@att.net To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Re: Fuel Delivery - Vapor Lock Date: Thu, 17 Jun 2004 13:36:48 +0000 Message-Id: <061720041336.12303.40D19E7000088B820000300F2160280651019D9B040A05@att.net> X-Mailer: AT&T Message Center Version 1 (May 27 2004) X-Authenticated-Sender: a2VsdHJvQGF0dC5uZXQ= MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="NextPart_Webmail_9m3u9jl4l_12303_1087479408_0" --NextPart_Webmail_9m3u9jl4l_12303_1087479408_0 Content-Type: text/plain Content-Transfer-Encoding: 8bit Guys, I could be wrong but mogas vapor pressure has been reported as usually higher than avgas.IMHO Kelly Troyer -- Dyke Delta/13B/RD1C/EC2 -------------- Original message from "Russell Duffy" <13brv3@bellsouth.net>: -------------- A couple of questions... Your pumps, filters, and regulator is in the cockpit, not in the tank as in 99.9% of the automobiles today? Correct. No good way to put the pumps in an RV wing tank. How far are your pumps from the tank fitting, and what size line feeds the pumps. The distance from the pickup, to the fuel pump inlet is less than 2 feet, and would be gravity fed until about the last 5 gallons or so of the tank. Do you run mogas? Yes. 87 octane. If you do run mogas, do you know the vapor pressure of the fuel you're running? Do you test it? Nope, and nope. I have read that mogas has a lower vapor pressure, which means it can vapor lock easier than 100LL. That's what I've always heard as well. I've also heard that they modify the vapor pressure for temp, so the worst case would be a hot day, in the winter. I've always wondered if they even bother changing the mixture here in FL though. Have you tested your installation to see if it will re-prime if you inadvertently run a tank dry? I haven't done that particular test, but the first time I ran the pumps after filling the tanks, the fuel pressure was almost instantaneous. I'll make a mental note to try this again when I get the tank low enough to easily drain the remaining fuel. Since I stole Tracy's fuel system, I only feed from one tank. If I run that dry, I would first have to transfer fuel (fairly slowly) from the other tank, then worry about priming the pumps. In other words, I don't plan to run the tank dry when there's any fuel in the other tank. I realize this is easier said than done, but that's the plan. Cheers, Rusty (hoping I don't get hit by lightning when I have a fuel leak) --NextPart_Webmail_9m3u9jl4l_12303_1087479408_0 Content-Type: text/html Content-Transfer-Encoding: 8bit

Guys,

I could be wrong but mogas vapor pressure has been reported as usually

higher than avgas.IMHO

Kelly Troyer

--
Dyke Delta/13B/RD1C/EC2

-------------- Original message from "Russell Duffy" <13brv3@bellsouth.net>: --------------
A couple of questions... Your pumps, filters, and regulator is in the cockpit, not in the tank as in 99.9% of the automobiles today?

Correct. No good way to put the pumps in an RV wing tank.

   How far are your pumps from the tank fitting, and what size line feeds the pumps.

The distance from the pickup, to the fuel pump inlet is less than 2 feet, and would be gravity fed until about the last 5 gallons or so of the tank.

   Do you run mogas?

Yes. 87 octane.

   If you do run mogas, do you know the vapor pressure of the fuel you're running? Do you test it?

Nope, and nope.

   I have read that mogas has a lower vapor pressure, which means it can vapor lock easier than 100LL.

That's what I've always heard as well. I've also heard that they modify the vapor pressure for temp, so the worst case would be a hot day, in the winter. I've always wondered if they even bother changing the mixture here in FL though.

Have you tested your installation to see if it will re-prime if you inadvertently run a tank dry?

I haven't done that particular test, but the first time I ran the pumps after filling the tanks, the fuel pressure was almost instantaneous. I'll make a mental note to try this again when I get the tank low enough to easily drain the remaining fuel. Since I stole Tracy's fuel system, I only feed from one tank. If I run that dry, I would first have to transfer fuel (fairly slowly) from the other tank, then worry about priming the pumps. In other words, I don't plan to run the tank dry when there's any fuel in the other tank. I realize this is easier said than done, but that's the plan.

Cheers,

Rusty (hoping I don't get hit by lightning when I have a fuel leak)

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