Message-Id: <5.1.1.5.2.20040526072258.011301e8@localhost>
Date: Wed, 26 May 2004 07:35:28 -0500
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
From: Mark Steitle <msteitle@mail.utexas.edu>
Subject: Re: [FlyRotary] Re: Fuel Pump Design
In-Reply-To: <list-90081@logan.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 10:17 PM 5/25/2004 -0400, you wrote:
>Mark Steitle <msteitle@mail.utexas.edu> wrote:
>
>  > > > >
>Bill,
>Yes, the regulator is mounted on the firewall and is located between the 
>pumps/filters and fuel rail.  Also, there is a fuel return line off the 
>regulator.
>  < < < <
>
>Wouldn't it make more sense to make the regulator the last thing in the 
>circuit?  This seems to be typical on just about all automotive EFI 
>installations, and millions of installations can't be wrong.  I think the 
>logic here is that regulator failures aren't sudden, and when they fail 
>they bypass more fuel than they should (ie, lowering pressure).  In this 
>setup there is no way that you can get an airlock, at least I don't see 
>how one would be possible.  Proven systems all seem to have the fuel pumps 
>as close to the tank as possible (inside the tank on most auto 
>installations), then the filter, followed by a direct line to the fuel 
>rail and injectors, then to the regulator, then the return.  On the 
>Eagle540 we put the fuel filters between the tanks and pumps, and they are 
>located just aft of the main spar, just inches away from the tanks (the 
>filter outlet screws directly into the pump inlet)... out of the pumps to 
>the selector, on through the flow transducers, then to the rails.  The 
>regulator is at the end of the circuit and returns through the (horribly 
>expensive) fuel selector as well to direct the return fuel back to the 
>tank from which we're pumping.  Everything has worked extremely well in 
>ground runs, and we are weeks away from first flight.  Just my 2c.
>
>  <Marv>

Hi Marv,
Yes, that was my original intention, but after asking around, I was told it 
really didn't matter.  Doing it this was lighter and simpler.  I may have 
to rethink that decision now.  Let me ask this... Would having the 
regulator at the end of the fuel rail cure the air lock problem?  The Subie 
group is having this problem and I think their pressure regulator is at the 
end of the fuel rail.  Maybe someone can do a test for the sake of the 
group?  As of this time I haven't had any problems with heat soaking after 
running, but I don't have the cowl installed at this time so that could 
change things.

With that said, I'm in the process of moving my primary injectors back to 
the intake ports.  This will result in two fuel rails (rather than one), 
and a change in plumbing.  Maybe now would be a good time to move the 
pressure regulator too.

Mark S.
(Tracy's design is looking better and better)