Hey Guys,

I'm sort of having trouble believing that this discussion is still going on
about returnless systems. Why?? Todd probably gets away with his system
because
he lives in a REALLY cold climate.  He would DEFINITELY have SERIOUS
problems in the 50 Deg C heat we regularly expereience on the tarmac here in
Oz in summer.  But then again,  maybe Lamar IS correct,  and that I AM a
lunatic!!
.
For the power output that most of you have (less than 250 BHP),  a 5/16"
high
pressure supply line is more than adequate,  and a 1/4" return line is more
than adequate.  For bigger power output (Hi Boost 13B & 20B engines,  say up
to 400 Cheveaux) and a Hi Flo EFI pump ,  maybe a 3/8" supply line,  and a
5/16" return line.

Whenever I do a turbo engine conversion on ROAD GOING early model RX7
('79-"85),  I just use the stock fuel lines (5/16" supply & 1/4 return),
and I have never have a problem.  One EFI pump is sufficient.  The
only reason we have 2 x HP pumps on an aircraft is redundancy in case one
fails at take-off and climb-out.

However, the size of the return line is not really that critical.  All it is
there for is to take the flow from the dumped pressure from the HP pump.  If
you are using the same pump as a car,  then you only need the same size
return.
Interestingly,  on the Mazda RX7 turbo cars,  they have a 2 stage control
(via voltage) of the EFI pump to cut the return flow at low load,  and boost
the supply at high load..

The SIZE of the return line is not really so much an issue as actually
having one - size is more of an issue with the supply line,  but only with
Mega-Pferd turbo engines.  The issue is that so long as there is a return
line so that
the fuel continues to circulate back to the tank,  and if that tank is in
the breeze,  the fuel will never get hot.

If the fuel is returned to the header / surge tank,  this MUST be vented
back to the main tank.  Otherwise you will get air/vapour locks.  If there
is a breeze directed over the header/surge tank,  then why do you need a $40
cooler??  As a famous megalomaniac once said,  "It's either them or us"
(referring to issues of mental stability).
I'm just totally flummoxed.

As Tracy said below,  the cooler is just a bandaid covering up a problem.
It also scares me witless when I read what Tracy wrote below about a
fatality actually occuring because of dicey fuel supply issues.

So please, ... this is a plea,  just follow normal EFI practice.
Have a look at the Toyota PDF link somebody posted a while ago about both
return & returnless systems.  Stick to the return system.  This is the way
it MUST be done.  Please DON'T
try to re-invent something that doesn't need to be re-invented,  and that
has been proven to work on millions of EFI road cars,  and thousands and
thousands of race cars.

Additionally,  that SDS link I posted the other day details how to do it
where there are multiple tanks involved.  There is a "critical minimum
complexity" in any system.  Try and simplify the system any further beyond
this "critical minimum complexity",  then the system no longer works
properly,  and will come back and bite you REALLY hard on your nethermost
parts when you least expect it!

Cheers,

Leon


----- Original Message ----- From: "Bob White" <bob@bob-white.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Friday, February 18, 2005 2:29 AM
Subject: [FlyRotary] Re: Returnless Fuel System - Fuel Cooler


>
> Hi Tracy,
>
> My alternative is to try to jam all the return fuel thru a 1/4 inch
> line.  It seems like that will cause problems also.  It's fairly
> substantial surgery to get a 3/8 inch return line in.
>
> I certainly agree that without the cooler it's a disaster waiting to
> happen.  I'm relying somewhat on Todd's positive experiences
> with his system, and further testing on my plane.
>
> Bob White
>
> On Thu, 17 Feb 2005 09:52:56 -0500
> "Tracy Crook" <lors01@msn.com> wrote:
>
> >   Even with the cooler, This scares me.  I know of at least 2 cases
where it has caused power failures, one resulted in fatality.  True, they
didn't have the cooler but it is a bandaid covering up a problem.
> >
> >   Tracy
> >
> >   Hi Jim,
> >
> >   Todd's system is a "quasi" returnless system.  The fuel is returned to
> >   the input of the fuel pump instead of the tank.  Without the cooler,
> >   much of the same fuel would circulate thru the fuel rail again and
agin
> >   picking up heat.  To see Todd's diagram and description go to:
> >
> >   http://www.rotarywiki.com/<http://www.rotarywiki.com/> and search for
"returnless".
> >
> >   Bob White
> >
> >
> >   On Wed, 16 Feb 2005 23:25:06 -0600
> >   Jim Sower <canarder@frontiernet.net<mailto:canarder@frontiernet.net>>
wrote:
> >
> >   > But I thought the purpose of the cooler was to cool the *return*
fuel.
> >   > If it's a one-way system, how does the fuel get hot enough to need
cooling?
> >   > What am I missing here? ... Jim S.
> >   >
> >   > Bob White wrote:
> >   >
> >   > >Todd,
> >   > >
> >   > >I'm going to build a returnless system based on your design.  I
found
> >   > >this fuel cooler at Jeg's for about $40.  Jeg's P/N 771-1009.  The
> >   > >finned area is 4.5 X 5 X 7/8 (inch), which I think is a little
bigger
> >   > >than the one you made.
> >   > >
> >   >
>http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=3532&prmenbr=
361
> >   > >
> >   > >I'm sure it's nicer looking than anything I could build myself.
I'll
> >   > >post pictures of my alternator bracket one of these days to prove
it.
> >   > >
> >   > >Bob White
> >   > >
> >   > >
> >   > >
> >   >
> >   > >>  Homepage:  http://www.flyrotary.com/<http://www.flyrotary.com/>
> >   > >>  Archive:
http://lancaironline.net/lists/flyrotary/List.html<http://lancaironline.net/lists/flyrotary/List.html>
> >   >
> >   >
> >
> >
> >   -- > >   http://www.bob-white.com<http://www.bob-white.com/>
> >   N93BD - Rotary Powered BD-4 (real soon)
> >
> >   >>  Homepage:  http://www.flyrotary.com/<http://www.flyrotary.com/>
> >   >>  Archive:
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> >
>
>
> -- > http://www.bob-white.com
> N93BD - Rotary Powered BD-4 (real soon)
>
> >>  Homepage:  http://www.flyrotary.com/
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