Re: Changing 165 fuel delivery

["Rob Higgins" <rhiggins@cavva.com.au>]

I have run a similar system in a 1972 Holden with great success
you just need enough supply pump to keep up
this was far easier than building an efi tank

Rob
----- Original Message -----
From: Garfield Willis <garwillis@msn.com>
To: <gmecm@diy-efi.org>
Sent: Wednesday, June 21, 2000 3:50 PM
Subject: Re: Changing 165 fuel delivery


> On Tue, 20 Jun 2000 22:00:06 -0400, Shannen Durphey <shannen@grolen.com>
> wrote:
>
> >I have a small power steering cooler mounted in the return fuel line
> >of my 57 Chebbie pickup, to cool the fuel before it returns to the
> >tank.  The reason for this is to reduce vapor formation in the in-cab
> >mounted tank and the odors associated with it.  I dunno if this is an
> >option in an XA application, but it's not unreasonable for me.  And it
> >can be positioned to help cushion supply surges that can be caused by
> >fuel sloshing in the tank on corners or acceleration.  Old carby tanks
> >are often unbaffled, unlike the newbies that put them to service in an
> >efi system.
>
> It would be an option, but many of the sump/reserve-tank designs are
> indeed baffled AND have an integral vapor separator; basically a swirl
> pot for fuel. Additionally, aircraft aren't required to have
> closed-system vapor containment (no "smog" requirements yet), so except
> for removing the vapor in the fuel system, the rest can be vented to
> atmospheric. Win some, lose some, eh?
>
> >Questions for ya...  Altitude affects boiling point.  Do you think a
> >trouble XA system would perform better on the ground?
> >Have you heard of any indication that this is a part of the
complications?
>
> Oh yes, altitude IS indeed a VERY important issue/variable with fuel
> vaporization problems. Most definitely. Good point/observation. The
> problems I mentioned earlier however are observed during hot ground ops
> even at MSL (we don't normally run clear fuel line, BTW; I mentioned
> that because it's a routine diagnostic step, if you can't solve a fuel
> system mystery. Put some temporary clear fuel line in, and watch for any
> signs of vapor entrainment.
>
> Hey, I'm looking at a Continental FI system book, gives the following
> interesting quote, I include for our mutual entertainment :) ...
>
> "A very important characteristic of fuel applied to either carburetion
> or fuel injection, is the formation of unwanted vapor due to the effects
> of altitude and high temperatures. A brief study of Fig. 12 will show
> the great amount of vapor formed under various combinations of these
> conditions". [Sorry, I can't include the graph, but you get the thrust].
>
> "As an example: If a climb from sea level to 15,000 feet is made with 20
> gallons of 100degF fuel, the natural formation of vapor in the tank and
> lines could amount to approximately 100 gallons [nope, not a typo]. This
> vapor must be removed from the fuel system to insure that only liquid
> fuel is delivered to the engine."
>
> [Here's our present saving grace with XA].
>
> "Fortunately, most of this vapor is vented to the atmosphere and only
> the vapor in the supply lines must be expelled or solidified [in the
> vapor separator] before entering the fuel pump."
>
> Case in point, in automotive we dasn't underestimate the job our fuel
> evap canisters perform. Not to mention the very definite AFR effects
> that can occur during canister purge. :)
>
> >Any
> >reports as to ambient temps in whatever part of the aircraft the
> >reservoir was mounted?
>
> Funny you should ask...oddly enough, on quite a few of these
> reserve-tank/sump installs, the sump is between the panel and the
> firewall. Yup, I kid you not. Many of us have cringed, coming from
> boat-building (me) or auto backgrounds, and then getting into XA, at how
> cavalier some of these designs, both old and new, are with "small" fuel
> tanks essentially INSIDE the cabin. Well, yes there's a wall or a metal
> tank that vents outside, but it's still right next to ya. One big
> forward crunch, and you're sloshin in it. Mitigations are that it's hard
> to put it anywhere else (unless directly under the seat! which is the
> case in one popular modern Burt Rutan design called the Dragonfly),
> without upsetting CG, so it ends up being standard practice more often
> than you'd expect, or wish.
>
> That should answer the question about ambient Temps. They're cabin
> temps. Helps some, but not entirely. Different mix, same variables
> really. Lots of fascinating cross-overs; that's why I'm hooked. :)
>
> Gar
>
>
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