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Here are a few examples of typical in-tank pumps:
http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=ford+fuel+pump+assembly&x=0&y=0
There's typically a 'sock' type strainer on the inlet, and a
mechanical bypass type pressure regulator on the pump's output,
buried in that mass you see in the pics. I suspect that it is needed
as a 'fuse' to prevent blowing something out if a line gets blocked
somewhere downstream. A float type level sender is usually in there,
too.
The sump idea is unattractive to me for my my application (low wing
plane) because I worry about it air-locking, unless I provide a vent
back to the main tank, which is even more complicated. (I've owned a
high wing homebuilt that used sumps, but they were vented back into
the wing tanks.)
Charlie
On 09/01/2011 04:51 PM, CozyGirrrl@aol.com wrote:
1. So there's no issues with hot soaked restarts of an EFI
engine?
2. We have a pair of Walbro GSL393 EFI pumps, suitable
for in or out of tank mounting though I am curious how they
were tank mounted.
3. Check valves. I thought that these pumps would not free
flow either direction if shut off thereby not needing check
valves?
4. If an EFI pump were mounted in a sump of approximately
1.5 qt capacity, this fed by a low volume/low pressure Facet
pump from the main tank, between the heat generated by the
pump itself and picked up in the circuit, would the flow of
the facet pump replenishing used fuel with the excess
returning to the main tank keep the pump, sump and circuit
fuel at a reasonable temp? What would the minimum volume be?
Keep in mind that the circuit fuel is mixing with the
replenished fuel so some heat is going as overflow back to the
main tanks.
Chrissi & Randi
www.CozyGirrrl.com
CG Products, Custom Aircraft Hardware
Chairwomen, Sun-N-Fun Engine Workshop
In a message dated 9/1/2011 2:39:12 P.M. Central
Daylight Time, shipchief@aol.com writes:
I'm running two of Tracy's original fuel pump
offerings, in parallel in my RV-8. I have finger
strainers in the tanks, then thru Van's fuel
selector valve, forward to the pumps. The pumps
are mounted to the floor next to the left rudder
pedal. Each pump discharges thru a vertical
mounted check valve on the back of the firewall,
then joins to the bulkhead fitting and on to a
High pressure filter and on to the fuel injectors,
in series. The stock Mazda pressure regulator is
the last point, then to the fuel return selector
valve and to the tank. All -6 tube and hose.
I didn't like the original Van's fuel tank pick
ups, so I used John Ammter's design, which is a
finger strainer in a doubler plate at the aft
lower corner of the inboard fuel tank rib.
I don't think I can get much better, unless I
put a hatch in the top of the tank and use an 'In
Tank' fuel pump. Then I'll lose some redundancy
and need to change the operating proceedure...I'll
have to think about that one....
My secondary injectors are mounted somewhat
like the Cozygrrls' lower manifold, but outboard
instead of inboard of the tubes. This is above the
exhaust manifold, so I have cooling air
directed in from the left cowl inlet. It feels
pretty warm in there after a test run.
-----Original
Message-----
From: Ed Anderson
<eanderson@carolina.rr.com>
To: Rotary motors in aircraft
<flyrotary@lancaironline.net>
Sent: Thu, Sep 1, 2011 5:34 am
Subject: [FlyRotary] Pump Suck Lock?: [FlyRotary]
Re: CG Products Intake Manifold
I don't see any problem
with the term "vapor lock" itself - because
when the pressure on the pump inlet gets low
enough, that is exactly what happens
- sufficient fuel enters a gaseous state to
interfere with the pumping of liquid fuel to
the high pressure side. So the term is not
that bad a description so long as we all
realize it happens on the Low pressure
(inlet) side of the pump and NOT the high
pressure side.
My experience with
"vapor lock" showed that by turning my boost
pump on (adding pressure to the "suction "
side of the EFI high pressure pump)
eliminated the condition - which again
indicates the problem is low pressure on the
inlet side of the EFI pump. If there were
liquid there, it would be pumped, so must be
vapor - so the pump is "vapor locked" but,
- not on the high pressure side.
Perhaps we should refer
to a more technical accurate descriptive
name , how about
"Pump Suck Lock" {:>) - just kidding.
Ed
Sent: Wednesday, August 31, 2011
3:07 PM
Subject: [FlyRotary] Re: CG
Products Intake Manifold
Data point: One of the big aviation engine/fuel
injection suppliers installs -4 lines everywhere
in front of the firewall up to the 'spider', on
all 4 cyl Lycs (up to 200+ hp) and if memory
serves, even on the 6cyl engines (230+ hp). The
individual lines from the 'spider' to the
cylinders are so small you'd be hard pressed to
get safety wire through them. This is on a
Bendix style injection system using a diaphragm
type fuel pump and no return line after the
pump. These systems run at between 15 & 30
psi. Logic is that minimum diameter line
minimizes quantity of fuel that can boil on the
engine side of the firewall.
With minimum diameter lines, as long as the pump
can provide pressure it won't take long to clear
any vapor as soon as cranking begins, or you hit
Tracy's 'cold start' button a couple of times.
(Vapor in the combustion chamber is a good thing
anyway, right?) :-)
As Al Wick pointed out, the only place vapor
should be a problem is at the inlet to the pump
itself.
Charlie
On 08/31/2011 07:35 AM, CozyGirrrl@aol.com
wrote:
Interesting Chad.
The people flying Subes and using
autogas were also guessing that altitude
was a factor in vaporlock. We won't be
using autogas due to variable formulation
eating up epoxy tanks.
We were thinking that if the regulator
was the last item in the chain and that
the rails were hooked up serially that it
would minimize vaporlock and also a few
seconds of the pump running before a hot
restart would cool and clear the rail.
Chrissi
& Randi
www.CozyGirrrl.com
CG Products, Custom Aircraft Hardware
Chairwomen, Sun-N-Fun Engine Workshop
I recently researched EFI
regulation a bit and found
something interesting. Many
modern (post-1995) vehicles have
"returnless" EDI systems where
the regulator is in or near the
tank, not the engine
compartment.
It turns out this isn't for
complexity reasons, though it
does save a bit. It's for
emissions. The heating of the
fuel in the engine compartment
transfers heat back to the tank.
The tank's emissions do count
even though they're not huge.
It's also one less part, hose,
and set of fittings to fail-
and get warranty calls on.
To deal with vapor lock they
just crank up the pressure to 65
or more psi. Very effective.
Not at all saying we should
do the same, but the purpose is
interesting, no? As well as the
vapor lock" solution"...
Regards,
Chad
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