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For what is worth, Charlie
My "sump" is a small header tank (approx 3/4
pint) on the front of my firewall as low down as I could get it. I
return fuel from my pressure regulator to his small header tank and have two
fittings on the bottom - one for each EFI tank to "suck" through. So in
effect each pump is pulling from the header tank. There is also a
vapor space volume at the top of this small tank - which the fuel is returned to
from the pressure regulator. So this design tries to provide a space for
any vapor (top of tank) separate from where the liquid fuel is (bottom of
tank). This avoided any returns back to the main tanks - worked for
me.
Ed
Sent: Thursday, September 01, 2011 9:14 PM
Subject: [FlyRotary] Re: Pump Suck Lock?
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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