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My Advanced Flight System EFIS \ EM shipped with a Stewart
Warner fuel pressure sensor. They have had a few failures and
now ship with VDO. Go figure.
Strange indeed. I can't find a listing anywhere for a VDO electric fuel pressure gauge nor can I find a VDO pressure sensor that specifically states that it is rated for fuel pressure use. The ones I found now state that they are NOT rated for fuel. Got a part number for it?
Tracy
On Tue, Dec 28, 2010 at 3:35 PM, Bobby J. Hughes <bhughes@qnsi.net> wrote:
Tracy,
My Advanced Flight System EFIS \ EM shipped with a Stewart
Warner fuel pressure sensor. They have had a few failures and
now ship with VDO. Go figure.
Bobby
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of
Tracy Sent: Tuesday, December 28, 2010 1:40 PM To:
Rotary motors in aircraft Subject: [FlyRotary] Re: Fuel rail
pressure
Hello Brian, Here is an excerpt from the updated EM2
installation guide. Note that this assumes that your EM2 has been
updated since this change was developed (last 2 months or so).
FUEL PRESSURE
SENSOR
The EM2 was originally designed around VDO pressure sensors and the fuel
pressure sensor was to be the same type as used for the Oil Pressure
sensor. VDO at some point changed the design of these sensor
and they are no longer safe to use with Fuel (they begin
leaking from the terminal end). The closest substitute
is a Stewart Warner
114875. These are
available from Summit Racing as PN
SWW-114875. To make it fully compatible with the EM2 you must
wire a 562 ohm resistor from the sensor output terminal to
ground. This can be added near the sensor or near the
EM2, which ever is most convenient. You must also
set the Channel 13(mixture) Low limit value to 1 instead of
0. The calibration values for the Fuel pressure channel (12)
should then be set to the following values: Scale factor –
6.922 , LOW END OFFSET – 0, SENSOR OFFSET ~ 963 , LOW ALARM LIMIT - ~28 , HIGH
ALARM LIMIT -~55. Tracy
On Tue, Dec 28, 2010 at 12:10 AM, <bktrub@aol.com> wrote:
Tracy,
did you ever find a suitable replacement fuel pressure sender? What are
you using now?
Thanks,
Brian Trubee
Sent: Mon, Dec 27, 2010 4:30 pm Subject: [FlyRotary] Re: Fuel
rail pressure
Just for another data point: I installed the fuel pressure
regulator prior to the fuel rails in my 20B installation so there is no fuel
flow to flush vapor from the rails on hot startups. This arrangement is
now used on most new cars. Even with this arrangement I have had no
trouble with vapor lock. Even if it should happen, the EC2/3
primer function would be able to vent the vapor from the rails. This
setup allows the use of a Floscan type fuel flow sensor with the EM2/3 since
there is no return flow from the fuel rails. No big advantage other than
being much easier to calibrate. Tracy
On Mon, Dec 27, 2010 at 6:53 PM, <bktrub@aol.com>
wrote:
It seems to me that the fuel would have to be pretty hot for the vapor
pressure to exceed 40 psi and cause vapor lock. Running the fuel pump in
such a case would cause coller fuel to flow through the rail and back to the
tank.
Brian Trubee
-----Original
Message----- From: Al Gietzen < ALVentures@cox.net> To: Rotary motors in aircraft
< flyrotary@lancaironline.net> Sent: Mon, Dec 27, 2010
3:49 pm Subject: [FlyRotary] Fuel rail pressure
Also remember that when you are starting the engine
you are starting it under a load. This is different then in a car
config where in a car you are starting it with no load attached to the
crankshaft. If the fuel rails are getting so hot that they are
vaporizing I would think this would cause an excess pressure in the fuel
system and be very dangerous. This is not a problem I have ever had in
a car. What is causing this besides poor
ventilation?
The pressure in
the fuel rail can never exceed the setting of the pressure regulator; which
should bear about 40 psi engine off. That’s true even if you call the
e-shaft a crankshaftJ.
Al
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