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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