Basic Fuel Injection Questions

[Berchmans]

I am installing a YIO360M1B on my 8 and have a couple questions. First of all on the throttle body/engine interface should there be a gasket or is this a metal to metal connection? Second question concerns the fuel vent port on the engine driven fuel pump...where does this route too? Third and final question for this post is where do I get the fuel pressure reading from? I might be ahead of myself and my reading here but sometimes its just quicker to ask.

[flyinga]

If you are using AFP FI ythere should be a gasket. Not sure about other systems but am pretty sure there should be a gasket.

Fuel drain goes to the aluminum "lip" at the lower left of cowling/firewall junction.

Fuel pressure is taken off of fitting at mechanical fuel pump. As I recall its a "banjo" type fitting. (cowl is on and my memory is not that good)

[Bevan]

The fuel pressure reading will be from a transducer (pressure sender) mounted to a manifold (VA-168 from Vans) located on the firewall. That transducer will be connected to the outlet of the fuel pump via a small diameter fuel hose and a KB-090T T-fitting on the fuel pump outlet. The fitting is available from vans. See

http://www.vansaircraft.com/cgi-bin/...=pump-fittings

Be sure to use a "restrictor" fitting (VA-128 also from Vans) to limit fuel flow in the event of a leak. see

http://vansaircraft.com/cgi-bin/stor...product=va-128

If you are going to order these, get three as you will need them for the oil and mainfold pressure sensing circuits as well. It is said that these transducers also "dampen" the oscilating pressure fluctuations at the transducer for smoother readings.

Bevan
RV7A

[Rupester]

The Silverhawk FI also has a gasket there.
If you're installing a bracket for the throttle and mixture cables, it has a gasket on both bottom and top .... I.e. One against the engine and the other against the servo.

[plehrke]

I did not take fuel pressure from off the fuel pump as that reads fuel pump outlet pressure. Instead i used one of the optional fuel line fitting locations on the fuel servo (I have the Bendix) so I was reading injector outlet pressure. I believe you can also get pressure off the spider as mine had a port there labeled "gage". That would give you true pressure entering the fuel injectors.
Not sure the proper place to take pressure but this seems to work. My rational was I could determine if the pump and servo where working by placing the gage after the servo. Placing it after the pump will just tell you if the pump is OK (granted the pump is what will typically fail).

[Walt]

Originally Posted by plehrke

I did not take fuel pressure from off the fuel pump as that reads fuel pump outlet pressure. Instead i used one of the optional fuel line fitting locations on the fuel servo (I have the Bendix) so I was reading injector outlet pressure. I believe you can also get pressure off the spider as mine had a port there labeled "gage". That would give you true pressure entering the fuel injectors.
Not sure the proper place to take pressure but this seems to work. My rational was I could determine if the pump and servo where working by placing the gage after the servo. Placing it after the pump will just tell you if the pump is OK (granted the pump is what will typically fail).

The "gage" outlet on the flow divider is used for fuel flow on some certified aircraft with a gage calibrated for FF (the pressure will vary with throttle setting as comanded by the servo). It is NOT where you should be monitoring fuel pressure, this should be on the outlet of the fuel pump.

[DanH]

Be sure to use a "restrictor" fitting (VA-128 also from Vans) to limit fuel flow in the event of a leak.

Better to put that money into very high quality hose. A 0.040" stream of fuel at 25 psi is more than enough for a large fire.

[Rupester]

.... the restrictor fitting is still the correct way to install a pressure sensing line.

[Bevan]

Originally Posted by DanH

Better to put that money into very high quality hose. A 0.040" stream of fuel at 25 psi is more than enough for a large fire.

Agreed. The fuel system is NOT the place to save ANY money. Only the best fuel lines, fittings, methods and inspections that you can provide are adequate. Some items on every aircraft are in the category of "life support" systems and should be treated as such when designing, fabricating and inspecting them.

Bevan
"no one is smarter than all of us"

[penguin]

Originally Posted by Walt

The "gage" outlet on the fuel distribution manifold is used for fuel flow on some certified aircraft with a gage calibrated for FF (the pressure will vary with throttle setting as comanded by the servo). It is NOT where you should be monitoring fuel pressure, this should be on the outlet of the fuel pump.

With due respect I disagree. The pressure indication at the servo provides much more information that at the pump. For example that fuel has reached the spider when priming, that fuel is flowing to the spider when the engine is running, and a zero indication means there is no fuel flowing to the injectors. Yes, the indicated pressure will vary with throttle opening. Reading pressure straight from the pump just says the pump is making pressure, doesn't say anything about the servo unit. I have both pressures measured, a sender in the spider should be rated to withstand engine vibration (or use a hose and a remote sender).

Pete