firewall placement of fuel return fitting

[Wayne]

I plan on using a IO-540 with a purge valve and thus need a fuel return line back to a tank. Since I dont have the engine yet and unsure of firewall "clutter" I was wondering where to put the bulkhead fitting for the return fuel line? It would be nice to install this with the wide open spaces as I am doing the rest of the fuel system.

Thanks

[Deems Davis]

purge line coming from purge valve

http://deemsrv10.com/album/Sec%20FF4.../DSC04985.html

purge line as it enters the center tunnel (enroute back to fuel tank)

http://deemsrv10.com/album/Sec%20FF4.../DSC04988.html

[Wayne]

Thanks Deem - thats what I was looking for. I had actually gone to your site and couldnt find the pic I needed.

Have a great 09

[David Clifford]

Can anyone tell me what the purge valve is for or does? When I plumbed the Cozy MKIV with a Superior XP IO-360, I did not use one and it starts and runs just fine. I am a ways off the decision point on my RV-10, but I do plan on using an IO-540 and would like to know if I should plan on using one.

[Mike S]

Originally Posted by David Clifford

Can anyone tell me what the purge valve is for or does?

Releases pressure from system at engine shutdown.

Acts as a backup engine kill.

Allows heat soaked fuel to be purged for easier hot starts.

[w1curtis]

Acts as a backup engine kill.

And sometimes act as a primary engine kill at the most inopportune time when not properly safety wired.

[Mike S]

Originally Posted by w1curtis

And sometimes act as a primary engine kill at the most inopportune time when not properly safety wired.

Yep, that was a big concern of mine.

I chose to use a different shaped/colored knob (handle?) for my purge control, and mount it slightly away from the primary engine controls.

http://aycu32.webshots.com/image/409...3100502_rs.jpg

Chrome "T" handle to the left of the black throttle knob.

It is also recessed a bit under the panel.

[DanH]

A few notes:

The firewall bulkhead fitting should be steel, not aluminum.

Locating the fitting and its line someplace other than the lower firewall cooling air exit region is a plus...fire follows airflow.

Consider backflow. Many installs run the purge line directly to a tank, or to a fuel supply line somewhere inboard of a tank. If the hose burns off a purge line firewall fitting mounted below the tank fuel level, there is nothing to stop gravity flow of fuel into the fire. A purge line firewall penetration mounted at some reasonable height above the fuel supply is one answer (easy with an RV). The other approach is a check valve in the purge line somwhere behind the firewall.

[Mike S]

Originally Posted by DanH

A few notes:

The firewall bulkhead fitting should be steel, not aluminum.

Locating the fitting and its line someplace other than the lower firewall cooling air exit region is a plus...fire follows airflow.

Consider backflow. Many installs run the purge line directly to a tank, or to a fuel supply line somewhere inboard of a tank. If the hose burns off a purge line firewall fitting mounted below the tank fuel level, there is nothing to stop gravity flow of fuel into the fire. A purge line firewall penetration mounted at some reasonable height above the fuel supply is one answer (easy with an RV). The other approach is a check valve in the purge line somwhere behind the firewall.

Dan, excellent observations.

Check valve ----- never thought of it.

I wonder if a high loop would do??

[frankh]

To avoid the gravity backflow if the line somehow broke off north of the firewall..Highly unlikely but as I had the option then why not.

Not sure what system your using but the 4 banger AFP system's purge valve is to th right of center line on top of the engine.
I basically came straight back, thru the rear baffle so my firewall hole is up high in board of the upper right engine engine mount.

Steel bulkhead fittings are available for cheap from your local hydraulics shoppe.

Frank