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How to pass 1/4" MAP hose through firewall?

sritchie

Well Known Member
Hey folks,

I've got two heavy wall 5/32" vacuum hoses that I need to get through the firewall. This is for an EFII system install - one of the hoses tees in front of the firewall to to the fuel pressure regulator while the other end connects to an EFII manifold pressure sensor. The other comes in and tees between a Dynon and EFII sensor.

My question is, what's the best way to get these hoses through the firewall?

Looks like I can use a 90 degree AN fitting for this purpose, but they're pricey: http://www.aircraftspruce.com/catalog/hapages/an848.php

Then again, the 90 degree might be nice if there's an engine fire and the hose burns off.


Another option is to bundle the two manifold pressure lines with my starter and regulator cables inside their 0.5" shielded firewall passthrough.

Thanks in advance, all!
 
I ran two aluminum, ( I know, but wait) -4 bulk head 90 deg fittings up high on the firewall and then aluminum tubing down to the two hoses that go to the map feed from the throttle body and one T off to the fuel pressure regulator, all my firewall pass troughs are steel, except I did aluminum up high thinking that a fire will be traveling down the exhaust pipe path......my three MAPs are on the sub panel, along with everything else. :rolleyes:
 
I would not run any type of combustible line thru the firewall. What about a 1/8 " copper line as used on the primer lines on some aircraft? I installed a Plasma III ignition in my RV and the module required a MP connection with a small plastic hose supplied. I used a brass compression fitting and connected the incoming 1/8" copper line to one end. I modified the other end by removing the threaded portion(throwing away the nut and furl) and machining a small barb end that would tightly fit the supplied plastic tube. I purchased small spring clamps from an automotive store that clamped the tubing nicely. I had to modify a few of these brass fittings as the run from the tee (line to Dynon prob) was plastic also I believe (could have been rubber) and I had to convert to 1/8" copper for the firewall. I searched for a proper fitting and could not find such a thing , but was very happy with the small light fitting I modified.
 
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Ron, that's a good option. I may go with the copper, but I'll keep the AN fitting idea in my back pocket just in case.
 
If you have access to a lathe, the following is a slick method:

1. Get an AN832 bulkhead fitting in the correct size for your hose, and a 1/4" push-to-connect air fitting with a 10-32 threaded end.

2. Cut off one end of the AN fitting and machine it flat. Drill and tap the hole for 10-32 threads.

3. Thread the air fitting into the tapped hole. Seal the threads with Permatex or your favorite sealant.

4. Install the AN fitting on the firewall with the usual AN924 nut, and washers as required.

5. Attach your flare hose to one end, and your 1/4" nylon line to the other.

Voila, custom bulkhead fitting that's also an adapter to go from AN flare hose to 1/4" plastic tubing.

The following is not quite the same configuration (different plumbing arrangement in this case) but the idea is the same:

20120617_fitting.jpg


Note: I wouldn't use this for anything with actual fluid flow - that fitting has a little tiny orifice - but for manifold pressure it's perfectly adequate.
 
I used -3 3003 aluminum tube. The vac tubing slides on and is nice and tight. Then connect more vac tubing on the other side. I ran this through my firewall egress point. I also use the -3 "connectors" as my restrictors. Fill with JB weld and drilll with #60 bit when cured. You'll want these to smooth out the vac signal, especially if you are tee'ing off and feeding a MAP sensor
 
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