Ironflight

Ironflight

VAF Moderator / Line Boy
Mentor
On the RV-8, I have Van's standard manifold pressure hose (VA-119) running from the number 3 cylinder to a nipple on the firewall (and then to the GRT manifold pressure sensor back behind the panel). I am going to be installing P-Mags to replace my aging Slicks, and need to "T" off the manifold pressure to the P-Mags. On our -3, I simply ran the manifold pressure to one leg of the transducer manifold (and used that to add a port for the P-Mags), but on the -8, the manifold is way over on the wrong side of the firwewall to make it convenient. So....anyone got an idea of a clean building-up of fittings to make this work? I can always make two hoses slightly shorter than the total length of the VA-119, and put a T-in the middle...but then I have to get some new hose ends, hose, etc....

Paul
 
One option is to take the pressure off the #4 cylinder the same way it's currently coming off #3 - just needs another fitting in #4. In TX you can probably get away with only #1 & #2 being primed.

Dan
 
DanBaier said:
One option is to take the pressure off the #4 cylinder the same way it's currently coming off #3 - just needs another fitting in #4. In TX you can probably get away with only #1 & #2 being primed.

Dan
Click to expand...

That's one good possibility Dan - in fact, I am getting away with NO cylinders being primed (took the primer solenoid off last year when I had a cracked line). Looking for the simplest idea - that one is good!
 
I am getting ready to instal a pmag and have just modified a 4d tee fitting. I cut one end flat, tapped it 10-32 and installed a 1/8" nipple from emagair. Now I will just have to take my existing 90* out and put in tee.
icpjxz.jpg
 
Paul, I solved this problem, many years ago in the archives, very similar to Kelly, except on a different leg of the fitting. Just rinse and repeat. Emag didn't have the hardware back then. Mcmaster is your friend.
 
Wherever you take the feed from, try and keep it running uphill.

I notice a distinct blueing of the line on our manifold pressure line to the pressure transducer on our P-Mags - presumably from residual fuel that migrates into the line.

On the 7, our transducer is low on the firewall, will be high on the 8.
 
FLAPS.

That means Friendly Local Auto Parts Store.

Get a "T" fitting for a vacuum line, they have all different size and configurations of them.
 
more fitting info needed

I am doing the same......but wonder, this is a pretty dang important MP line, so is a barb fitting sufficient? Should it be double clamped at least? If the fitting were to 'pop off', what's the result....no advance, or a LOT?

also, should there be a little baffle or filter inline, to keep oil or crud from getting into the MP sensor? I see that running it 'uphill' is a hedge against this problem, but......?

thx
 
I used an unused node on the VA-168 Sender Mount as a distribution point for the Engine Monitor and the LSI ignition brain box. Seems to work fine. And yes, try for some sort of an uphill run to hedge against fuel vapor condensation at the MP sensors...
 
The line is under negative pressure (slight vacuum) so "popping off' should not be an issue except in the case of a backfire. Also the air in the line has come through the intake air filter so should be clean.
 
I used a manifold with three ports. Plumbing was straight forward.

Port 1 - input from cylinder #3
Port 2 - output to manifold pressure sensor
Port 3 - install a barb fitting and run your line (with a T fitting mid way) to your Pmags.

all%2Bhose%2Bsizes.JPG


With 10.5 hours on the hobbs, this has worked well :)
 
Last edited:
drill_and_buck said:
I used a manifold with three ports. Plumbing was straight forward.

Port 1 - input from cylinder #3
Port 2 - output to manifold pressure sensor
Port 3 - install a barb fitting and run your line (with a T fitting mid way) to your Pmags.
Click to expand...

I'm set up this way as well, EXCEPT my Pmag T fitting is screwed into the manifold. Also, I found that compression fittings work just fine on the silicone hose supplied by Emagair as long as you use the type with the inner brass tube. So I have a brass T fitting with a 1/8NPT end, and 2 compression fittings. The NPT end should be on the "run" so that you have room to thread it in without hitting the firewall. The compression fittings make a secure, but easily removable hose assembly.
 
Last edited:
Just to close the loop on this, I came up with a simple solution with a couple of AN nipples, a QD Static line fitting, a "T" from the auto parts store, and two short hoses (to replace the one long hose (Thanks to TS Flightlines, getting a custom hose is a piece of cake!). The BEST way (IMHO) is to just use Van's manifold (as several have suggested), which is how we did it on Junior. Since this is a retrofit on the Val, the manifold is on the wrong side of the firewall, and would lead to a lot of extra plumbing. This is a "no pressure" line (compared to oil and gas lines), so it's pretty easy to connect. I wasn't the first to use the static line QD's for the P-Mag vacuum sense lines (got the idea from DR's plane), but they work extremely well. I just didn't want to put them directly on the engine - I don't think they'd like to be exposed to full cylinder head temps.

Pictures when I finish up the installation....maybe next week (I have this -3 to fly...)

Paul
 
Paul:
all I did on Both of my 8s was to go to the local Bo It Best Hardware, Aviation dept.
And picked up a Barbed "T" fitting and tapped into the Vans line, three hose clamps and it works like a charm
Nordo
 
You must log in or register to reply here.