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View Full Version : Help Needed: VU-4 Plumbing



fahrenheitfarmer
09-14-2014, 11:15 AM
Looking to upgrade from my paddle setup to a used switchspeed kit that I purchased. I could use some advice before I start putting everything together.

1) Looking at the VU-4 manifold, the PO seems to have used 1/8" PTC fittings on the threaded side. I assume these were for pressure sensors. I'm looking to use my current Dakota Digital gauge and VDO sensors with the VU-4. Will this be as simple as just plumbing the VDO sensors straight into a bushed 3/8 to 1/4 fitting?

2) The IN/EX ports on the short sides of the manifold, are both sides to be supplied? Or is it a 'one or the other' setup?

3) I ordered new water traps but am not sure if it is best to plumb them inline with the feed to the manifold, or inline with the compressors. I was leaning towards inline with the manifold, as that's really the main concern for rust/moisture, but wanted to get some advice first.

4) Running dual 444's, how necessary is one of those Stinger relays? Ended up not getting one from the PO, but I run a fairly nice Optima battery as well. Thoughts?

5) Will the VDO pressure sender that I use now for my Dakota Digital gauge work if spliced into the harness for the digital tank pressure sensor? I've seen the 3-prong sensors for about $40, but didnt want to commit to one if my VDO would work.


I appreciate all of the help!

Oh Damn, it's Sam
09-14-2014, 12:16 PM
1. Those ports on the top of the VU4 should be 1/4" NPT, correct. Each port corresponds to a corner, as you suspect.

2. The ports are opposite ends of the same manifold, so you either need to use both, or plug one.

3. I'd have water traps before the tank, especially if you have a steel tank. If you have aluminum, it's less of an issue where the traps go. Obviously you want the traps as far from the compressor as reasonable so the air has a chance to cool a bit and for more water to condense out of it. I still always recommend a drain, because water traps are nowhere near 100% effective.

4. Twin standard automotive relays will work fine, one relay per compressor. I see no reason for a proprietary relay split into two loads when two cheaper relays work just as well.

5. This I do not know. The digital sender that AccuAir supplies is 5V and reads 0.5V at 0 psi, and goes up from there. I'm guessing it's designed to read 5V at 200 psi, but that's just a guess. If you can verify your existing sender has the same specs it may work. That said, $40 isn't a ton of money, and I don't know how the pressure sensing is going to behave with two devices reading off it simultaneously.

fahrenheitfarmer
09-14-2014, 12:59 PM
Appreciate the help. Ive got two of the standard relays for the compressors, so I should be fine. As far as the VDO pressure sensor, ill just order the digital one then, so i wont have to splice the harness.

I may have mispoke about the VU-4. It has the side for 3/8 PTCs (which i will be reducing down to 1/4), but the threaded opposite side has what looks like 3/8 NPT to 1/8 PTC fittings on it.

Oh Damn, it's Sam
09-14-2014, 02:28 PM
The input, exhaust, and output to bags on a VU4 with PTC fittings are all 3/8" PTC. The threaded ports at top are 1/4" NPT.

So sayeth Accuair themselves (http://www.accuair.com/airmanagementproducts/vu4-4-corner-solenoid-valve-unit-3).

fahrenheitfarmer
09-15-2014, 05:04 PM
But either way, there shouldnt be any problem just bushing them out to accept my VDO sensors to the dakota digital, correct?

Oh Damn, it's Sam
09-15-2014, 05:20 PM
I can't imagine there would be. Pressure is pressure, so far as your gauges are concerned, and it's not like they need any kind of high flow rate to function.