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DIY OBA with tank.

6K views 21 replies 12 participants last post by  PlayerZer0 
#1 ·
So i decided i wanted an OBA system. As most of us are, I was strapped for cash. I pieced together my own OBA set up with for about $100. It can be less or more depending on what parts you get and from where.

Parts you NEED:
5 gallon air tank from Harbor Freight $27
compressor of your choice +/- $60 (i got mine for free)
Air hose ($10 for 50' of 300 PSI 3/8" airline)
brass fittings and couplers as needed $5-20

Parts I recommend to make life easier:
quick disconnect 1/4" brass fittings (set of 5 male and female $10 at HF)
20' coiled air hose $10
Press and release air chuck (free with HF tank)
Viair pressure switch


So first I dealt with the tank. It currently resides in the back of the X but once I slap in my flowmaster 40, it could easily find its way next to the gas tank.



From here i drilled a 1/2" hole (and still had to file some metal away) right by my anchor point. I fed the hose through the pre-cut carpet hole and underneath. I fed the entire airline through the frame rail until the front fender well.



From here it's really a matter of preference but I led the air hose
up through the fender and into the engine bay by the battery. Then i put it back down through the headlight opening and into the bumper. Now if you have no skid plate or bumper to mount the compressor on, you could have stopped a while ago and mounted it either inside, under the truck or in the engine bay but i decided to go for the bumper.

The air hose first goes through to a hole in my bumper, then T's off through the hole and to the right section of my bumper. This is where i bolted it in.









How you arrange the brass fittings is up to you and whatever works best for you.

Pressure Switch

If you decide you want a pressure switch, remove the pressure gauge from the compressor and replace with a viair pressure switch. The one with the relay is not needed. If you open up the the switch assembly on my compressor, you can clip the two switch wires and splice the pressure switch leads into the ground (one end of the PS going to one of the relay switch wires and one going to the dash switch) and the other relay switch wire going straight to the dash switch. This allows you to control when the compressor pressure switch is active and then allows you to let it run when you are on the trail without worrying about over filling the tank or burning out the compressor. I used an 85-105 PSI pressure switch because both my tank and compressor are limited to 120 PSI.



I'll get photos of the wiring later, but for right now, It's rainy, windy and miserable and i dont want to go outside.


Enjoy 5 gallons of not waiting for your budget air compressor.

 
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#5 ·
A couple of points, in case it becomes relevant later/you want to clarify:

Is the compressor one of those models that can be exposed to weather/submersion, etc? (Not while running of course...)

With a 105 psi limit, and a 5 gal tank, you have enough air to do about one tire....

....which then begs the question, what is the duty cycle of the compressor?

Most inexpensive compressors are rated for a 30% or lower duty cycle, and, if you need it to run a long time to do the other 3 tires, it might burn out the the compressor over time.


Adding more/larger tanks would of course help capacity a lot, unless the compressor burns out from the long re-fill cycles, etc. (You can fill tanks ahead of time, in ~ 5 minute runs to avoid overheating, and then leave on the trip with everything all charged up...and so forth)


OBA's are great, and a real time saver...especially appreciated by me as I used a cig lighter plug-type compressor for decades, until my knees decided I could not spend so much time kneeling by tires waiting for them to fill up again, etc.

:wink-big:
 
#6 ·
A couple of points, in case it becomes relevant later/you want to clarify:

Is the compressor one of those models that can be exposed to weather/submersion, etc? (Not while running of course...)

With a 105 psi limit, and a 5 gal tank, you have enough air to do about one tire....

....which then begs the question, what is the duty cycle of the compressor?

Most inexpensive compressors are rated for a 30% or lower duty cycle, and, if you need it to run a long time to do the other 3 tires, it might burn out the the compressor over time.


Adding more/larger tanks would of course help capacity a lot, unless the compressor burns out from the long re-fill cycles, etc. (You can fill tanks ahead of time, in ~ 5 minute runs to avoid overheating, and then leave on the trip with everything all charged up...and so forth)


OBA's are great, and a real time saver...especially appreciated by me as I used a cig lighter plug-type compressor for decades, until my knees decided I could not spend so much time kneeling by tires waiting for them to fill up again, etc.

:wink-big:
i dont think its entirely waterproof. But I did read a thread on some jeep forum about a guy who took one of these and stripped it down, made it more efficient and waterproofed it. I might do something like that.

With 105 PSI and a 5 gallon tank, I can get 2 tires to 35 PSI from 25 PSI without it being slow enough to say it's running on only compressor.

the manual on this model says its a 50% duty cycle. 20 minutes on, 20 minutes off. More than enough considering it only takes a couple minutes a tire without a tank.

Ultimately this wasnt all about increasing speed of airing up. Although that was a main motive, the other i was going for was convenience of flipping a switch in the cabin and plugging a hose into my bumper.
 
#8 ·
That's sounds good!

25-35 psi is not as much as the 15-35 or so I'm used to, and 50% duty cycle means its a more robust model.

Waterproofing sounds like a great idea, as the bumper is immersed/splashed under there typically.

Bafs 120 psi boost over the 105 psi sounds about right too.
:wink-big:
 
#9 · (Edited)
You can always cheat too before you head out and just use your big compressor (if you have one) to fill up the tank. This is what we did with my brother's drag Prelude.

We'd deflate the slicks (or later the drag radials as they wouldn't allow him to earn points in the "4 banger" class with slicks), and use the 10 gal tank (honestly can't remember now..) to fill them back up for the trip home. We just used the 25ish to 30ish gal (again can't remember, just use it lol) vert compressor to fill it ahead of time.
 
#12 · (Edited)
ill see if i can find it.

edit: so i cant find it, but basically, he opened it up and closed off a few ports (but i wouldnt bother with that) and he took off the red metal box. He that sprayed the motor housing with that handle-dip vinyl for coating tool handles. I would just attack the cracks with rtv sealer. to leave that metal dissipating as much heat as possible. it was a bit of a PITA to get the compressor into the bumper so i might just remove the filter and plumb some of the extra 25 feet of airline i have left into the airbox. That will help keep it dry and filtered so i can run on dusty roads. However, i dont know if that will cut back the airflow to the engine. Kragen and pepboys sell this tiny 1.5" verson of a high performance cone filter that i might use instead of the POS filter thats already there.
 
#13 ·
Reps. Well done Zach. Reminds me that I need to get on my plans for roof top OBA on my X. I have the same compressor as you and intend to buy a long, skinny tank and hard mount them both in my air dam storage basket. Suppose this will only work with a 2nd gen. I figured since I never really use the basket except to hold wet clothes and stuff, I'd make it more practical and fun.

:)
 
#14 ·
Reps. Well done Zach. Reminds me that I need to get on my plans for roof top OBA on my X. I have the same compressor as you and intend to buy a long, skinny tank and hard mount them both in my air dam storage basket. Suppose this will only work with a 2nd gen. I figured since I never really use the basket except to hold wet clothes and stuff, I'd make it more practical and fun.

:)
i really want to see that when its done.
 
#16 ·
I'll totally post a DIY about it. The issue I'm having is finding a good tank that's small enough.
the smaller the tank the less it's worth it. you have plenty of space under your truck, why not find a space there for a 5 gallon tank.
 
#17 ·
I know...... but when I get an idea in my head that I want something to work a specific way, I just can't let it go. Thus most of the fights I get into with the wife.

:nick-big:
 
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