My on-board air system consists of a converted A/C compressor, a couple small propane tanks for storage and a pressure regulator to run my ARB locker.

My particular compressor came from an '88 - '90 Suzuki Swift.  They used two models.  One with a V-belt pulley which I have, and another with a serpentine belt pulley.  Make sure you get the one with the V-belt pulley.  The Swift had a couple engine options those years.  I believe the V-belt type is used on the SOHC engine and the serpentine type is used on the DOHC engine.

This compressor is a NipponDenso model.  It is an axial piston design.  It has 6 (I think) cylinders arranged longitudally around the circumference of the compressor.  The pistons are driven via a swash plate from the pulley and may be double ended for 12 pistons total.  I'm not really sure on the specifics of this one though as I haven't dis-assembled it to see. 

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This is the compressor compared to a much larger York compressor.  Don't let the size fool you though.  It really moves a lot of air. The top adjusting bracket is made from 1" channel. Here you can see the need for a very short compressor so it'd fit with the turbocharger.

There are many different axial types of A/C compressors out there.  I chose this one because it was the smallest and shortest I could find.  It normally wouldn't be a problem, but mine is a very tight fit because of the turbocharger. 

The bigger ones will move more air, but this one does quite well if you rev the engine a bit.  I can run air tools off it.  Idling at 1200 rpm I used an air impact to rotate my tires with no problem.  Revved up to 2500 rpm or so, I can fill a 33x12.5" mud tire from 10 psi to 28 psi in less than a minute.  I haven't actually timed it, but I'd guess in the 30 - 40 sec range from what I remember.  I'll do some timed fillings later.  A larger drive pulley on the crank would help as well so I don't have to rev it as much.

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You can barely see the bottom bracket.  It adapts the stock alternator/air pump bracket to fit the compressor. Here's the belt arrangement using the stock air pump pulley on the crank. The now unused air rail is capped with a 1/2" NPT female cap.

Because the compressor can put out very hot air (like several hundred degrees), I routed it through a piece of 3/8" copper tubing before it joins my plastic air line.  I can tie the compressor clutch switch into the electric fan relay to turn the fan on when the compressor is working, but I haven't done it yet.  Right now I just turn on the A/C as well if I need to run the compressor continuously.  Turning on the A/C does kick the cooling fan on as well.

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This is the copper cooling tube mounted in front of the A/C condensor. Another view looking down.  The blue thing mounted to the front bumper is the filter / oil separator.  The valve at the bottom of it is reached through the holes in the front facia.

The hose coming off the compressor is indended for high pressure steam cleaners.  It's rated at 350 psi @ 325 F.  The air fitting to the compressor is a quick dis-connect as well.  I designed the mount so that I could easily remove the compressor to get to the turbo, hence the quick-disconnect.  I can remove the compressor in about 2 - 3 minutes with no hassle.  The dis-connect is not your standard compressed air dis-connect.  It uses a high temp silicon O-ring and is rated for around 350 F.  Standard dis-connects are rated around 125 I think.

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Here's the high temp quick dis-connect connected... And dis-connected.  The brass fitting on the outlet is a " NPT fitting.  The inlet is bigger, but smaller than " NPT.  It's just shy of 1" in diameter and a 1" crankcase breather filter fits it perfectly. This is the aluminum air manifold I'm using.  It uses 3/8" fittings and tube for the main air lines and smaller " fittings and tube to the multiple air tanks.

My old air tank was a 5 gal tank I mounted over the rear axle.  It was quite large, but un-necessary after I got my compressor installed.  I wanted to use the space for a dual battery box and possibly a large water tank as well.

My new tanks are small propane tanks like used for camp stoves.  I used old, empty ones of course.  You can buy a little brass fitting at hardware stores that screws onto the tank and is intended to re-fill them from larger tanks.  The nipple inside the fitting comes out though and I drilled the hole out to " for better air flow.

I also drilled out the schrader type valve in the propane tanks as well.  If you do this, I'd suggest keeping the neck of the tank full of water.  You don't want a spark coming off during the drilling process as even an empty tank still has fumes inside.  I drilled the neck out to " as well.  

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View looking forward showing the tanks mounting up behind the rocker panel. Another view. They sit a couple inches higher than my nerfs so they're well protected.

The tanks are mounted on the passenger side behind the rocker panel.  They are mounted high and are well protected.  Right now I'm using only two tanks.  As I empty some more from camping, I'll probably add two more to the driver's side as well.  My 150 psi safety valve is mounted to the air manifold which has enough free fittings that I can fit as many as 4 more tanks and just plug them in.

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The mounts are pieces of " angle welded into the corner of the floor and rocker panel. A " rod is welded offset into the angle.  Just enough to let the hose clamp fit through behind it. The tanks mount in the hose clamps then and they're large enough (the tanks) that they draw up against the floor and rocker panel before they touch the rod so they fit tight and don't rock or rattle.

I haven't done much with oiling yet.  I know a lot of people that use these type compressors just run some Slick 50 or something similar through them once a year or so and haven't had a problem.  I've just been periodically squirting a few ounces of oil into the inlet for lubrication.  There is a website somewhere of a guy that has a completely re-circulating oil system.  Oil is filtered out after the outlet to a reservoir and is allowed to drip back into the inlet.  Haven't gotten that far yet though.

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A view from the back side.  There is a small schrader type valve on the inlet that I use to squirt oil in through periodically.  This is an ideal place to fit a hose for an automatic, closed circuit oiling system.

Some final notes:  

This compressor does require the removal of the smog pump.  That pump though only does any work at startup for a few minutes until the engine is warm.  If you really wanted to, you could run your compressor all the time to keep tank pressure up, then run a large (for volume), regulated (for low pressure) line to the air rail and switch it with the same signals used to switch the smog pump.  I don't think I'll be doing that much though.

To remove the pump, I pull off the upper tensioning bracket and a bolt from the front of the lower bracket.  The compressor then pushes back about " - " and pulls strait up.  To remove the lower bracket though, I have to remove the large smog pump / alternator bracket.  The large bolt on this bracket is inserted from the rear and I can't do that when the bracket's on the engine because of the turbo so the adapter has to be installed to the stock bracket before it itself is bolted back in.

I'm using an air compressor switch to turn the compressor on around 90 psi and off around 130 psi.  I use a pressure regulator to knock this down to around 70 - 80 psi for the ARB though.  The switch is not the ideal type though as it mounts in the air line in parallel.  i.e.  air pressure is routed to it, not through it.  Look for one that routes air through it and has a check valve.  Right now I don't have a check valve and the air will bleed back through the compressor when it's off.  Pressure drops enough to kick the compressor back on every 5 - 10 minutes or so.

And finally, all the hoses and fitting came from McMaster Carr (  I can't say enough good things about this place.  They literally have just about anything industrial you'd need and their web site is excellent for searching and ordering.  The down side is that they won't send you a print catalog, so if you don't know what you want or don't know what it's called, it's hard to search for it on the site.

My air lines are high pressure Nylon 11 lines and I use the instant fittings for them.  Nylon 7 will work as well.  It's stronger, but much stiffer and doesn't bend as well.  These fittings are the type you just push in to connect.  To dis-connect, you push the line in, pull and hold the collar down and the line will pull back out.  They're air-tight and very easy to connect and dis-connect for re-routing lines or whatever.

For the main lines that *all* the air goes through, I use 3/8".  For the lines from the manifold to the multiple air tanks, I use smaller " since they all work in parallel and don't have to pass as much air individually.

Any questions or comments?  Give me a shout.


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Created by: Dan Houlton
This page was last updated on 14 Apr 2004