ac to air compressor conv.

[Subruise]

ive heard rumors of being able to convert your ac compressor to an air compressor complete w/hoses etc. anybody heard of this? id like to attempt it if its possible/ doable for someone like me or someone i know

 

RV

[TheLoyale]

I like that idea, seems pretty easy when you get down to brass tax. All you would need is to put a fitting on the out-let end of the A/C pump and then run your hose. Unless you want to rig up a holding tank somewhere. I dunno how much pressure the A/C pump will push out OR if it can handle any type of major pressure (100psi)

[Subruise]

i think it would be cool to psi in the tires at will. super low on the trail/snow, then back to street level for the drive home, no quarters required!

 

RV

[TheLoyale]

i think it would be cool to psi in the tires at will. super low on the trail/snow, then back to street level for the drive home, no quarters required!

 

RV

 

Why not just get a ACC Air compressor and keep it in the car?

[Subruise]

simply because that is not cool enough. i want to keep a coil of hose in the spare tire spot, pop the hood, and use tools if i want:grin: the weird looks couldnt be any worse than when non-believers see a tire under there

 

RV

[TheLoyale]

simply because that is not cool enough. i want to keep a coil of hose in the spare tire spot, pop the hood, and use tools if i want:grin: the weird looks couldnt be any worse than when non-believers see a tire under there

 

RV

 

LOL! I sooo agree!

[corvette6698512]

Some guy brought a jeep into a shop I was at that had the tube bumpers welded up and those were the air tanks. He said the ac pump is the compressor so it is possible.

 

Another interesting idea they used to do back in the day. take a boxer 4 aircooled vw engine and turn two of the cylinders into air pumps that are powered by the other two. If your interested its the volks air kit by dunn right inc.

[Numbchux]

take a look on pirate4x4, you'll find it's not uncommon.

 

The challenge, is keeping the compressor lubricated. I don't know a lot about it, but I think some compressor designs are better than others in that regard.

[WoodsWagon]

The problem with using a subaru A/C compressor for air is that it depends on the oil mixed in with the refrigerant for lubrication. When you're using it as an air compressor, it has no oil and will get hot/seize if used for extended periods. Will it work for filling a tire now and then, yes, possibly even all 4 if you give it breaks inbetween. But running air tools off of it will kill it quick.

 

You need to filter the air going into it at a minumum, and should filter the air coming out of it.

 

The right A/C compressor to use is a York built one. They have a separate sump for the oil and are able to run as air compressors without damage. Some early subarus were equipped with them as a dealer installed air package, but the best place to find them is older vans and cars from the 70's.

[TheLoyale]

Since you brought that subject up Chux, Yes trying to keep the stock A/C pump lubricated is gonna be the key point to this. If you run that pump dry its gonna burn up mighty quick. But you don't want enough oil where its going to be pushed into your added on Air hose assy. Also, you will have to watch what kind of lubricant you use as the wrong type could cause drag and still burn up the pump. That thin green A/C R-12 stuff acts as the lubricant for the pump.

[Scoobywagon]

You CAN use the A/C compressor as an air compressor. The problem you'll run into is that the A/C compressor really doesn't generate much air flow. So you need a fairly large tank and some run time if you're going to run air tools. If you REALLY want to do this, I'd recommend against using the stock A/C compressor. Instead, use a York-style compressor. They are most commonly found in buses and some older Dodge rigs. The nice thing about the york-style compressors is that they have a lubricated crank case and, thus, do not require lubricant in the refrigerant. They also provide plenty of flow, since they are generally intended to operate in larger vehicles.

[Yo'J]

^^+1 on the York style comp. I believe Jim Greene's in monroe has all the info there and parts. Its a hot rod shop that was in lynnwood. Fittings Inc. has the cheapest parts, hoses and fittings, that I've found in the pnw. They supply everyone else and you can just walk on in.

[GeneralDisorder]

You can use any AC compressor including the one's that are used on Subaru's - you just have to know a bit about compressed air systems and how to build it. You would need an oil seperator and an orificed suck-back line to insure the oil stays in the compressor. And of course you need a check valve on the outlet side, and an air tank of some sort plus a regulator system to shut it down at an appropriate psi - at the very least a pressure switch, etc.

 

It could definitely be done and someday I may build one - but I wouldn't sugest that most people try it without a lot of research - compressed air in the 100+ psi range can be very dangerous if you don't know what you are doing.

 

The first step is to aquire your air filter, oil seperator, air tank, etc and then plan out your plumbing and mounting. Any good fitting and hose supplier should be able to modify the AC inlet/outlet flanges for use with JIC fittings and then it's a simple matter of some plumbing.

 

Lots of commecial air compressors (mostly the rotary screw type) are oil-flooded and depend on oil-seperators and suck-back systems to insure the oil stays in the compressor. The york pumps are arguably not a better choice because the oil-flooded pumps will last longer and stay considerably cooler at higher pressure.

 

GD

Edited November 12, 2010 by GeneralDisorder

[Subruise]

good insight, thanx. its probably more than i can handle right now but i still want to try it. better start reading

 

RV

[Scoobywagon]

The york pumps are arguably not a better choice because the oil-flooded pumps will last longer and stay considerably cooler at higher pressure.

 

GD

 

This is true and yet, for this application, is also immaterial. The high-side of most A/C compressors will get to 250 psi pretty quick. I've seen some that would go up over 500. In this case, you'd be regulating pressure down to 120 or less. Probably more like 100 psi. So, from the compressor's point of view, there are NO high pressures involved. Heat should not be much of a problem, because you just aren't working the compressor that hard regardless of type. So the real question is, which type will deliver higher volumes of compressed air? Generally speaking, that goes to the York compressors hands down. This type of compressor is still common in larger applications, such as buses, for just this reason.

 

Either compressor will do the job and the OE compressor has the added benefit of already being in the car. However, a York compressor will be easier to implement in a scratch build.

[GeneralDisorder]

This is true and yet, for this application, is also immaterial. The high-side of most A/C compressors will get to 250 psi pretty quick. I've seen some that would go up over 500. In this case, you'd be regulating pressure down to 120 or less. Probably more like 100 psi.

 

It is not at all immaterial - you neglect that temperature AND pressure play in important role here. Not just the temp of the high side, but also the incomming temp and pressure of the low side - which is usually in the 40 to 50 F range and around 25 to 40 psi with refrigerant. When pumping air you have an incomming air temp of ~70 F and pressure of 14.7 psi. The discharge temp of refrigerant is typically about 130 to 150 F at 220 psi while compressed *air* near the same pressure would be (off the top of my head) up around 500 F (no f'n way you would get there in a single stage either - even the York's would catch fire).

 

You could not run a single-stage AC compressor at more than 100 psi with ambient air temps and pressures - that's nearly 8:1 compression ratio in a single stage - you would burn it up at anything higher than that. Remember that it's all about the ratio - pushing 35 psi refrigerant up to 225 psi is only a 6.5:1 compression ratio - and with half the incoming gas temp.

 

Even running at "only" 100 to 120 psi the temps would be high compared to refrigerant - having the oil cooled compressor would be a huge advantage.

 

People use the York compressors because it's an easy choice - and likely very few people use them for very long at a stretch - but the advantages of an oil flooded compressor are obvious when you consider the temps involved in compressing air versus compressing refrigerant.

 

Now - if you used TWO compressors with an intercooler between - one to get ambient air to about 45 psi, then the next stage compressor could push it up to 200 psi without much problem...... though I'm not sure what I would use that for on my wheeler

 

GD

Edited November 13, 2010 by GeneralDisorder

[Scoobywagon]

Now - if you used TWO compressors with an intercooler between - one to get ambient air to about 45 psi, then the next stage compressor could push it up to 200 psi without much problem...... though I'm not sure what I would use that for on my wheeler

 

GD

 

Well, duh....you would obviously use that when you REALLY need to get a cheap HF impact gun spinning! I'm not actually sure what 200 psi would do to a HF impact gun, but I am pretty certain it would be entertaining...you know...from a safe distance.

[Scoobywagon]

I'm sorry, I was a bit unclear. You're quite correct that temp has a lot to do with the goings on here. I'm not forgetting or ignoring it. My point was that the increased internal displacement of the york-type compressor will yield lower duty cycles when regulated to 100 psi, compared to the, admittedly more common, rotary type A/C compressor. Reduced duty cycle translates very directly into less heat buildup as does the reduced system pressure. Regulating to 100 psi is still plenty to run air tools and inflate tires. And it represents a 6.8:1 ratio. That's well within the operating parameters for any A/C compressor. Both of these compressors will run a bit hot in this application, but, in the end, I still feel that the increased displacement of the york-type compressor makes it a bit better choice here.

[DaveT]

Yes, you need to provide oil to the input. Probably want an oil separator after the output. The output can run near 300PSI when running as an A/C compressor, so a regulator and a high limit switch to disengage the clutch it would be a good idea!