This may be one of the most useful thing you can do to your Jeep. A winch may only be used once in a blue moon but a air compressor is used for airing up after each day of offroad. If the compressor is big enough you will be able to use air tools. There are two choices for on-board air, one is to convert a old A/C compressor into a air compressor and the other is to get a electric air compressor. Your main concern is the cfm or Cubic Feet per Minute. The larger the cfm rating the better you're off. Most A/C conversion are able to produce 4 to 9 cfm while electric compressors are able to produce 2 to 4 cfm. A K-Mart blue light special will work and only costs $20 but it's really not up to the task of airing up a 33" or taller tire anytime soon.
I chose to go with a electric compressor for its small size and reasonable cfm rating. There were 4 different choices . Three of them come in Portable and Hard mounted styles. The ARB ($199) was the smallest of the group at 0.95 cfm. The next one in the group was the Quick Air from Sun Performance Products. The Quick Air ($175) is rated at 1.19 cfm but is a little small for airing up 33" tires. The largest of the group is the Ready Air compressor rated around 4 cfm. The only problem is that it costs $600 and is fairly large for a electric compressor. I ended up with a a new Quick Air 2 from Sun Performance. It is similar to the original Quick Air but in name only. The new Quick Air 2 is rated at 2.18 cfm at 0 psi and is only slightly larger than the original. At $299 for the portable version, it's not that great of a deal but you get a nice storage box and a coiled hose. I thought the better deal was to get the hard mounted version or $260. It comes with nothing other than 13 ft of wire. The Quick Air 2 also has almost twice the cfm as the Quick Air making it a better deal.
I bought the 2.5 gallon air tank that Sun Performance has or $60. Only problem is mounting the air tank someplace. I found out that the 6"x24" tank to be too large to mount under the hood. This was a big disappointment. The other place you an mount the air tank is under the Jeep tub next to the drive shaft. You shouldn't have to worry about rocks hitting the tank since rocks are going to push the tank through the floor before it ever punctures the tank. I chose to keep everything mounted high in the Jeep to keep the compressor clean and dry. The only place to do this was inside the Jeep mounted to the rear wheelwell. This posed one problem and that was getting bolts through the wheelwell. First you have to remove the splash liner. This takes a removing 4 bolts or so and 5 drive rivets. To remove the clips you will need pliers and some WD40. Pull the pins out from the center ad the base will come out with the pin when it slides to the end. If the pin removes completely that is ok too. After removing the liner you can go ahead and drill 4 holes for the tank and 3 holes for the compressor.
You will have to buy some rubber washers along with some metal ones. I found some large washers to spread the pressure more evenly across the wheelwell. The rubber washers are used to keep the tank from rattling and to help flatten the wheelwell since it is somewhat ribbed. One all the holes are drilled you a go ahead and mount the tank and air tank. The air tank has threaded legs so the bolts have to go from the bottom while the compressor uses sheet metal screws. Be sure to use a pilot hole so as to prevent drill bit wander. Choose the final drill bit slightly larger than the inside thread for those who don't now. With the tank on the wheelwell, Amounted the compressor on the front side of the same wheelwell. You will only be able to drill three holes because of the roll bar but it should be strong enough.
Once you're done mounting everything, next comes the wiring. With 13 ft of red cable you can easily pass the wire through the firewall and straight to the battery. You can wire another switch on the dash to run the compressor for convenience but I didn't at the time. With the wiring done you're next problem is getting all the fittings and hoses to connect the compressor to the tank. This was the most difficult part. If you have $80 on hand you can buy an Mounting Kit from Sun Performance which comes with all the fittings and a small pressure gauge. It might be worth it after rushing around three towns looking for parts. I ended up buying some Quick Fittings a set of three male/male adapters, 300 psi hose, Compressor to tank hose and a 140 psi pop-off valve. I bought a 140 because the tank is rated at 150 psi and the compressor is rated at 105 psi. This means the pop-off valve will blow 5 psi before the tank hits its max. I am currently not running a pressure switch because of cost but a pressure switch and pop- off valve would be a better choice since it would shut off the compressor at well before max rather than just releasing the pressure at max while the compressor still churns.
So is the Quick Air comparable to a A/C compressor? No, but when you don't have the space available, it's better then nothing.
