Installing a Compact Air Compressor that Fills a Tire in 90 SecondsPosted in How To: Wheels Tires on July 19, 2017
A source of compressed air is essential when venturing off-road. Inflating tires using CO2 tanks is quick, but tanks have a limited supply. Portable compressors are simple, but take a long time to fill four tires. These limitations make a permanently mounted, high-capacity air compressor a particularly compelling option. Combining the ability to quickly fill a tire with an endless supply of air makes a high-flow compressor a great solution.
Focusing on performance at a useful, tire-filling 30 PSI, the familiar brands offer some worthwhile choices. Two of the major manufacturers, Viair and ARB, offer good products; but Viair offers a 1.86 cubic-feet-per-minute (CFM) single-cylinder compressor, and ARB offers a 2.34 CFM single or 4.68 CFM double-cylinder compressor. Although Air-Zenith (AZ) is not as well known in the off-road world as Viair or ARB, its AZ OB2 air compressor can produce 4.25 CFM from a single cylinder, and pressure up to 200 psi at a 100 percent duty cycle. Key to this ability is large cooling fins on both the cylinder and cylinder head, and an electric cooling fan on the cylinder head. This second-generation design is very robust, providing high reliability under constant use. The OB2 was developed for the air suspension market, which tends to put more hours on a compressor than off-road customers do, and the entire compressor and motor can be easily disassembled and rebuilt with spare parts available from the manufacturer, if necessary.
In order to evaluate the compressor it was installed on a Jeep JK Wrangler Unlimited Rubicon. Your selection of a mounting location should take into account accessibility as well as environment. While a compressor can be mounted under the vehicle or in the engine compartment, those locations can be wet, muddy, dusty, or hot. Those conditions are enemies of a compressor’s performance and lifespan. In the JK Wrangler there is enough room under the passenger seat for a compressor, which is a clean and cool environment. This location gives access to the air at the passenger door, and is also relatively close to the battery so wiring for power is short and convenient.
Air-Zenith offers a complete kit, including compressor, hose, wiring, and air tank. However for our application, the tank was not needed. Ordering the compressor alone still included the basic wiring harness, relay, and leader hose. Additionally ordered were an 80-amp fuse and holder, a master switch, a pressure switch, and an air manifold.
Installation was fairly straightforward. The passenger seat was removed to access the mounting location and the compressor was mounted to the floor. Wiring and plumbing were then completed. The details are shown in the photos.
How did it perform? While the compressor made noise while running, it was not an objectionable frequency or sound level. With the engine running, we measured it at 80 db at the driver’s location, compared to 52 db with the compressor off. Current draw was less than 30 amps at 40 psi. Voltage drop at the compressor was only 0.22 volt while running, indicating the wire size is appropriate for the length and amperage. As far as inflation performance, a factory 32-inch tire was inflated from 15 to 30 psi in 90 seconds. While your Jeep’s tires are likely larger, it’s doubtful they would take too much more time to refill after a day of wheelin’.
The installed compressor was out of the way but offered easy access to the power switch and air coupling. Filling a tire is now a simple process of plugging in a hose and flipping on the switch. Follow along as we show you how it was done.
Tool ListWire cutter/stripper/crimper
Socket wrenches—13 & 18mm
Rivet nut installation tool
Parts List—Estimated Cost: $400Air-Zenith AZOB2K Compressor
Air-Zenith pressure switch
T-Spec 80 Amp fuse
6-gauge wire, 7 feet
16-gauge wire, 5 feet
Electrical toggle switch
Assorted crimp lugs, shrink sleeve, screws
3/8-inch FPT manifold or T, and 3/8-inch to 1/8-inch reducer
Air quick disconnect coupling, 3/8-inch MPT x 1/4-inch I/M
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