Computerize your car

SUVs, minivans, and hatchbacks were built to make the most use of the interior space. The challenge is finding an unaccounted-for cavity to mount the CPU. The first place to check is behind the interior body panel by the rear wheel wells. Larger SUVs will often put big interior panels over those spaces to create a space for electronics, a jack, and other roadside repair tools. Other possible mounting locations may be found under seats, inside the dash, or inside the center console.

Sedans, coupes, and convertibles that include a trunk offer good mounting options all over the cargo area. Hanging the unit upside down under the rear deck allows you to keep all of the cargo space while making the unit accessible. Make use of false panels if you cannot find space. A false panel can be simply constructed of particleboard and matching carpet. It is important to keep the CPU clear of speakers. Magnets used in car speakers can adversely affect your computer components.

After you find a good mounting point, consider the path for your wiring. There are few direct routes, so most wires will have to be run under carpet, through body panels, and under seating. Although all wires are subject to radio interference from the alternator and various vehicle electronics, the video and audio leads are most susceptible. Shielded video cable may be more expensive but will be less likely to suffer from picture-distorting interference. The same rule applies to your run of audio cable from the rear of the car to the amp or head unit. Shielded audio cable prevents engine whine from coming through the speakers.

The last part of the assessment is finding power. The ground connection is the simplest to find; it's best achieved through securing a self-tapping screw directly into the vehicle's interior sheet metal. Make sure you know what's on the other side! Continuous 12V power can come directly from the battery or an always-on connection in the car. Some cars' cigarette lighters are always on; some are not. Use a voltmeter to see if the power is switched off after the key is out. That leads us to the last part: 12V switched. Somewhere in your vehicle's wiring harness and fuse panel is a circuit of 12V power that is live only when the car is on. If your test shows that the lighters are live only after key-on, you've found a good source for 12V switched power. Wiring diagrams are available through off-the-shelf manuals such as Chiltons, which can be had at your local bookstore or auto parts shop. Poking around the wiring harness with a voltmeter is a risky option for vehicles with sensitive onboard electronics. Placing the meter on a data wire may short out a very expensive onboard safety or fuel management system. Once you find your power sources, run the wiring through the vehicle. Make sure the wiring gauge is appropriate for the power needed by the components. Basic car computer applications will rarely need anything thicker than 12 gauge.

Toolbox
Having the right tools will be a big time-saver. If you'll be removing body panels, get a panel tool, which runs about $10 at auto parts stores. A good wire stripper/cutter and crimper can make your install go very quickly, with quality results. Invest in a Klein or similar electrician-grade pair of crimpers and stripper/cutters. Fish tape lets you route wires through things you never thought possible, and zip ties make everything neat. Foam-backed double-sided tape is good for permanently securing USB hubs and small devices. Self-tapping sheet-metal screws save you from drilling pilot holes. Black and red 12- to 16-gauge wire will handle your CPU's power requirements, and an in-line fuse kit protects all your expensive electrical components.