This page is about installing an earthing system in my 1995 Subaru Impreza. For my inspiration, I referred to A guide to installing an earthing system in a Subaru Legacy. Use this information at your own risk - always be careful when working on your car, especially the electrical system.

  The theory of the earthing system is this: A car's electrical system, as it comes from the factory, is not optimally grounded. Many things plug into each other sequentially, and in turn connect to the car's body, which then runs to the negative terminal on the battery. Every connection that electricity must go through means more resistance in its path back to the battery. The more resistance, the less efficiently the current flows. If many devices use the same path to ground, some of the more sensitive devices can pick up electrical interference due to voltage fluctuations or unexpected resistance. The sensitive equipment we're mainly worried about is the ECU - the computer that governs the engine's operation and processes information from the various sensors. If there are impurities in the ECU signal, engine performance can suffer. Most people don't have serious electrical issues, but some have reported that installing an earthing system has improved a rough idle, it's improved audio quality in a car's sound system (due to the system being better grounded), and some people even report better fuel economy and performance boosts after installing an earthing system.

  Taking what information I could from the above web site, plus information from discussions on the newsgroup alt.autos.subaru, I set about my task. I needed the following items: about 20 feet of heavy gauge wire and about ten connectors big enough to handle the wire. I didn't have much luck at first finding any connectors; I finally settled on some household screw-down solderless terminals from Home Depot. Home Depot is also the place where I picked up the stout, 6 to 8 gauge 19-strand wire; I think it was around $.25 a foot. The terminals I bought weren't big enough to fit onto the strut mount bolts, so I had to go looking again. This time I found some gold-plated ring type connectors at a car parts store. When I was done shopping, I was about $25 into the project.

  I attached one of the household connectors to the negative battery terminal in my car. Once that was done, I took a circuit tester and checked various places in the engine compartment for good grounding points. The Legacy web site suggested a point at each strut tower, four on the intake manifold, and one on the alternator. Long story short, I ended up only being able to stuff three of the heavy gauge wires into my connector on the battery terminal, so had to cross-link at several points. I also only put three household connectors on the intake manifold; I have one on the alternator and ring type connectors on the strut tower bolts. The photo below illustrates my installation (I know, it isn't pretty, but I was just messing around to see how hard it would be to install). The connectors circled in green are the household screw-down connectors, and those circled in red are the gold-plated ring type connectors.

  I've got three wires running straight from the negative terminal on the battery: one to the alternator, one to the battery-side strut tower, and one to the battery-sde intake manifold. I ran a wire from the passenger side (right side of the car) strut tower to the alternator connector, which gives it an almost direct path to the battery. I ran the two right side manifold connections to the left side strut tower, which is then connected directly to the battery. I figure the gold-plated connectors there minimize the resistance at that point.

  Final verdict? The car doesn't seem to run much differently. I'll drive it for a while and see if I notice any improvements in fuel economy or performance. I'd say that an earthing system may help some people, but even if you don't have any noticeable gains from it it's pretty cheap insurance for a smooth electrical system.