Recently, more attention has been paid to the overall benefit of providing multiple ground points to an engine. There have been plenty of articles in enthusiasts' magazines that show small but real increases in horsepower by simply adding additional ground or "earthing" wires, and not changing anything else. Proponents also point to easier starting, smoother idle, less headlight dimming, and improvements in just about anything electrical in the car. Whether or not you're a "believer," this mod is safe and can't really hurt anything, which is more than you can say about a lot of other mods.
Conventional thinking used to be that grounding was an "all or nothing" phenomenon. Either your battery was grounded, or it wasn't. However, there appears to be both a quality and quantity of the electrical return to the battery that has potential for improvement. Earthing or grounding kits are now hot selling aftermarket items. Nismo, the racing division of Nissan, makes one for the new 350Z. Prices of these kits can run upwards of $100. The materials for this "home made" earthing kit were less than $10.
Tools and materials needed
- pair of wire crimpers and strippers
- metric socket set
- 5-6 ft power cable, 4-8 gauge, or whatever gauge you like
- bunch (dozen) of cable terminal ends
- shrink wrap
- lighter / heat source
Difficulty: 1.5 out of 5, or pretty dang easy. I like to call this the easiest, best mod you can do to your Z for less than ten bucks.
Time: about an hour
I went to a local electronics supermarket, and bought "Super Deluxe 8 gauge DC Power Distribution Cable." You could buy 4 gauge, which is heftier, but I would not go any smaller than 8 gauge. I bought red cable to match my car and silicone hoses, but since these are ground wires then purists may want to use black. Well, purists may not accept the idea of an earthing kit in the first place, lol
The first two photos show my completed earthing "kit" which is simply four power cables cut to length, with the connectors crimped onto the ends and sealed in shrink wrap. The shrink wrap is sold as little black rubber tubes and is the black band at the base of the connection. The shrink wrap cuts to length with scissors. I like the finished look and extra water proofing the shrink wrap gave. I just used a Bic lighter to shrink fit it.
I simply 'eyeballed" the cable lengths by holding the cable up to the connection points I chose under the hood, and then cutting the cable on the spot, without using a measuring tape.
These connections are in SERIES, i.e. where one cable ends, another one starts. These connections are just suggestions, you can use any available grounding points. There are lots of different ways you can hook up a grounding kit. Some prefabricated kits have one end of each cable connected directly to the battery. So the negative battery terminal becomes a central hub, with all the cables coming off of it like legs on an octopus. I chose a series style of connections for reasons I will not completely go into here, other than saying my research supports it. One nice thing about series is a "cleaner" look since they aren't as many cables sprouting off your negative battery terminal. I believe the benefit is just as good, if not better, by hooking up the cables this way as in the "octopus" style.
Here are the exact locations I used for my connections on my '92 Turbo: The first and shortest cable starts from the driver's side fender well, on either one of the two bolts that holds the fuel filter bracket onto the car, shown by the green arrow in the right, lower corner. The other end of this cable goes to the second connection at a nearby plenum bracket bolt that is holding, among other things, a guide for the throttle cable. You can see this connection by the green arrow in the upper, left corner, and the yellow oil dipstick for orientation. The second earthing cable starts at this same bolt, and passes under the fuel lines toward the rear of the plenum.
The good thing about the connection chosen at the plenum is that this bolt is also connected to a bracket that goes down to the engine block, which makes it a better ground.
The distance to the third connection is the longest of the four cables. Direct the cable toward the firewall, then a 90 degree turn to the left along the back of the plenum, parallel to the firewall. There is a bolt on the top, rear of the plenum, nearer the passenger side as shown in the picture. This bolt was already being used as a ground for a connection coming out of the main harness, and for nothing else, as far as I could tell. You are about 2/3 the distance to the battery at this bolt. The photo also shows the rear of the plenum, the balance tube, and the fuel damper in the lower middle part of the photo to orient you. The driver's side is toward the right.
The bottom of the picture is toward the front of the car.
Start another cable from this bolt and go to the negative battery terminal next. Run another cable off the negative battery terminal to the mounting bracket on the fender well that holds the cruise control as well as the AIV and EGR solenoids. This is the final and fifth connection. Leave enough slack in the cables connected to the battery such that if you remove the negative terminal connector, you can still get the battery out without having to disconnect the earthing cables from the terminal connector. I'll post photos of these final connections when my car gets out of the shop.
Easy as pie. The cost of the cable, connectors, and shrink wrap was under ten dollars. Don't overtighten any bolts into the plenum, which is soft aluminum. After I connected the earthing grounds at the battery, the car idled smoother, which I took to be a good thang. I think the car also ran smoother and started easier with this mod, but I don't have any objective evidence to support this.
Even before installing this earthing kit, the car already had one extra, stock, battery grounding point. Very near the battery, the negative battery cable was stripped bare and attached to the firewall, before continuing onto the transmission bell housing. So along with the preexisting stock, negative battery grounds, this mod yields a total of six ground points, reaching all the way across the engine bay, from fender to fender.