Hotrodpez Posted November 3, 2008 Share Posted November 3, 2008 I've been considering relocating my battery to the trunk area. Why? Because it would be different (read: cool) and also give me a place to put my coilpacks. I've done some searching and the main drawback I find is that most recommend running a separate heavy gauge ground wire from the negative terminal to the engine block. Why is this? I know many cars (e.g. Mazda Miata, BMW 325i) that have the battery mounted in the trunk and they only ground to the body / frame. Is this a Z specific recommendation? Or is it even necessary? I can't see that the body / frame rails could have so much impedance that it would cause problems. Quote Link to comment Share on other sites More sharing options...
BurnoutZ Posted November 3, 2008 Share Posted November 3, 2008 People always put batterys in the trunk. esp. for sound systems. If your going to add alot of extra weight in the back, I would stiffen the rear suspension... Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted November 3, 2008 Share Posted November 3, 2008 Boy - did that ever answer his question. Good one there. Maybe he can run a ground strap to his beefed up rear springs! The Z (earlier S30's) are known for crappy wiring and poor grounding. So much so, that even Courtesy Nissan sells an upgraded wiring kit to solve a lot of the grounding problems on the Z. I am in the exact same boat, however, my car has been hand wired by the PO, (who over-engineered the car anyways) using 14ga. and better wiring throughout the car. My battery is in the trunk, and grounded to the chassis back there. I also have a ground from the starter bolt to the battery tray (chassis) I'm going to run it for a little this way and see if I encounter problems. For safety sake though, I am probably going to get a long cable and ground just as you recommended. It won't take long until an "informed" member on this forum can put us straight on this subject - I would think. Quote Link to comment Share on other sites More sharing options...
Dave Posted November 3, 2008 Share Posted November 3, 2008 It is best to take the ground cable to the block using the same size cable as the positive. If you do run the negative to the body as a ground you need a ground from the block to the body that is the same size as the positive cable. I see that some even ground the head or heads to the block with a cable. If you don't have the block to body ground you will find the clutch lines, throttle and choke cable will start acting as grounds. How about a Stainless braid fuel line acting as a ground as the car is being started? As 2eighTZ4me said "The Z (earlier S30's) are known for crappy wiring and poor grounding" just don't make it worse. Quote Link to comment Share on other sites More sharing options...
Oddmanout84 Posted November 3, 2008 Share Posted November 3, 2008 Boy - did that ever answer his question. Good one there. Maybe he can run a ground strap to his beefed up rear springs! The Z (earlier S30's) are known for crappy wiring and poor grounding. So much so, that even Courtesy Nissan sells an upgraded wiring kit to solve a lot of the grounding problems on the Z. I am in the exact same boat, however, my car has been hand wired by the PO, (who over-engineered the car anyways) using 14ga. and better wiring throughout the car. My battery is in the trunk, and grounded to the chassis back there. I also have a ground from the starter bolt to the battery tray (chassis) I'm going to run it for a little this way and see if I encounter problems. For safety sake though, I am probably going to get a long cable and ground just as you recommended. It won't take long until an "informed" member on this forum can put us straight on this subject - I would think. Motorsport (thezstore.com) also sells an engine grounding kit which they claim takes a lot of noise out of the electrical system. I've been thinking about it myself... Quote Link to comment Share on other sites More sharing options...
S30TRBO Posted November 4, 2008 Share Posted November 4, 2008 I relocated my battery to the rear. I have one ground to the chassis and another one running to the engine bay. As it was put to me as I originally ran just the short 36" chassis ground. If I don't run a ground to the engine: the lights will not be full brightness, etc. as the ground side of things at the front of the car will have to deal with a voltage drop (yes, even on the ground side) due to using the body/chassis as a ground to connect to the negative post on the battery. The battery will also never really get a good charge. If you don't have a big (as big as the positive cable) negative cable going from the battery to the engine block and chassis near the headlights, then I suggest that you put one in. The second ground runs along with the positive up to the engine bay: Quote Link to comment Share on other sites More sharing options...
Hotrodpez Posted November 4, 2008 Author Share Posted November 4, 2008 If you don't have the block to body ground you will find the clutch lines, throttle and choke cable will start acting as grounds. Yes, I've seen this happen on VW bugs when the trans-to-pan ground strap fails. Its a good way to go through clutch and throttle cables really fast. Quote Link to comment Share on other sites More sharing options...
junglist Posted November 4, 2008 Share Posted November 4, 2008 What are the grounding points on the car that the MSA and Courtesy grounding kits use? Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted November 6, 2008 Share Posted November 6, 2008 If you relocate your battery, run both a power and a ground wire to the engine bay. Expect to spend a good $50 for the appropriate gauge wires. I'd say 4 gauge is the minimum (read: smallest wire) I would use for the job. Grounding through the chassis is lazy on the part of auto engineers and they invariably cause issues as the car gets older. NOT something you'd want to do on a 30 year old car. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted November 6, 2008 Share Posted November 6, 2008 Doesn't mean it's right but I have not experienced any problems grounding to the frame. I use one of the old seatbelt retractor bolts. Make sure you ground the engine to frame either way. Cameron Quote Link to comment Share on other sites More sharing options...
Zmanco Posted November 6, 2008 Share Posted November 6, 2008 In theory using the chassis would be a great idea because of the large surface area (the electrons mostly flow on the surface of the conductors, not through the center). But in practice, the chassis isn't one continuous piece of metal and over time corrosion will develop at the various seems which will add resistance. So for our old cars, as was said above, it's best to pull both +12V and ground cables to the battery wherever it's mounted and to use at least 4 gauge or larger (size, not number). That said, it's probably not a big deal if you use the chassis if the car has lived its life in a less corrosive environment (Arizona for example) and if the battery, starter, and rest of the engine are all in good condition. But separate cables would be better. Quote Link to comment Share on other sites More sharing options...
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