[g6civcx]

I apologise if this is getting into a different area than the original question. If you feel that this needs to be pruned and broken down into a different thread, then please do so.

Before we get into a big debate, please read this statement carefully:

Stock electronics are NOT as sensitive as aftermarket electronics. The accepable range of resistance to ground for stock electronics is much, much broader than the tolerances for sensitive electronics.

If you accept the statement above as being generally true, then grounding with stock electronics is not as crucial as grounding for aftermarket electronics.

So if you're just running stock electronics with a few gauges here and there, grounding is not as crucial. You can follow the factory grounding scheme and you will generally be okay.

If you're running extremely sensitive sensors and electronics that operate on a very narrow range of resistance, grounding becomes more crucial.

Originally Posted by Bigsyke

Why is the engine block grounded at all? let alone in 2 places almost opposite of eachother (IM then the rear of the head), We all know the sensors/harness grounds could be directly extended to the chassis itself. If the engine is grounded to the chassis, why go through the engine. We also know pure water will not conduct, but once a coolant or contaminant is added - galvinized corrosion, electralysis will occur on almost all aluminum or soft metals. Why do we isolate the heatercore, and radiator from the chassis.

I do not understand your question. Generally the engine has weak electrical connectivity to the frame. If we insulated the engine completely from the frame, we will build up excess electrons in the engine as I discussed above.

Originally Posted by Bigsyke

ive seen service bullitins say the engine is grounded in 2 opposite places is mainly for a path of least resistance so an underpar electrical system will not energize the aliminum. However if the chassis becomes energized the current can flow back to the engine block.

This factory grounding scheme is done mostly for convenience and cost control, and for reasons above (namely stock electronics are not sensitive).

Originally Posted by Bigsyke

My understanding is by grounding only 1 engine ground to the same spot as the bat - on the chassis, in the event of the chassis becoming energized from an underpar electrical system, the current can skip the chassis and directly access your engine block. Every aluminum engine ive seen has spaced out the -bat ground from all the other grounds, because the chassis is like an insulator, the engine is also like an insulator thus the sensative sensor grounds ended up being on the engine not the chassis. People have ran that circle of earth grounding systems and had a hole eat right through the water pump, radiator and heater core. There is just too many factors you have to dynamicaly acount for, like having an MSD system.

I also don't understand your comments.

Originally Posted by Bigsyke

Thats just what ive heard/read, ive never seen anything like that, but ive been toying with these stupid grounding systems from years on 5 different cars, I also picked up about 300ft of 2-4ga wire when Circuit city went under. I just upgraded the OE wiring and found that OE isnt "damaging" anything. But your diagram does seem interesting.

The OE wiring is done mostly for convenience and cost, as discussed above. To be honest, I don't place much stock in OE Nissan wiring.

As discussed above, I have just as much electronics design experience as a typical Nissan engineer. The advantage is that I'm not limited by assembly line efficiency, cost, and bureaucracy.

Originally Posted by Bigsyke

Why do you have only 1 ground going to the chassis? doesnt this leave room for energy to pass through half the engine?

The diagram above assumes that all engine accessories that see current are properly grounded to the head and/or block.

Of course, if you have any insulated component that sees current, you need to ground that component to the block or the chassis ground.

The concept is to reduce what's called a "ground loop". This is when 2 different components see different amounts of resistance to ground.

In this situation, the current can recirculate between the 2 components and cause unpredictable behaviours.

You want a single grounding point for all the electronics so that all components see a fixed amount of resistance to ground.

There will always be small variations based on the ground wire length, but you try to reduce these variations as much as possible.

Variances on the scale of 10 or less Ohms may be acceptable for all electronics. 10-1000 Ohms may be okay for stock stuff, but may not be okay for aftermarket stuff.

1000+ Ohms of variances may not be acceptable for even stock stuff.


If I can plot a 3D graph of electrical conductance on the unibody frame, you can see the variations. The frame is not a ubiquitous piece as we all assume. Some spots are more conductive, while other spots are not (e.g. spot welds, insulation, glue/tar, etc.).

To eliminate these variations, you choose a single point on the chassis to ground the entire system to minimize these variations.


Current will follow the path of resistance. So even though the engine may be grounded, albeit weakly, to the frame, when you connect a single ground wire from the block to the frame, you hope that all current flow will be via the ground wire because the ground wire has less resistance than any other path.