DIY Grounding for Nissan 200SX S13

DIY Grounding (Nissan 200SX S13)

Copyright © 2004 Jack Choo 1

DIY Grounding (Nissan 200SX S13) Why Ground? Fuel injected cars rely heavily on electronics to function optimally. Looking at the 200SX service manual, you’ll get an idea just how many sensors the ECU depend on just to make seemingly simple decisions such as how much fuel to inject etc etc. These sensors give an electrical voltage back to the ECU to indicate its status. If we all know our basic science well…all electrical voltage measurement is taken with reference to GROUND or 0V. To illustrate this, imagine that your AFM is supposed to send back a 4V reference back to the ECU. Now, in the ideal case where GROUND is truly 0V, this is not a problem. What if the GROUND is not 0V? If it’s polluted with spikes and irregularities, it can spike up to 1V or 0.5V at certain intervals due to engine operation sometimes or other sources. When this happens, 4V is not 4V anymore, with a 1V spike in the GROUND, your ECU reads 3V and compensates accordingly to that reading; which is wrong! Personally, I am not clear as to how these spikes can occur but based upon what I know, on older engines, bolts tend to loosen and various parts tend to shake a little more when in operation. The motion causes electrical induction (akin to shoving a magnet through a metal coil) on the metal parts that are mostly grounded, causing spikes or ‘noise’ in the GROUND. An effective GROUND from one point to the battery negative terminal (0V) is the path of LEAST RESISTANCE. Minimal resistance means that better conductor is required and laid over the shortest distance possible. Key Ground Points I believe what I did was overkill but here goes

- 4 points on the engine block - 1 point near the turbo - 1 point at the AFM - 1 point at the centre of the firewall - 2 points at the throttle body (one to the body and the other close to the AAC solenoid portion) - allocation made for compressor, alternator and O2 sensor but I need this done in a workshop

because the access points are hard to get to from the top.

Engine Block - 2 at the sides and 2 at the top. The 2 side grounding was from the previous owner so I kept it there (but can be improved!) so I added another 2 at the top of the engine block. These are where the plugs are located. Since the plugs are fired based upon a voltage trigger from the ECU, my thoughts were to put good grounding as close as possible to the plugs. Turbo - This is as close as I can get for the O2 sensor. AFM (Air Flow Meter) – Grounded this to the entire AFM enclosure. Throttle Body – Grounded to the rear of the throttle body and close to the AAC (Auxiliary Air Controller) solenoid. The solenoid opens and closes the amount air going through to the throttle body at idle. I put this here because I was worried that even when the car is moving, the poor grounding can attribute to the solenoid responding when it should not. I’m paranoid, I know. Firewall – This panel is where most of the interior electronics is hooked up to.



Materials Where? Sim Lim Tower at Jalan Besar Which Floor? Basement and/or 3rd floor electrical hardware shops What I bought? And how much? 1m of AWG4 OFC (Oxygen Free Copper) power cable (4-5SGD) 5m of AWG8 OFC power cable (10-12SGD) Power Distribution Blocks, gold plated x 2 (between 7-15SGD each, you should find one that can be mounted easily to your chassis or strut bar) Garden Shears, for cutting the wires (4SGD, a good pair scissors will do to) Razor blade, knife to strip the wires (cost nothing, cos’ you’d probably have one at home) Metal lugs for connecting the wire to the bolt (70-90cents each) Cable tie (about 3-4bucks a pack, these guys are useful. Buy the bigger ones) Cable heat wrap (buy about a meter or so to suit AWG4 and AWG8, about 2 bucks for both) Total cost: not more than 60SGD General Connection Diagram

AWG4 OFC Cable

AWG8 OFC Cable

AWG8 OFC Cable AWG4 OFC Cable (already present in stock condition)

Ground Distributor (use Power distribution blocks)

Bolt/Screw Connection

First Distribution Point

Second Distribution Point



Implementation Photos I admit I overdid this so you may need less wires or even only one distribution point which means cheaper by almost half the cost. Here are some pictures from my implementation.

Battery – I used thicker 4WG wire from the negative terminal to the 1st distribution point.

Distribution Points – I like the ‘look’ of this thing. Looks like something out of the hi-fi world (which incidentally, it is!). I like it also because it’s easy to screw in the wire directly. The strut-bar actually forms a good ground point.



Throttle Body – one from 1st distribution point to the back to the body then from the back of the body to the AAC unit.

Firewall – direct from the 1st distribution point



Engine Block – from firewall or 2nd distribution point is ok. Better still direct from the battery terminal but I opted for this. 2 connections to the top cover bolts and the other 2 at the side of the engine.

Turbo – direct from 2nd distribution point. If you can somehow find a way direct to the O2 sensor or closer even better!



AFM – wanted to bolt on the smaller screw at the side of the AFM but opted for the bolt between the airbox and the AFM cos’ it was easier to remove. Preparation

- cut wires to the correct lengths according to your plan - strip both sides by cutting the insulation off - insert the lug and crimp it good (make sure its real tight!) - to protect the connection, insert the heat wrap to cover the metal part except the lug hole, they

should be real loose - use a hairdryer or lighter on the wrap and you will notice that the heat will shrink it to a really

tight fit around the connection - do for all the wires! If you are connecting to the ‘screw’ type distribution point like mine you will

only need a metal lug on one end

Installing - find a good spot to fix the distribution point - for me, it is the strut bar base which happened to have some screw holes so I drilled a hole right

through the distribution blocks and bought correct screws to mount that on - if you are having problems with this then perhaps get a strong adhesive or some sort of

conduction adhesive to fix it onto the strut bar base snugly - to remove tough bolts (I found the throttle body bolts to be rather tight), use WD40 and spray

on the bolt, leave it for 10 minutes then try again, it should come out easier - be careful not the drop the bolts, you may not be able to recover the again if it drops into some

crevice in the engine bay! - Use your imagination for the distribution point! The one I use may not be

suitable for your case!

Documents

DIY Grounding for Nissan 200SX S13