"Grounding mod" - Major Improvements!

morgie · Post by **morgie** » Sun Jul 06, 2003 4:19 pm

Since my hesitation problems had came back, i got tired and decided to try this simple mod..

For those who haven't done it yet, GO AND DO IT NOW !!! hehe

major improvements after having done it, even my Air/Fuel meter showed different reading (i was MAX green, pretty rich, very different than the reading i had before doing this mod)

Pics :
http://public.fotki.com/morgie/morgie/l ... nding_mod/

The hesitations has miraculously disapeared after doing this... let's now see if they will come back after one week !! hehe

eastbaysubaru · Post by **eastbaysubaru** » Sun Jul 06, 2003 4:56 pm

Interesting results. I've been pondering over this for a while now. It's good to get some feedback from someone here. Thanks Morgie!

-Brian

sullione · Post by **sullione** » Sun Jul 06, 2003 6:28 pm

Is this some kind of kit that's available? Where to buy? I suffer from the hesitation thing now.

I would love for it to go away!

morgie · Post by **morgie** » Sun Jul 06, 2003 6:45 pm

Simply go in an electric / electronic shop , and buy a 15-20" of 10gauge wires (would cost like 5$), and buy connectors for 10gauge. any clerk there can help you. it's pretty easy to do. you might need a "criper" too.

Grant · Post by **Grant** » Sun Jul 06, 2003 6:52 pm

My battery ground cable was badly corroded about a year ago and I was working at a Home Electronics/Car Audio store so I bought a foot of the 2 gauge Competition Series Monster Ground Cable and some good quality connectors. It improved some little electrical stuff and the engine ran a little better. It also seemed to shut down better. Straight turn off instead of kind of a sputter off. I always planned on using better cables for all the ground wires but never got around to it. Also, I have never had any hestitation either.

teaguespeed · Post by **teaguespeed** » Sun Jul 06, 2003 11:15 pm

Could you possibly make some kind of diagram of where all the connections are, and where each wire goes. I may be under the impression that everything to do with cars is terribly complicated, oh well.

Post by **Legacy777** » Mon Jul 07, 2003 2:30 pm

Morgie,

yeah if you could list out what all the connection points you made, that would be helpful.

Grant · Post by **Grant** » Mon Jul 07, 2003 3:26 pm

Three cables: 1st one is parallel to firewall and attaches near ignition wires. 2nd one is the one with your hand near coolant tank and attaches to the ground on your starter I'm guessing. The third however, I have no clue of where it's going. Flux capicitor?

morgie · Post by **morgie** » Mon Jul 07, 2003 3:45 pm

i had a quite 'random' and 'non scientific' approach

1 - I grounded each strut tower since there is a "stock" grounding wire on each.

2 - I wanted to have a ground near the coil-pack, so i attached it to the easyest bolt i found, the bolt that holds the spark-plug-wire bracket. Also, i Wanted to have a ground near the Alternator.. so another ground on the big bolt that holds the alternator and A/C compressor... since i was short on cable, i linked it back to the connector under the spark-plug-wire bracket.

3 - I wanted to replace the big "Stock" grounding wire that attatch to the Starter or the engine, not quite sure.. and since i was short on wire, i hooked it up to the connector on the strut

hehe

teaguespeed · Post by **teaguespeed** » Wed Jul 09, 2003 1:03 am

Any scientific reason why this works?

morgie · Post by **morgie** » Wed Jul 09, 2003 1:25 am

I think the only "realy usefull" wire is the one following the main engine ground.

our engine seems to only have 1 ground connector (located under the Turbo cooling reservoir), and over time it gets corroded. By "Refreshing" the wire (by adding a new one), you get better connection / electrical flow.

I talked about that mod to some other persons. One told me that for DSM's, there is a "Grounding kit" that sells for around 100$ !!! and it basically consists of "connectorised wires" that you hook onto your engine... hehe

DIY is once again cheaper and usefull

I grounded the body via the strut tower bolts just in case that the stock body grounds were corroded. Since i had 15' of wires... gotta use them ! hehe

ciper · Post by **ciper** » Wed Jul 09, 2003 2:20 am

teaguespeed: Have you ever had a AV component that buzzed whenever you plugged it in? Its usually from grounding issues.

The ground mod basically zero's all these spots to the same level. I dont think it would make a difference to most components, I feel the benefit is from getting a cleaner signal from the various sensors (crank cam and knock most likely).

Just my guess. What I do know is that I performed this mod and it was noticable. Id say it was similar difference to when i changed to all synthetics (both diffs, transmission and oil).

vrg3 · Post by **vrg3** » Wed Jul 09, 2003 5:32 pm

It's not really completely well understood. Or, if it is, I've never seen it very well explained.

It is absolutely correct that adding these extra grounding straps helps make sure that all sensors and in fact all electrical components have the same reference level for their signals. The car's chassis and engine block and almost all other metal parts serve as a ground bus to carry this reference all over the car. Some parts actually have a noticable resistance, so when current goes through them there is a voltage drop. This basically means that the device's reference voltage is a little higher. Many sensors also have very high impedance outputs, so they can be affected more.

So, yes, you help eliminate ground loops. And there is much empirical evidence that this helps the engine run more smoothly, at least at first. Some people report that the ECU seems to "learn around" the improvements after a week or two, negating the improvement.

But, it's not entirely clear precisely which signals benefit from it. Let me try to enumerate the potential beneficiaries:

Cam and crank angle sensors don't benefit too much, since their signals are variable reluctance spikes which don't really use a fixed reference anyway. That is to say, both sides of their signal go along wires to the ECU. Internally, the ECU does ground one side, but the "quality" of the signal isn't a big deal. The spikes are either there or not there.

The vehicle speed sensor isn't under the hood, but in any case, its signal is also either on or off, and nowhere in between, so the grounding improvement shouldn't matter there either. Naturally the same should hold for the various switches (idle switch, air conditioning switch, neutral switch, etc).

The injectors and ignition coil both have their grounds run back to their own ground pins on the ECU. So do the throttle position sensor, the pressure sensor, and the mass airflow sensor. So these guys don't really use the ground path through the chassis either.

The solenoids (like the idle air control valve, the pressure exchange solenoid, and the wastegate control solenoid) tend to ground through their respective control transistors in the ECU, as in a switched-ground system. So they don't use the chassis ground paths.

The coolant temperature sensor's ground wire is connected to the shield used for a few other signals, but it does connect directly to the ECU's sensor ground pin.

The knock sensor does ground through the engine block. So the "grounding mod" can clearly help improve the signal path from the knock sensor to the ECU. I don't have a clear understanding of how the ECU interprets the signal from the knock sensor, so I can't comment much on this. It's possible that this signal benefits from a clearer reference and it's possible that it doesn't.

The oxygen sensor doesn't have its own ground pin on the ECU, but its ground wire is connected to the ECU's ground wire. It's a 3-wire oxygen sensor. However, I do believe that this ground is only for the heater and not for the signal itself (4-wire sensors have a ground wire for the oxygen sensor signal).

Ah ha! Doing the grounding mod can help the oxygen sensor signal become clearer for sure! If I'm correct, the sensor grounds through the exhaust piping. This is sub-optimal. The exhaust develops oxidation on it which doesn't conduct well (unless you use stainless steel, but stainless itself is not a great conductor anyway). Furthermore, as the temperature of the exhaust piping changes, the resistance changes. This means sensor readings for the same air/fuel ratio can vary depending on the temperature.

Huh... I wonder... Would you get almost the same results as the grounding mod by just running a ground wire to the oxygen sensor itself? You could get some wire... 14 or 12 gauge ought to be fine... Strip the end of it and attach it to the sensor itself with a hose clamp. You could get asbestos-coated wire from the hardware store if you're concerned about the heat. It's expensive -- like a buck a foot -- but still... Then you could run that either to the ECU itself, to another sensor's ground, or maybe even just to a strut tower or another random bolt.

The ECU does get its learning feedback from the oxygen sensor and the knock sensor, and these two sensors in particular don't have direct ground paths back to the ECU. Wow.

teaguespeed · Post by **teaguespeed** » Wed Jul 09, 2003 7:08 pm

wow is right. we have some friggin genius' on here.

so why are all those wires connected to the negative terminal on the battery? (i get a feeling that might be a stupid question, oh well.)

morgie · Post by **morgie** » Wed Jul 09, 2003 7:30 pm

Vrg3 : That seems to be a very logical explanation. But one little question / maybe ommision from you : Why do subaru used a big 2 or 4 gauge wire to ground the engine, if it's only used by the knock sensor and o2 sensor? (ok you'll answer me the starter / alternator / AC compressor surely).

What could be the effect of the "grounding mod" on Spark Plugs ? Alternator ?

vrg3 · Post by **vrg3** » Wed Jul 09, 2003 7:42 pm

As a nitpick, those big 2 or 4 gauge wires aren't actually grounding the engine... Generally, the engine block is considered to be the actual ground on a car. So it's considered more accurate to say that those straps are grounding the battery and the chassis. In reality it's all the same. The engine, the chassis, and any other metal part of the car, is part of the ground plane and the purpose of the factory ground straps is to make sure they really are well connected to each other.

You're exactly right in that they are important for the starter, alternator, and ignition. Think about the spark plugs -- they ground through the cylinder head. The alternator grounds through its bracket, and it generates up to 70 amperes that need to get around the car. The starter grounds through the transmission/engine, and its current needs to come from the battery.

From what I can see, the grounding mod shouldn't really affect ignition or charging too much, since there should already be a good enough ground path between the battery and the cylinder heads or battery terminal, and neither of those is really a noise- or level-sensitive signal.

But this raises a good point. Many people have said that using big fat wire is overkill for the grounding mod. They say you're wasting your money by using 8 gauge wire or whatever, since 10 or even 12 gauge would do for the currents used by the sensors. The problem is what happens should your factory ground strap fail. Without these extra grounding wires, your charging system would basically fail or work really badly. With these grounding wires, the alternator will try to charge through them. Try running 70 amps through a 12 gauge wire and you will cause a fire. That's why using heavy gauge is a good idea for this mod. In my opinion, anyway.

ciper · Post by **ciper** » Wed Jul 09, 2003 7:59 pm

Interesting.

Im going to run a ground wire from the knock sensor bolt and try to wire in a ground directly from the oxygen sensor.

The dash gauge temp sender grounds through the engine, the ECU temp gauge has two pins, so it grounds directly to the ECU right?

Can anything think of other devices we have missed that could benefit from this mod?

How abot the transmission, it grounds through that small strap near the firewall but nowhere else.

vrg3 · Post by **vrg3** » Wed Jul 09, 2003 8:28 pm

ciper wrote:Im going to run a ground wire from the knock sensor bolt and try to wire in a ground directly from the oxygen sensor.

Yeah, you should be able to use a ring terminal for the knock sensor. Off the top of my head, I think a 5/16" or maybe 3/8" ring ought to be right.

For the oxygen sensor you can just wrap the wire around the oxygen sensor and secure it with a small hose clamp.

Please let us know how that does!

The dash gauge temp sender grounds through the engine, the ECU temp gauge has two pins, so it grounds directly to the ECU right?

Yes, the sensor for the gauge grounds through its body, but the sensor for the ECU has a ground wire going back to the ECU's "sensor ground" pin.

Can anything think of other devices we have missed that could benefit from this mod?

I went through everything connected to the ECU. I don't know as much about the other electrical systems. There's a pressure sensor for the air conditioning, right? It probably wouldn't matter much though, even if it was just grounding through its body.

How abot the transmission, it grounds through that small strap near the firewall but nowhere else.

As far as electrical parts go, the 5MT only contains switches for neutral and reverse. I'm not as familiar with the 4EAT but I would think it would only contain switches and solenoids. These would all be on/off devices, so they're probably okay. The TCU reads off the ECU's sensors I think. I don't know if it gets their grounds though or even whether or not that matters. I guess you could put a grounding strap between the ECU and the TCU.

But, hmm... I wonder if it's possible that some peoples' problems with 4WD or torque converter binding have to do with bad grounding of the transmission body. I would think it would still be okay since the bellhousing bolts to the engine, but still, hmm.

ciper · Post by **ciper** » Wed Jul 09, 2003 11:13 pm

I was thinking speed sensors, there are two right? Or is the front one part of the speedo?

vrg3 · Post by **vrg3** » Wed Jul 09, 2003 11:25 pm

My understanding is that VSS1 is built into the automatic transmission (manuals don't have one), and VSS2 is built into the gauge cluster.

But, both of those sensors output a square wave (the line just alternates between 0 and 5 volts). A slight voltage offset due to bad grounding shouldn't make any difference.

ciper · Post by **ciper** » Wed Jul 09, 2003 11:40 pm

I think your right in both cases.

Post by **Legacy777** » Wed Jul 09, 2003 11:52 pm

You could actually use a multi-meter and test different spots around the engine and see which ones don't have perfect continuity.

vrg3 · Post by **vrg3** » Wed Jul 09, 2003 11:57 pm

Yes, you can do that... Measure how much resistance there is. Remember also that resistance changes with temperature.

It'd be interesting to, for example, measure the resistance between the oxygen sensor body and the ECU body when the engine is cold and when the engine is hot. See how much of a difference the ECU has to deal with.

91White-T · Post by **91White-T** » Sat Jul 12, 2003 6:01 pm

Well I just did this the other day, and basically saw no results whatsoever, oh well, looks like I wasted 18$

vrg3 · Post by **vrg3** » Sat Jul 12, 2003 11:19 pm

91White-T, which did you do? Run grounds all over the place, or just to the oxygen sensor and knock sensor?

Can you describe more about what you did? What gauge wire did you use? Did you sand away paint and oxidation where you were attaching ring terminals? Did you attach all the grounding straps to the battery terminal, the engine block, or some other location? Did you run a star pattern or a circle pattern? Did you reset your ECU afterwards?

I'm sorry you spent money to no reward, but maybe we can learn from it... Most people say they do experience an improvement.

legacycentral bbs

A forum for 89-94 BC-BF(BJ) Legacy Owners and Fans

"Grounding mod" - Major Improvements!

"Grounding mod" - Major Improvements!