Manifold Earth Wire

[smokn4]

the earth wire thats bolted on the end of the manifold by the fuel rails,

does that HAVE to be ground there or on the manifold or can it be moved to another location????

on the heads or block somewhere maybe ??? ???

chur

[Stoffa]

Has to be manifold. some of the main grounds from your ecu go to the manifold so it has to be well earthed to the chassis

[WRXONP]

an earth can be mounted anywhere - its only earthing after all - all earths connect to a metal surface and lead back to the battery terminal - it just has to be a good earth

[Guest]

 WRXONP said:

an earth can be mounted anywhere - its only earthing after all - all earths connect to a metal surface and lead back to the battery terminal - it just has to be a good earth

Epic fail - Brad . ECU earths MUST go to the manifold or engine block, that way they are "above earth" for the heavy currents of starter etc

Placing ecu earths to the chassis will cause issues

[gazzy2000]

i have found the earthing on subarus to be not that black and white..

meaning an earth is not 'just an earth and any old earth will do" when it comes to Electronic Fuel Injection

I guess 'an earth is an earth" at the end of the day, but its how and where the electrical sensor/component finds that earth is the key here..

Different types of Earths on a subaru EFI:

- sensors that get an earth straight to ground

- senors that get an earth supplied from the ECU (i.e. not stright to ground but via a pin on the ECU and controlled by the ECU from there, offering noise suppression etc)

- the shields from the shielded wires do not go to ground, once again the ECU supplies this on its own pin(s)

- the main ECU earths

The main ECU earths do go to ground, but before you go running new earths down by the ECU you have to know exactly what pins these main earths are, or you may earth out some sensors that are not meant to go directly to ground resulting in CELs or erroneous running.

A good example: on a GC8 (or around that year(s)) your AFM has an earth wire yea?, but that earth goes directly back to a singular pin on the ECU fully dedicated for the AFM and nothing else.. ppl have unassumably earthed that wire stright to ground and they end up getting a CEL.

I have broken it down here http://www.clubsub.org.nz/forum/index.php/topic,10158.0.html after working through a full rewire of a v3/4 (have done it twice now).

rant over, fiddy cents paid!

[WRXONP]

realistically the best earth for anything (thats not a sheild wire or one which is earthing into the ecu itself then earthing through the ecu earth wire) is the battery terminal - as thats where they all end up anyway - the only thing different with a earth going INTO the ecu is that it will effect resistance 


the engine block needs to be earthed to the chassis (duh) as the engine sits on rubber mounts - the block earths via a earth strap as sensors earth onto the motor itself ( 1 wire sensors) and spark plugs of course / starter motor etc - if a wire is earthing to the block (earthing to the manifold is just going through the block and earth cable to chassis and then to battery terminal) - how is it any different to earthing directly to the terminal or to a good earth on the chassis???

a earth is a earth if its bolting to metal connecting to the car - its the ecu earths that are different and sheild wiring

the better the earth the better - adding earth cables can help -

heres a scenario - u add a earthing kit - u earth 1 to the manifold - its large 4 gauge or bigger cable - how is that any different from taking the earth wiring off the manifold and joining it staight to the battery terminal ?? its exactly the same

opinions expressed here are that of the writer, please seek electrical advice from a professional

[D-Style]

Cars arent connected to earth. Completely different electrical theory...

-VE, 0V etc. correct terms should be used.

Connections are placed where they are for reasons.

[Guest]

 WRXONP said:

realistically the best earth for anything (thats not a sheild wire or one which is earthing into the ecu itself then earthing through the ecu earth wire) is the battery terminal - as thats where they all end up anyway - the only thing different with a earth going INTO the ecu is that it will effect resistance

the engine block needs to be earthed to the chassis (duh) as the engine sits on rubber mounts - the block earths via a earth strap as sensors earth onto the motor itself ( 1 wire sensors) and spark plugs of course / starter motor etc - if a wire is earthing to the block (earthing to the manifold is just going through the block and earth cable to chassis and then to battery terminal) - how is it any different to earthing directly to the terminal or to a good earth on the chassis???

a earth is a earth if its bolting to metal connecting to the car - its the ecu earths that are different and sheild wiring

the better the earth the better - adding earth cables can help -

heres a scenario - u add a earthing kit - u earth 1 to the manifold - its large 4 gauge or bigger cable - how is that any different from taking the earth wiring off the manifold and joining it staight to the battery terminal ?? its exactly the same

LOL - you fail to understand electronic components and having these sensors stable

So why dont they earth all the wires at one point then...???

or why dont the ECU sensor earths and power earths, actually earth at the ECU instead of the manifold

I await your reply ......

oh, and direct from Link ecu

10.4 Power Ground

These wires supply the high current earth for the output drives. Since these wire will carry

substantial currents, ensure they are well terminated to a clean earth point on the engine block. It

is also essential that there is a good clean connection between the engine block and battery

negative terminal.

IMPORTANT!

The Power Grounds MUST be run as SEPARATE wires. DO NOT be

tempted to join them together at the ECU and run as a single wire. Also

beware of poor earth points around the engine. Some manifolds and

other attaching parts may be rubber mounted and therefore have poor

earth bonding. A good rule of thumb is to use the engine BLOCK or

HEAD rather than attaching parts.

[WRXONP]

why would they waste wiring on a mass produced car?

and how ugly would it look with a million wires on the battery terminal?

so how is earthing it on the manifold any different to earthing on the chassis or straight onto the battery terminal ??

ive moved wiring around on lots of different models of cars - moved earths off the motor and nothings changed at all

[gazzy2000]

i always thought this was a bit ghey... see pic bulletin from Link and my questions raised after:

EDIT: this Link doco is refering to the main ECU earths.. not sensor earths

1) it says not to run the new earths to the battery.. instead to the manifold

i have a str mtr 'earth sized' cable going from batt earth straight to that earthing point on the manifold.. so what would be the difference to those ECU earths if the went straight to the batt? fark all i'd say.. as the earths are good and fat + multipathed EVERYWHERE incl chassis (in my case at least)

2) it says dont join the two wires (i assume its becuse they need to be good earths with correct wire rating and yud need a bigger cable if u use a singlular one)

these are not special earths.. they are just ECU main earths, if you joined them at the ECU into one big wire (the right gauge) and then straight to the battery.. it would be fine, long as the earth from batt to engine/manifold we mint. SO really it wouldnt matter what location

[WRXONP]

that is sort of some of my point - so u have wires earthing on the manifold right

u add a earthing kit that earths on the manifold - current allways takes the easiest path - which would be down the added earth cable (hence y u add extra earths in the first place) - its basically going straight to the battery isnt it -

[gazzy2000]

 WRXONP said:

u add a earthing kit that earths on the manifold - current allways takes the easiest path - which would be down the added earth cable (hence y u add extra earths in the first place) - its basically going straight to the battery isnt it -

yes, for these main ECU earths at least, long as you had a earthing kit you cant go wrong.

I mean look at the fat arse earth going from batt to str mtr on most subarus, i.e. the engine/mani has an earth direct from the battery regardless

[WRXONP]

which is the wiring in question - which is being said u cant earth it to the battery

[Guest]

 WRXONP said:

why would they waste wiring on a mass produced car?

and how ugly would it look with a million wires on the battery terminal?

so how is earthing it on the manifold any different to earthing on the chassis or straight onto the battery terminal ??

ive moved wiring around on lots of different models of cars - moved earths off the motor and nothings changed at all

Well they are wasting wiring in your eyes , because they run those earths to the block instead of the chassis at the ECU

I dont care if you have moved wiring - but did you mov your ECU power earths to the chassis or batt terminal

Earth kits improve the loss in std earth cables - sometimes over 200Mv - (0.2v)

READ The last post I added details from Link

[Guest]

Brad are you pulling my leg or are you convinced that you can run ECU earths direct to batt terminal instead of block

[Guest]

And, I never said - you couldnt run wires where ever the heck you feel. Just that its WRONG !!

[gazzy2000]

 Ichi Ban said:

Brad are you pulling my leg or are you convinced that you can run ECU earths direct to batt terminal instead of block

i say you cud no worries, mainly if yu hv a good gauged earthing kit as well.. but a question in my mind is why wud u wanna stray too far away from what/how it was setup in its stock factory form?.. there is a remote chance something will not like it etc.

Different if you are wiring in a fully new ECU (i.e. not a plug in)

edit: so are we going in circles here or what? lol

[Guest]

 gazzy2000 said:

2) it says dont join the two wires (i assume its becuse they need to be good earths with correct wire rating and yud need a bigger cable if u use a singlular one)

these are not special earths.. they are just ECU main earths, if you joined them at the ECU into one big wire (the right gauge) and then straight to the battery.. it would be fine, long as the earth from batt to engine/manifold we mint. SO really it wouldnt matter what location

The reason for NOT joining the wires is that should a resistance build up at the earth point then the wires will cross feed

Must have seen 100 Link installs with issues from bad earthing and also having these wires joined

Maybe link know what they are on about !!

[gazzy2000]

 Ichi Ban']

[quote name='gazzy2000 said:

2) it says dont join the two wires (i assume its becuse they need to be good earths with correct wire rating and yud need a bigger cable if u use a singlular one)

these are not special earths.. they are just ECU main earths, if you joined them at the ECU into one big wire (the right gauge) and then straight to the battery.. it would be fine, long as the earth from batt to engine/manifold we mint. SO really it wouldnt matter what location

/quote]

The reason for NOT joining the wires is that should a resistance build up at the earth point then the wires will cross feed

how do you mean, they both earth at the same earth point so if that degrads (i assume thats what u mean by resistance) both cables will have a bad earth full stop

edit: just like they would if it were one cable

[Guest]

Nope not going round in circles - not at all

If you or Brad cant see why manufactures fit there Ecu earths to the block/head/manifold (inc Nissans Brad!!) Then just go for it- wire direct to the battery

I end up making good $$ from peeps or cars they have induced faults into by not reading and following instructions and advice

[Guest]

 gazzy2000']

[quote name='gazzy2000 said:

2) it says dont join the two wires (i assume its becuse they need to be good earths with correct wire rating and yud need a bigger cable if u use a singlular one)

these are not special earths.. they are just ECU main earths, if you joined them at the ECU into one big wire (the right gauge) and then straight to the battery.. it would be fine, long as the earth from batt to engine/manifold we mint. SO really it wouldnt matter what location

/quote]

The reason for NOT joining the wires is that should a resistance build up at the earth point then the wires will cross feed

how do you mean, they both earth at the same earth point so if that degrads (i assume thats what u mean by resistance) both cables will have a bad earth full stop

edit: just like they would if it were one cable

One wire may be they injector drive earths, and the other the tps and AFM, if they are looped by joining them and the EARTH POINT builds resistance THen you will have an issue with cross feeding

[gazzy2000]

 Ichi Ban']

[quote name='gazzy2000 said:

2) it says dont join the two wires (i assume its becuse they need to be good earths with correct wire rating and yud need a bigger cable if u use a singlular one)

these are not special earths.. they are just ECU main earths, if you joined them at the ECU into one big wire (the right gauge) and then straight to the battery.. it would be fine, long as the earth from batt to engine/manifold we mint. SO really it wouldnt matter what location

/quote]

The reason for NOT joining the wires is that should a resistance build up at the earth point then the wires will cross feed

how do you mean, they both earth at the same earth point so if that degrads (i assume thats what u mean by resistance) both cables will have a bad earth full stop

edit: just like they would if it were one cable

One wire may be they injector drive earths, and the other the tps and AFM, if they are looped by joining them and the EARTH POINT builds resistance THen you will have an issue with cross feeding

yea i dunno aye, i am not convinced (unless i am missing some thing here) if they have the same earth point on the manifold they are essentially joined anyways? meaning if the earthing point is bad they will both be bad earths yea?

dont get me wrong i followed the factory wiring to the tee in both my BG5a conversions, but was always left wondering why run the two wires... plus i ran massive thick overkill sized earth wires

[gazzy2000]

actually, if back feeding (cross feeding) was such a problem here, the best solution would be to run both wires to their own separate earthing points, so if one got a bad earth it wouldnt try and find an alternative path (back feed) through the other cable/cricuit/path.

Then i go back to one of my original statements, if those two wires ARE earthed on the same junction point and that junction has a bad connection, how can back feeding occur if they both have the same crappy route to earth connection i.e. neither either wire has a better alternative earthing route,

All that would be is a crap earth connection not a back feeding hazzard.

Infact it wouldnt surprise if after the millions of dollars spent on R&D that the internal circuits in subaru ECUs are fully protected from just such back feed problems (using diodes or the like)

[Koom]

What about if you shift the ECU and sensor ground location to the -ve battery terminal and forget that the majority of the sensors are grounded directly where they mount so you could then be setting up some dodgy ground loops that change the signal that the ECU see's from the sensor?

This is because the sensors get there ground reference from the ECU, if you move the ECU's grounding point to the battery, and the sensors are grounded to the engine (where they are mounted) then you are opening up the possibility of the sensors GND to be at a slightly higher voltage than the ECU's, therefore the signals will be bung. They all must have the same ground plane and just putting bigger cables from manifold to the battery cannot guarantee that as you still have connections to pass through.

[gazzy2000]

 Koom said:

What about if you shift the ECU and sensor ground location to the -ve battery terminal and forget that the majority of the sensors are grounded directly where they mount so you could then be setting up some dodgy ground loops that change the signal that the ECU see's from the sensor?

This is because the sensors get there ground reference from the ECU, if you move the ECU's grounding point to the battery, and the sensors are grounded to the engine (where they are mounted) then you are opening up the possibility of the sensors GND to be at a slightly higher voltage than the ECU's, therefore the signals will be bung. They all must have the same ground plane and just putting bigger cables from manifold to the battery cannot guarantee that as you still have connections to pass through.

most if not all of the main EFI sensors do not directly go to ground where they mount (refering to GC's here as an example here) they all get their earth from Pins on the ECU

yes there are a couple that directly ground where the mount i.e. speed sensor, knock sensor

Trust me i know, i snipped off ALL 4 plugs off at the ECU on my first BG5a single T conversion and started the wiring right from scratch to mirror WRX v3/4. I studied the v3/4 wiring diagram from woe to go.. followed it to the T. Then did all again (or very similar) on my latest single T conversion.

Once again its all broken down & explained here http://www.clubsub.org.nz/forum/index.php/topic,10158.0.html