Manifold Earth Wire

[Guest]

 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.

+1

Prob the way for guys to look at it in basic terms.

If the main battery earth fell off the engine , and you go to start the car - Where will it earth through ? throttle cable will be fried but as the ECU earths are at the engine itself then the starter current WONT try going thru thye sensors (like Knock, single wire coolant, and 3 wire 02 ) and thru the ECU to earth

As the sensors have already lost there earth when the main cable fell off

Ok this is a total failure situation, but imagine a 40 or 50ohm resistance in the main cable or fixings, The same applies above. System voltage will be down but wont harm ECU

[gazzy2000]

chaps.. none of the main engine sensors go to ground where they mount. (single wire coolent is for temp gauge its a non EFI sensor, 3 wire 02 gets earth through manifold earth point, not the sensor body)

The ECU earths its two main earth cables on the mainfold... yes this is true, but it may as well be at the battery.. i say this because where do you think the engine and manifold get its main earth from anyways?? yip, that big fat negative cable on the starter mtr which for all intents and purposes could be on the manifold (but is better by the str mtr)

[Guest]

Exactly - so by the ecu earthing the sensors and the PWR GND there the are ABOVE earth and cant be damaged if the main cable has an issue (which they do )

You obviously cant see what a ground LOOP is, and I have tried to expalin to the best of my ability from brain to fingers

Just for giggles put your multimeter on Mv and measure the voltage between your engine block and the battery earth terminal

You'll normally find 50 - 100 Mv (0.05v or 0.1v) over 200Mv = faulty earth cable or fixings

Sorry if my explaination cant let you see what I'm trying to explain, by wire direct to battery at your own risk !

Yes car will run, not saying that it wont

[gazzy2000]

yea yip, well we are all pretty much speaking the same language then...

[Guest]

 gazzy2000 said:

chaps.. none of the main engine sensors go to ground where they mount. (single wire coolent is for temp gauge its a non EFI sensor, 3 wire 02 gets earth through manifold earth point, not the sensor body)

Yes 02 gets earth thru manifold, which is why they do it , then you dont get an earth loop in it !

If it was earthed to the batt the you can and will get earth loop and can have residual starter current flowing thru that loop

[D-Style]

People need to learn about potential difference and equipotential.

[kamineko]

hmm yeah it really is much more complex than it seems. WRXONP your opinions are welcome but i'd appreciate that you don't state your miss-understanding of electronics as fact

anyone who has built hifi equipment will understand earthing problems, you can HEAR it (and this doesn't mean you understand the solutions, sorting it can be a real pain - there are whole books written on earthing)

its not just the voltage drop over the cable, each circuit in a car generates or is sensitive to certain electrical noise, dealing with this is quite complicated - hence things like separate earths at the ECU that apparently look like a waste of wire

find a schematic of the factory ECU and you might start to understand its not just (+) and (-)

[gazzy2000]

 kamineko said:

its not just the voltage drop over the cable, each circuit in a car generates or is sensitive to certain electrical noise, dealing with this is quite complicated - hence things like separate earths at the ECU that apparently look like a waste of wire

yip, all this talk of back feeding, loops, above earth, ground loops etc etc is all good and well but its my belief that the ECU supplies earths for the sensitive EFI sensors for the main reason of reducing induced noise on the wire.

yea yea the sensors get an earth at some point (which is just an earth at the end of the day) but not until they have been through the noise suppresion circuits (or WHY) in the ECU.. a clean earth if you like, free of noise.

[Guest]

OK then Gazzy- you do as you want, as you say an earth is just an earth

You have obviously never had anything to do with diagnoising earth faults

Have you ever seen a car that has it parklights on and they turn off or turn indicators on when you brake.... ummmm Earth fault

[Stoffa]

or brake lights flashing when you turn the indicators on, had that before

[WRXONP]

That can also just be the trailer plug wiring if you have it - really common when 5 core gets a rubin

[Guest]

 WRXONP said:

That can also just be the trailer plug wiring if you have it - really common when 5 core gets a rubin

Brad , we are talking the O/E car, your mention of earthing kits and add ons that can cause additional issues such as trailer wiring

Yes your correct it 5/7 core can causes issues tho

[gazzy2000]

 Ichi Ban said:

OK then Gazzy- you do as you want, as you say an earth is just an earth

You have obviously never had anything to do with diagnoising earth faults

Have you ever seen a car that has it parklights on and they turn off or turn indicators on when you brake.... ummmm Earth fault

LOL you obviously missed what i am saying + that post apart from missing the point completely and being irrelevant, it makes you sound like a mechanic whos been trained on the basics of automotive electrical theory.. fixed one trailer and is now an expert LOL

I am/was an auto electrician by trade, i never found earthing to be a big mistery either when doing full vehicle rewires or fixing a brake light.

Dare i say it, but in the name of keeping it real, its normally the ones that throw big theories and words around that dont know what the F they are doing :-X

[boon]

Just gonna throw it out there but if all the grounds in the vehicle are correctly installed and of sufficient size then there physically cannot be a difference between grounding to the chassis, manifold, the block or the negative terminal of the battery. If everything is done right, the resistance between these items is functionally 0 ohms hence the voltage drop, which is easily calculated via V=IR, is also 0v. Hence the wave/signal/whatever will be identical.

If you can see a voltage (or resistance) of more than 0 between any 2 of the body/chassis/block/negative terminal on the battery then you have a bad ground somewhere.

[gazzy2000]

 boon said:

Just gonna throw it out there but if all the grounds in the vehicle are correctly installed and of sufficient size then there physically cannot be a difference between grounding to the chassis, manifold, the block or the negative terminal of the battery. If everything is done right,

yup zactly, even better if you go over all the factory earths n file them up, clean up or fit new batt terminals, fit an earth kit etc etc

just as important to make sure chasis has good earths for other electrical systems (other than EFI) and yup they will/should all be zeroid volts if the earths are good everywhere.

SO that being the case, and after getting lost in all the BS lol..... going back to the original post/question in this thread, put the earths where ever you like (i.e. block, mani, different place on block or mani etc etc) just cover your ass and make sure you do have a good earth cable from batt to mani/engine i.e. fit an earthing kit, clean your terminals etc and your are done!

[Guest]

Well being an Auto sparky you should have some idea, and know why ECU is earthed to the block/manifold and not the chassis

Dam this thread is now the funniest thing so far this year

Keep throwing, bold statements around that earth points dont matter so as they are there and you'll soon find out why they are!!

When EVERYTHING IS 100% - YEs it all works fine, BUT....open your eyes to the potential failures from the main batt earth degrading !

If you can be bothered... and maybe you'll actually learn something

Draw a battery

and draw a line anywhere near it, ( this is the earth circuit ) , at one end put a circle for ecu earths, in the middle draw a circle for the starter

Now draw a line from your batt -ve point and attached it to the middle of the first line

Just for giggles - extend that first line past the ECU earths and put the main batt -ve point on the line past the ECU earths --

Oh- maybe now you'll see that ECU earths are "above" earth and the ECU can not be damaged by main earth cable degrading ( WHICH THEY DO !!)

[gazzy2000]

 Ichi Ban said:

Well being an Auto sparky you should have some idea, and know why ECU is earthed to the block/manifold and not the chassis

Dam this thread is now the funniest thing so far this year

Keep throwing, bold statements around that earth points dont matter so as they are there and you'll soon find out why they are!!

When EVERYTHING IS 100% - YEs it all works fine, BUT....open your eyes to the potential failures from the main batt earth degrading !

If you can be bothered... and maybe you'll actually learn something

Draw a battery

and draw a line anywhere near it, ( this is the earth circuit ) , at one end put a circle for ecu earths, in the middle draw a circle for the starter

Now draw a line from your batt -ve point and attached it to the middle of the first line

Just for giggles - extend that first line past the ECU earths and put the main batt -ve point on the line past the ECU earths --

Oh- maybe now you'll see that ECU earths are "above" earth and the ECU can not be damaged by main earth cable degrading ( WHICH THEY DO !!)

you are now talking about being "above earth", sorry but "above earth" is not the right terminology, above earth is like the electrical wiring on a ship, it dosent touch ground/chasis what so ever to stop/combat electrolysis.

What you are on about is more like earth redundancy or multipath earths... actually fark knows what you are on about! LOL

If the ECU earths were "above earth" they wouldnt have any circuit to the chasis or engine, nor would any of the electrics to make the whole above earth theory work (just like a ship), but the ECU earths bolt friggin straight onto the manifold bud! LOL i.e. direct path back to battery.

That means that the whole engine, chassis, manifold etc etc is one big earthing point so in theory they could go anywhere.

(yes earths degrade we all know that, thats not the point here)

[Stoffa]

 smokn4 said:

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

ok how about it doesn't HAVE TO but like this thread it may do your head in later trying to figure it all out??

[gazzy2000]

 gazzy2000 said:

going back to the original post/question in this thread, put the earths where ever you like (i.e. block, mani, different place on block or mani etc etc) just cover your ass and make sure you do have a good earth cable from batt to mani/engine i.e. fit an earthing kit, clean your terminals etc and your are done!

this ^^ forget all the rant.. and what stoffa said!

[WRXONP]

grabs pop corn

[gazzy2000]

 gazzy2000']

[quote name='gazzy2000 said:

going back to the original post/question in this thread, put the earths where ever you like (i.e. block, mani, different place on block or mani etc etc) just cover your ass and make sure you do have a good earth cable from batt to mani/engine i.e. fit an earthing kit, clean your terminals etc and your are done!

/quote]

this ^^ forget all the rant.. and what stoffa said!

LOL no no, i meant forget all the rant PLUS what stoffa said = good

should have worded "what stoffa said and forget all the rant LOL"

so stop cooking the pop corn! lol

[Koom]

 gazzy2000']

[quote name='Ichi Ban said:

......

When EVERYTHING IS 100% - YEs it all works fine, BUT....open your eyes to the potential failures from the main batt earth degrading !

.....

/quote]

.....multipath earths... actually fark knows what you are on about! LOL

If the ECU earths were "above earth" they wouldnt have any circuit to the chasis or engine, nor would any of the electrics to make the whole above earth theory work (just like a ship), but the ECU earths bolt friggin straight onto the manifold bud! LOL i.e. direct path back to battery.

That means that the whole engine, chassis, manifold etc etc is one big earthing point so in theory they could go anywhere.

(yes earths degrade we all know that, thats not the point here)

How about the ECU earths must be kept at equal or higher potential than the starter which has been Ichi's point the whole time and degrading earths will cause bigger issues than its worth just for the sake of not mounting the ECU earths where they should be.

[caspros]

 Ichi Ban said:

If you can be bothered... and maybe you'll actually learn something

1) Draw a battery

2) and draw a line anywhere near it, ( this is the earth circuit ) , at one end put a circle for ecu earths, in the middle draw a circle for the starter

3) Now draw a line from your batt -ve point and attached it to the middle of the first line

4) Just for giggles - extend that first line past the ECU earths and put the main batt -ve point on the line past the ECU earths --

Oh- maybe now you'll see that ECU earths are "above" earth and the ECU can not be damaged by main earth cable degrading ( WHICH THEY DO !!)

[Stoffa]

aaah that makes more sense, where would we be without those technical drawings skills?

[caspros]

 Stoffa said:

aaah that makes more sense, where would we be without those technical drawings skills?

Dude, I still think I got it wrong.