how many earthing points in the engine bay??

Post Sun Jun 12, 2005 2:56 pm

i am looking to upgrade the earthing around the engine bay so it will stop the dimming of the lights when i install some ICE.

i have found one place where i can see an earthing link from the engine to the chassis which is just below the alternator.

are there any other areas around the engine bay which have wiring going from the engine to the chassis??

Post Sun Jun 12, 2005 3:09 pm

Why would you want to earth your ICE to the engine?
If you're fitting one of these ridiculous megawatt ICE systems, use the earth point on the offside front suspension turret, where the battery negative connects.
Engine earth strap coonects to front chassis rail,one side or the other, depending on engine, and there is an earth stud beside /behind the left headlamp. Beware, models with an oil level sensor have a parallel earth path to the engine earth strap, meaning you will do serious damage to your engine loom if you try to start the car with the strap desconnected or with a poor connection.

Post Sun Jun 12, 2005 3:12 pm

If the stereo is that loude it makes the lights dim i'd say buy a bigger alternator.
Or a hearing aid

Post Sun Jun 12, 2005 4:59 pm

Bigger altenator won't help although the regulator can sometimes have an effect as it can't keep the voltage constant during unexpected loads (like subs). You probably want bigger batteries

(note the use of plural) and possibly a split charger system that isolates the amp supply from the rest of the car.

Try a stiffening capacitor, I am not that impressed with them as I don't think they can actually deliver as much instantenous current as a battery can, although the rate at which it can deliver it might be higher. I know all the theroy behind this but I have never really had to need to figure out current or time constant characteristics for each.. if you do go for a cap, get the one with the lowest ESR (Effective Series Resistance)

And yeah earth it back at that turret, or directly back to the battery negative terminal.. you wouldn't belive the number of people (including 'professional' ICE Installers) that say doing that is very bad, they say it causes earth loops and hum and whine... strange to only place I have ever seen that happen is when you earth at the boot somewhere.

Post Sun Jun 12, 2005 5:18 pm

Brianmoooore wrote:Why would you want to earth your ICE to the engine?
If you're fitting one of these ridiculous megawatt ICE systems, use the earth point on the offside front suspension turret, where the battery negative connects.
Engine earth strap coonects to front chassis rail,one side or the other, depending on engine, and there is an earth stud beside /behind the left headlamp. Beware, models with an oil level sensor have a parallel earth path to the engine earth strap, meaning you will do serious damage to your engine loom if you try to start the car with the strap desconnected or with a poor connection.

what's that about the parallel earth path, can you explain more?

my m30 has an intermittant running problem which is either fuel or electrical, can't work out what's causing it. i have one main earth strap and another for the alt (just to be sure) then one extra loom connection to earth. i think all earths are good but i'm starting to woder if my loom is damaged somehow cos i can't find any other problems

cheers!

Post Sun Jun 12, 2005 8:13 pm

Toby_Unna wrote:
what's that about the parallel earth path, can you explain more?

I found out about this recently, when I bought a 320 touring on the strength of a couple of photos on an internet auction.
The car was described as having had an underbonnet fire, and had been declared a total loss by it's insurance company.
When I collected the car, the engine loom had been stripped open, and I could see one very fried wire, as well as damage to loads more where it had burnt into them.
I trailered the thing home, and fitted in a spare engine loom that I had around and tried to fire up. I was immediately rewarded with smoke from the loom so I thought I'd better investigate further.
The burnt wire in the old loom was a brown/orange earth wire which ran from the oil level sensor to the small earth terminal on the right hand suspension turret. I pulled the plug off the oil level sensor and found that there was no electrical contact between the engine earth strap and the bolt on the sump to which it was bolted
The bolt was tight and there was no obvious sign of any corrosion, but it took two attempts at dismantling, cleaning and reattaching, to re establishing proper contact.

The damage done to the engine loom (possibility of multiple short circuits to the earth wire in question) would vary from loom to loom depending on what wires were bound against what.

Post Sun Jun 12, 2005 8:35 pm

cheers for that Brian better double-double check my earths!

another post going up in the tech section shortly to try to solve this damn problem

Post Mon Jun 13, 2005 9:15 am

i have already got a split charging system installed, i just wanted to be sure that i do it right

Post Mon Jun 13, 2005 9:21 am

BLOKE do it properley. I can get u a gel battery 900amp these r designed to run huge ice instals and these r Ãƒ”šÃ‚£175 inc p&p no need 4 split charg sys which wont really work if the batts r acid as ther cant deliver the power that is needed that quickly and run the rest of the system as well.

Post Mon Jun 13, 2005 1:22 pm

Again, this should be in the Technical Section.

Post Mon Jun 13, 2005 3:35 pm

TOURINGDADDY wrote:BLOKE do it properley. I can get u a gel battery 900amp these r designed to run huge ice instals and these r Ãƒ”šÃ‚£175 inc p&p no need 4 split charg sys which wont really work if the batts r acid as ther cant deliver the power that is needed that quickly and run the rest of the system as well.

i have already got the split charging system,will see how it goes with this as my install is nothin 'big' anyway

my secondary battery is a red top optima so i think that should be ok..