was going to start a thread about earthing, I was reading about the Mazda boys who do it (as Mazdas have the same duratec lump).

It seems popular to earth the throttle body (mostly but also seen other bits like the fuel rail). They seem to earth to the neg. battery terminal. They say it improves throttle responce by improving the ground (or neg. signal) because other wise it has to go through the loom as it certainly cant go through the plactic inlet manifold. They also seem to think it helps to cure the low end jerkyness when pulling away.

I was thinking of trying this but can't be bothered to muck aroung under the bonnet in this lousy weather.

Anyone tried this? Any difference?

Yes I also did this but removed it on the advice of one the engineers at work as the Throttle body has it's own built in earthing in the harness from the PCM.

It made no difference BTW the short time it was on.

ALWAYS Earth to the Body.

Try the head earth though, you will notice the difference. The head has to earth through the head gasket into the ally block then out to the ally alternator mounting bracket, through the alternator body to the main earth harness which is about 1m long going round the back of the engine to the battery terminal.

Thanks for the reply Dave (and Steve for chopping the post to a new thread).

I'll probably wait till I can tinker on the car outside in the daylight and warmer weather (if we ever get any ).

So I guess pick a suitable fixing on the head and run it to somethere on the inner wing, suspension turret or somwhere suitable. Also if I'm making up a small wiring harness do you think it's also worth picking up the throttle body and fuel rail?

You can buy earth straps ready made from places like halfords etc

Ok, might have a look at Halfrauds (although Maplin is good for cable, probably end up there), but I was thinking along the lines of something about the size of amp cable with some suitable crimp connectors. I can then link an earth to the other bits too, all in one job.

Surely I can't be expecting a huge amout of current going back to earth or you would get a jolt then fiddling under the bonnet with the engine running.

Also do you know why I shouldn't connect to the neg battery terminal?

Theres a fair bit of current but its the voltage that pushes the current through your body and there is simply not enough to push any decent amount of current through your body

The cable from the engine needs to be as thick and insualted as the earth cable from the battery.

No voltage runs through the body.

You always mount earths to the body, it's the done thing, I don't know the exact reason why it was what I was taught.

Even when you use jump leads you should always earth to the body not the battery.

I di the with my previous car, honda civic type R. I noticed that there was an issue with the headlights dipping and extra load from opening electric windows etc. The earthing kit removed the slight increase in revs noticed when using more load on idle. it clamied to give a 5bhp gain - i never felt a thing though!