Jim;
You've posted some good advice. "Ground loops" are a headache and following
your suggestions will avoid lots of electrical system trouble.
Regards, Neil Tucson, AZ
-----Original Message-----
From: Waldron, James [mailto:James.Waldron@CWUSA.COM]
Sent: Tuesday, June 10, 2003 7:10 AM
To: land-speed@autox.team.net
Subject: RE: Race car wiring
Snip.
>-----Original Message-----
>From: Albaugh, Neil
>
>Watch those ground connections-- the
>current's gotta go back to the battery somehow.
YES! Getting the current back to the battery is just as important as the
wiring. That ground lead connected to the body may run through the bolt
that holds the body to the frame (with a rubber bushing! - an insulator!).
When in doubt, run a 'ground strap' between the two metal objects (Heck,
even when not in doubt). Tie everything on the car frame/body/engine/etc.
together with good grounds. (Technically, low impedance grounds, non
technically, FAT wires and good connections.)
If you don't you run the risk of having multiple ground paths. So, let's
say one of those paths runs through a bolted connection that is not
electrically perfect - it has some resistance. Instant voltage drop. The
voltage in 'that' ground path is now 'different' from the voltage in another
ground path. Anything that connects across these two ground paths will have
that voltage difference imposed upon it.
Potential problems. Your fuel injection sensor is grounded to the engine
block. Your fuel injection 'brain' is grounded to the body. If there are
differences in these grounds due to a poor connection between one of them
and the eventual negative terminal of the battery (loose bolt, dirt, paint,
whatever) then 'the voltage difference will show up on the sensor'. The
sensor will not be telling your injection system the truth!
Or, another scenario, your tach could read a little high or low.
Or, whatever needs power will use whatever else is available to return the
power to ground (the starter will try to use the sensor wiring as ground -
frying the brain and the wire and ruining you day).
Worse case, the grounds floating around as connections rub and move (or
spark!) create all sorts of 'gremlins' and unrepeatable problems.
All electronics can be explained in 4 words.
Battery looking for ground.
Thanks,
Jim W.
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