battery relocation help!

Was just about to post the exact same question, myself. My battery's already relocated to the trunk in one of those plastic battery boxes, like you'd use for a deep cycle batt in a boat or something, and it's secured nicely with two J-hooks and a cross bar. But I dunno, either, if that kinda box would pass through tech at the track, being that the inspectors usually go over Mustangs with a fine-tooth comb because they're more seriously modded on average than, say, a Crown Vic - they didn't even have me pop the hood on my Interceptor when I took it to KCIR a few years back. Probably going to invest in one of those aluminum/steel Summit Racing or Jeg's NHRA-legal boxes at some point, more so for looks and durability than anything.

As far as an Optima vs. standard battery, I doubt they'd care either way. A battery's a battery to most inspectors.

And as far as the shutoff switch, the only place I've found that's handy would be right next to the fuel filler, since my battery's on the passenger-rear side, anyway, and it'd be a short run from there to the negative terminal. It'd look funny, and I worry that some bozo would always be messing with me at work by turning it off ... but then, I suppose one could always just bypass it when not at the track and then route it back through the switch on track day...?

Also heard of guys making up a flip-down bracket for their license plate (like on the old 70's cars with the hidden fuel filler door) and hiding the switch behind that, but that'd take a bit more fabrication...

Rear mounted battery ground wiring. Follow this plan and you will have zero ground problems.

One 1 gauge or 1/0 gauge wire from battery negative post to a clean shiny spot on the chassis near the battery. Use a 5/16” bolt and bolt it down to make the rear ground. Use a 1 gauge or 1/0 gauge wire from the rear ground bolt to a clean shiny spot on the block.

One 4 gauge wire from the block where you connected the battery ground wire to the chassis ground where the battery was mounted up front. Use a 5/16” bolt and bolt down the 4 gauge engine to chassis ground, make sure that it the metal around the bolt is clean & shiny. This is the alternator power ground.

Crimp or even better, solder the lugs on the all the wire. The local auto stereo shop will have them if the auto parts store doesn't. Use some heat shrink tubing to cover the lugs and make things look nice.

The computer has a dedicated power ground wire with a cylindrical quick connect (about 2 ½”long by 1” diameter. It comes out of the wiring harness near the ignition coil & starter solenoid (or relay). Be sure to bolt it to the chassis ground in the same place as you bolted the alternator power ground. This is an absolute don’t overlook it item for EFI cars

You must either have a sealed battery box such as the Taylor box or an aluminum or steel firewall in the hatch area of the car. As for the cutoff switch, many people mounted the switch behind their license plate. They attached the license plate with hinges on the bottom so it can be moved up and down.

The switch needs to be acessable at all times, must shut the car off completely, so needs to be wired to the alternator also.

Jricher makes a good point with running a computer ground, most people skip this step. It can definetely cause the car to run poorly.

Also beware if you put the switch behind the license plate, the plate is moved out 1+ inches, thus you licensed plate lites illiminate nothing, i know, because i was pulled for it twice.

I didn't know you need so much wire for this relocation...

2000xp8 said:

Also beware if you put the switch behind the license plate, the plate is moved out 1+ inches, thus you licensed plate lites illiminate nothing, i know, because i was pulled for it twice.

Click to expand...

This is true. I know of a guy who drilled a small hole in his license plate so his switch can poke through when the handle for the switch is removed. It kept his license plate in near stock location.

For a battery cut off switch, see
http://www.moroso.com/catalog/categorydisplay.asp?catcode=42225
is the switch

Seehttp://www.moroso.com/catalog/images/74102_inst.pdf for
installation instructions.

Use the super duty switch and the following tech note to wire it and you will be
good to go.

Use the Moroso plan for the alternator wiring and you risk a fire. The 10 gauge
wire they recommend is even less adequate that the stock Mustang wiring.

There is a solution, but it will require about 40' of 18 gauge green wire.

Wire the battery to the two 1/4" posts as shown in the diagram.

The alternator requires a different approach. On the small alternator plug
there is a green wire. It is the sense lead that turns the regulator on when
the ignition switch is in the run position. Cut the green wire and solder the 40'
of green wire between the two pieces. Use some heat shrink to cover the
splices. See http://fordfuelinjection.com/?p=7 for some excellent
help on soldering & using heat shrink tubing.

Run the green wire back to the Moroso switch and cut off the excess wire.
Try to run the green wire inside the car and protect it from getting cut or
chaffed. Crimp a 18 gauge ring terminal (red is 18 gauge color code for the crimp
on terminals) on each wire. Bolt one ring terminal to each of the 3/16" studs.
Do not add the jumper between the 1/4" stud and the 3/16" stud as shown it the
Moroso diagram.

How it works:
The green wire is the ignition on sense feed to the regulator. It supplies power
to the regulator when the ignition switch is in the run position. Turn the
Moroso switch to off, and the sense voltage goes away, the voltage
regulator shuts off and the alternator quits making power.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-90 wiring and lots more…

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

Diagram courtesy of Tmoss and Stang&2birds.

why couldnt you just reground the block and ground the battery and be fine and dandy? If its necessary to ground the computer then why dont we do it even if its not relocated?

TheChevyEater said:

why couldnt you just reground the block and ground the battery and be fine and dandy? If its necessary to ground the computer then why dont we do it even if its not relocated?

Click to expand...

The computer must have a good ground. The stock ground is a 10 gauge wire that comes off the battery negative cable. It has a pigtail with a quick disconnect that looks like a inline fuse holder. Uncople this and watch Hondas pass you like you're driving a lead sled.

If you don't think grounds are important, I highly recommend some more education in the electrical department.

im fairly good with electrical just the actual 5.0 harness is what im not completely familiar with.. so basically your making a heavier ground than the stock?

sort of. As said above, the EEC ground was originally connected to the negative terminal of the battery. If the battery is in the trunk, the EEC still has to be grounded some how. That is why it has to be grounded to the same spot of the chassis of the alternator ground.

So let me get this straight...

Grounds:
- From battery terminal to chassis
- chassis ground to block
- block to ground (for the computer)

So there will be two wires coming from the same spot on the motor, right?

cjman15 said:

So let me get this straight...

Grounds:
- From battery terminal to chassis
- chassis ground to block
- block to ground (for the computer)

So there will be two wires coming from the same spot on the motor, right?

Click to expand...

You got it right...

Heres a shot of my old 88 GT with a custom stainless steel battery box I had a friend make.

You can see the vent tube running out from the bottom and running out the car where the factory grommet is. I used the other side for the nitrous vent tube. Almost like they were made for it.