In my quest to lower the cars weight (a few years back), I bought an Odyssey PC680T dry cell battery. It weighs in at about 15 lbs versus our 55 to 65 pound OEM batteries (depending on your car's equipment). Of course that's a very good first step but I decided to go just a bit further and now I relocated the battery to the rear of the car and in a low area behind the right wheel well area.
BATERRY RELOCATION :
Here's the battery in its new location. By putting it here it as a lower centre of gravity, it also helps shift the weight back in the car and it also helps adjust the cross weight of the car.
Here we see a close up of where the negative or ground of the battery is hooked up to the car. I used one of the two bolts that hold the rear bumper/shock absorber assembly together. We used the original OEM ground cable.
We then passed a red 4 GA wire from the rear to the front. We also inserted that cable into a loom.
We went through the firewall at a point on the front right side of the car just above the heating system's air box.
This is where it came out on the other side, between where the OEM battery would usually sit and the heating system's air intake/filter is located.
Now the second operation of the day was certainly it bit more involved. Again we are going to relocate a major component with several other components associated with the primary one needing to move.
ECU RELOCATION:
This involved not only relocating our primary subject but the removal of some relays below the ECU within the car’s cockpit. Additionally all sensors (wide band, the two O2 knock sensors, the low prestone warning sensor and others plus two grounds) had to be moved because they were part of the main ECU electrical harness. We also redirected the main harness around the heater core’s hoses to get more length out of it.
First we located an area in the firewall where we would pass the ECU’s main harness through. We then proceeded to make a pilot hole to start the procedure.
This shot shows the hole before we finalised its shape and size. We made it bigger for it to accept the harness and its connectors.
Some of the sensors that also had to be relocated.
Here we see three things; the ECU’s main harness sitting on top of the motor. The OEM battery plastic shelf which will be removed and the elongated and off centre OEM cut out in the second firewall (for RH drive cars I assume). Just beside this hole you see the heater core hoses going through the fire wall.
OEM battery shelf removed.
The ECU harness going through the main firewall into the cabin area.
The ECU’s main harness and some of the relays that were in the cabin but on the other side of the car above the OEM fuse box. As you can see it entered the cabin just above the main heater/AC plenum and we redirected it to the right side of the unit so that it is almost centered in the car but on the passenger side. The ECU and all relays will be secured in that area… but that’s another story for later.
We used the OEM rubber plug that was modified to allow the harness through and re-installed it in place.
The sensors/connectors are now secured in place below the ECU’s main harness and between the firewalls. The two grounds are now secured to the main firewall by one of the bolts that held the plastic battery shelf in place.
This is where the ECU used to reside.
There is no need to keep the ECU’s box in place anymore so it was removed totally. Of the hundreds of wires that were in that area (mainly in the ECU’s harness) all that is left is two wire for the low brake fluid warning, four wires for the wiper motor and the boost gauge vacuum hose. You can see some of the power wires (red) inside the hole in the cabin. This is where some of the relays were located. Some of them are now on the other side with the main harness. Some more may be relocated or we will have to run a 4 GA wire from the centre of the car to the left side to feed these relays and connections.
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Originally Posted by Jet Jockey
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