While waiting on the engine build, I had decided that one of the things I wanted to do was to try to move some weight off of the nose of the car and try to relocate it to the passenger side and as far rear as possible.
Thoughts of things to do included:
- Replace the front bumper support with something lighter
- Move the fuse box and ECU from the driver's side front rail into the passenger floorboard area
- Relocate the battery from the passenger firewall area inside the engine bay to the passenger rear trunk area
- Relocate coolant reservoir
After pulling the front bumper cover off and taking a look at the bumper support again, I realized that it already had a lot of holes cut into it, so it really would require replacing it with something more custom. Additionally, we originally had planned to make a trip down to Mazda Raceway-Laguna Seca for a big Miata event. Since I would be running the car on the track, I decided that having the additional crash protection was worthwhile. So, that idea is currently on hold.
Also on hold is the relocation of the coolant reservoir. It would be of some benefit, but I'm currently unsure of the venting needs, as well as the fact that it would require finding a lot of custom hoses to do it.
That left relocating the fuse box, ECU, and battery.
The fuse box and ECU come from the factory sitting on the driver's side frame rail and the cross member between the two rails that is located in front of the engine.
The ECU is on the left with multitude of wires going into two plugs, while the fuse box is the white base with black top.
The picture shows the ECU with a metal cover on it that would be going away. It was more of a protective piece as the factory airbox used to sit on top of it. The ECU and mount only weigh around 2 pounds, while the fuse box without any of the wiring or actual fuse panels weighs around a pound. So, between the two, it's not a lot of weight to relocate, but by the time you add in all the wiring, etc. it is an improvement. Again, it is moving it from the front, driver's side to the passenger floorboard.
Of course nothing is ever simple, and this is probably one of the most challenging things I've done to the car. Reason being that it's not as simple as just moving the two items out of the engine bay onto the passenger floorboard. The wiring is really the hard part.
Of note, I did all of this prior to removing the old engine out of the car. I wanted to make sure that the car still ran correctly after the re-wiring and before putting the new built motor in the car.
Most of the wiring that came from these two items entered the passenger compartment in the driver footwell area. This wiring then went to the gauge cluster, the pedals, fuel tank, etc. So, with the relocation, a number of these wires would be able to be shortened. However, the engine harness itself would need a lot of wires lengthened. The easiest way to extend the engine harness would be to purchase an additional harness and use it. This would allow all the wiring to remain the same throughout the car. In order to place the ECU and fusebox where I wanted, it would require running the engine harness along the firewall inside the engine compartment instead of inside the passenger compartment. Not a major change, but it did allow the use of almost two feet less wiring than would have been required to run it inside the passenger compartment.
Again, by having an additional engine harness, it was as "simple" as matching up the wires. Of course, it wasn't really "simple." There are a LOT of wires in the current generation cars. The great thing about that is the ability to use the factory ECU on crazy builds.
The amount of time spent thinking about routing things, cutting, splicing, etc. was rather insane really, but in the end it would be worthwhile. Ultimately, there probably isn't a wire in the car that I haven't cut and either shortened or lengthened. I'm proud to say that everything is correctly color coded, so if I ever have a problem, I can use the factory wiring diagrams to determine which wires I need to find.
I used non-insulated terminals to splice the wires together and colored heat shrink tubing. Some of the major car manufacturers have gone to using terminals instead of solder. Not only is it easier, but it arguably creates stronger connections. By using color-coded heat shrink tubing, it keeps things weather resistant, as well as again, keeping factory color coding throughout the wire.
Most of the wires were routed through the hole that previously held the heater core connections on the passenger side firewall. Below is the view from the engine compartment and then from inside the car after all was done.
The only remaining wires that now went through the driver's side hole were for the starter and brake fluid reservoir. Again, as on the passenger side, I used aluminum sheet to plug the hole, with grommets surrounding the wiring looms.
And the finished product inside the passenger compartment.
The wiring is placed such that a passenger seat could still be run in the car. The passenger obviously would need to be careful with their foot placement. ;-)
Now for the battery move. We had been running a small Odyssey battery on a little shelf in the engine compartment tucked up against the firewall on the passenger side.
This was already a relocation, as the factory placement was on the cross member between the two frame rails. It had required extending the positive cable and running the negative to the engine.
Since we had been dealing with a slow drain on the battery, I decided that in addition to moving the battery to the rear passenger corner of the trunk, I would also go back to a full size battery. We have to add weight to the car anyway to meet the minimum weight requirement, so why not put some extra weight where it's needed most?
To additionally combat the battery drain, I picked up a heavy duty, high amp 4 pole battery kill switch. The alternator in newer cars has to put out a lot more amperage to run everything, and the old-school switches weren't rated to handle this.
This relocation would require an even longer positive battery cable, so I ordered up some bulk wire, and then soldered on the ends to put everything at the exact lengths I wanted them.
I was able to re-use the factory lower battery box to mount the battery in the car which made for a fairly simple mounting. The new ground wire goes to the old jack mount. As extra insurance, I bought a braided ground wire and connected that between the engine and the firewall to make sure everything was properly grounded.
Not the best picture, but this is the finished product. I also installed a Battery Tender harness for ease of keeping the car charged up.
And finally, a shot of the engine compartment showing how much cleaner the front end looks. I'll be mounting the remote reservoirs for the shocks on the frame rails very soon.
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