We drilled a hole for our “00” AWG battery cable in the transmission tunnel just above the factory rear seatbelt threaded anchor hole. We used a rubber grommet to prevent any abrasions of the battery cable.
Next, we pulled the “00” AWG battery cable through the rubber grommet.
The battery cable is routed neatly below the E-brake cable and then makes a 90-degree bend toward the front of the car. We drilled a small hole in the top of the transmission tunnel and riveted a zip-tie holder in place to hold the battery cable at the top of the tunnel, away from the driveshaft and exhaust.
We attached two rubber-insulated cable clamps to the factory heat shield bolts to hold the battery cable up and out of the way. There is so much room in the transmission tunnel when routing the cable this way that there is no reason not to run the thickest battery cable possible. Thicker cables have less resistance and will supply the starter motor with more of the battery’s power.
This 7-foot span of “00” AWG cable is by far the longest segment of battery cable in this relocation kit. “00” AWG cable is 0.579” in diameter and weighs 0.478lbs per foot, making our 7-foot cable weigh in at 3.4lbs. By comparison, a commonly used 2 AWG cable is 0.419” in diameter and weighs 0.241lbs per foot. If we went with 2 AWG cable, we would save 0.16” in diameter and 1.7lbs, which is an insignificant weight reduction and does not make routing the cable any easier, but comes at a noticeable electrical performance penalty. Therefore, it’s a no-brainer to run “00” AWG battery cable.
We drilled one more hole in the transmission tunnel for another zip tie mount to hold the battery cable up and out of the way. The 7-foot span of cable is the perfect length to connect the battery mounted in the rear bin to the starter motor. Wiring the battery directly to the starter reduces the overall length of battery cable and gives the electrical current a direct path to the starter when cranking over the engine.
12 comments
Great article. JP3 Motorsports makes a nice mount for the fuse block so it’s not zip tied or flopping around in the engine bay.
https://jp3motorsports.com/collections/mazda-fd3s/products/mazda-rx7-fd3s-battery-fuse-block-bracket-relocated-batteries
Awesome update. You always do such quality work. I can’t wait for the next one.
Didn’t see a fuse for the fuel pump at first glance (page 5, 1st pic ) Then I looked again.
FYI Lots of motorsports guys complain about those circuit breakers… they say they have had them vibrate open during operation. I’m running 2 on my car and haven’t had an issue yet.
I know that this is going to sound crazy, but recently I had a family member’s car serpentine belt fail and it ended up damaging the pulley. I was not able to source a new pulley in the location it was in, so we decided to try and run the car as long as possible without the serpentine belt (thus sans alternator, power steering, and AC). Fortunately, the battery was almost brand new and fully charged.
Interestingly enough, the car started and ran well for the 10 mile trip home! No issues whatsoever.
This makes me think that you could conceivably run a time attack car with the alternator removed!
Yes, this is totally crazy, but ‘racecar’, right?
Not only would you save a significant amount of weight, but you would reduce parasitic losses on the drivetrain. With a powerful enough lithium-ion battery, I am sure that you would have no issues running like this for one-lap.
Anyway, food for thought.
That is very common in SCCA sprint racing, especially in the smaller bore Prod and GT classes.
I don’t know about a modern racecar with all the electrical load. Our time attack car draws over 140 amps when everything is going full ti;t.
Was your classic to engine 2awg black ground wire able to reach north bolt holes with slack? Mine is very very tight and will not even bolt up
I think we relocated it to the 13mm bolt just below the brake master cylinder.
I have the same problem. The cable that comes with the kit is NOT long enough. Mine even came in a little bit longer at 16in. Pretty disappointing, gonna have to order another cable.
Yep, 15 inch is just barely too short in my set up (using Banzai motor mounts). Had to order a 17 inch cable, although 16 inch probably would have been ok.
What do you do if you don’t want to remove the Electrical harness and take out the old power and ground cables? Would like to leave them in there so it can be put back to original. Thank you
Would look nice with the JP3 Fuse Block Bracket.