New power and ground wires from Battery Cables USA will greatly improve the electrical performance of our car.
The new 2 AWG cable now connects the fuse box to the starter motor.
The fuse box was originally mounted to the battery to provide power to the starter motor.
Now, the starter motor is supplied power directly from the rear-mounted battery through the new “00” AWG cable (in the shadows above the starter). This will ensure the starter motor gets as much voltage as possible to start the engine. From there a new, thicker 2 AWG cable connects the starter motor to the main fuse box. Notice the snake skin electrical sheathing protecting the starter motor’s trigger wire.
The original alternator power supply wire (top) is made up of two ~12 AWG wires, which is equivalent to 0.1616” in diameter (0.0808” x 2) and is smaller than the 0.2043” diameter 4 AWG ground wire we are replacing it with.
The new alternator wire connects to the back side of the fuse box. We replaced the aftermarket red power wire with this DR25-covered mil-spec wire to supply power to the aftermarket gauges inside the cabin.
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.