Wiring for Race Cars

Totally Wired


When we first built this car, according to “The Plan,” the stock electrical system was good for the job. The existing harness was in good shape, so the contacts were cleaned and some additional wiring was added for gauges, line lock, and MSD ignition. Everything worked as it was supposed to work and rarely let us down, even during those critical inspections in the Der Renn Kafer Cup years, when everything had to work, otherwise points were deducted.


Fast forward to 2006. We’ve been running in the PRA class “Super Gas” (11.90 index) starting with the 2004 season and the overall electrical needs have changed. Due to several changes to the existing wiring harness over the course of the last seven we have been racing, we feel it’s time to change out the stock harness for a system geared toward racing. Although this is another departure from the original plan to keep the car as close to stock as possible, the original wiring harness has been modified beyond reasonable repair from a restoration standpoint and would have to be replaced anyway. That will be a project for another day and has been covered by the magazine previously.


The “New Plan” calls for a centrally located control box. I’ve selected the  six switch unit from ARC (Auto Rod Controls) for it’s simplicity and durability. ARC has been building switch panels for race cars for well over 20 years, and I like the way they are laid out. I initially looked at the Painless Pro Street complete wiring set-up, but determined it was simply too much and too complex for the need. The ARC switch panel has six switches including a momentary start switch and all switches are internally fused.

 Also being incorporated into the new system will be Painless Performance Wiring’s “Cirkit Boss”. This unit, to be mounted to the main panel in the package tray area, will provide fused links to subsystems powered either directly to the battery (constant hot) or activated by the ignition circuit. We had always run a relay for the starter to ensure maximum voltage to the starter. We will leave that in place.


The stock alternator, which put out just 13 volts, is being replaced by an ultra mini race alternator that puts out well over 14.5 volts. This is a “One Wire” unit by East Coast Electric and weighs 6 pounds. The elimination of the cooling tin and exchanging the alternator results in a weight savings of almost 20 pounds. We got caught in the staging lanes once with a low charge condition on the battery because the stock alternator wasn’t keeping pace with the car’s electrical demands, and we assumed that it was. It almost cost us the round and very well should have.



The ARC Control panel with cover removed. The big wire is the main lead and is a 6 Gauge wire that goes directy to the battery, ensuring full voltage to the switches

Below is the Painless "Cirkit Boss". This hooks directly to the battery and has a switched wire that activates a relay, providing 4 "Ignition On" and 3 "Constant Hot" circuits.

Below is a shot of the motor with the new alternator installed

We will start with the removal of all the existing wiring. We want to start with a “clean slate.” Our objective is a “no compromise” system that will provide solid, reliable performance. The stock wiring harness has never been removed from the car. A little coaxing got it out. I'm really not looking forward to the day when it needs to be put back, if in fact, it ever does go back in.


The first phase of the installation will be hardware mounting. The EFI controller, MSD and battery will stay in their existing locations, under the back seat. The ARC control panel, which will take on the duties of the stock dash controls such as ignition, lights, interior fan, etc., will be mounted to the passenger side of the tunnel next to the e-brake handle. A large 8 gauge wire runs from the battery and powers all systems from there. The big departure will be that rather than the “Grand Central Station” for the wiring to be behind the dash, it will now be in the package tray area. Gone will be the gaggle of connection multipliers, extra wires plugged into the fuse box with “T” connectors along with wiring no longer used. The only wiring to go forward of the ARC control panel will be for those accessories mounted in front such as gauges, lights, line lock and fuel pump. All critical systems will now have a much shorter wiring path. Stock systems left out of the wiring scheme will be wipers and turn signals.


Now that all of the hardware is mounted, the route for the main section of wiring is plotted. All attempts are made to keep from having to drill any more holes. Most of the main harness from the ARC control panel will run along side the tunnel to run under the back seat and connect into the Cirkit Boss. These include start, ignition, EFI activation, MSD activation, and line lock. From the ARC control panel forward, head and tail lights, brake lights, interior fan, dash lights, and ignition power for the gauges. The fuel pump is activated by the EFI controller which is in another wiring harness. Some wire will have to pulled from front to back for certain things like the tach feed, oil pressure gauge sender.


The main power lines for the MSD and EFI controller go straight to the battery. To make clean work of having several 'direct-to-battery' connections, I used two Jegs Terminal Blocks, which are shown in the photo at right and fed with heavy 6 gage cables. Since the EFI controller needs a tach signal, we’ll take it short and direct from MSD to EFI, splitting it off to go up front to run the tach.


Turn signals will not be used in this particular scheme, so a "Bell" was made from aluminum bar stock to make an nice transition from column to steering wheel, since the stock steering wheel will still be used.

Up front, a much simpler wiring scheme with only the wiring for what needs to be there. Gauge hot leads, front lights, interior fan, tach and oil pressire gauge leads. A terminal junction block is used to make clean connection points for everything, making possible multiple connections to a single source lead, such as gauge hot leads for two gauges with one input wire.

While being a long way from "Show Car" wiring, the layout is clean and simple, very easy to trace, and nothing is there that doesn't need to be there. The dome light eaven works off a switch from the control panel. Necessary? Not totally. But it makes reading an ET slip a lot easier at those night races.

Above, the ARC control panel in place along side the drivers seat, within easy reach. Below, the wire routing out of the box, along the tunnel, and under the rear seat.

Above, looking down onto the battery, Cirkit Boss and the cable terminal blocks. Between the battery and the Cirkit Boss is the starter relay. The relay on the outside is the relay that activates the Cirkit Boss.

Above is the finished "Bell" to replace the turn signal switch for a finished appearance. Below the completed wiring behind the dash. While I took no "before" photos of that, I guarantee there is a lot less wiring there!