Project Lexus SC300 Road Racer: Part 4 – Beginning the Epic Rewire


When all was said and done, a giant pile of stuff came out of the car. Including the heater core, HVAC blower, wire, and other components, easily over a hundred pounds of stuff was removed. The car already had a fairly gutted interior, but it’s amazing how much stuff was still in there.
In fact, even with a lot of the interior components already gone before I started gutting, I still managed to remove TWELVE control units from the car.

Remember that a car that debuted in 1992 likely began being engineered as early as 1989, if not earlier. The late ‘80s were not the paragon of automotive electrical engineering, although Japan was definitely leading the way. Toyota’s solution to everything at the time seemed to be an individual control unit. Mirrors and seat position? There’s an ECU for that. ABS? There’s an ECU for that. Cruise control? There’s an ECU for that. Headlamps? There’s an ECU for that too. TWELVE. No joke. Ten pounds of little plastic and metal boxes. Fortunately all of this stuff will be replaced with only a small fraction of the amount of junk that came out.

When it comes to the electronics aspect of building a race car, a solid plan is paramount. Mr. Cooper’s wisdom, again, rings true: “The 5 Ps: Prior Planning Prevents Poor Performance” While most people think about running to Autozone or even Home Depot to start buying toggle switches, ATC fuse holders, and relays, I wanted this to be a proper motorsports job from the ground up.

A word of warning: This is not the type of project for the faint of heart. Or those with small budgets.

The plan for this project is to ultimately use high-quality components: wire, heat shrink, connectors, devices, and more. It requires the use of high-quality tools: crimpers, heat guns, and more. I am even using the type of industrial-grade software that Formula One and high-end manufacturers use to plan wiring projects.

There is a reason that harness work on mid-level race cars costs $10-$20,000 – not including the electronic devices! It is time consuming work that must be done with precision and care, and must be done correctly if it is to survive the harsh operating conditions. It requires a plan, and that plan takes a long time to put together, especially when you’re doing it part-time and have to refer to someone else every few minutes for questions. This is also likely the reason that most people don’t invest in doing it right. Either they don’t have the time, don’t have the money, don’t have the connections, or don’t have any of them. This is not to say that I will get everything right. I probably won’t. But I will sure try. After all, the journey is not about the destination.

Speaking of journeys — they all begin at the beginning. And, if the beginning is planning for what to put into the car, then selecting a solid lineup of components is a good first step.


The true heart of any car, when it comes to electronics, is actually the battery.

While the alternator and charging system makes sure that the battery stays topped off, a quality battery can make or break everything. Ever wonder why your car is hard to start with that silly lawn tractor battery? Probably because it’s a silly lawn tractor battery. XS Power has come aboard to provide quality juice. They helped me determine that their S925 starting battery would provide enough oomph to turn the car over no matter what, but also be relatively small and lightweight to keep vehicle performance in mind. They provided a host of accessories to go along with it, too.


Note that this is a picture of the CDI version of the harness, which uses an M&W Pro-16 capacitor discharge ignition (CDI) unit. I have the “HPI” version of the harness, which uses a Haltech-manufactured ignitor. Anyway.

The engine control harness was already taken care of by Haltech’s plug-and-play unit. While it is not a high-end motorsports-grade harness (for reasons that will become evident as this wiring series unfolds), it already utilizes factory connectors, is cut to the right length, is pinned properly at the ECU end, uses reasonably high-quality components, and is well understood by Haltech and their engineers.

It’s also not 24 years old like the rest of the wiring in this 1992 SC300, and I know that it successfully ran the car with the Platinum Sport 2000. Starting from scratch could have resulted in something slightly more durable, but would have involved greater cost and more headache. Staying with this harness was a compromise I was willing to make, and not a significant compromise at that. Some heat wrapping in smart places will go a long way to ensure the harness stays safe and provides a long and event-free service life, and, if I really wanted to get crazy, I could take it apart and put it back together with some improvements. Maybe someday.

Leave a Reply

Your email address will not be published. Required fields are marked *