Project Lexus SC300 Road Racer: Part 10 - Finish Wiring the Back and Prep the Front Harness

by Erik Jacobs


We finally had begun wiring Project SC300 in the last installment. With the main trunk harness mostly complete, it was time to start buttoning things up. We still had the matter of the wheel speed sensor harness to attend to and probably a few thousand other things, too.

The most successful race teams win their races off the track. Much how like airline pilots spend a tremendous amount of their practice time and study preparing for the potential ugly situations, races are won via extensive preparation, practicing and planning for problems. Since the majority of NASA’s ST-2 races in the South East region are sprint races, it means that there is not a lot of time during a race weekend for something to go wrong and be fixed. Helping make problems easy to diagnose is important, and in some ways, a simple thing like a label goes a long way. That’s where Dymo comes in.


You probably know Dymo for their hand-held home-type labelers or maybe the desktop label printers. But, Dymo does a lot in the industrial space, too.

Recently, Dymo released a new line of industrial labelers to go above and beyond the existing Rhino-brand lineup. These XTL labelers are targeted at hard-core industrial use cases. Think about computer data centers, manufacturing facilities, and so on and so forth. Conveniently enough, Dymo produces a range of label tapes that also meet milspec standards and offer them in a heat-shrink tube variety. Perfect!


The labelers come with neat carrying cases!

The XTL series are pretty large labelers. They feature rechargeable built-in batteries that last a really long time. They also offer USB connectivity to a PC so that they can be controlled from your computer. In a shop setting where you are producing a lot of wiring harnesses, that could be a useful feature.

The smaller XTL 300, on the right, also comes with a lanyard so that you could carry it around. I find that offering rather amusing because that thing is heavy. I certainly wouldn’t want to carry it around my neck all day. Then again, I carry 6+lbs of camera gear routinely, so…


Dymo offers a full spectrum of shrink tube sizes for the XTL series.

We have a lot of different size wiring bundles on this project. The harnesses on main circular milspec connectors going through bulkheads are quite big. The individual 2-pin connectors are pretty small, however, being able to cover the spectrum of wire bundle sizes is nice.

Two things to note: The XTL 300 cannot accommodate the full 2” wide label tapes. With a 3:1 shrink ratio, the 1/4“ label tape will not really shrink down small enough to be able to label an individual 20AWG milspec wire.

On the large side, you could use a regular milspec-rated label and then a larger piece of milspec-rated clear shink tube and spend less for the XTL 300. But, if you are doing a lot of harness work, it might make sense to spring for the XTL 500. The 500 is the big boy and really is desk-bound. Sure, you could bring it over to a car to do some work, but it’s by no means a “hand held” unit.

On the small side, labeling individual wires may or may not be important to you. It really just depends on how much time you want to spend and how anal you are. A multimeter in continuity test mode can “find” wires in a loom pretty quickly, provided both ends are available. It’s kind of a toss-up.

The other thing is that the Dymo labelers and the label tapes are quite pricey. There are other labelers on the market that have a much lower cost of entry, but they don’t go as large (2” tapes).


The labeler has some smarts and knows what tape cartridge is inserted.

Loading the labeler is pretty easy- just insert the cartridge. It figures out what’s going on and offers some intelligent presets.


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Dan DeRosia
Dan DeRosialink
Tuesday, April 25, 2017 7:24 AM
I have to say, yay to Dymo for bringing these things to a less expensive market segment than most of the other options. Are the XTL heatshrink labels oilproof? The Rhino ones weren't - though at the price of a Rhino 4200 I judged it good enough for my purposes.

Funny enough I first saw the remote mount sensor for oil pressure on the last car I built with my dad - local shop that preps nationals level SCCA cars had it as part of their Spec Miata oriented kits.

I know you're not getting a lot of commentary but I know I at least am following along and taking notes.
Tuesday, April 25, 2017 9:57 AM
My dad's first Spec miata built did not remote mount the oil pressure sender and the vibrations cause the brass fitting to break. Not ideal but did not lose enough oil to lead to damage. Always will remote mount oil and fuel pressure sensors.
Tuesday, April 25, 2017 1:06 PM
Did you use SAE bolts for those nut plates (page 8), or metric? The only metric ones I've seen are like a couple bucks each, which is just silly.
Dusty Duster
Dusty Dusterlink
Wednesday, April 26, 2017 11:44 AM
I know Auto Meter sells remote mounting kits for their gauges, as well, if you don't have the aptitude to fabricate.
Wednesday, April 26, 2017 5:11 PM
Dan, for standard motorsport use you'd take care of the oil problem by putting a piece of clear shrink over the white or yellow shrink label. That also keeps the ink from getting worn off from handling, and keeps the white or yellow shrink from getting dirty. I wouldn't make a harness of this type without the clear shrink.
Dan DeRosia
Dan DeRosialink
Wednesday, April 26, 2017 8:17 PM
Yeah, ended up doing that at work too. Suppose it's not really a big deal.
Thursday, April 27, 2017 9:02 AM
Following this rewire. Its great to see how and why people do it the way they do.

I know that projects snowball, but would it have been much effort to redo the brake lines to the master?

Is the brake proportioning valve for the rear brakes not located in the ABS unit?
Thursday, April 27, 2017 2:56 PM
This series makes me want to spend on my money on wiring tools. And I hate wiring. Great article!
Monday, May 08, 2017 8:57 AM
Many of the "old school" style pressure sensors have a huge (heavy) can and a small threaded body. With some of the "newer school" style sensors like the AEM it might be a little less risky, but for a couple of bucks worth of fittings and stainless tube and some time you can really safeguard those fluid systems.

@GasInMyVeins - To be honest, I'm not sure. The car has become a mishmosh of SAE and Metric things, including lots of both socket cap as well as hex cap bolts. You are right, though, that the metric ones are significantly more expensive. H Craft obtains them, generally, from Coast Fabrication. Part of the reason the metrics are more expensive is that they are typically aerospace use and the supply/demand is much different.

The Dymo XTL labels are rated for fluids. They are UV, water, oil, and chemical resistant. They meet MIL-M-81531, MIL-STD-202G, SAE-DTL- 23053/5 (Class 1 & 3). They are also flame retardant. The clear shink could be an extra level of protection, though.

@HellaFabrication Redoing all of the brake lines would have been another option, but we still would have had the problem of tees to get the 2-channel master cylinder out to three channels plus the port for the pressure sensor. If we install a motorsport ABS unit in the future we will likely need to plumb new lines, but that's a long ways off.

As for the proportioning valve, given that the ABS unit had distinct front and rear inputs/outputs and that the master cylinder has two outputs my sincere hope is that the proportioning is "built in" to the master cylinder itself. In other words, the F/R bias is baked into the master cylinder. Where I would potentially be able to adjust "bias" in this setup is by using different brake compounds to tune the balance.
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