Project Lexus SC300 Road Racer: Part 7 – Sealing the Things


Tom lays up the outlines of where mounting and through holes will go.

The opening isn’t very large, but we are trying to fit three connectors through it. Accuracy and precision are important. Fortunately for us, the military specification includes mounting panel diagrams with sizes and tolerances.


The final product is temporarily bolted in place to test fitment. You can see that there was not a lot of real estate to work with.

As we said before, the two smaller connectors are for the kill switch and wheel speed sensor circuits. The remote/external kill switch will be mounted on the cowl near the driver. This means the harness needs to pass across the engine bay near the firewall. Unfortunately, a JZ engine has the exhaust on the passenger side of the vehicle. This means that we are routing a very critical circuit- the kill switch- near hot stuff. A fabricated heat shield and additional shielding wrap will be used to ensure that the turbo downpipe doesn’t cook the harness.


This panel is two pieces and is “joggled”.

The great Wikipedia says: “Joggling,[4] also known as joggle bending, is an offset bending process in which the two opposite bends are each less than 90° (see following section for how bend angle is measured), and are separated by a neutral web so that the offset (in the usual case where the opposite bends are equal in angle) is less than 5 workpiece thicknesses.[5] Often the offset will be one workpiece thickness, in order to allow a lap joint which is smooth on the 'show-face'.”

In our case, the joggle is used to provide a flush mounting surface to connect the two pieces together. There is a big hole where the heater core passed through the firewall, and this seemed like the best place to route the one-piece Haltech 2JZ harness. Having a two-piece panel makes it easy to get the harness through the firewall if it needs to be removed, and allows us to make the opening as small as possible.


Nutserts are again used to give us a way to secure the panels together. These are tiny!
A big grommet is sliced in one place to allow it to go over the harness. Then, it is inserted into one side of the panel. The other side of the panel is then brought together with the first, and the two pieces are bolted together.
The panel is then bolted to the firewall.

You can see, the turbo blanket and original narrow-band O2 sensor blurry in the foreground. As we mentioned before, it gets hot here. Providing the harness with some shielding and protection from the heat will be very important. This O2 sensor is still a little too close to the turbo, and  it is a narrow-band unit. Since the Haltech Elite 2500 supports automatic tuning adjustments via the Haltech WBC wide-band O2 sensor, we'll be permanently mounting the WBO2 towards the end of the downpipe and blocking up this O2 sensor port.

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