Wiring

Wiring

You have two basic choices to make your new SR20DET run. The simplest is to use the harness and ECU from a Silvia or 180SX. Once again, your life will be easier if you have a front clip to pull parts from. If you can't get the harness and ECU and you have a harness from a 1991 or later U.S. car, it's possible to convert a U.S. harness and ECU to run the SR20.

Unfortunately, the SR20DET uses a direct coil-on-plug ignition system with four coils, and U.S. ECUs are only capable of driving a single coil. The Japan-only non-turbo rear-drive SR20DE uses a single coil and distributor that can used on the SR20DET, if you can find one. Once this distributor is in place, Jim Wolf Technology can reprogram the ECU for the new engine. A few of the crank angle sensors and coil wires may have to be moved, but JWT has detailed instructions for this change.

Because we had a front clip, of course, we used the Silvia ECU and harness. The harness obviously plugs into the engine, but because of the switch from right-hand to left-hand drive, the harness tries to place the ECU at the driver's feet. Apparently, if you don't mind sloppy harness routing, it's possible to simply twist and stretch the harness into place in a left-hand-drive car. We took a more complex, but ultimately far more sanitary approach.

All our harness work was left in the capable hands of Ralph Kenyon, the Northern California Silvia enthusiast who guided us through most of this swap. He unwrapped most of the harness, laid it out on a board that already had the proper wire lengths marked out on it, started cutting and lengthening wires appropriately. Having done this harness conversion enough times to justify making the board, he has also salvaged enough wires from other harnesses that he was able to lengthen the wires using the exact same wire. Unless you want to send your harness to him, you'll have to use the engine compartment as your board. (Kenyon will convert JDM Silvia harnesses for a fee; his e-mail address is SPRISO_SILVIA@hotmail.com.)

Start by unwrapping the main stem of the harness from the firewall grommet to the area where the injector leads fork off. Plug in the injectors, temperature sensors, idle air bypass, knock sensor and crank angle sensor wires and lay the main stem along the back of the firewall so the firewall grommet can sit in the hole where it belongs. You'll now see the wires to the A/C compressor, power steering pump, mass airflow sensor, O2 sensor and the five wires to the igniter need to be lengthened. If you're shy about lengthening the igniter wires, simply mount the igniter closer to the harness, but we preferred to use the stock mounting location and stock bracket. By the way, if you have a missing or damaged igniter, a '92 or later Infiniti Q45 igniter, part number 22020-50F00, is a direct replacement.

The O2 sensor wires and the mass airflow sensor wires are both shielded, and should be lengthened with shielded wire as well. Any large electronics supply store should have suitable wire. Once everything is the right length, simply rewrap the harness with electrical tape and whatever wiring loom you prefer.

The remaining complication with the Silvia harness is two connectors in front of the battery tray. Apparently, Nissan has standards for which color wire it used for different functions, and what kind of connectors it used, but when the wiring harness teams designed the U.S. and Japanese harnesses, there was no common standard for which pin on the multi-pin connectors each wire should go to.

Several wires therefore have to be swapped around in each of these two connectors to make them match the U.S. connector. A small tab holds each pin in to the connector, and if you depress that tab with either a special pin removal tool or a shaved-down paperclip, you can remove the pin and relocate it. Simply rearrange the wires so the colors match (red wire to red wire, green wire to green wire, etc.).

There are only two tricky parts in these connectors. On the car side of the brown connector, there are two brown wires. You want to connect the outer one to the brown wire on the engine side of the plug. On the engine side of the grey plug, both the black/red and the blue/red wire need to be connected to the black/red wire on the car side of the connector.

Finally, the white connector under the dash needs its pins rearranged to match the car and the wires need to be lengthened slightly.