Nissan sentra turbo - Getting the Pieces
63I know I can't be alone in the feeling that every time I step into the garage I'm suddenly transported into a time warp where hours pass by in minutes. Normally, I don't let this bother me but at some point in every project you just want to be done with it. To my surprise my frustration wasn't with the expected Pandora's Box; the wiring harness. Every wire and plug fit into their slot and loom route perfectly. If you remember the picture from our last article, scary hardly describes it. It's not that it's really hard to do any of this but the harness was most likely placed when most of the interior was out of the car. The process is tediously slow but you have to find a route to free each cable from the harness.
Compounding the difficulty here was the aftermarket installs of Alpine amplifiers and alarm system. There were so many splices and butt connectors that it amazed me all this stuff worked for as long as it did. It was just one hack job after another. It's laughable that the place I had this done calls themselves "Good Guys." The guys that worked on my car must think that the cigarette lighter has divine power from the god's because they used it to tap power for just about every part they installed. This just reiterates my belief that nobody will be as careful and cautious as you will be with your car. Although, all their wiring still works so maybe the trash talking should come my way. Most of the time it's just best to figure it out yourself or bribe a friend who knows what they're doing.
To provide power to our revived electrical system we turned to Optima for one of their deep cycle Yellow Top™ Batteries. Our project isn't a garage queen but it doesn't see daily driving use either. Sustained periods of low voltage drain from the alarm system was enough to drain the battery to a point where it would barely start. Repeating this a couple times a month was enough to kill conventional batteries.
Optima's Yellow Top™ is ideal for our application because it's built to handle starting applications after long periods of low amperage draws. Optima designs their batteries with SPIRALCELL TECHNOLOGY. It provides more plate surface, closer plate spacing and the ability to use high purity lead. The result is low internal resistance that provides more power in a smaller battery that recharges faster and has cleaner voltage characteristics during discharge. The plates inside the battery are locked into place for improved vibration resistance. This makes the battery ideal for racing applications and provides the ability to secure in almost any position. We don't have a full competition stereo or a DVD/Surround Sound setup but this battery will see the charger eventually. With the new battery we have the piece of mind knowing we can discharge the battery and rapidly recharge it for a blast down the road.
Our wiring problems plagued us with some weird gremlins. While we worked on the harness we sent the ECU down to the tuning experts at JWT. Upon investigation they discovered that a trace had been blown on the ECU (more on that later.) Alternators are prone to voltage spikes but these irregularities are usually dampened by the battery. In our case since the battery is relocated to the trunk and we have a distribution block in the front of the car to run all the powered accessories. We need to make sure that the power from the alternator is going directly to the battery instead of from the alternator to the distribution block then to the battery. It turns out we had power going from the alternator to the distribution block first then the battery. Oh-no! Technically everything seemed like it was working like it should but we probably contributed to part of our own demise here. Once we figured out the proper wiring we made the proper connections.
To add insult to injury we found that the one of the pins on the ECU's power relay was shorted to ground! It caused our recently-fixed ECU to blow on the very first cycling of the key. To find the problem we disconnected the ECU and put a 10A fuse between the two poles of the relay. With the ECU disconnected, only two things were hooked up to the grounded pin on the relay: the crank angle sensor in the distributor and the Mass Air Flow meter (MAF). We disconnected both and found that there was still a short (since our fuse kept blowing). Must be the wiring! We then found where the power wire split from the relay and went in two directions, one to the distributor and one to the MAF. Separating these, we discovered that the ground was in the MAF wiring!
The stock MAF wiring consists of two wires (ground and signal) enclosed in a shielded insulator as well as a separate power wire. In order to use the Cobra MAF, the wire had to be extended. To do so, an extension cable was used that contained three wires all enclosed in a single shielded insulator. All three wires from the stock harness were connected to the extension, and the shields were soldered together. However, the hard solder on the shield was left exposed and was pressing against the power wire's (relatively) soft insulation, and eventually a pinhole-sized hole developed, causing the power-to-ground short!
Another problem with the wiring job was that the power wire was run right next to the signal, which is not how the stock wiring was done. This is akin to running a power wire next to your speaker wires - you'll hear an increasing whine in the speakers as the engine RPM builds due to electromagnetic interference on the power wire. So we cut the power wire from the extension and ran a separate wire from the stock harness to the MAF. That will ensure a cleaner MAF signal to the ECU. We also used heat-shrink around the soldered part of the shield to ensure this problem doesn't happen again.
Confident that our wiring was now done right, we plugged in the ECU and the system worked perfectly. The gremlins were gone and our electrical system was happy again.
Its been a good 10 months since we fired the car over, so out came the 20w50 oil we had in the car for racing and replaced it with synthetic 10w30 for everyday use. We pulled the fuel pump fuse and cranked the engine over with a few short cranks to lubricate the turbo and engine before we fired it over. Pop the fuse back in and all 750 CCA's of our new battery brought life back to our Turbo SE-R again. We sat back and appreciated the moment with our Frankenstein for a minute. Ah, we've looked at it long enough, time to go destroy some gears! Special thanks go out to Mike Mager for his wiring troubleshooting and JWT for their suggestions and fixing the ECU twice.
