Project Nissan Silvia: Part VII

Power is nothing if you're afraid to use it. That fact has been a guiding principle for Project Silvia, forcing us to spend more effort on the mundane details of traction, balance, durability and cooling than we spend on making big dyno numbers.

The result, so far, has been a car that is fun, flexible and stunningly fast in a huge variety of conditions, with relatively little fear of ending up on the back of a flatbed. More power is on the way, but not before we deal with a few more of those mundane details.

First is to put the finishing touches on a cooling system robust enough to handle midsummer track days. That means shedding the waste heat of 280-wheel hp for 20 minutes at a time in 100-degree heat. Then we'll tackle the need for more consistent boost control so we can actually tell if upcoming changes are improving things.

KEEPING IT COOL
Until now, we've had to choose between either overheating or killing the battery. Thanks to a typical engineering cascade effect, we were forced to wire Project Silvia's electric fans to turn on with the headlights, meaning we either overheat in traffic, or drive with the lights on during the day, forget about them, and then kill the tiny Odyssey battery with 220 watts of lights and 180 watts of fans when we park.

The cascade that caused this chronic problem worked like this: We wanted to mount the intercooler as far back as possible to shorten intercooler plumbing, since this would minimize the small portion of boost lag that results from pressurizing all that plumbing and keep the intercooler hidden from view. Doing this forced us to move the radiator back about six inches, though, which forced us to remove the stock belt-driven fan. We replaced the fan with a slim, powerful, twin 10-inch Flex-a-lite fan, but had no way to control it.

In a perfect world, when Jim Wolf Technology reprogrammed our ECU, it would have made the stock ECU control the fans. The Silvia's ECU is so packed with outputs for the individual coil packs that there aren't enough pins left to control an electric fan. There is a simple solution. Air-conditioned Silvias had an auxiliary electric fan controlled directly by a temperature sensor in the lower radiator hose.

Early U.S. cars, luckily, use this same system, so you can simply buy a lower radiator hose from an early, air-conditioned 240SX (part #21503-40F65 and less than $40), wire it to a relay and be done. For reasons even we don't understand, we never bothered with this simple solution, instead wiring the fans to the pop-up headlight relay that, obviously, has nothing left to pop up. This let us use either the pop-up headlight switch or the headlights themselves to power the fans manually.

We had been planning to add both a real temperature gauge (the stock gauge doesn't move between about 150 and 210 degrees, so it's little more than a three-position indicator) and an oil temperature gauge when we stumbled upon the Power Enterprise Power Fan Controller, which happens to not only be both the gauges we need, but also the fan controller we need, all packed into a single 60mm analog gauge.

The coolant temp portion of the gauge reads off the stock temperature sensor, and the instructions-if you can decipher them-tell you the ECU pin locations for this signal on most Japanese cars. The oil temperature signal comes from an additional sensor you have to buy separately.

Mounting the sensor in the oil pan requires some drilling and welding, so be prepared to remove the pan-this is relatively easy on the SR20DET. The sensor is some tapered metric thread, and we found it very difficult to find an appropriate tap. A 10mmx1.0mm nut, though, is very close to the same thread, but without the pipe thread taper used to make the fitting seal. The sensor housing is soft brass, fortunately, and deforms to fit the nut. With a little Teflon tape, it seals perfectly.

There are four dip switches on the back of the power fan controller that are used to set the coolant temp calibration to match the sensor you're using, and to determine whether the fan should trigger based on coolant temp or oil temp. (The only reason we can think of to use the oil temp mode to control the fans is if you're using the oil temp sensor to measure something other than oil or if you're triggering something other than a fan.)

Setting these switches should be quite simple, but the instructions are completely unintelligible. Not only is the translation from Japanese quite poor, but the dip switch diagrams are easily misinterpreted. For the stock S13 SR20DET temperature sensor and a coolant-based fan trigger, we ended up with all four switches off. This only after several calls to Power Enterprise. Luckily, during one of these calls they told us they had just hired a technical writer to redo their instructions, so you should have better luck than we did.