All SR20s run hot, but this goes double for 280-whp, turbocharged SR20DETs in flat black cars on the racetrack in 100-degree weather. The problem, I'm convinced, is a bad water pump design, but since nodboy seems to have made a better water pump, the solution has to be a bunch of bandages.
We've already applied the biggest, most effective bandage, a Koyo aluminum radiator. Coupled with the 160-degree thermostat that came with our junkyard engine, the car runs alarmingly cool most of the time. But in the searing heat of a California summer, there are a few more steps that can be taken to help the SR shed some BTUs.
Airflow
We've made two inexpensive changes to improve cooling. The first is simply to let more air hit the radiator and intercooler. The stock Silvia nose has a clear plastic panel between the headlights. Air doesn't go through clear plastic. Recognizing this, the Japanese aftermarket offered countless grilles to replace this panel. We got one--don't know what kind--from Spriso Motorsports. They got it from a junkyard in Japan. Next came the cutting. The Silvia front bumper includes an ungainly license plate mount. Since our front plate mounts solidly under the carpet in the trunk somewhere, we cut out the mount and made it into a vent.
Air tools will come in very handy here. To cut the bumper, we marked the rectangle, used a 1/2-inch drill bit to drill the corners of the rectangular hole, and then connected the dots with an air-powered body saw. The saw uses miniature hacksaw blades and cuts through the plastic more easily than any knife has ever gone through butter. The saw is a little hard to steer, though, so we cut slightly inside the rectangle, leaving a drunken, weaving cut. The edge can then be cleaned up with an air-powered die grinder.
Once you're through the plastic, you have to cut the styrofoam bumper. Here's a tip: you'll still be able to see some styrofoam when you look in the new vent, so hit it with some black spray paint.
Next, you'll hit metal. Japanese bumpers are thin, single-layer deals, so it's relatively easy to cut through. If you have a plasma cutter, you don't need me to tell you what to do next. We don't, so we used an air-powered cut-off wheel and some patience. The body saw probably would have worked too, but making sparks is fun. This will, of course, weaken the bumper, but it wasn't exactly a battering ram before anyway.
The final touch was a wire mesh grille. Go to www.mcmaster.com and you'll find every kind of wire mesh you can imagine, and they even tell you what percentage of the mesh is air. Hint: more airspace means better cooling. We used a woven mesh because it looks cool and is mostly air. To mount it, we simply bent it 90 degrees and bolted the horizontal part to the underside of the bumper. The vertical part just stands there looking grille-like.
Waterflow
The next cooling mod is surely the more effective one. Mitsubishi and Subaru have been putting intercooler and occasionally radiator sprayers on their cars for years now. There's no magic to an intercooler sprayer. It takes heat to evaporate water, so evaporating water sucks heat out of whatever it's near. This phenomenon is why you sweat. Don't believe it? Stick your hand out the window of a moving car and spray some water on it. Cold, huh?
Both Mitsubishi and Subaru use windshield-washer-based systems. A plastic tank and a pump nearly identical to the windshield washer pump are used to make the spray. That, and a fortuitous trip to the garden section of the hardware store gave us an idea. There, we found row upon row of 1/4-inch garden sprinklers in an astounding variety of spray patterns. These sprinklers are connected with 1/4-inch flexible PVC hose, and a huge variety of tees, valves and junctions are available to facilitate your creative routing desires. Amazingly, this PVC hose is nearly the same size as the windshield washer hose.
We bought two 90-degree fan spray nozzles, two tee-fittings, two on/off valves, and a few feet of hose. The first tee divides the windshield washer hose into two, one that goes to the windshield and one that goes to the intercooler. An on/off valve goes in each line, so you can turn off the windshield and turn on the intercooler spray at the track. We then split the intercooler hose with another tee and put one nozzle spraying on the intercooler, and another on the radiator. Mounting the nozzles takes some creativity, and you have to be sure not to mount them lower than the washer tank, or all the fluid will dribble out.
We tested the system at the 100-degree track day for the annual Mt. Shasta All Datsun Meet. Despite the heat, we were able to stay balls-to-the-wall for most of a 20-minute session. Only when the water started running out at the end of the day did the lapping sessions have to be cut short. Now, in most cases, the windshield wipers would be going crazy, so you should unplug the wiper motor at the track. In our case, though, age and crappy wiring have taken care of the problem for us. The intermittent setting doesn't work on our car.