Super Street | How-To - Project Vehicles

Project Nissan Silvia: Part VII

The Towing Package

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.

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.

The power fan controller offers a fairly comprehensive set of ECU pin-out diagrams to show you which wires to tap into for the factory water temp signal, fan relay and ground. This doesn't actually include the S13 diagram, but this one is close enough, offering at least the correct placement of the temp signal.

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.

The Tomei pan uses two simple hinged trap doors to keep oil in the center of the pan near the pickup. Since they aren't spring loaded, they can fall open and get stuck against the windage tray if your engine is upside-down on a stand. We had no such trouble installing the pan right-side up in the car. Note the thick flange and how it overhangs the extensions on the side. Tomei provides all new hardware to fit this flange.
Mounting the adaptor is incredibly difficult. The oil filter mount on the block is stuffed below the intake manifold, behind the alternator, and above the engine mount. Just changing the filter is difficult, but mounting this adaptor, with its giant oil lines and bulky fittings, is nearly impossible. The fittings can't be installed with the adaptor in place, so the oil lines have to be pre-routed and pulled up to the top of the engine compartment so they can be threaded into the adaptor. The one 45-degree fitting also has to be clocked very precisely through tedious trial-and-error.

We expected to see frighteningly high oil temperatures. The SR20DET has a tiny, four-quart oil capacity, and the heat and high stress loads from 300 hp should really cook that tiny reservoir of oil. It takes sustained high-speed driving to really get oil hot, though, and all our previous track excursions were before we had an oil temp gauge. We were probably running dangerously high oil temps, but luckily, what you don't know can't hurt you.

In normal street driving, oil temps usually hover around 50-60 C (122-140 F). Chasing a Ford GT down Ortega Highway, we managed to get the oil temp up to 75 C (167 F), but that was still only a few short bursts between traffic jams. It's important to remember that while more power makes more heat, it also gets you up to speed sooner, so the engine spends less time working hard. In street driving, our Silvia doesn't seem to need an oil cooler.

Normal driving isn't what this car is about, though. Project Silvia sees regular track duty, and on the rare occasions when we can go 20 minutes without setting something on fire, we'd like to keep the oil supply steady and cool. It may not be sexy or chrome, but happy oil is absolutely critical for keeping the insides of a ridiculously high-output engine where they belong.

We tackled this in two ways. First, a bigger oil pan will allow that heat load to be spread out through more oil so it won't get as hot. There are two commonly available high-capacity pans for the rear-drive SR20. GReddy's finned, cast-aluminum pan is the most common, but we chose the slightly smaller steel Tomei pan, imported by Group5 Motorsports in San Diego, for a simple reason.

We were already whining about the difficulty when we fired up the car and all the fittings leaked. Turns out it's difficult to tighten them enough when the adaptor isn't bolted down. Our solution was to carefully mark the orientation of the angled fitting, then stuff a NAPA 17mm socket and 1/2-inch extension into the center bore of the adaptor to hold it while we tightened the fittings like we meant it.

The day before we removed the stock pan to weld in the temp sensor bung, we hit one of those asphalt waves that get slowly kicked up when thousands of overweight trucks stop in the same place. The ridge of asphalt was high enough to hit the front anti-roll bar, lifting the car off the ground, bending the bar's pivot bushings and slamming the bar into the oil pan. The stock steel pan escaped only slightly dented, but we fear an aluminum pan would crack under a similar impact. If you're going to be sloppy, haphazard drivers like us, steel may be the way to go.

The Tomei pan has a thick flange, which requires longer bolts. These are included, as are studs and nuts for the mounting holes that sit above the extensions on the sides of the pan. The space between the flange and the pan's side extensions is too narrow to insert a bolt, and even a bit tight for handling the tiny 6mm nuts Tomei supplies, but the pan goes on with only minor finger yoga. The Tomei pan also comes with an extra fitting that seems perfect for an oil temperature sensor. Naturally, it was the wrong size for ours. We welded on another 10mmx1.0mm nut.

The second, more obvious side of our cooling plan is an oil cooler. Since the oil runs perfectly cool in normal city driving, we didn't want the cooler over-chilling the oil. The thermostatically controlled sandwich block we used fits between the engine and the oil filter and routes most of the oil through the filter and directly back to the main oil galley, like normal. A small portion is bled off through the oil cooler before going to the engine, though. As the oil gets hotter, a thermostat in the adaptor opens up, sending more and more of the oil through the cooler.

We got a Mocal thermostatic sandwich adaptor, a 146x235mm Setrab oil cooler, six feet of Goodridge -10 lines and a fistful of fittings from Brits in Sonoma, Calif. Brits also sent along some Goodridge fire sleeve to put around any parts of the oil lines that might contact the car or engine. While the sleeve is intended to protect lines from heat, it can also serve to keep the hard, abrasive braided steel lines from sawing through whatever they rub against.

We mounted the cooler in front of the left front tire where the stock Silvia intercooler went. The Silvia bumper is already designed to direct air here, and the fender liner is louvered to let air out from behind the cooler. If you don't have a louvered fender liner, you should cut a hole for exit air and rivet in some mesh to protect the cooler from the rocks the front tire will fling at it.

It would be temptingly simple to just hang the cooler by its upper mounting flanges, but the constant tension and vibration could easily pull the cooler apart over time. An oil leak in front of your front tire is a bad idea, so we made a flange out of some hardware store junk to support the bottom of the cooler.

With the extra oil capacity and the cooler, oil temperatures are surprisingly low, even during relentless pounding in 100-degree weather. In 20 minutes of shameless flogging, the oil temperature never went above 80 C (176 F), and the coolant temp never went over 87 C (190 F). We have achieved robustness.

Looking up at the filter adaptor from below, you can see why we were crying so much. The line in the background actually goes through the engine mount, while the line in the foreground has to be precisely angled to squeeze between the mount and the alternator.
Mash the throttle at 4000 rpm under the same conditions and full boost takes only a second. With the quicker spool-up, the bleed valve spikes to nearly 19 psi. The Power Enterprise controller doesn't spike under either condition, making it far more trustworthy for the higher boost to come.

Now, to achieve consistency. When we first cranked the boost on our SR20DET, we did it by stuffing an $11 ball valve from McMaster-Carr into the wastegate line. We later upgraded to an adjustable bleed valve from Jim Wolf Technology that was slightly less prone to boost spikes, but still mechanical and still inexpensive. The problem with a passive, mechanical system like either of these boost controllers is that when the conditions affecting the turbo's performance change, the controller can't change to adjust for them.

Day and night are the most obvious examples of this phenomenon. We first adjusted our bleed valve to reach 15 psi of boost on a mild afternoon in San Diego.

Now, on a blazing L.A. summer day when the air is thin, it only makes 13 or 14 psi, but spikes over 18 psi in the cool, dense night air. This is only mildly annoying, and actually makes the car really fast at night, but it will be dangerous as we push closer to the limit of the SR20 and our 91-octane gas. If we tune to the ragged edge at 17 or 18 psi and suddenly the car starts spiking to 21 psi, things could get ugly. It's time to call in the electrons.

When we did our boost controller comparison test back in July 2002, the GReddy Profec B stood out as the simplest, most easy-to-use controller. It worked with just two knobs-one to adjust boost, one to control how quickly it spooled up-and no unnecessary complexity. It was the easiest to set up, took the fewest test runs to reach the target boost and worked very consistently.

The constant, switched, and illumination power wires were sourced from behind the instrument cluster. Once they were identified with a multimeter and good old trial and error, these, plus all the signal wires, were run through a hole we punched in the defroster vent. Dragging this wad of wires up through this hole is also a pain in the ass. Be sure to drill a generous hole, then send something strong up through the hole first. If you're a real man, you'll use a piece of welding rod. If you're a soft little mama's boy, you can use a coathanger. Either way, tape all the wires to the end of the rod (stagger them so there isn't a big wad) and pull them through. With the connectors on the gauge end of the harnesses, we had to pull ours through from the top down.

Ironically, we are not using a Profec B on Project Silvia. The Power Enterprise Power Boost Controller we did settle on takes the Profec B's two-knob simplicity and adds one key extra feature. It's built into an analog boost gauge. That means there's one less magic box to mount in the car, and several fewer wires we have to chase through the dash.

Both boost controllers work by reducing the pressure signal to the wastegate actuator. The bleed valve does it by poking a carefully calibrated hole in the wastegate line. The Disco Potato turbo's wastegate actuator is designed to open at 11 psi, so setting the bleed valve to 15 psi means opening up that hole until 4 psi leaks out.

The Power Enterprise boost controller (and most electronic boost controllers, really), uses a solenoid valve to completely block the signal to the wastegate. When the boost target is approaching, the valve can slam open, letting the pressure open the wastegate, then quickly cycle between letting boost in and burping it out to keep the wastegate opened just so. The magic of electronics means it can watch the rate of boost climb and anticipate if it has to open early to keep from overshooting the target.

Indeed, when we compared the two controllers in cool evening air, the bleed valve caused substantial boost spiking when we slammed the throttle open at 4000 rpm. The Power Enterprise controller saw how quickly boost was rising and managed to prevent the spike.

Like the power fan controller, the instructions for the power boost controller are a little tough to interpret, but the controller is actually easier to figure out than the fan controller is. Our only design gripe is that the gain knob (the one controlling how fast the turbo spools) is on the back of the gauge, forcing you to remove the gauge if it needs adjustment. In reality, the gain adjustment is just used to prevent boost spikes, and even with the adjustment maxed out, there was no spiking at 15 psi of boost.

We mounted both the Power Enterprises gauges, plus an A'PEXi EGT gauge salvaged from Project Matrix in a CarbonTrix gauge pod we salvaged from the same car. The pod is mounted to the windshield using the same double-stick tape used to hold on body kits. The pod has never threatened to fall off the windshield, even in the kind of heat that melts flesh.

Wiring the gauges is no harder, or easier, than any other. All three need power, ground, switched power and illumination wires, so we ran just those four into the pod, then split each three ways inside the pod. Jamming all these plus the signal wires for the three gauges, and their sometimes bulky connectors through the tiny hole in the back of the gauge pod is one of the biggest challenges, exceeded only by figuring out how to get the wires down into the dash and through the firewall.

The difficulty of this unusual mounting arrangement is, as usual, all for good reason. Mounting the gauges high puts them closer to the driver's line of sight. Mounting them on the windshield puts them as far away as possible, reducing the amount of refocusing the driver's eyes have to do. And mounting them all on the same plane, rather than staggered up the A-pillar, means you can take it all in one glance. Meaningless details? They don't feel meaningless when you're sideways at 100 mph.

What do they call a bigger radiator, an oil cooler, bigger brakes and more power? On my sweet Chevy van they called it a towing package. Great, we now have the ultimate flat-black tow vehicle. Now it's time to get back to the business of making power. We'll start turning those knobs next time.

We mounted the map sensor and boost control solenoid to one of the air filter box mounting flanges. The big knob in the foreground is the old bleed valve boost controller.