ilPistone.com: Qualche dritta per la 350Z

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What would you do?

You have one of four 350Zs in the country. You have it for one week. And no, Mexico is not an option.You would test it, take it apart, try to make it faster, test it again, take it apart again, and put it back together so nobody could tell you had been there.

And you would jam pack every one of those tasks into a single week so you would only have six hours to actually tune the thing.
We know you would, because that's exactly what we did.

With such limited time, we set out to answer one simple question. Will the Z be easy to improve, or will it be one of those rare cars so carefully parked on its sweet spot that any changes just make it worse? Here's what we found.

Wheels and Tires
Picking a wheel and tire should be simple, but having never seen a Z wheel well, we had very little to go on. With some digging, we learned the stock tire sizes (225/50R-17 front and 235/50R-17 rear) and the stock wheel sizes (17 x 7.5 inch, 30mm offset front, and 17 x 8 inch, 30mm offset rear) but we still had no idea how much more room there would be.

Wanting to guarantee better performance with our new wheels and tires, we decided to make a conservative step up in size, a massive step in stickiness, and keep the wheel diameter the same. Oh sure, it feels unnatural not doing at least a plus one, especially when we knew Nissan would offer 18-inch wheels on some models, but 17s are lighter and have less rotational inertia.

Finding wheels that come in 8 and 9 inch widths, with a 30mm offset is easy, but finding those wheels without chrome, polished lips, fake bolts or dozens of extra pounds turned out to be nearly impossible. We eventually slightly compromised on offset, choosing Black Racing Pro-N1 wheels in 17 x 8 for the front and 17 x 9 in the rear, both with a 38mm offset. This would push the wheels inboard 8mm, but we brought along a set of 5mm spacers to push them back out if necessary.

The Pro-N1s are cast aluminum, but are still reasonably light for their size, at 20 lbs for the 17 x 8 and 21 lbs for the 17 x 9. The deeply contoured spokes appeared to give plenty of clearance for big brakes, and the bronze finish made it look like we drove the snot out of the car, covering the wheels with brake dust.

Black Racing wheels are available from Bozz performance or, perhaps, 5Zigen. We're not really sure. When we called Bozz, it said the wheels were on their way, but then 5Zigen dropped them off. Very mysterious.

For tires, we chose an old favorite, the Toyo Proxes RA1. The RA1 is a no-BS road-racing tire that happens to be street legal. These tires have impressed us in the past with their exceptional grip and comfortable demeanor. Breakaway is always smooth and predictable, and the RA1 gives you a good degree of control at high slip angles.

Neither the RA1, nor any of the R-compound tires we considered, came in any sizes that match the 350Z's very tall stock rolling diameter. The stock tires are 25.9 (front) and 26.3 inches (rear) tall. Looking for front tires between 235 and 245 section width, and rears between 255 and 265, there simply aren't any R-compound tires any taller than a 40 aspect ratio. Ending up with 235/40R-17 and 255/40R-17 tires meant dropping the tire height to 24.4 and 25.0 inches, more than an inch shorter on both ends. The shorter tires may not look quite right in the Z's massive wheel wells, but the payoff is an effectively shorter final drive that will ultimately make the car faster.

So did they fit? Hah! Turns out the Z's wheel wells are bigger than we ever could have imagined. We ran the front wheels without the 5mm spacers simply because the wheel studs were not long enough. It's always wise to have at least one stud's width of thread engagement. In the case of a Nissan 12mm x 1.25 wheel stud, that means 12mm of thread engagement, or 15 turns of the lug nut. We only got about 7 turns with a spacer in place. The rear studs were longer, so we used the spacers there.

Despite a significant increase in width, the tires were lost in the huge wheel wells. The 255/40R-17s we used on the rear actually fit on the front, and would probably do so with anything from the 38mm offset we used to at least a 32mm offset. In the rear, 275s or even 285s should fit with no problem.

Suspension
We learned early on that the 350Z would share its suspension geometry with the Nissan Skyline, a.k.a. Infiniti G35. Months before we even laid eyes on the Z, we borrowed a G35 and drove it 450 miles to Ground Control's suspension development lair outside Sacramento, Calif. With no time for trial and error, we told the engineers they had one day to build a suspension for the 350Z that would work on the first try.

They didn't even blink.

Three months later, we replaced the front spring and shock with Ground Control's Advance Design coil-overs. The lightweight, aluminum bodied shock was designed and built in-house at Ground Control. Since they're used to building race suspensions, building a custom-valved shock with specially-fabricated mounting hardware is just another day at the office.

With the space constraints in the rear spring seat, there was less than two inches of adjustment in the rear spring perch. At the top of its adjustment, the car sat very low. We had been provided with a stiffer alternative rear spring, which would compress less and allow us to raise the rear, but after a quick test drive at this height, we were amazed to find the Z's suspension has so much compression travel that it actually worked.

The lower stance transformed the car visually. What once was thick and somewhat chunky was suddenly long, low and sleek. Driving through the city and up in the mountains, the car looks entirely different with it's new stance. Though the Ground Control suspension does work properly at this height, it is low enough to make speed bumps, driveways and discarded burrito wrappers into serious road hazards. If we wanted to drive this car for more than two days, we would probably raise it a hair.

At the top of each shock is a three-way adjustment for compression damping, and a continuous adjustment for rebound. Driving on the street, the shocks were perfectly matched to the provided spring rates, even with our first guess adjustments. On the slalom, however, with the opportunity to repeat the same exercise with different settings, we found increasing front compression damping to sharpen the steering and improve our times.

The adjuster for the rear shocks is inaccessible when the shocks are installed. Removing the rear shocks is fairly simple but, even with power tools, it's still a 15 minute operation at best. We stuck with our first guess adjustment throughout the test. In the future, Ground Control may invert the rear shock to place the adjuster on the bottom.

Handling with the new suspension and tires was stunning. The already impressive 70.2 mph slalom speed jumped to 71.2, and the stock 0.88g on the skidpad seemed like the work of a tricycle next to the 0.98 it could pull now.

On the road, the car felt untouchable. The steering response and massive level of grip was in another world but, strangely, the stock viscous limited-slip diff didn't appreciate the extra grip. Even in stock form, the diff felt weak, allowing the inside tire to spin briefly before transferring torque to the outside wheel. With the stickier tires, though, it was completely overwhelmed. Mash the throttle in a tight, second gear corner and the stock car would deliver a glory slide, but with the RA-1s, the inside tire simply spun. Aftermarket limited slips will be welcome in the new Z.

Brakes
Planning our six-hour tuner attack, we didn't even consider doing brakes. Engineering and installing a usable braking system on an entirely new car in such a short time is simply too complex.

Or so we thought.

Somehow, somebody at Stoptech heard about our plans and decided they were up to the challenge. All other work came to a halt as they started bombarding Nissan with questions. With persistent interrogation, they learned the Brembo brakes available on the Track Package are the exact same brakes offered on the R34 Skyline GT-R. Perfect. If R34 brakes bolt to the Z, then Stoptech's 13- and 14-inch upgrades for the Skyline would fit as well.

Then they learned we were using 17-inch wheels, which were too small for either of their massive brake upgrades. Undaunted, they took the mounting dimensions of the Skyline, and designed new caliper brackets to use with their smaller 332mm rotors. With the rotor and caliper mounted, selecting piston sizes was the next challenge. Stoptech can build its calipers with eight different piston sizes ranging from 28mm to 44mm. Piston size directly affects caliper clamping force and pedal feel. With 1,000 psi of brake fluid pressure, for example, a four-piston caliper with 28mm pistons will exert 3,820 lbs of clamping force. (That's 3.82 square inches, times 1,000 lbs per square inch.)Bigger pistons mean more surface area and more force. However, more fluid is needed to fill the space behind the pistons, so the master cylinder has to travel farther to deliver all that fluid. Make the pistons too big and that extra travel is felt as mushy brakes.

Somebody at Stoptech must know something about somebody at Nissan. The 350Z on these pages hit U.S. soil in a FedEx plane just four days before these pictures were taken. Somewhere between the airport and our camera, though, Stoptech engineers had their big, throbbing heads in the wheel wells measuring caliper sizes, pad dimensions and backing plate clearance.

Based on the stock brake dimensions, they initially chose a 96 percent brake torque reaction. This means that, at the same pressure, the Stoptech brakes would exert only 96 percent of the braking torque of the stock front brakes. This puts more braking force to the rear to compensate for most manufacturers' tendency to use too much front brake bias. This also means you have to push slightly harder to get the same braking force. Coupled with braided steel brake lines that don't expand with the higher fluid pressures, and Stoptech's rigid caliper design, the end result is firm, hard pedal feel.

Surprisingly, though, the result was not shorter stopping distances. The stock 350Z was able to drop anchor from 60 mph in 113 feet, and our newly modified car was doing it in 119 feet. Curious, we temporarily disabled the ABS and the traction control by unplugging an electrical connector on the rear diff for the rear wheel speed sensors. Stopping au natural, the brakes turned out to be frighteningly rear-biased.

Undaunted, Stoptech's Steve Ruiz whipped another pair of calipers from the back of his truck, this one sized for 100 percent of the stock brake torque, and swapped them on the spot. Theoretically, of course, ABS should compensate for the rear bias on a full maximum-effort stop like this. Theory turns out to match reality in this case.

So how in the world can big, sticky, R-compound tires and giant brakes add up to longer stopping distances? One word: camber. When we lowered the car, we ended up with several degrees of camber front and rear.

That camber did wonders for our handling, ensuring that with body roll and tire carcass flex, the entire contact patch would be put to good use. In a straight line, though, the tilted tire simply meant that only the inner half of the tread was touching the ground. We proved this with our big, smoky burnouts. After six or seven monster displays of our collective manhood, the inner tread blocks were gone, with a scant few molecular layers of rubber protecting steel belts from our prying eyes. The outer tread blocks, on the other hand, were literally untouched. The front tires were tilted in exactly the same way.

Before releasing this brake kit, of course, Stoptech has planned its full barrage of fade and brake balance tests, all with alignment specs that will allow the brakes to work to their maximum effect. They also plan to offer larger diameter upgrades for those less intent on small wheels.

Exhaust
With no cars in the country and no useful dirt on any Nissan executives, we weren't able to plan ahead on the exhaust. Instead, we found a well-qualified volunteer willing to fabricate one while we installed the suspension, brakes, wheels and tires. That volunteer was Jon K. of JIC USA, who also leant us his shop.

As the U.S. importer and R&D man for Japan's JIC, the plan was to fabricate a true dual exhaust using JIC's new oval can titanium mufflers and stainless-steel mandrel bends. Then, if the design proved effective, to use it as a starting point for a production JIC exhaust made entirely from titanium.

That plan evaporated the instant we got the car on the lift. Thanks to an uncooperative rear anti-roll bar, there's no room to get two exhaust pipes past the rear diff. The space we intended to use for the passenger's side muffler also turned out to be full of evaporative emissions control hardware. That forced us to mimic the stock muffler-in-the-middle layout.

Thinking quickly, Jon grabbed two of the polished stainless-steel mufflers he usually uses on Porsches. These mufflers use a perforated core flow-through design that happens to make a u-turn and exit on the same side the exhaust enters. Butting two of these mufflers up against each other, Jon, Yas Uchida and Michi Kawamoto managed, in a few short hours, to fabricate a beautiful, mandrel-bent exhaust that fit perfectly and sounded incredible.

As for power, despite a slight increase in diameter from 60mm to 65mm where the exhaust was still a single pipe, the car lost 3 hp with the exhaust. This is, unfortunately, how exhausts are developed. Trial and error. This will surely not be the last 350Z exhaust to meet the junk pile in a search for the right balance of power, weight, looks and cost. With the unique demands of the Z's packaging, Jon expects JIC will end up with a new titanium muffler designed specifically for the Z.

At the Strip
With a few missing horses and tires cambered for the skidpad, was the Z doomed at the strip? Hardly. Luckily, our tire choice saved the day. The effectively shorter gearing from our shorter tires made up for the lost power and grip at the launch and the 60 mph mark. It also proved to be enough of an advantage at the end of the quarter mile to knock a tenth of a second off the time and add 1.1 mph. Final score for the quarter: 13.9 at 100.3 mph. Our egos needed that.

And that was it. This modified 350Z prowled the streets of Los Angeles for only 26 hours but, in that time, taught us a lot. We know now, for example, that Nissan has delivered a piece of hardware that can easily be made into a giant-killing track machine. We also learned they didn't screw around with the engine. The simple stuff, like the muffler and intake, were pretty well done from the factory. There will be gains to be had there, but nothing huge. Simple tricks with ignition timing probably won't yield much either, as this car appeared to be visiting the knock sensor even in stock tune. Handling is easy and stopping shouldn't be much work.

OK, tuners. Get to work under the hood.