Yahoo Autos How a New Zealander Transformed a Nissan 300ZX Into a Supercar
From the April 1991 issue of Road & Track
Perhaps you've seen him on television driving a Porsche 944 Turbo (the one that pops out of a tunnel, does a 180-degree turn and stops in the road facing the camera), piloting one of two Nissan 240SX coupes in a motorized pas de deux (to the tune of "Me and My Shadow"), gunning a 300ZX around ATC's high banking or testing the Sentra that "I would build if I owned a car company."
If you were fortunate enough to attend Le Mans in 1990, you may have seen him at the wheel of a Nissan R90CK Group C car, setting a race lap record that earned him rookie-of-the-race honors.
"Him" is Steve Millen, an expatriate New Zealander who years ago turned his life over to the automobile by racing Formula Atlantics in his native land and throughout Asia; preparing rally cars upon his arrival in California in 1982; banging wheels (and winning the 1986 and 1988 championships) in a Toyota-backed off-road pickup truck in the Mickey Thompson Entertainment Group stadium racing series; and driving in-car commercials, print advertisements and, sometimes, for Road & Track covers and road test features.
"I love cars," says Millen. "I like to fiddle with them, modify them. I'm not a guy who can go to the beach on Sunday." Unless, of course, that beach is Daytona, West Palm, Miami or Long, where you'll find Steve behind the wheel of an IMSA GTO car, the Nissan Performance Technology Incorporated 300ZX Turbo. A contract driver for NPTI, Millen had a respectable 1990 season, winning at Miami, Mosport and Road America and finishing 4th in the championship-in spite of four DNFs caused mostly by fluke mechanical problems.
"Racing is number 1 with me," says the 37-year-old Kiwi. So what sort of road car suits someone who has gone 230 mph on the Mulsanne Straight? "I think the ZX is neat," says Millen. But he didn't mean just any ZX. Given Steve's penchant for tinkering, it wasn't long before he began to massage his new 300ZX Turbo. Cosmetic stuff came first: front air dam and rear lip spoiler, 17-in. Momo wheels with Yokohama AVS tires. Serious modifications came later. "I thought it would be neat to give the ZX extra power. But then it needed brakes. And suspension."
Like Topsy, the project began to grow. While poring over parts catalogs, searching for the right components, Steve was buttonholed by a local Nissan dealer who suggested that Millen Sports Cars build an all-out, limited-edition 300ZX Turbo. Something that would not only go fast, but also look the part. And that, in a nutshell, is how the GTZ was born. Distinctive or outlandish, depending on your mindset, this super Z delivers impressive numbers. From a standstill, 60 mph is just 5.0 seconds away; the quarter mile, 13.5 sec. In a broken field run through the slalom, the GTZ averages 67.3 mph. a new R&T record.
Yet, the car is equally at home tootling through traffic because it retains most of what the factory put into it. "The engine has never been opened up," claims Millen, who explains that with the exception of a couple of body pieces, all of the components that make up the GTZ bolt on. Of course, they're available to the public, through Steve Millen Sports Cars of Santa Ana, California, a company co-owned by Millen and Dave Scholium, a fellow Kiwi who backed Millen in his early racing endeavors.
Our guided tour of the GTZ begins on the outside with the body, which has a vented front air dam and a louvered air intake that fits between the headlights and increases airflow to the twin turbos. A Ferrari F40-style rear wing is complemented by a molded lower bumper surround. Steel-framed vents with perforated metal backing are incorporated into front and rear fenders. Strictly cosmetic on the prototype, they are meant to direct air to the auxiliary transmission and rear differential coolers.
Three-spoke wheels, built to Millen's specifications by Elite, use billet aluminum centers welded to spun aluminum rims. Seventeen inches tall, the 9 1/2-in.-wide rims are shod with Z-rated Yokohama A008R tires and tinted a titanium hue to complement the color of the bodywork.
For art's sake, the GTZ is painted a golden orange. The various Sikkens lacquers, blended and applied by Maurice Alvarez and Don Penny of Autotrends in Santa Ana, include 12 base coats of orange, three coats of gold pearlescent and four coats of clear urethane. Although it's not exactly the color one would choose for a stealth bomber (or a stealth car), it's perfectly appropriate for a showpiece-and a cover car.
Our tour continues with the suspension: progressive-rate springs, adjustable shocks (Koni up front, Tokico at the rear), adjustable anti-roll bars (28 mm front, 21 mm rear). A complete non-Turbo 300ZX rear subframe with differential replaces the Turbo's Super HICAS setup, saving some weight and improving performance by reducing the final drive ratio from 3.69:1 to 4.08:1. The subframe is held in place by Delrin hard plastic bushings that keep everything glued in place when the driver buries his boot in the firewall and unleashes those 430 lb.-ft. of torque.
The brakes are extra large with 11.6-in. rotors that are cross-drilled and vented axially. They're Nissan factory parts borrowed from the Skyline Group A racing cars that compete in Japan and Australia and used in concert with carbon-metallic brake pads that are the same as those used on NPTI's GTO racer.
The next-to-last stop on our tour of the Millen GTZ brings us to the engine. Stock on the inside, it's fitted with high-flow fuel injectors, larger-than-stock Garrett turbochargers and 50-percent larger intercoolers. There's a low-restriction air filter that's part of an HKS package containing a Vein Pressure Converter and modified air-mass sensor. The idea here is to increase airflow to those hefty compressors.
Their output is handled by an HKS Electronic Valve Controller (EVC) that regulates the operation of the turbocharger wastegates, which are fitted with HKS electronic control valves. Hot stuff, which explains the engine oil cooler that's part of the modification.
A special exhaust system designed by Millen Sports Cars bolts on behind the catalytic converter and feeds the spent mixture into a pair of Flowmaster mufflers.
To ensure that the twin-turbo V-6's 460 bhp makes it to the gearbox, there's a Centerforce clutch with a special dual friction disc that uses a bronzelike coating on the engine side and a more conventional, fiberlike covering on the other surface.
Last stop: the GTZ's interior. Note the Momo Panther steering wheel and leather shift knob. Steel pedal pads (a Millen product) fit atop the stock rubber ones and keep your feet from sliding off. Open the glovebox and observe the command post that controls the engine's output and monitors its performance: an HKS boost control unit (for the EVC) with buttons that call up boost settings of 50 and 100 percent over stock (12.0 and 16.0 vs. 8.0 lb.) and a knob that dials up as much as a 200-percent gain in boost pressure; a 20-psi boost gauge with recording telltale; two telltale-equipped exhaust temperature gauges (one per turbo) to keep tabs on fuel mixture and ignition timing; control panel for the HKS Vein Pressure Converter.
Tour complete, it's time to take the GTZ to Carlsbad Raceway where we find that by opening the glovebox and turning the HKS control module's knurled knob almost fully clockwise (to 5 o'clock),we crank in 17.0lb. of boost, the most Millen recommends with 92 RON unleaded pump gasoline. For test purposes, Steve has filled the tank with 102 octane. Tweak goes the boost knob, nearly to the stop (kids, do not try this at home). He makes a run and finds the telltale frozen at 19 psi.
Dozens of runs-carefully monitored by the IMSA GTO racing crew-show us that the GTZ likes its high-energy diet. The quickest pass with tires alight produces a quarter-mile time of 13.5 sec. at 109.5 mph.
These are impressive figures, but not nearly as remarkable as the speeds the GTZ reaches in the slalom. With R&T ace pylon-shaver Kim Reynolds at the wheel, the super Z notches up a personal best of 67.3 mph. On the skidpad, the show is almost as good-0.93g-second highest for a production-based automobile. Credit for this goes to the suspension and those extra-sticky Yokohama A008Rs keeping all four wheels locked onto their trajectory.
But what good's a supercar if you can't drive it on the road, right?
So we did. And found that the GTZ attracts attention (it's difficult not to notice that orange paint job and treetop-tall rear wing). Knowing this, we drove discreetly. Okay, maybe not all the time because it's an absolute carnival ride to tip into the throttle, hear those twin turbos spool up and hang on as the Millen reels in the horizon.
Unlike the stock 300ZX Twin Turbo, the GTZ feels turbocharged. Even at the low (50 percent) setting response is immediate. At 100 percent (high), it's not only immediate, it's breathtaking. Wheelspin can occur easily in lower gears until those sticky Yokohamas take hold. Then the power builds, to the redline and beyond-to about 7500 rpm when the limiter kicks in. Fun it is. Play it's not. At 100 percent or more, a tip of the throttle delivers the automotive equivalent of rapture of the deep. Not what you want when the road surface is less than ideal.
As expected, handling is superb. The GTZ is like a radio-controlled ballistic missile that zeroes in on a target. Response is superb, and roll nonexistent. Braking is exceptional (there's more braking than any road car will ever need). But the competition pads are squeaky, making it difficult if not impossible to be unobtrusive.
Here's a surprise; In spite of shorter, stiffer springs, the GTZ's ride isn't much harsher than the stock 300ZX Turbo's. And (can you believe it?), the car does not scrape its spoiler at every driveway and speed bump.
A tractable, smooth road car that performs, handles and feels like a race car: That's the GTZ. See what happens when you let an automobile enthusiast and successful race driver build a road car?
