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Saturday
Nov292014

New Z06 takes performance to a stunning new level, especially on the track

Note: Worked with Autoweek's Mac Morrison at ridiculously fun Road Atlanta to test the new Corvette Z06. 

“I don’t see any cones … ” observes sports-car racing champion, Cadillac factory driver and Autoweek road-test ringer Andy Pilgrim, eying the Road Atlanta circuit as the SUV carrying us toward the paddock crests an access road. “This will be interesting.”

No cones mean no chicanes installed temporarily at the blistering 2.54-mile road course that rises and falls into a terrorizing bevy of quick, blind corners. “Interesting” is Pilgrim-speak, translated loosely, for, “Don’t be stupid when you get out there. Slow your hands down, and don’t get over your head. You don’t want to be that guy.”

At least, that’s what we hear as a realization manifests: The Corvette team is about to turn us loose, relatively unchecked, around this place in its new 2015 Z06.

A brief recap: The quickest series-production Corvette in history goes on sale in December with a new LT4 6.2-liter supercharged V8 producing 650 horsepower at 6,400 rpm, and 650-lb.-ft. of torque at 3,600. Chevrolet says the base version reaches 195 mph, and 186 mph when equipped with full aerodynamics (keep reading). Our own testing of a seven-speed manual gearbox model yielded 0-60 mph in 3.3 seconds, and the quarter mile in 11.5 seconds at 123.8 mph; Corvette engineers say an 8L90 eight-speed-automatic equipped car does 2.95 and 10.95, respectively.

Built on the same aluminum frame as the C7 Corvette Stingray, the 2015 Z06 is 20-percent stiffer than the C6 Z06, according to Chevy. This allows the coupe to come standard with a removable roof; a true convertible arrives in early 2015 and neither require additional chassis reinforcements to handle their increased performance beyond the Stingray.

One look at power, torque and acceleration numbers means the LT4 might be reason enough to place your order. Other than the block, it’s effectively an all-new engine, with different aluminum heads, titanium intake valves and forged aluminum pistons among the upgrades over the Stingray’s LT1. A 1.7-liter Eaton supercharger with shorter rotors spins up to 20,000 rpm, 5,000 more than the C6 ZR1’s supercharger. Power and torque delivery borders on devastating, as a loud, glorious exhaust note roars throughout the rev range on wide open throttle. There is almost no supercharger whine polluting the aural sensation either inside or outside the cockpit; you hear it only when listening hard for it, and even then only on partial throttle and not during hard driving.

Yet for all the Z06’s snorting on-paper capability, it rides and behaves on public roads as comfortably and docile as any new Corvette. Base Z06 spring rates within the standard, industry-leading magnetically adjustable suspension are just slightly higher than the Stingray’s, so ride quality remains excellent for an extreme performance car. Drive the Z06 plebeian-like on the street, even with the stiffer Z07 package (more on that shortly), and you might be hard-pressed to feel much difference between it and the standard car. Of course, this first drive occurred on reasonably well-maintained Georgia roads, so we'll wait to see how it fares as a daily driver for those who live with it on, for example, the battle-scarred routes snaking around the Detroit area where Corvettes are conceptualized. 

No need to even start the engine or resort to the spec sheet, however, to know immediately the Z06 is far from typical Corvette fare. It shares doors, roof and hatch with the Stingray, but fenders, quarter panels and carbon fiber hood are its own, as are the half-NACA/half ramjet quarter-panel snorkel ducts feeding air to the gearbox (left side) and differential (right side) coolers. Flared bodywork accommodates front Michelin tires 1.5 inches wider than the Stingray’s (P285/30ZR19); rear’s are 2.0 inches wider (P335/25ZR20). Front fenders extend outward 2.2-inches combined, rears 3.15.

There’s plenty of conspicuous aerodynamic addenda, too, and it soon becomes the day’s favored topic, causing more head shakes than even the pupil-dilating power. Pilgrim, who spent five seasons driving for Corvette Racing in the American Le Mans Series, quickly picks up on it at Road Atlanta.

“For instance, going down the hill in turn four, you’re rolling on a little more speed and when you turn in—it’s a downhill off-camber right-hander—you feel it’s getting some help,” he says. “You immediately realize this car, with the Z07 pack, has some downforce, you can feel it. And the additional damping [35 percent higher spring rate than a base Z06] works with it very well.”

By “some” Pilgrim means the most downforce, easily, either he or we have experienced in a stock road car. Though we’ve yet to run instrumented tests on new hypercars such as Porsche’s 918 Spyder or Ferrari’s LaFerrari, whether or not they can lap racetracks quicker than the Z06 is mostly irrelevant, as their million-dollar price tags, give or take, place them far outside the Corvette’s competition canon. 

How much downforce you get is both somewhat unquantifiable and dependent on how you equip your Z06. Unquantifiable because, as Corvette chief engineer Tadge Juechter explains, “A lot of times [people] say a total vehicle has downforce, which typically really means downforce on the back but still lift at the front. We don’t like to say a pound figure; there are so many different ways to calculate and estimate that [by] extrapolating from wind-tunnel data, and every tunnel is different. … So if we put a number out there somebody would cherry pick it and then you start a war between manufacturers, and it turns into this technical debate how you’re measuring it.”

This explanation might sound convenient if not apocryphal. (Editor’s note: It’s certainly reasonable, however; see the ongoing absurdity surrounding manufacturers’ claimed Nürburgring lap times as Exhibit A when it comes to unchecked rules of engagement. Speaking of which, an official Z06 ’Ring time is not yet available.) But any doubt about the Z06 out-aeroing and out-lapping rivals like Porsche’s GT3, Ferrari’s 458, McLaren’s 12C and Nissan’s GT-R vanishes when you drive one—notably, one outfitted with the $7,995 Z07 pack.

Z06s start at $78,995, and feature a front splitter with small, bolt-on wickers, and a rear spoiler. Ticking the option box for the $3,995 carbon aero package adds a larger carbon-fiber front splitter with winglets, carbon side-rocker extensions, and larger rear spoiler with a fixed wickerbill. For ultimate grip, add Z07 to the carbon pack (required) and the car benefits from larger, removable front-splitter winglets, and larger, adjustable outboard wickers on the rear spoiler; it also boasts a removable, clear wicker bridge. In other words, there is a solid range of aero adjustability here, which some owners will undoubtedly make even broader by drilling their own holes for extreme spoiler attack-angles. Z07 also includes 15-inch Brembo carbon-ceramic brakes front and rear, and Michelin Pilot Sport Cup 2 ultra-performance rubber, rather than standard Pilot Super Sports.

Such is the Z07’s influence on overall performance, its additional aerodynamic drag reduces the car’s top speed on Road Atlanta’s backstraight in Pilgrim’s hands from 161.8 mph to just more than 155—but with a two-plus second improvement in lap time due to increased cornering speeds. The circuit’s famous, downhill and blind final turn, in particular, showcases the additional Bernoulli-derived wallop.

“The amount of grip through there is very surprising,” Pilgrim comments. “You’re having a moment where you’re thinking to yourself, ‘We’re looking at some seriously-prepared race-car apex speeds here,’ about 119 mph at the curb and then 126 mph at the exit.

“And then down the frontstraight and through turn one, the track loses camber as it goes uphill. It’s a place where a lot of cars, even though they have reasonable handling, they will lose the rear coming up out of turn one and transitioning over flat road into turn two. This car is saying, is that all you’ve got? So OK, we’ve jumped to a level of race-car performance here.

“You start challenging the car and it gives you everything you ask of it; you tend to forget it’s a street car. I’m going to a limit that’s stretching that envelope, and it’s just astonishing the amount of grip it has. And the way it gives it to you, it’s not suddenly snappy. When you do get a little bit of oversteer, it’s controllable.

 “On the absolute limit in midspeed corners it will slide the rear a little bit, and then coming through 12 it has a nice drift aspect. So it’s very balanced at high speed thanks to the good aero setup, and a little more tail happy in the midspeed corners.”

While Pilgrim pounds around on the limit, our own lapping reveals his definition of “tail happy” indeed is not on-edge fear, but is a pro driver’s appreciation for controllable and exploitable slip angle. We never get close to the Z06’s ultimate limits stringing together one fast lap, and not only due to lacking our contributor’s 30 years racing experience: The car’s limits are so high, we need a solid amount of time just to come to terms mentally with its aero-enhanced grip levels. Take your Z06 to the track and prepare for the intimidation factor as you work up to speed, especially on a circuit as fast and blind as Road Atlanta. But the 50/50 weight-distributed chassis is exceptionally stable, meaning in most cases the driver is the biggest performance limiter. Regardless of what aero package you have, the car’s overall handling and tire breakaway characteristics are similar; only the total amount of grip changes significantly. The Z06 delivers a very neutral balance straight out of the box without sliding into frustrating moments of plowing understeer, yet neither does it snap into breath-sucking moments of rear-end mayhem.

“You can get some oversteer on turn-in a little bit,” Pilgrim nods, “but that’s mostly when being very aggressive. Oversteer comes in the most when you’re back to power—and it’s an aggressive back to power. Even with the extreme provocation I’m giving it, the oversteer is very manageable.”

At this point, our initial thoughts about becoming “that guy” and landing in the guardrail have faded. We’ve even begun to stop worrying about applying exceptionally methodical throttle and brake inputs, lest the bane of previous Z06s exposes itself and spits us into the wall.

“Trailing throttle oversteer?” Pilgrim replies at the mention of it. “Oh, pffff, nothing. Yes, the previous Z06 was tricky on corner entry due to that, it could really bite you. But this car has deleted that completely.”

Not long after and as if to make the point, under a bright Georgia sun that brings ambient temperature above 85 degrees, a glance toward pitlane sees Pilgrim with tire gauge in hand. A brief discussion with Corvette engineers and down come the pressures, out goes the driver for one more flying lap to cap the afternoon.

Two minutes later a white Z06 rockets down the hill at turn 12, its V8 producing a shriek not heard all day. Despite the high heat and being driven hard already for many laps, and riding on tires with a fair amount of running on them, the lap timer flashes 1 minute, 29.8 seconds as Pilgrim crosses the line. Info pulled from the onboard -- and must-have for track drivers -- Cosworth-developed Performance Data Recorder’s telemetry shows a 1.5 lateral-g spike. Consider: a Camaro Z/28.R’s pole-position time at Road Atlanta for October’s IMSA Continental Tire Challenge Series race was 1:31.6 -- and the Z06’s lap time puts it within three seconds of the slowest qualifier, an Audi R8 LMS, in this year’s Petit Le Mans’ GT Daytona class at the same circuit.

When you realize a good set of slicks should knock four or five seconds off the Corvette versus race-car delta, the day’s final result isn’t just interesting as anticipated, but rather shocking. Of all of today's series-production performance cars, if you measure success by lap time, the Z06 is a remarkable achievement. The fact it is equally at home on quiet public roads on the way to and from the circuit, or as a daily driver, make it outright astounding.

We're still shaking our heads.