2009 Chevrolet Corvette ZR1: The Mother of All Vettes

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2009 Chevrolet Corvette ZR1: The Mother of All Vettes
Like Lincoln at Gettysburg, General Motors chairman Rick Wagoner uttered but a few select words to inspire a whole new Chevrolet Corvette. Reacting to plans for the $65,800 Z06 outlined by chief engineer Tadge Juechter no score and three years ago, Wagoner mused, "I wonder what this team could do for $100,000?"
The answer is the 2009 Corvette ZR1, engineered to be the most powerful, best performing, highest priced Chevy in history. While the figures remain in flux since this blog star is still nine months from fruition, count on more than 600 hp, a top speed of more than 200 mph, 0-to-60-mph acceleration well below four seconds, and a sticker price that easily tops Wagoner's six-figure vision.
The irony is that, while the ZR1 remains loyal to tried-and-true pushrod technology, its name recalls the Corvette's brief dalliance with overhead camshafts. For six seasons, starting in 1990, Chevy teamed with Lotus to power the era's top Vette with a 32-valve, 5.7-liter V-8 that delivered 375 hp initially and 405 hp at the end of a 6939-car production run (see sidebar).
That was then, and the ZR1 is now what Juechter characterizes as, "the king of the hill, with the best of everything, in contrast to our lean and dedicated Z06 track machine. We kept changing the name to try to fool you guys as to what this new Corvette would really be called. The Blue Devil code kept the program under the corporate radar while we awaited approval.
"After debating half a dozen potential names, we decided to revive the ZR1 badge, because it fits best. Like the previous edition, this is the Corvette for our most enthusiastic customers who want top performance and the best of everything to go with it."
THE ENGINE
The star of the underhood team is a Roots-type supercharger manufactured by the Eaton Corpora-tion. Carmakers have used the supercharging gambit for more than a century because it works: when you blow more air into an engine, more power comes out.
According to Juechter, a belt-driven blower wasn't the only power booster considered. "We crammed a turbocharged car together to investigate that alternative. While it successfully demonstrated that our existing architecture could handle more power, the test car burned to the ground at Milford , ending the turbo program before I got to drive the mule."
According to assistant chief engineer Ron Meegan, who's responsible for the Corvette ZR1's new LS9 V-8, the Eaton supercharger is a sixth-generation design that debuts here. One turn of the blower's driveshaft delivers 2.3 liters of air under pressure. Configuring each of the two rotors with four lobes and twisting the lobes 160 degrees over their length boosts thermal efficiency more than 70 percent. Efficiency is important, because it determines the power required to spin the blower, the intake charge's temperature rise, and the amount of noise and vibration generated.
To avoid the top-fuel-dragster look associated with supercharged V-8s, the blower is mounted low in the engine's valley. Air enters the front of the blower, is compressed to a maximum of 10.5 psi, and is then exhausted to the intercooler positioned directly above the supercharger. Nearly a gallon of antifreeze - circulating between two heat exchangers packaged inside the intercooler housing and a third located ahead of the radiator - helps lower the charge air temperature by up to 100 degrees Fahrenheit. The belt that spins the supercharger 2.3 times crankshaft speed is a husky, eleven-rib design that also powers the water and power-steering pumps.
What lies beneath the blower is the healthiest, hardiest small-block ever. While the basic 6.2-liter cylinder case is shared with trucks and the LS3 Corvette, it's stuffed and covered with premium everything: steel (instead of sintered metal) main bearing caps, a forged-steel crankshaft, 9.1:1 forged-aluminum pistons, titanium connecting rods, a dry-sump lubrication system, and special "roto-cast" cylinder heads. According to Meegan, rotating the molds during the casting process yields a more consistent material density, thereby boosting the aluminum cylinder heads' high-temperature strength.
The heads are retained by bolts increased from eleven to twelve millimeters in diameter and sealed by new four-layer head gaskets. To save reciprocating weight, the intake valves are titanium and the exhaust valves have hollow stems. Oil jets aimed at the bottom sides of the pistons help reduce their temperature under duress. The entire exhaust system - including the hydroformed headers, catalysts, three-inch pipes, and muffler bypass valves - is an LS7 (Z06) hand-me-down.
In the interest of longevity, the LS9's flywheel is attached to the crankshaft by nine instead of the usual six cap screws. A dual-mode fuel-delivery system feeds the injectors at 36 psi during low speeds and at 87 psi when the driver indulges the throttle. While peak power and torque figures are yet to be determined, the LS9's redline has been set at 6500 rpm.
THE TRANSMISSION
The Mexican-made Tremec TR6060 transmission, overhauled for 2008 with lighter, quicker shifting, is back for another stint with fresh upgrades. The spread between first and sixth gears has been tightened by 36 percent in the interest of vitality. Armed with a 3.42:1 final-drive ratio (same as in the Z06), the ZR1 bolts to well over 60 mph in first gear. Top speed moves from fifth in the Z06 to sixth with the ZR1's closer gear ratios and lower redline. One downside is that this will be the first Corvette stricken by a gas-guzzler tax.
To provide a 50 percent increase in torque capacity with no nasty side effects, the ZR1 has been blessed with a dual-disc clutch assembly. According to transmission expert Bob Puri, the new clutch has significantly less rotating inertia, a boon to shift quality.
THE CHASSIS
Considering the dynamic strides achieved with the Z06, you might expect Corvette engineers to rest on their chassis laurels. You would be mistaken. While the hydroformed-aluminum spaceframe, rack-and-pinion steering, and core suspension components are for the most part carryover, the brakes, dampers, antiroll bars, wheels, and tires have all been upgraded for the ZR1's mission.
A practical rule of thumb is that braking capacity must rise in step with acceleration and speed potential. In accord with this non-Newtonian law, the ZR1 is upgraded with the Corvette's first carbon-composite brake system. The Brembo-supplied stoppers are described by Juechter as among "the largest carbon-ceramic rotors available on the planet." Measuring 15.5 inches in diameter in front and 15.0 inches in diameter in back, these radially and laterally vented discs were originally designed for Ferrari's FXX and Enzo, respectively. The Brembo monobloc calipers house six pistons in front, four in back.
Goodyear and Michelin periodically face off to see who deserves the honor of manufacturing the Corvette's footwear. Michelin won this go-round, so the ZR1 is shod in Pilot Sport 2 ZP (zero-pressure, or run-flat) tires, sized 285/30YR-19 in front, 335/25YR-20 in back. Twenty-spoke spun-cast Speedline aluminum wheels will be offered with a choice of a chrome or silver-painted finish.
The ZR1 also will benefit from larger-diameter antiroll bars and second-generation MR (magneto-rheological technology) dampers, which are said to be versatile enough to cover everything from flat-out racetrack lapping to smooth-road, civilian-speed touring. Juechter reports that the hardware and the software were both significantly improved for 2008.
THE BODY AND INTERIOR
Last year's comprehensive interior upgrade should nicely appease sniffy Corvette customers who will expect near perfection for their $100,000. That said, the leather-wrapped-everything package, which costs an extra $8005 in a 2008 Corvette, won't be tossed into the ZR1 for free. Juechter cites flexibility as the reason. "We're offering a fairly basic car for the track crowd and one option package with practically everything for more typical ZR1 customers," he says. For 2009 models, the high-zoot leather will be available in an expanded color palette.
About half of the ZR1's exterior panels are shared with the Z06, and the remainder switch to carbon fiber to save weight. The hood, front fenders, roof, and rocker extensions are all made of the stiff, light material to trim fat. Key pieces - the rockers, the splitter attached to the front fascia, the roof, and the B-pillar bow - are left unpainted to wow the rubes. According to Juechter, these are the auto industry's first visible carbon-fiber panels that won't yellow and crack over time due to ultraviolet light exposure. The breakthrough is a secret elixir costing $60,000 per gallon that, when added to the clear coat, blocks the harmful rays better than Bain de Soleil.
The cherry on top is a polycarbonate window - measuring roughly seventeen by nineteen inches - in the hood that provides a partial glimpse of the beast residing within.
Ready to rumble, the ZR1 should hit the streets weighing 3400 pounds or possibly a bit less, according to Juechter. The new Corvette king tops the Z06's power-to-weight ratio by about ten percent and the $270,000 Ferrari 599GTB's ratio by twelve percent.
THE BOTTOM LINE
We predict that Juechter's next presentation to his boss will prompt the GM equivalent of hugs and high fives. The ZR1 is another great addition to the Corvette's rich performance portfolio. To filch a thought from the chairman, we can only wonder what this team would do with a $150,000 price and permission to move the engine behind the driver.
In reviving the ZR1, GM taps into a storied - but no always glorious - past.
The new ZR1 might break new ground - it's the first Corvette to sport a factory-installed blower, the first to carry a gas-guzzler tax, and the most expensive Chevy in history - but the idea of an over-the-top, factory-built Corvette isn't new. Neither is the ZR1 name, which first appeared in 1970 as a $969 option for the base Vette, consisting of a 370-hp V-8 and a few drivetrain and suspension upgrades.
The next car to bear the ZR1 badge arrived in 1990. GM tapped Lotus to develop a four-cam, aluminum-block V-8 for the fourth-generation Corvette, with the goal of 400 hp and 400 lb-ft of torque. The 375-hp engine that resulted was indeed leaps and bounds ahead of the ordinary Corvette's iron-block V-8 - then producing a mere 245 hp - but it was also forty pounds heavier and far more expensive. Making matters worse, thanks to Chevy's insistence that the iron V-8's bore spacing and displacement be preserved, the bore-to-stroke ratio suffered. Ironically, Chevy's DOHC V-8 had mutated into a long-stroke compromise that wasn't optimized for high rpm.
Regardless, customers lined up to buy the 180-plus-mph, $58,995 ZR1, even though it commanded an absurd $27,000 premium over the base Vette. (Initial demand often pushed actual transaction prices beyond $100,000.) A six-speed transmission, wider rear tires, and new body panels came along for the ride. Yet demand dropped sharply after two years, and ZR1s stacked up on dealer lots. Just over 6900 cars had been sold when production ended in 1995. As for that fancy new V-8? It went the way of the dodo, shoved aside by a redesigned version of Chevy's pushrod small-block - one that was lighter, cheaper, and more compact. Given enough time, it would eventually far surpass its DOHC cousin in output, too: the current Z06's 505-hp, 7.0-liter pushrod V-8 is proof positive that complexity isn't always the best answer.

-Sam Smith

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