Zazzle Shop

Screen printing

Wednesday, October 29, 2008

The Corvette Z's- which to choose

The glory days of the Corvette have generally coincided with the availability of an alphanumeric soup of engine and equipment packages. Go back to the 1960s and early ’70s, and all sorts of near mythical combinations show up, with the LT1, L88, LS6, ZR-1, and Z06 being the most notable. Contrast that with the Vette’s Dark Ages between the OPEC oil crisis and the introduction of the fourth-generation Corvette, the C4, in 1984, when the options lists were limited to some slightly more powerful engines and sportier suspensions.

The C4 and the subsequent C5 marked a return to form—and evocative alphanumerics associated with performance again appeared on the options lists. The 375-hp ZR-1 model debuted in 1990, though it was pricey—nearly double the sticker of a base 245-hp coupe. A Z51 suspension package was also available through the C4’s (overly long) 13-year life. There was no ZR-1 for the 1997–2004 C5, but the Z06 performance model, latterly with 405 horsepower, commanded a premium of less than 20 percent over a base Corvette.

With the sixth-generation car, the C6, what’s old is new again. Introduced in 2005, the C6 has now spawned Z06 and ZR1 variants, while the Z51 suspension-option remains. The cynical might suggest that the $105,000 ZR1 merely represents a serious profit center for GM, but the other view is that this 638-hp supercar reflects confidence in the Corvette brand and in Chevrolet’s ability to engineer a car deserving such a price tag.

To see where the ZR1 (now hyphenless, kids!) stacks up, we decided to compare it with its stablemates. One could argue that we should be pitting the ZR1 against a Porsche 911 Turbo, but we reckon a 911 Turbo buyer is no more likely to cross-shop a ZR1 than a Yankees fan is to buy season tickets to the Red Sox. We think it’s better to know what the ZR1 offers—if anything—beyond the Z06 and the regular coupe.

Spot the Differences

With the cars lined up alongside each other, all our drivers made the same observation: The base yellow Corvette coupe, which ordinarily stands out on the road like a tiger in a room full of domestic cats, seems a little dowdy.

The Z06 and ZR1 look more taut and chiseled, thanks to wider front and rear fenders, more-aggressive front fascias, and a profusion of slats and scoops that channel cool air and exhaust heat. The ZR1 adds sills, an air-dam extension, and a roof made of carbon fiber; a more prominent tail spoiler; somewhat tacky ZR1 badges; and a transparent panel in its carbon-fiber hood.

All three Corvettes roll on big rims: 18 inches up front and 19s in back on both the base and Z06 models. On the ZR1, there are 19s at the front and 20-inch rears. Large red brake calipers play peekaboo behind the wheels of the Z06, with blue ones on the ZR1. Chromed wheels are optional, ranging from $1850 to $2000, but this treatment seems a touch passé.

Inside, all our test cars came fully loaded and featured an optional full-leather treatment that is way classier than the standard vision in plastic. The nicely stitched leather, however, jars with some cheap plastic moldings in the center stack and a lame faux-carbon-fiber finish that runs through the cabin. That leather costs $8055 in the base car, $6515 in the Z06, and $10,000 in the ZR1, bundled with a navigation system and upscale audio. (The touch-screen nav system is a $1750 stand-alone option on the two other models.) There’s a $55,410 difference in price between the ZR1 and the Z51, but interior changes are limited to a boost gauge in place of a battery-voltage meter, a 220-mph speedometer, and the ZR1 name emblazoned on the seatbacks and the gauge cluster.

ZR1 and Z06 buyers might not get a whole lot of extra interior equipment for their money, but they do get a lot more hardware. The base car comes with a 430-hp, 6.2-liter LS3 V-8 engine mated to a six-speed manual or automatic transmission. Our test car came with what we regard as the most significant option, the Z51 performance package, which incorporates stiffer springs and anti-roll bars, retuned shocks, shorter gear ratios, and larger-diameter brake rotors (13.4 inches in front and 13.0 inches in back, up from 12.8 and 12.0 inches). At $1695, the Z51 package looks like a value. We also like the $1195 dual-mode performance-exhaust system, which increases output from 430 horsepower and 424 pound-feet of torque to 436 and 428, respectively. A base Corvette coupe equipped with the Z51 package and exhaust system would run $50,785, but Chevy saddled our test car with another $13,155 of options.

For $23,655 above the cost of our Z51 test car, the Z06 adds plenty of performance-enhancing equipment. The LS7 engine uses a different block than the LS3 and displaces 7.0 liters. With the aid of lightweight titanium valves and connecting rods, it revs to 7000 rpm, 500 more than the LS3. It uses a race-type dry-sump oiling system compared with the LS3’s wet sump. This engine makes a stout 505 horsepower and 470 pound-feet of torque.

To handle the increased power and torque, the Z06’s clutch, transmission, and half-shafts have been beefed up. The frame is aluminum instead of steel, and there are cast suspension pieces in place of welded items. There’s even a magnesium front cradle instead of aluminum to save weight and add strength. The suspension design is carried over from the base car, with stiffer springs and anti-roll bars. The brakes are uprated, with 14.0-inch-diameter front and 13.4-inch rear rotors and six-piston front and four-piston rear calipers.

The ZR1 costs $31,745 more than the Z06. Like that car, the main news is under the hood. The supercharged 6.2-liter LS9 engine is based on the LS3 but with many changes. It has a forged steel crankshaft, titanium connecting rods, a dry-sump oil system, and hollow-stem exhaust valves. Titanium is also used for the intake valves. An Eaton R2300 supercharger and Behr intercooler force fuel and air into the engine, resulting in 638 horsepower and 604 pound-feet of torque.

To cope with the power, a two-disc clutch is fitted, and the gearbox and rear axle have been further strengthened. The gear ratios are closer than those of the Z06. The ZR1’s suspension is shared, for the most part, with the two other models, although the fitment of magnetorheological variable-damping shocks allows for a softer ride than the Z06’s. For the first time, a Corvette is equipped with carbon-ceramic brakes—massive 15.5-inch-diameter front and 15.0-inch rear Brembo rotors. They’re a slightly smaller version of the brakes used on the Bugatti Veyron.

All three Corvettes are spectacularly fast. The base model goes from 0 to 60 mph in 4.1 seconds and hits 100 mph in 9.0 seconds. The Z06 needs just 3.6 and 8.3 seconds for the same tasks, while the ZR1 hits 60 mph in 3.4 seconds and 100 mph in a stellar 7.6 seconds. That 100-mph time betters the likes of the Nissan GT-R, Porsche 911 Turbo, and Ferrari F430.

The 30-to-50 and 50-to-70-mph top-gear acceleration times are impressive, as is skidpad grip: 0.99 g for the coupe, rising to 1.07 g for the ZR1, which also has the best braking of any production car we have ever tested—it needed just 142 feet to slow from 70 mph to a standstill. The base car managed 152 feet (better than the last 911 Turbo we tested), and the Z06 took 150 feet.

Road Warriors

The base coupe is the most livable of the three. The highway ride is surprisingly supple, tire noise is relatively muted—except for some intrusive slap over expansion joints—and the engine hums away at 2000 rpm at 80 mph. We even managed to average 25 mpg during our test in the coupe, close to the EPA-highway figure of 26 mpg. That’s astonishing when one considers that the car spent an afternoon being thrown roughly around Grattan Raceway Park in western Michigan.

On bumpy back roads, the Corvette was very composed, had tons of grip, and ate up the straightaways while being perfectly composed under braking. It sounds terrific, too, bellowing hard under full throttle. The only weaknesses are steering that isn’t particularly communicative, even if the weight and accuracy are first-class, and a notchy shifter.

The Z06 is almost too much car for regular roads. On the highway, the ride is quite compliant, but it gets choppy over high-frequency, small-amplitude ripples. Surprisingly, it’s quieter than the base car at 70 mph, though the engine is more raucous under hard acceleration, when the V-8 snarls in a harsher, less mellifluous manner. The shifter still has a manly action but was a lot smoother than the base car’s. An observed fuel economy of 20 mpg is impressive considering the Z06’s capabilities.

Although the Z06 is even faster and grippier than the base car, it’s not as easy to drive hard on bumpy back roads, darting here and there in the braking zones. It crashes hard over the most pockmarked surfaces, and the steering feels a little less linear and more aggressive on turn-in.

The ZR1 is a more civilized ride than the Z06, although one needs to make sure the adjustable shocks are set in “Tour.” “Sport” is as firm as it is in the Z06, whereas the softer setting is almost as supple as the base car’s. Highway cruising is more rowdy, however, thanks to the shorter gear ratios and the noise emitted by the giant tires. The ZR1 got a woeful 12-mpg average, although the car did spend an awful lot of its time lapping around Grattan. The attainable EPA highway number of 20 mpg is a lot more respectable.

The car tends to tramline, unlike the other models, which means the driver needs a firm hand on bumpy back roads. We rated the ZR1’s steering as the most linear and involving of the three cars. The brakes are stellar, despite some initial pedal softness. Like the two other cars, there’s a marked step in power at roughly 3000 rpm, except that there’s simply more thrust in this car. The engine noise is sublime, a sonorous exhaust growl that swells in volume with revs, accompanied by blower whine that creates a V-8 symphony.

Track Stars

Let’s get this straight: The seats in all three cars are unacceptable. They’re okay for street use, but they just don’t provide the lateral support needed on a track. We all found that our legs hurt after driving at Grattan because we had to use them to brace ourselves under hard cornering.

Otherwise, all three are weapons on the track. The base coupe is very good, with nicely predictable on-the-limit handling. It will run wide if the driver tries to dive-bomb into a corner on the brakes or with the throttle closed, but the attitude can be converted to neutrality and then to progressive oversteer with power.

The Z06 is 2.1 seconds faster per lap than the Z51 but is hairy at the limit. We’ve said it before, but the combination of light-switch oversteer, instant breakaway from the Goodyear tires, and a slight numbness in the steering makes for a ride that’s like one of those giant roller coasters: alternately so scary and exhilarating that you’re not sure whether you enjoyed the experience.

The ZR1 is a far more sanitary device, despite going 2.1 seconds faster per lap than the Z06. It feels softer than the Z06, which gives the driver more warning of incipient breakaway, and the Michelin tires are much more progressive when they relinquish grip. Plus, the steering has more feel, and the brakes could stop a run on Wall Street. At Grattan, it was about as good as a road car can get on a circuit.

Verdict: A Corvette Wins!

The loser among these three is the Z06. In the past, we’ve given the car something of a free pass simply because it provides such stupendous performance for about $70,000. It is still a great value, but the Z51 and the ZR1 highlight its major fault, namely that it’s really difficult to drive hard on a track, which is supposedly its raison d’être.

The base coupe is also a great value and mighty fine to drive, too. It is relatively comfortable on the highway, very practical, and really fast on road and track. Sure, the interior is Third World standard unless you order the $8000 optional leather package, but one can live with that for a base price of less than $50,000. As one test driver noted, “This is as much Corvette as I really need.”

The ZR1 is a spectacular car. Yes, it has an interior that wouldn’t pass muster in an $18,000 Hyundai let alone a $105,000 sports car, and it looks, well, like a Corvette (on steroids). But it is a great piece of work: faster, easier to drive at the limit, and more comfortable in daily use than the Z06. It is one of those rare cars, such as the Ferrari 430 Scuderia and the BMW M3, that make its driver look more heroic than reality suggests. To do that with a car that has such formidable performance is a rare feat.

Katech Corvette Z06 ClubSport

The Corvette from Katech

On paper, the formula for the ClubSport Z06 from Clinton, Michigan–based Katech Performance sounds inviting. Take a Z06, remove 201 pounds, fit a double-adjustable coil-over suspension, add a Brembo brake kit, and install super-grippy Michelin Pilot Sport Cup tires. On the test track, it delivers: The Katech car was as fast from 0 to 60 mph as the ZR1 (3.4 seconds), and it hit 100 mph in 7.8 seconds. It beat all the Corvettes on the skidpad with 1.12 g of grip, owing to the tires. It looks pretty wicked, thanks to a subtle Katech body kit, a carbon-fiber hood, and striking wheels, along with its lowered stance.

In the real world, there are a number of problems. It sounds amazing, although 99 decibels at wide-open throttle gets incredibly wearing after, oh, about five miles on the highway—as does the ride, which is race-car stiff.

One might think that its true métier would be the track, and up to a point, that’s the case because it took 1.5 seconds off the Z06’s lap time. But although the steering feel is more engaging than the Z06’s, it’s even twitchier at the limit, and the car gets knocked off line over the slightest bump.

Sure, it’s nearly as fast as the ZR1 around the track, but this driver needed to take plenty of bravery pills before attempting a quick lap, whereas the ZR1 was actually much friendlier. And while you might think that the Katech route would end up being cheaper than the ZR1, it isn’t. The base price for this one is an eyepopping $109,000.