This is the third incarnation of the ZR1 namepale on Chevy's flagship. In 1970, the ZR1 was an option which paired the potent 370hp small-block LT-1 350 complete with transistorized ignition, a close-ratio four speed heavy-duty manual transmission, an aluminum (vs. copper-brass) radiator, heavy-duty power brakes, and suspension upgrades to make it a sort of unofficial factory racer. The ZR1 package was $968.95, and true to its intentions, many luxury/convenience options such as air conditioning, radios, and even power steering were not available.
In 1987, there were rumblings of a new version of the Corvette, one which would feature a Lotus designed twin cam V8. When the rumors became reality, the 1990 ZR-1 was given the nickname "King of the Hill", but it, like the 1970 forebearer, was more than an engine package. While the engine was designed with the help of Lotus (owned by GM at the time), it was not the Lotus engine which they had shown in 1983. The engine was made more compact, because in the Corvette factory, engines are installed from the bottom of the car. This being so the engine had to be made narrower with more compact Dual Overhead Cam cylinder heads to fit between the frame rails.

Dubbed LT-5, the engine was all-aluminum and carried a tough race-engine inspired main bearing girdle which secured each main bearing with six-bolts. The engine was termed a "bi-modal" engine meaning it would have good low-speed drivability with outragous high speed capability. When the ZR-1 finally arrived, the output was 375hp, and would later be bumped up to 405 in 1993.

While the ZR-1's most recognized feature was the 5.7L twin cam engine, the ZR-1 was more than the engine; instead it was a complete package. There were specific body panels, with unique doors, rear quarter panels, and rear bumper fascia. In 1991, all Corvettes received a similar rear bumper, the ZR-1's did not include the third brake lamp in the bumper panel, all were still roof-mounted.

In addition to the bodywork, the cars also had the huge 11" wide rear wheels, concealed by the widened rear fenders. The Select Ride suspension system gave ZR-1 a comfortable everyday ride in Tour mode as well as maximum driver control when operated in Performance mode. ZR-1's were priced more than $27,000 above a base coupe leading to the suggestion that the LT-5 engine was all you were buying.

No, the ZR-1 was a total package, featuring the engine, but also included chassis, bodywork, and interior enhancements. When 2009 rolls around, the new ZR1 will replicate its most recent forebearer, combining speed, comfort, and exclusivity.

The Body
In 1990, Chevrolet wanted to ZR-1 to make a low key statement, with only minimal styling revisions to tell it apart from its stablemate. This led to some critisism from the buyers whom for the extra money invested, wanted a car that looked different. Even the wheels had the same styling cues. This issue has been corrected in a big way for the 2009 ZR1. The Corvette team has made several significant changes to the ZR1, both in appearance and materials.

While the Current Z06 uses carbon fiber for the front fenders and the floorboard coverings, the '09 ZR1 is much more carbon fiber intensive. Carbon fiber replaces the sheet molded compound composite for the hood, roof panel, roof bow, lower rocker panel extensions, and the front airdam splitter. Moreover, in all the applications except the outer hood panel, the weave pattern is exposed, covered only with a specially formulated clearcoat to suppress UV effects. Cabon fiber has been used on other Corvettes; the 2004 Z06 Commermorative Edition featured a outer hood panel made of carbon fiber, at that time the largest single panel used on a production car.

The use of carbon fiber allows the ZR1 to make a powerful statement. By leaving the weave pattern bare, the carbon fiber take on an intense, sinister appearance. Many racing cars leave carbon fiber in its natural state, mostly to save weight. The use of it for the roof panel and bow are an excellent place to save weight, because those areas are the highest points on the car, and even small weight savings (7.7lbs) up high translate into a lower center of gravity, which results in a more stable, better handling car.

The current Z06 uses carbon fiber for the front fenders, amd the ZR1 has them as well, though shaped differently. The fenders are wider to cover the 285mm section front tires as well as have a dual outlet vent . The rocker panel extensions, are designed to manage airflow around the lower body and include a deflector to direct air around the rear wheels.

And what about the wheels? These are the most expensive looking and exotic wheels ever to be bolted onto a Corvette. The wheel design was influenced by those used on the all-conquering C6-R race car campaigned in FIA Endurance and American LeMans competition. The thin multispoke wheels enhance the theme of the ZR1, with their minimalist, purposeful look. The wheels will be painted Sterling Silver as standard, while as one of the two available options, the wheels may be specified to be chrome plated. Thesewheels are the largest offered on a Corvette, measuring 19 x 10 inches up front, and 20 x 12 in the rear.

Corvette engineers knew if the ZR1 was to be stable and secure at its anticipated 200 mph top speed, additional steps needed to be taken to tie the beast down. The newly shaped carbon fiber front airdam splitter was designed to reduce front end lift at the double-century mark. With a downforce increase at the front of the car, a larger rear spoiler had to be incorporated. On the Z06, a taller central spoiler than on the coupe/convertible is used, but on the ZR1, the spolier is full width, with raised outer sections, and a depressed center.

While the visual differences between ZR1 and the rest of the Corvette lineup are bold, none is as bold at the hood. The raised carbon fiber hood includes a clear polycarbonite window into the ZR1's engine bay. Clearly visible is the engine's supercharger/intercooler upper proclaiming "LS9 Supercharged" for passerbyers to admire.

The Powerteam

Peering from beneath the polycarbonite window in ZR1's carbon fiber hood is the most potent powerplant ever to rest between the frame rails of any production GM automobiles. The engine, dubbed LS9 displaces 6.2 litres, is topped by a supercharger that administers a positive pressure of 10.5 pounds. The net result is estimated to be 620 hp (pending SAE certification, scheduled for March 2008) and 595 lb/ft of torque. Both numbers are achieved at 6500 and 4000 rpm respectively.

The Induction System

The supercharger is supplied by Eaton and incorporates a liquid-to-air intercooler to lower air temperatures by as much as 140-degrees F. The supercharger/intercooler is similar to that employed by the 4.4L Supercharged Northstar V8 used in the Cadillac XLR-V & STS-V. Two coolant filled brick-like heat exchangers rely on a dedicated cooling system to keep the system at a regulated temperature. Air passes accross the bricks from both sides after it passes thru the compressor and transfers the heat from compression into the coolant. Unique to the ZR1 is a four-lobe rotor, twisted at 160-degrees for increased smootheness & lower pumping losses. The capacity of the sixth- generation Model 2300 Eaton supercharger is 2.3 liters, ample volume to keep the LS9 fully boosted at high engine speeds. In order to handle the additional stresses on the accessory drive system, there is a seven-rib serpentine belt with a substancial width increase. Even the water pump has been made more robust with stronger bearings to handle the increased drive belt load.

With the increased airflow entering the cylinders, the fuel injection had to be upgraded. The fuel circuit uses a center feel design which distributed the fuel more evenly to each cylinder with the added benefit of reduced noise. The fuel injectors are rated at flow rate of 48 lbs per hour, and are supplied fuel at two different pressures. Depending on the demand, fuel is delivered at 250 kPa or 600 kpa. The lower pressures are used during idle and low speed conditions. When the engine is operating at high rpm or wide-open-thottle, the fuel pressure jumps to the higher setting. And that throttle opening is now a large 87mm unit.

The Internals

The LS9 6.2L V8 is a mix of advanced components of the Z06's LS7 and the standard Corvette's LS3. The bore and stroke are the same as the LS3, a 4.06 inche bore, with a stroke from its forged steel crank of 3.62 inches. The forged aluminum pistons ride in cast iron cylinder liners and are dished rather than domed, common in pressurized engines. Like the Z06, the connecting rods are constructed of titanium, chosen for the low reciprocating mass and incredible strength.

The engine block is constucted of cast aluminum and has the six-bolt main bearing caps common to all LS-x series engines. Additionally, the block has enlarged vent windows between the second and third bulkheads for better bay to bay breathing. During the finish bore honing process, a deck plate is installed to simulate the block distortions when the cylinder heads are secured. The use of the deck plate ensures a higher degree of accuracy and promotes piston ring fit and cylinder head sealing. Sealing the cylinder heads to the block is a stronger four layer head gasket in place of the contemporary two layer.

Dry sump lubrication is used on the LS9, although with increased sump and pump capacity compared to the pioneering LS7 found in the Z06. Additional oil based cooling is provided by oil jets that squirt the bottoms of the pistons. Inside the sump is an internal oil cooler, necessitated by the higher engine temperatures encountered by a boosted engine.

The cylinder heads of the LS9 work with the pistons to reduce the compression ratio to 9.1:1. In the 80's in unboosted configuration, this would have been consodered a high compression engine, but today compression ratios in excess of 10:1 are common. The heads have a design similar to those found on the high-output L92 engine found in the Cadillac Escalade by have many differences. The heads are "spun cast" of premium AT356T6 alloy, which reduces the porosity of the aluminum, making a much stronger unit. On the intake side of the head, the ports feature swirl inducing wings which are part of the casting process. These wings would be considered obstructive in a non-supercharged engine, but under boost they enhance the air delivery into the cylinder. The intake valves, measuring 2,16 inches, are constructed of lightweight titanium while the exhaust valves, sized at 1.59 inches are sodium filled stainless steel units. Topping the cylinder heads are a revised rocker arm covers to which the ignition coil packs are attached, without much of the bracketry found on other LSx engines, for a lower profile.

Because of the performance envelope of the engine and the power excesses of the supercharger, the camshaft profile is not as agressive as found on the Z06. The gross lift is only .555 inches for both the intake and exhaust. The camshaft is much more docile in the valve operation as well, with less overlap and valve closing speeds, utilizing the supercharger to make strong low-end torque. The roller lifters and rocker arms are shared with the LS3, however the valve spring retainers are from the Z06's LS7.

Transmission / Rear Axle

In order to achieve the anticipated top speed of 200mph, the gear ratios had to be juggled a bit. First gear was made taller at 2.29:1 versus a 2.66 in the Z06 to allow it reach 60 mph in first gear despite the LS9's 500 rpm lower redline of 6500 rpm. All of the first four gears are a bit taller and more closely spaced than the Z06 (and other Corvette manual transmissions) however, the fifth and sixth gears are shorter allowing for top speed to be achieved in sixth gear, rather than fifth in other models.

A high performance dual disc clutch was chosen to increase the clamping power by spreading the delivered engine torque over a larger surface area. The new clutch employs a pair of 260mm discs, which offer a 25-percent reduction in inertia over the Z06's 290mm single disc unit. A further advantage to the dual disc system is a potentially longer life through more efficient heat dissapation.

The final drive ratio of the ZR1 is 3.42:1, the same as all other manual transmissioned Corvettes. To handle the extra power, the ring gear and the axle shafts have been made tougher. With the wider rear tires, the axle shafts are much more parallel to keep the tires footprint flater.

Chassis / Rear Axle

As the ZR1 is not intended to be a super Z06, a different approach to the chassis was taken. The Z06 is more a a track machine that can be driven everyday, while the ZR1 is a car that can be driven everday, yet hold its own on the track. The ZR1 uses an enhanced version of the Magnetic Selective Ride Control available on coupes and convertibles. By using the shocks whose fluid changes density by varying the electo-magnetic charge affecting the alignment of the metallic particles suspended in the fluid. This allowed for softer spring rates while employing largest stabilizer bars offered on a Corvette. The Select Ride system, able to adjust damping rates of 1-millisecond (1000 times per second), is tuned to provide great traction when launching the car, yet be compiant enough to offer high levels of grip over uneven surfaces.provide greater traction

Since 1984, Goodyear has been the exclusive supplier of tires to Corvette. From the pioneering 16-inch Eagle VR "Gatorbacks" of the all-new C4 to the Eagle F1 Supercar tires on today's Z06, all Corvettes have ridden on Goodyear tires. The 2009 ZR1 will break that tradition by utilizing Michelin Pilot Sport 2 tires which were engineered for the car. The construction is unique for ZR1 as Michelin took into account all the vehicle dynamics such as weight distribution, aerodynamic loads, vehicle weight, and top speed potential during tire development. The tires are sized as P285/30ZR19 for the front and 335/25ZR20 in the back and feature ZP (Zero Pressure) technology so a spare tire is not required, as on all Corvettes. A point of interest is that ZR1's front tires, measuring 285mm wide, are as wide as the rear tires on Corvette coupe & convertible.

Bringing the ZR1 to a halt are a set of brakes normally reserved to the most powerful of supercars. The braking system employed retain the Six-piston front and four-piston rear of the Z06, however the cast iron brake rotors are traded for exotic carbon ceramic ones. Carbon ceramic is the material of choice for Formula 1 and LeMans stlyle racing cars due to the low rotaional mass and the uncompromising durability under the harshness of a race weekend. On ZR1, using these rotors save eleven pounds of weight per corner yet have the durability to last the life of the vehicle under normal conditions. The rotors measure 15.5" in the front and 15" for the rear with the the front brakes having 148 sq. cm of surface area, dwarfing the already impressive 70 sq. cm area of the Z06.

Interior

Inside the ZR1 you'll find the familiar, well laid out interior. A boost gauge replaces the voltmeter in the instrument cluster, and a blue ZR1 logo is emblazened on the tachometer. The head-up display will also contain a boost gauge. The speedometer on the ZR1 will now read to 200-mph, indicating the higher top speed potential.

The base seats are similar to that of the Z06, being low in weight with more support than Corvette's base seats. The seats will also have ZR1 embroidered into the headrests. Optional on the ZR1 with the luxury package will be an all-leather interior with power-adjustable sport seats included. The luxury interior is one of two options planned (the other being the chromed wheels) and in addition to the seat will include the navigation system as well as Bluetooth connectivity.

Conclusion

Chevrolet stresses that the ZR1 is not an enhanced Z06, and based on the upgrades and additions, they look to be correct. While the Z06 is a great starting point, the ZR1's uniqueness and collection of exotic materials push it to a point far beyond. The performance will certainly be on par with and most likely beyond that of the established "supercars", most being priced double and beyond the expected price of $100,000.

King of the Hill...and then some!

C1	- 1953 to 1962
C2	- 1963 to 1967
C3	- 1968 to 1982
C4	- 1984 to 1996
C5	- 1997 to 2004
C6	- 2005 to Current
C7	- the Future Corvette