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2009 Chevrolet Corvette ZR1, officially revealed for all the world to see

http://jalopnik.com/cars/detroit-aut...lly-334923.php

http://media.gm.com/servlet/GatewayS...74&docid=42156

This is it. The speculation, rumors and half-truths can now be set aside -- this is the 2009 Chevrolet Corvette ZR1, officially revealed for all the world to see. Powered by a supercharged LS9 6.2L small-block engine, the ZR1 hasn't even received an official horsepower number from the engineers toiling away at the General. All Harlan Charles, project manager for the Corvette team was able to tell us last week was the new high-powered 'Vette engine is "capable of producing at least 100 horsepower per liter. That's at least 620 horsepower, and approximately 595 lb.-ft. of torque." Chevrolet wasn't even able to give us a time on the 0-60. Charles was only willing to say "it's in the low three seconds." The small-block engine under the hood is only able to hit those massive numbers due to the addition of the positive-displacement Roots-type supercharger with a new, four-lobe rotor design plus an integrated charge cooling system that reduces inlet air temperature for increased performance. That's the "go" end, but the "whoa" end is just as impressive. The ZR1 gets some simply huge carbon-ceramic, drilled disc brake rotors. They're so big and are required to be so powerful they're using the same 15-inch-diameter discs found on the front of a Ferrari 599. Except on the ZR1, they go on the 20" tires in the rear. In the front, they'll be getting even larger 15.5-inch-diameter rotors. Yup, they're simply breathtaking to see up-close. For the time being everyone else will have to check out the gallery below or the full press release after the jump. In case anyone's wondering -- the magazine and website all about the Trend in Motors are the sleazy bunch of d-bags who broke the embargo seven hours early. We just followed suit. We'll have more time to talk about that later -- now go and read the press release and look at the pretty pictures.

CHEVROLET ENTERS THE WORLD OF SUPERCARS WITH 2009 CORVETTE ZR1
New, Supercharged LS9 V-8 is the Heart of the ZR1

DETROIT - Chevrolet officially announced the 2009 Corvette ZR1 - an American supercar that brings the technology and engineering refinement of carbon-fiber, ceramics and electronics together in a distinctive design.

"Chevrolet's goal with the new ZR1 is to show what an American supercar can deliver, at a price that trumps exotics that cost two, three or four times as much - and does so with exceptional driveability," said Ed Peper, Chevrolet general manager.

The ZR1's basic stats:

* All-new LS9 supercharged 6.2L V-8 targeted at producing at least 100 horsepower per liter, or 620 horsepower (462 kW), and approximately 595 lb.-ft. of torque (823 Nm)
* Six-speed, close-ratio, race-hardened manual transmission
* New, high-capacity dual-disc clutch
* Higher-capacity and specific-diameter axle half-shafts; enhanced torque tube
* Specific suspension tuning provides more than 1g cornering grip
* Twenty-spoke 19-inch front and 20-inch rear wheels
* Michelin Pilot Sport 2 tires - P285/30ZR19 in front and P335/25ZR20 in the rear - developed specifically for the ZR1
* Standard carbon-ceramic, drilled disc brake rotors - 15.5-inch-diameter (394-mm) in the front and 15-inch-diameter (380-mm) in the rear
* Larger brake calipers with substantially increased pad area
* Standard Magnetic Selective Ride Control with track-level suspension
* Wider, carbon-fiber front fenders with ZR1-specific dual vents
* Carbon-fiber hood with a raised, polycarbonate window - offering a view of the intercooler below it
* Carbon-fiber roof panel, roof bow, front fascia splitter and rocker moldings with clear-coated, exposed carbon-fiber weave
* ZR1-specific full-width rear spoiler with raised outboard sections
* Specific gauge cluster with boost gauge (also displayed on the head-up display) and 220-mph (370 km/h) speedometer readout
* Only two options: chrome wheels and a "luxury" package
* Curb weight of approximately 3,350 pounds (1,519 kg)

The specialized components of the new ZR1 work harmoniously to deliver the most powerful and fastest automobile ever produced by General Motors. Performance estimates will be announced closer to vehicle's summer 2008 launch.

"Preliminary testing shows the ZR1 builds on the highly respected Corvette Z06 in every performance category, from acceleration and braking, to cornering grip and top speed," said Peper. "It all boils down to the power-to-weight ratio and the ZR1's is exceptional - better than the Porsche 911 GT2, the Ferrari 599 and even the Lamborghini LP640. In fact, the ZR1 is expected to be the first production Corvette to achieve a top speed of at least 200 mph."

Supercharged LS9 engine

The new LS9 6.2L small-block engine is the power plant the supports the ZR1's performance capability. The enabler of the LS9's performance and refinement is a large, positive-displacement Roots-type supercharger with a new, four-lobe rotor design. It is augmented with an integrated charge cooling system that reduces inlet air temperature for maximum performance.

A sixth-generation supercharger developed by Eaton helps the LS9 make big power and torque at lower rpm and carries it in a wide arc to 6,600 rpm, as it pushes enough air to help the engine maintain power through the upper levels of the rpm band - the area where supercharged performance tends to diminish. Heavy-duty and lightweight reciprocating components enable the engine's confident high-rpm performance.

The LS9 is hand-assembled at GM's Performance Build Center, in Wixom, Mich., and incorporates specialty processes typically seen in racing engines to produce a highly refined and precise product. For example, cast iron cylinder liners are inserted in the aluminum block and are finish-bored and honed with a deck plate installed. The deck plate simulates the pressure and minute dimensional variances applied to the block when the cylinder heads are installed, ensuring a higher degree of accuracy that promotes maximum cylinder head sealing, piston ring fit and overall engine performance.

Transmission and axle

The LS9 engine is backed by a new, stronger six-speed manual transmission and a twin-disc clutch that provide exceptional clamping power, while maintaining an easy clutch effort. ZR1-specific gearing in the transmission provides a steep first-gear ratio that helps launch the car, and top speed is achieved in sixth gear - a change from the fifth-gear top-speed run-outs in the manual-transmission Corvette and Corvette Z06.

As the term implies, the twin-disc clutch system employs a pair of discs, which spreads out the engine's torque load over a wider area. This enables tremendous clamping power when the clutch is engaged, while also helping to dissipate heat better and extend the life of the clutch.

The twin-disc clutch system also contributes to the ZR1's exceptional driving quality, with smooth and easy shifting. The twin-disc system's design enables a 25-percent reduction in inertia, thanks to smaller, 260-mm plates, corresponding to a pedal effort that is similar to the Corvette Z06's 290-mm single-disc system.

The rear axle also is stronger in the ZR1 and features asymmetrical axle-shaft diameters that were developed after careful testing to provide optimal torque management. The axles are also mounted on a more horizontal plane that correlates with the wider width of the rear wheels and tires.

Ride and handling

The ZR1 is built on the same aluminum-intensive chassis as the Corvette Z06 and features similar independent SLA front and rear suspensions, with aluminum upper and lower control arms. Where the ZR1 differs is the suspension tuning, which was optimized for the car's steamroller-wide front and rear tires.

Magnetic Selective Ride Control is standard and tuned specifically for the ZR1. The system's ability to deliver a compliant ride with nearly instantaneous damping adjustments enabled engineers to develop a surprisingly supple ride quality in a supercar that still delivers cornering grip of more than 1g.

From a high-performance perspective, Magnetic Selective Ride Control helps the rear axle remain planted during launch for smooth, hop-free acceleration. It also helps suppress axle movement when cornering on broken or uneven pavement.

Brakes, wheels and tires

Commensurate with the ZR1's engine output is the braking system, which is headlined by carbon-ceramic brake rotors. Found on only a few exotics and more expensive supercars, carbon-ceramic brake rotors are made of a carbon-fiber-reinforced ceramic silicon carbide material . Their advantage comes in low mass and resistance to wear and heat. In fact, the rotors should never show any corrosion or require replacement for the life of the vehicle, when used in normal driving.

The vented and cross-drilled rotors on the ZR1 measure 15.5 inches (394 mm) in diameter in the front and 15 inches (380 mm) in diameter in the rear - making them among the largest carbon-ceramic rotors available on any production vehicle.

Clamping down on the high-tech rotors are six-piston front calipers and four-piston rear calipers, each painted a ZR1-exclusive blue. The front pads are equivalent in size to the largest on any production car with a single-pad design - double that of the Corvette Z06's 70-sq.-cm. front pads.

http://forums.corvetteforum.com/show....php?t=1892397

Chevrolet's new LS9 V-8 is the latest in a line of engines that first saw the light of day way back in 1955. In the planning for this engine, the GM Powertrain team led by Sam Winegarden and Ron Meegan had a number of goals. Not only did they want the most powerful production Corvette engine ever, it had to compete with the best engines in the world for both power and refinement. After all, the ZR1 is intended to be docile and easy to drive at low speeds while still having the capacity to exceed 200 mph.

When the LS7 V-8 in the current Z06 Corvette debuted a couple of years ago, it was deemed to be the pinnacle of what could be achieved from a normally aspirated small block. The displacement had been boosted to 7.0L with an output of 505 hp and 470 lb-ft of torque. Although more power is certainly possible, it would have come at the expense of long-term durability, and since GM won't release an engine for production unless the design is validated for at least 100,000 miles, the LS7 approach was deemed a dead end for now.

Getting past that 500 hp wall with this architecture would require forced induction provided by a new Eaton Rootes type supercharger. However, the pressures generated by going much past 500hp would have been too much for the 7.0L block. In order to get the necessary robustness to make the engine last, the GM Powertrain engineers reduced the displacement back to 6.2L in order get the cylinder wall thickness they needed. The block was also beefed up in other ways. Fillet radii (a fillet is the curved surface at the joint where two other surfaces meet) were increased in the block bulkhead area improving strength by 20% even as passages were opened up to improve fluid flow.

When cylinder heads are bolted to an engine block and torqued down, the cylinder bores undergo some deformation. That's part of why pistons have to be smaller than the bore, and spring loaded rings are used to follow the cylinder wall and provide a seal for the combustion chamber. The production tolerances inherent in manufacturing all these parts leads to loss and inconsistency of power delivery. To help overcome this problem, a deck plate is used during the boring and honing process of the block. A steel plate is bolted to the block and torqued down to distort the bores of the cast iron cylinder liners prior to machining. When the plate is removed the block relaxes, but the distortion caused by installing the cylinder heads restores the bores to their condition when they were machined. The end result is bores that are much closer to being parallel and round allowing a tighter piston fit and more consistent performance. The bore and stroke of the LS9 come out to a nicely over-square 103.25mm x 92mm.

The heads themselves are based on the design from the L92, LS3 and LS6 engines with a few modifications. A wing cast into the intake port induces some swirl in the air/fuel mixture as it passes the 55.0mm titanium intake valves. The spent gases exit past sodium filled exhaust valves on their way to the same fabricated dual wall stainless steel headers used on the LS7. The heads themselves are made from a premium A356-T6 aluminum alloy that is rotocast. The rotocasting process rotates the mold as the aluminum is poured in. This helps get gas bubbles out of the mold and the molten metal, reducing porosity and increasing ultimate tensile and yield strength. The material change provides a 15% increase in strength with a further 9% coming from the rotocasting. The same process is used on the heads for the 2.0L turbocharged engine used in the Sky Red Line and other vehicles.

Like the block and heads, the reciprocating parts of the LS9 have to withstand tremendous pressures. The LS9 has a 9.1:1 compression ratio along with 10.5 psi of boost pressure. The pistons are forged from aluminum with polymer liners on the skirts to reduce friction. The tops of the pistons are sumped to allow clearance for the valves without the use of valve pockets. The continuous surface helps to improve the strength of the piston, which is further enhanced by anodizing. More titanium shows up in the connecting rods, which add strength with lower reciprocating mass. At the bottom end, a forged steel crankshaft is held in place by six bolt steel main bearing caps.

Generating power in an engine requires air and fuel. More power takes more air and more fuel. In this cast, the extra air comes courtesy of the latest 6th generation Eaton Rootes supercharger. The new rotors now have four lobes and there is significantly more twist. The old unit had 60 degrees of twist while the new version has 160 degrees. The result is much improved efficiency and quieter operation. The LS9 supercharger has 2.3L of displacement and at its maximum speed of 15,000 rpm draws about 80 hp as compared to 120 hp for a gen 5 supercharger. The radiated noise from the blower case has been reduced by 10 dBa.

This is the first known use of the 6th generation Eaton supercharger by an OEM in a production application. Roush uses the unit on some of its vehicles and also offers various sizes in the aftermarket, including the 2.3L unit from the LS9, a 1.9L and a 0.9L for smaller engines.

The fuel side of the equation is taken care of by a dual pressure fuel system. Getting smooth low speed operation out of such a powerful engine requires a lot more dynamic range from the injectors than is currently available. At maximum output, the fuel system needs to be able to supply 58 g/s. Injectors that can supply enough gasoline to feed an engine with this much power tend to be hard to control at the low flow rates required at idle. To help achieve this, a separate fuel system ECU is mounted next to the fuel tank. Based on demand it can adjust the fuel pressure to either 600 kPa at high speeds or 250 kPa at low speed. With the lower pressure, the flow rate at the injectors can be more easily modulated. By way of comparison, the LS7 system only provides 40 g/s of fuel flow. This same issue is why the the LS9 is not currently set up for flex-fuel capability. The high octane characteristics of E85 would be well suited to an engine like the LS9. However, according to Sam Winegarden, the higher fuel flow rates required to make up for the lower energy density would have had too much of a negative effect on low speed drivability.

Packaging was a major challenge for the LS9 engineers. They only had one extra inch in height to work with in the ZR1 engine compartment and less than that in length. In order to make everything fit, the air to liquid inter-cooler uses two heat exchangers spread apart with the air flow going horizontally and then back down into the intake ports. The inter-cooler lowers the temperature of the intake charge by 140 degrees F. Because of the limited space, there was no room to add a separate drive belt for the blower, so a revised two-belt setup was devised. An 11 rib belt drives the blower, water pump and power steering pump. To withstand the added loads, the water pump also gets a beefier bearing.

The pressures generated by the blower and combustion displace the cylinder head by up to 16 microns. Since each of the two active layers of the multi layer head gasket in the LS7 can take up 5 microns, the LS9 gets a gasket with 4 active layers. Also helping to keep the cylinder heads tightly sealed to the block are larger 12mm head bolts (the LS7 uses 11mm bolts).

Keeping all the metal parts moving smoothly requires a lot of lubrication. The LS9 keeps the LS7's dry sump system but with some enhancements. An extra gravity-fed 2.75 qt reservoir ensures that the oil pickup never goes dry even under the most severe cornering conditions that the ZR1 can generate. A dual gerotor oil pump carries over from the LS7 with one rotor pumping oil to the engine while the other scavenges the sump, all the while oil temperatures being regulated by an oil cooler mounted on the side of the sump. A new feature of the LS9 is the block-mounted oil squirters. These units mounted below each cylinder barrel shoot a spray of oil toward the underside of the pistons. This has the dual effect of cooling the pistons and increasing the lubrication between the piston and cylinder reducing both friction and noise.

All these precision machined parts give the LS9 a red-line of 6,600 rpm and an output of at least 620 hp and 600 lb-ft of torque. That's enough to push a 3,340 lb ZR1 to 200 mph and beyond. The use of the supercharger gave the engineers more flexibility in tuning the cam-shaft to improve low end drivability of the LS9 compared to the LS7. The LS9 cam has less lift and 27% less overlap than the LS7, which provides a steadier idle. The twin-plate 260mm clutch has more than enough capacity to handle the LS9 prodigious output while requiring the same or less effort than the single plate 290 mm unit in the Z06. The Tremec 6060 six-speed gearbox has a 2.29:1 first gear ratio and 3.42:1 final drive, a combination that allows it to make the all important 0-60 mph run without having to shift to second gear. The revised shift linkage takes 20 percent less effort to move over a 12 percent shorter distance.

The LS9 won't be getting its final certification until about March, but so far GM has put over 6,800 dyno hours on the new engine. They have run an engine for 100 hours continuously at wide open throttle and done both simulated and real 24-hour track cycles similar to what the GT1 C6.Rs run on the dyno and in the car. Thanks to the extensive simulation and modeling done prior to building any parts, the engines have been remarkably reliable. To date, through three years of development, they have never had a failed piston, connecting rod or crankshaft in testing. The simulations have gotten so accurate that the first prototype engine on the dynamometer ran within 3.5% of the simulation throughout the entire power and torque curve.