2009 Chevrolet Corvette ZR1
Recently Chevrolet has announced the much-anticipated Corvette ZR1 will have a manufacturer’s suggested retail price of $103,300, including the $850 destination charge. And in the current trend of higher gasoline prices, surprisingly the super Vette is able to check in with an estimated EPA fuel economy of 14 mpg city and 20 highway, not bad for a car that can rocket from 0-60 mph in just 3.4 seconds with a top speed of 205 mph.
About five years ago chairman and CEO Rick Wagoner had posed this question in a staff meeting: If GM could build the stellar-performing Corvette Z06 for $59,995, what could the team do for $100,000? And so the Corvette Team, led by then-chief engineer Dave Hill and assistant chief engineer Tadge Juechter, began investigating a super Vette. Its internal name was Blue Devil, said to be in homage to Wagoner's alma mater, Duke. Thus the rumors started. Since then, Hill retired and Juechter is now chief engineer of the Corvette and Cadillac XLR.
But blue isn't just part of the code name. Because the accents on the Z06 are red, and yellow just isn't as pretty as blue, the color will be used for the badges, engine rocker covers and brake calipers. And in production, it won't be named Blue Devil, SS or Stingray; it will simply be called ZR1, which harkens back to the C4 ZR-1. Note the lack of a hyphen in the new car's name.
At the heart of the ZR1 is the 6.2-liter supercharged LS9 V-8. The design goal was 600-plus horsepower. And the team started by looking at the Z06's 7.0-liter LS7, but to reach that power level an 8.3-liter displacement would be needed, and this was deemed unrealistic for a small block. A V-10 wouldn't fit in the current Corvette, so forced induction was chosen. In the end, the engineers managed to achieve an impressive 638 bhp and a whopping 604 lb.-ft. of torque. That'll make the LS9 the most powerful engine from GM — ever.
Development on the LS9 small block started three years ago. The bore and stroke are those of the LS3 — 103.25 and 92.00 mm. Reinforced bulkheads improve block stiffness by 20 percent over the LS3. High-strength-steel bearing caps are used, rather than sintered metal. Pistons are forged and, for the first time on a small block, there are oil squirters to boost cooling and decrease noise. Titanium connecting rods shorter than those used on the LS7 account for the decrease in compression to 9.9:1, and the rods are attached to a unique forged-steel micro-alloy crankshaft.
Because of the supercharger, additional modifications to the head and intake were necessary. The standard 2-layer head gasket of the LS7 was not enough to absorb head lift-off, so the LS9 uses a thicker 4-layer gasket, while the intake tract includes a swirl wing to improve mixture. This technology would restrict the breathing of a naturally aspirated engine, but is less of a concern on a supercharged powerplant. Although the valves are the same size as those in an LS3, the intakes are titanium to allow a 6600-rpm redline, and the exhausts are sodium-filled to help dissipate the increased heat of the powerplant. The cam has reduced lift from the LS7's 15.0 mm to 14.1 mm, and also reduced overlap, which helps improve idle quality and smoothness.
The Eaton supercharger is sandwiched between the engine and the Behr air-to-water dual-brick charge cooler. The supercharger pumps 2.3 liters of compressed air on each rotation and, with a 2.3:1 pulley ratio at 6600 rpm, the blower is spinning at 15,300 rpm (that's 20.7 cu. ft. per second, folks!) and producing a maximum of 10.5-psi boost. The team claims that the more efficient 4-lobe design makes less noise than a conventional unit. An 11-rib V-belt runs the supercharger as well as the power-steering and water pumps. A toothed belt was used during testing but abandoned as too noisy for production.
To reduce the height of the engine, the intercooler was designed to have side-by-side left- and right-bank units. Air exits the supercharger upward and then left or right through the charge coolers and is returned down into the intake runners. Each cooler contains only 0.4 liter and the entire system uses 3.6 liters of dedicated coolant. To keep packaging simple, the coil packs are mounted directly to the rocker covers, which are otherwise identical to those used on the LS3. Naturally, the peak fuel demands of such a powerful engine are high; as a result, there's a unique electronic fuel pressure regulator that switches between 87.0 psi and 36.3 psi to maintain proper fuel delivery at high and low rpm.
The C6 ZR1 is intended as a pure performance car, thus there is no option to include the 6-way adjustable passenger seat. However, a power tilt/telescope steering wheel is standard on the argument that it's needed for achieving proper driving position. With its supercharged engine and beefier components, the ZR1 is expected to weigh in about 150 lb. more than the Z06's 3150-lb. curb weight. It's a small penalty for a big boost in power; however, the ZR1 will not be as finely balanced as the Z06 since weight distribution has moved from 50/50 to a little more nose-heavy 52/48. That said, the ZR1 should still be quicker around the track than a Z06.
Filling the wheel arches are larger wheels and tires, 19 x 10 in the front and 20 x 12 at the rear. The ZR1 sports forged wheels shod with custom Michelin Pilot Sport tires, size 285/30R-19 front and 335/25R-20 rear. Inside the wheels are the largest carbon-ceramic brakes to come standard on any car — massive 15.5-in. Brembos in front and 15.0 in. at the rear. To support the extra loads generated, larger bearings are used. If you could get them, the brakes, wheels and tires would be expensive bolt-on modifications to a Z06. An interesting tidbit: The front rotors are the same as those on a Ferrari FXX and the rears are off the front of an Enzo! The rotors are nearly identical to those on a Bugatti Veyron and optional on a Ferrari 599. Mammoth pads encased in the monobloc calipers double the surface area of those of a current Z06 and if used only on the street will likely last the lifetime of the car. If you do wear them out, a sensor molded into the pads alerts you via a dash indicator. Starting with the ZR1, Bosch components replace Delphi-sourced brake parts, a trend that continues with all 2009 Corvettes.
For the first time on a high-performance Corvette, the Magnetic Ride system is used. This second generation of the Delphi electronically controlled damping is similar to that used on the Ferrari 599 GTB. The new system is more resistant to the extreme heat and for use on the track. There are two modes to the MR system in the ZR1 — Tour and Sport. Because the MR system can significantly affect wheel motions, the composite leaf springs were softened and the anti-roll bars stiffened. The result is a roll stiffness that is similar to a Z06's, but in touring mode, the car is said to be considerably more compliant. A neat feature of MR is the ability to improve standing-start launches. It does this by recognizing a hard launch and completely softening the rear shocks on compression with full stiff on rebound. Thus the car will squat and go, rather than bounce. And to minimize rear-wheel hop, the left-side halfshaft is larger in diameter than the right. Thus if an oscillation starts, it does so at different frequencies. Why the left side? Because it offsets the right rear-mounted battery.
Sumber : http://autos.yahoo.com/
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