When it arrives next summer, the 2009 Chevrolet Corvette ZR1 will be themost powerful and fastest production car ever produced by GeneralMotors, with performance enabled by a new, supercharged 6.2L LS9small-block V-8 engine.
Incorporating the engineering experience already found in the CorvetteZ06's LS7 engine and the new-for-2008 6.2L LS3 of the Corvette, GMPowertain is targeting 100 horsepower per liter for the LS9, or 620horsepower (462 kW), and approximately 595 lb.-ft. of torque (807 Nm);final SAE-certified power levels will be available in early March 2008.
It is, indeed, the ultimate small-block engine for the ultimateCorvette.
"When you experience the LS9 in the Corvette ZR1, the terms performanceand refinement take on a new meaning," said Tom Stephens, group vicepresident for GM Powertrain and Quality. "The LS9 demonstrates anoutstanding performance range, with smooth driveability at low speeds,and surprisingly fierce performance when the customer wants more power."
The enabler of the LS9's performance is a new, largepositive-displacement Roots-type supercharger - with a unique four-lobedesign - developed for the engine by Eaton. It is teamed with anintegrated charge cooling system that reduces inlet air temperature formaximum performance. The LS9 represents the first of several new,supercharged small-block engines that will be introduced in GM vehiclesin the near future, each using superchargers of similar design.
"The small-block V-8 once again demonstrates it boundless horsepowerpotential, versatile design and an architecture with proven quality,durability and reliability," said Stephens. "We haven't yet realized thesmall-block's performance potential."
Performance range
More than just its tremendous peak horsepower and torque numbers, thesupercharged LS9 makes big power at lower rpm and carries it in a widearc to 6,600 rpm. GM Powertrain testing shows the engine makesapproximately 300 horsepower (224 kW) at 3,000 rpm and nearly 320lb.-ft. of torque (434 Nm) at only 1,000 rpm. Torque tops 585 lb.-ft.(793 Nm) at about the 4,000-rpm mark, while horsepower peaks at 6,500rpm. The engine produces 90 percent of peak torque from 2,600 rpm to6,000 rpm.
Heavy-duty and lightweight reciprocating components enable the engine'sconfident high-rpm performance, while the large-displacement Eatonsupercharger pushes enough air to help the engine maintain power throughthe upper levels of the rpm band.
"The sixth-generation design of the supercharger expands the 'sweetzone' of the compressor's effectiveness, broadening it to help makepower lower in the rpm band," said Ron Meegan, assistant chief engineer."To put it simply, the low-end torque is amazing."
The LS9 is assembled by hand at GM's Performance Build Center, a unique,small-volume engine production facility in Wixom, Mich., that alsobuilds the Corvette Z06's LS7 engine and other high-performance GMproduction engines.
Cylinder block and reciprocating assembly details
The LS9's aluminum cylinder block features steel, six-bolt main bearingcaps, with enlarged vent windows in the second and third bulkheads forenhanced bay to bay breathing. Cast iron cylinder liners - measuring4.06 inches (103.25 mm) in bore diameter - are inserted in the aluminumblock and they are finish-bored and honed with a deck plate installed.The deck plate simulates the pressure and minute dimensional variancesapplied to the block when the cylinder heads are installed, ensuring ahigher degree of accuracy that promotes maximum cylinder head sealing,piston ring fit and overall engine performance.
Nestled inside the cylinder block is a forged steel crankshaft thatdelivers the LS9's 3.62-inch (92 mm) stroke. It features asmaller-diameter ignition-triggering reluctor wheel and a nine-boltflange - the outer face of the crankshaft on which the flywheel ismounted - that provides more clamping strength. Other non-supercharged6.2L engines, such as the base Corvette's LS3, have a six-bolt flange. Atorsional damper mounted to the front of the crankshaft features akeyway and friction washer, which also is designed to support theengine's high loads.
Attached to the crankshaft is a set of titanium connecting rods andforged aluminum pistons, which, when combined with the cylinder heads,delivers a 9.1:1 compression ratio. This combination is extremelydurable and lightweight, enabling the LS9's high-rpm capability.