When it arrives next summer, the 2009 Chevrolet Corvette ZR1 will be the most powerful and fastest production car ever produced by General Motors, with performance enabled by a new, supercharged 6.2L LS9 small-block V-8 engine.
Incorporating the engineering experience already found in the Corvette Z06's LS7 engine and the new-for-2008 6.2L LS3 of the Corvette, GM Powertrain is targeting 100 horsepower per liter for the LS9, or 620 horsepower (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 ultimate Corvette.
"When you experience the LS9 in the Corvette ZR1, the terms 'performance' and 'refinement' take on a new meaning," said Tom Stephens, group vice president for GM Powertrain and Quality. "The LS9 demonstrates an outstanding 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, large positive-displacement Roots-type supercharger - with a unique four-lobe design - developed for the engine by Eaton. It is teamed with an integrated charge cooling system that reduces inlet air temperature for maximum performance. The LS9 represents the first of several new, supercharged small-block engines that will be introduced in GM vehicles in the near future, each using superchargers of similar design.
"The small-block V-8 once again demonstrates its boundless horsepower potential, versatile design and an architecture with proven quality, durability and reliability," said Stephens. "We haven't yet realized the small-block's performance potential."
Illustration by David Kimble
More than just its tremendous peak horsepower and torque numbers, the supercharged LS9 makes big power at lower rpm and carries it in a wide arc to 6,600 rpm. GM Powertrain testing shows the engine makes approximately 300 horsepower (224 kW) at 3,000 rpm and nearly 320 lb.-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 6,500 rpm. The engine produces 90 percent of peak torque from 2,600 rpm to 6,000 rpm.
Heavy-duty and lightweight reciprocating components enable the engine's confident high-rpm performance, while the large-displacement Eaton supercharger pushes enough air to help the engine maintain power through the upper levels of the rpm band.
"The sixth-generation design of the supercharger expands the 'sweet zone' of the compressor's effectiveness, broadening it to help make power 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 also builds the Corvette Z06's LS7 engine and other high-performance GM production engines.
Cylinder Block and Reciprocating Assembly Details
The LS9's aluminum cylinder block features steel, six-bolt main bearing caps, with enlarged vent windows in the second and third bulkheads for enhanced bay to bay breathing. Cast iron cylinder liners - measuring 4.06 inches (103.25 mm) in bore diameter - are inserted in the aluminum block and they 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.
Nestled inside the cylinder block is a forged steel crankshaft that delivers the LS9's 3.62-inch (92 mm) stroke. It features a smaller-diameter ignition-triggering reluctor wheel and a nine-bolt flange - the outer face of the crankshaft on which the flywheel is mounted - that provides more clamping strength. Other non-supercharged 6.2L engines, such as the base Corvette's LS3, have a six-bolt flange. A torsional damper mounted to the front of the crankshaft features a keyway and friction washer, which also is designed to support the engine's high loads.
Attached to the crankshaft is a set of titanium connecting rods and forged aluminum pistons, which, when combined with the cylinder heads, delivers a 9.1:1 compression ratio. This combination is extremely durable and lightweight, enabling the LS9's high-rpm capability.