For Release: Jan. 1, 2004, 12:01 a.m.
Source: GM Media Archives
DETROIT - GM today announced the new 2005 Corvette will feature the most powerful standard engine ever in Corvette history: the 400 horsepower, 6.0-liter, small-block V-8.
The new 6.0-liter LS2 is part of the fourth generation of GM's small-block engines. The small-block debuted in 1955 with 265 cubic inches and 195 horsepower. Since then, this legendary family of engines has been an integral component of Corvette's performance history.
"It's almost impossible to talk about Corvette without the small-block," said Dave Muscaro, GM Powertrain's assistant chief engineer of small-blocks for cars. "As Corvette has grown into a world-class sports car, the small-block has grown with it. The LS2 is a state-of-the-art engine that draws on a rich heritage of performance."
The LS2 also raises the bar for standard performance in the Corvette, delivering 400 horsepower at 6000 rpm and 400 lb.-ft. of torque at 4400 rpm - an increase of 50 horses and 40 lb.-ft. of torque over the previous Corvette's LS1 engine.
"More than dynamometer numbers, the LS2 engine's range of power and torque is broad and very usable in everyday driving," said Muscaro. "This engine is smoother, and more refined, but at the same time retains tire-thrashing output."
Design changes for the better
Compared to the Gen III-based LS1, the LS2 incorporates several significant changes that help improve performance, reliability and serviceability:
Valves measure 2 inches for the intake and 1.55 inches for the exhaust. The valve springs also have been upgraded to withstand the engine's increased power and rpm range.
The LS2's new oil pan was developed to ensure oil delivery commensurate with Corvette's high-performance capability. Extensive track testing has shown the new design to provide better oil control under the extreme demands of high-rpm/high g-force driving maneuvers. The elimination of the previous "gull wing" oil pan design also reduces the engine's oil capacity from 6.5 quarts to 5.5 quarts with a dry filter.
Engineers also increased the efficiency and reduced the mass of the exhaust manifolds. Wall thickness of the manifolds is reduced from 4 mm to 3 mm, eliminating weight and helping enhance airflow by approximately 4 percent.
"We sweated the details to ensure the engine maintains a balance between performance and efficiency," Muscaro said.
Several of the new features of the LS2 were incorporated as continuous improvements to later versions of the Gen III engine, including long-life, iridium-tip spark plugs; pistons with full floating wrist pins; a redesigned water pump that significantly reduces the probability of a leak; and a stronger, long-life timing chain.
Building on a proven foundation
The LS2's Gen IV architectural roots lie in the proven LS1 5.7-liter Gen III V-8 that was standard in the Corvette C5. It was an engine that redefined performance and efficiency expectations of cam-in-block architecture.
Like the venerable small-block engine introduced in 1955, the modern small-block features a 90-degree cylinder bank arrangement and 4.40-inch bore centers - the distance between the center of one cylinder and the center of the next. The Gen IV builds upon the strengths of the Gen III small-block architecture, including:
Aluminum block with iron cylinder bore liners: The lightweight block is cast from 319-T5 aluminum with cast-in-place iron cylinder bore liners. A die-cast aluminum valley cover and upper deck rails tie together the cylinder banks, increasing torsional and bending stiffness.
Deep skirt block: Structural rigidity and operating smoothness is enhanced because the engine block extends below the crankshaft centerline.
Cross-bolted main caps: Two horizontal cross bolts for each main bearing cap complement four traditional vertical main cap bolts and contribute additional strength and smoothness to the engine's rotating assembly.
Gerotor oil pump: Simple and compact in design, the gerotor-style oil pump fits the shallow oil pan and offers superior pumping capability.
Balanced cylinder head design: Performance and efficiency is enhanced with identical airflow and energy direction for each cylinder.
Coil-near-plug ignition: A separate ignition coil pack and short spark plug wire for each cylinder maximize the efficiency of the delivered coil energy, enhancing fuel efficiency and power.
Electronic throttle control (ETC): Instead of a mechanical linkage between the gas pedal and engine throttle, an electronic throttle control system improves driveability and reduces overall system complexity by eliminating typical conventional mechanical items, such as the idle air control motor, cruise control module and throttle relaxer (traction control).
Because the LS2's new engine controller incorporates ETC commands, the separate ETC module used on the LS1 is no longer required. This allows faster communication of the controller to the throttle, as well as reducing the mass and complexity of the system. Additionally, emissions are slightly improved with the damping of unnecessary throttle movement.
Improvements to the engine's crankcase breathing and ventilation were made similar to the LS6 engine, including moving the crankcase ventilation system's PCV valve away from the rocker covers and into the block valley.
"The small-block V-8 is a powerful and continually refined package that stacks up with the best engines around the globe," said Muscaro. "The Corvette is simply the best way to showcase its world-class traits."
Advances in catalyst substrates made possible catalytic converters that are at the same time more effective and less restrictive for the LS2's exhaust. The new converters are mounted closer to the exhaust manifold for quicker lightoff and reduced cold-start emissions. As a result, the more restrictive quad catalyst design of the LS1 - with its small, auxiliary "pup" converters - was not necessary to meet emissions requirements. An additional benefit of the exhaust system's development was the elimination of the LS1's air injection reaction system.
Subtle adjustments were made to the C6 exhaust system itself to improve its performance. Sharp angles in the tubing have been replaced with more gradual bends. A larger muffler volume and tri-flow technology eliminated certain periods prone to unwanted noise, particularly between 1500 and 2400 rpm. An inline muffler that flows more efficiently replaces the laterally mounted muffler in the C5. These changes, coupled with one converter per exhaust bank, reduced backpressure in the system and contributed to the LS6's 400 horsepower and 400 lb.-ft. of torque.
The 2005 Corvette continues to offer drivers thrilling driving dynamics, whether they prefer shifting or leaving it to the transmission. The Tremec T56 six-speed manual is standard and the Hydra-Matic 4L65-E four-speed automatic is optional.
Corvette engineers thoroughly revised the Tremec gear box and added proprietary technology not offered on other automakers' high-performance transmissions. The six-speed transmission also has revised gearing when selected with the Z51 performance option. With the Z51, the Tremec is tailored with numerically higher gears to improve acceleration. Also, a lower fifth gear gives the Z51 better fuel efficiency and a higher top speed than base models. To increase durability in sustained high-speed situations, the Z51 and the base European manual-transmission models have a transmission cooler.
Smoother shifting six-speed
C6 Corvette drivers will find more pleasing, performance-oriented shifts with the six-speed transmission. They're smoother and more precise, with shorter overall throws. The gear shift lever is now an inch shorter, and travel for all synchronizers is reduced by 10 percent. An all-new shift linkage and shift-rail bearings contribute to a more positive, confident feel. Computer Aided Gear Selection (CAGS) continues as a fuel-economy enhancement function for the manual transmission.
Durable 4L65-E delivers automatic performance
The available automatic transmission in the C6 is the new Hydra-Matic 4L65-E four-speed. An upgraded version of the C5's 4L60-E, the "L65" is strengthened and revised to accommodate the LS2's 400 lb.-ft. of torque.
To beef up the internals, a five-pinion planetary gear set was added - replacing a four-pinion gear set. The extra gear reduces friction and loads carried by all the gears. The washers between the gear sets are made from Teflon, allowing optimal operation at high speed.
For protection from the high temperatures that are generated by high speed, a four-plate oil cooler has been added. When the transmission fluid reaches 127 degrees Celsius (approximately 260 F), the torque converter lock does not disengage, except briefly during shifts. This prevents fluid shear in the torque converter from adding heat to the transmission.
The 4L65-E uses a highly advanced electronic controller that has been specifically calibrated for Performance Algorithm Shifting. This technology automatically selects the optimal gear for a given driving condition, making it a willing accomplice for performance driving and hard cornering. The 4L65-E transmission shifts at higher rpm, compared to the C5's 4L60-E, to take advantage of the LS2's higher horsepower and rev range.