Driving the C6's New,
400-hp Engine
The 2005 Corvette's six-liter (366 cubic inch), 400 horsepower, LS2 V8 is the largest, most powerful standard engine ever put in a Vette. It's, also, the most refined, most fuel efficient and least polluting.

This new engine powers a C6 coupe with a six-speed manual transmission and the Z51 Performance Handling Package to 0-60 and quarter miles times just short of those of a 2004 Z06 and the only things that keeps the '05 from waxing the 405-hp, "zed-ought-six" is 61 pounds and rear tires a bit less wide.

Top speed? Last spring, a production 2005 coupe went 186 mph in testing done to validate Chevrolet advertising. Fold the mirrors back and tape over the directional signal lights and you'll get 190.

So–what's this new engine like to drive? THR's test driver, after taking his first freeway onramp in an '05 Vette and feeling the new engine's improved low-end and mid-range acceleration, remarked to Tom Peters, who was riding with him at the time, "Whoa... this baby has some low-end grunt!"

Later, he had a second torque experience, this time inadvertently starting out in second gear at a stop sign. Because of the LS2's greater torque and better throttle response off-idle; he almost didn’t notice the error.

Jordan Lee is a GM Powertrain Division Staff Engineer who worked on the LS2. He told THR, "At the bottom end, the LS2 is so much fatter than the LS6 (346-cuin., 405-hp engine in '02-'04 Z06es). A lot of people think, when they drive high-performance sports cars, they're tuned only for high rpm. People perceive that because the bottom end is so weak. You step in the throttle at low rpm and the engine's flat, but then, all of a sudden, it feels like it's 'comin' on the cam.'

LS2 Techside

The key to the LS2 making 50 more horsepower from a package that: is the same physical size, weighs a little less than, gets about the same mileage as and emits less pollutants than C5's LS1 was improved engine controls and better air flow in and exhaust flow out of the engine. Add 20 more cubic inches of displacement and a slight increase in compression and you get 400-hp@6000 rpm, 400-lbs/ft torque@4400 rpm and a 6500-rpm red line.

C6's induction system, from the air inlet to the intake manifold is new. The air filter assembly, intake duct, mass airflow sensor, 90-mm. throttle body and intake manifold are improved designs. In total, there is a huge, 31% reduction in intake restriction compared to the LS1.

There has been a major change in the engine's crankcase ventilation system. Both air-oil separators were redesigned for improved efficiency. CFD, with the addition of a proprietary GM software code called "rain drop analysis," allows modeling airflow systems where liquid droplets are present. It was used to analyze crankcase vapor flow through the engine and that information was applied to the new separator design. The net result is less oil consumption, especially at high rpm.

LS2's exhaust manifolds are 33% lighter and 4% less restrictive. C6es use only two catalytic converters and they are a low-restriction, close-coupled design which increases performance and reduces emissions. The exhaust system downstream of the cats has, also, been redesigned with higher-flow mufflers which mount lengthwise, eliminating four 90-degree pipe bends. All of this was worth a 10%, total reduction in back pressure, compared to the '01-'04 LS1.

For 2005, because higher compression makes the engine a little more liable to detonate, the knock sensing needed more speed and accuracy. In addition, more accurate control of air metering, fuel metering, exhaust emissions controls were desired.

The engine's rev limiter is now at 6600. Lastly, GM wanted to move the electronic throttle functions from a separate module into the ECM. All this required a more robust controller and the new, LS2 Engine Control Module (ECM) is faster acting, has more memory and can control more devices..

The first time you drive a C6 six-speed, you'll notice the shorter throw and the more precise feel. When measured, shift effort goes up 3% but that's virtually impossible to feel. Judged subjectively, the effort seems the same as that of a C5.

Six-speed transmissions in Z51s are different in two ways: 1) they have lower ratios in the first three gears resulting in better acceleration and 2) because they are intended for severe duty, have a cooling system. A pump on the front of the trans., driven by the countershaft, sends lubricant through the same cooler in the radiator used by automatics.