Archive | October 25, 2012

Next-Gen LT1 6.2-Liter V-8 for 2014 Corvette Revealed with 450 HP, New Tech

For years, car enthusiasts have debated what would come of Chevrolet’s iconic small block V-8. Would there be a next-generation engine? Would it get smaller? Would it still have pushrods? Would it have direct injection? Today, all of those questions have been answered.

Billed as the biggest change to the venerable small block V-8 engine in its 57-year history, the Gen-5 edition retains the trademark bore spacing, overhead-valve/cam-in-block valvetrain, and a few other key details, but the engine bristles with high-tech features. Direct fuel injection? Check.

Variable valve timing? Got-it. The above was widely leaked common knowledge, but now we can tell you the rest of the story. Some 99.9 percent of the engine is new, with  the engine’s carryover parts fitting in a Ziploc bag. Two starter bolts, a piston pin and a retainer bolt or two are all that remain of the LS3. Zero-to-60 mph performance for the new base Corvette is expected to be under 4 seconds. Efficiency is increased, making this one of the most fuel efficient 450-hp vehicles available. That’s right, an estimated 450 horsepower at 6000 rpm and 450 lb-ft of torque at 4000 rpm.

Displacement is indeed 6.2 liters, not 5.5 liters as rumored, and the RPO number is LT1, a designation well-known to the Corvette faithful. The key enabling feature of the new small block is cylinder deactivation. The Corvette was to be first with that technology, but the layout of the car was unsuited because of the rear transmission and various mounting solutions, it was an NVH nightmare in 4-cylinder mode.

Those problems have been overcome now, and the system has been optimized to allow a wide operating range in the 3.1-liter V-4 mode. As it turns out, fuel economy is BETTER with a 6.2-liter engine, because smaller displacements reduce the amount of time the engine can operate in 4-cylinder mode, so bigger displacement saves more fuel. Counterintuitive, but true. Active Fuel Management applied to a performance valvetrain is unique, Chevy says. With its 6600-rpm engine speed fuel cutoff, this is the highest-speed valvetrain with cylinder deactivation. Cylinders 1, 7, 6, and 4 get deactivated.

Next-gen technologies have been key to improving performance and efficiency, while maintaining the compact size and high power density while preserving oiling under very high g loads. Direct injection, Active Fuel Management (GM-speak for cylinder deactivation), and continuously variable valve timing are the key enablers. Also on that list, according to Jordan Lee, the chief engineer and program manager for small block engines, is a “radically new combustion system with 11.5:1 compression ratio.” That compression ratio improves both power and efficiency. In addition to the estimated 450 horsepower and 450 lb-ft of torque, Chevy is also predicting 26 mpg.

According to Lee, direct fuel injection and the extensive air-fuel mixing dynamics in the cylinder combine to provide maximum in-cylinder cooling, so that the engine can tolerate a higher compression ratio. The advanced combustion system he spoke of is meant to burn every molecule of fuel, extracting all the energy possible. Millions of hours of computer processing time was spent developing the top surface of the piston to optimize air-fuel mixture flow and combustion dynamics.

Hundreds of combustion systems were analyzed. Over 6 million hours of computer processing time was dedicated to combustion system optimization while reducing knock sensitivity even under extreme climatic conditions.