The first small block V8 engine debuted in the 1955 Corvette. It displaced 4.3 liters (265 cubic inches) and was rated at 195 horsepower. Chevrolet’s first V8 had a four-barrel carburetor.
When Chevrolet Corvette arrives late next year, most of the sports car will be all new, but not the 6.2-liter V8 engine. The latest Corvette LT1 engine, the first of the so-called Gen 5 family of small block engines, combines several advanced technologies, including direct injection for the first time, cylinder fuel shut off and continuously variable valve timing to support an advanced combustion system. Zero-to-60 mph times of less than four seconds are predicted for the base car. The new LT1 is the third engine in the Corvette’s history to be so-branded, with previous versions introduced in 1970 (Gen 1) and 1992 (Gen 2).
Real output, performance, and fuel economy numbers will not be finalized until early next year, but the Chevrolet publicity machine is making several claims. If the output numbers stand up to certification, this will be the most powerful and quickest standard Corvette ever, (and no doubt the most expensive) with preliminary output of 450 horsepower (335 kW) and 450 lb.-ft. of torque (610 Nm). It’s also expected to be the most fuel-efficient Corvette ever, exceeding the EPA-estimated 26 miles per gallon on the highway on the outgoing 2013 model.
“More than just great horsepower, the LT1 has been optimized to produce a broader power band,” claimed Sam Winegarden, vice president, Global Powertrain Engineering at a preview in Michigan. “Below 4,000 rpm, the torque of the Corvette LT1 is comparable to that of the legendary, 7.0L LS7 out of the current Corvette Z06. The LT1 is a sweetheart of a powerplant and drivers will feel its tremendous torque and power at every notch on the tachometer.”
Chevrolet said that more than 10 million hours of computational analysis were conducted on the engine program, including 6 million hours dedicated to the advanced combustion system. The LT1 alone in the performance engine world remains a push rod engine. Virtually all of the claimed benefits arise from direct injection. It allows exact control of the mixture motion and fuel injection spray pattern. Direct injection also keeps the combustion chamber cooler, which allows for a higher compression ratio. Emissions are also reduced, particularly cold-start hydrocarbon emissions, which are cut by about 25%.
Virtually all of the claimed benefits arise from direct injection.
The LT1 cylinder head has smaller combustion chambers designed to work with the volume of the new shape of the pistons’ heads. The smaller chamber size and sculpted pistons produce an 11.5:1 compression ratio, while the head has large, straight and rectangular intake ports with a slight twist to enhance mixture motion. There is a reversal of the current intake and exhaust valve positions when compared to the previous engine design. The spark plug angle and depth have been revised to protrude farther into the chamber, placing the electrode closer to the center of the combustion to support “optimal” combustion.
