Just got a new Motor Trend with a two page spread on the new LT1. Here are some excerpts:
Billed as the biggest change to the venerable small-block V-8 in its 57 year history, the Gen 5 edition retains the trademark bore spacing, overhead-valve/cam-in-block valvetrain, and other key details, but the engine bristles with high-tech fetures. Direct fuel injection? Check. Variable-valve timing? Got it. Two starter bolts, a piston pin, and a retainer bolt or two are all that remain of the LS3. Chevrolet expects 0-60 mph performance for the base C7 to be under 4 seconds, with efficiency to make it among the least-thirsty 450 hp vehicles extant. That's right, Chevrolet expects at least 450 hp at 6000 rpm and 450 lb-ft at 4000 rpm, yet with a 26 mpg-plus EPA highway number.
The LT1 will be the first pushrod engine with gas direct-injection, and a key enable to the power-efficiency equation is cylinder deactivation, but with the car's rear transmission, it was an NVH nightmare in four cylinder mode. Chevy claims those problems have been overcome, with a system optimized for a wide operating range in the 3.1 liter V-4 mode. Smaller displacements reduce the amount of time the engine can operate as a four-banger, so bigger displacement, like 6.2 liters, can save more fuel. With its 6600-rpm fuel cutoff, this is the highest-speed valvetrain with deactivation, cutting cylinders one, seven, six and four. The LT1 will offer wet and dry-sump lubrication.
The LT1 also comes with a "radically new combustion system with 11.5:1 compression ratio" that improves power and efficiency, says Jordan Lee, chief engineer and program manager for small-block engines. The high-strength aluminum pistons are shaped like those in supercharged engines, with a high-compression pop-up. another factor contributing to the high compression is maximum in-cylinder cooling from the direct fuel injection and extensive air-fuel mixing dynamics. The high-flowing intake and exhaust ports are twisted to direct air for peak tumble. Intake and exhaust valves have swapped sides, which gives slightly better flow and better enables the spark plug to be centralized for peak ignition efficiency.
Chevy claims its naturally aspirated LT1 is a match for some top turbo engines on the market. BMW's 4.4 liter, twin-turbo V-8 produces 400 hp and 450 lb-ft. It weighs 503 pounds and stands 29.6 inches high. With 50 more horses, the LT1 weighs 465 pounds and is just 25.3 inches tall.
More to come later
Billed as the biggest change to the venerable small-block V-8 in its 57 year history, the Gen 5 edition retains the trademark bore spacing, overhead-valve/cam-in-block valvetrain, and other key details, but the engine bristles with high-tech fetures. Direct fuel injection? Check. Variable-valve timing? Got it. Two starter bolts, a piston pin, and a retainer bolt or two are all that remain of the LS3. Chevrolet expects 0-60 mph performance for the base C7 to be under 4 seconds, with efficiency to make it among the least-thirsty 450 hp vehicles extant. That's right, Chevrolet expects at least 450 hp at 6000 rpm and 450 lb-ft at 4000 rpm, yet with a 26 mpg-plus EPA highway number.
The LT1 will be the first pushrod engine with gas direct-injection, and a key enable to the power-efficiency equation is cylinder deactivation, but with the car's rear transmission, it was an NVH nightmare in four cylinder mode. Chevy claims those problems have been overcome, with a system optimized for a wide operating range in the 3.1 liter V-4 mode. Smaller displacements reduce the amount of time the engine can operate as a four-banger, so bigger displacement, like 6.2 liters, can save more fuel. With its 6600-rpm fuel cutoff, this is the highest-speed valvetrain with deactivation, cutting cylinders one, seven, six and four. The LT1 will offer wet and dry-sump lubrication.
The LT1 also comes with a "radically new combustion system with 11.5:1 compression ratio" that improves power and efficiency, says Jordan Lee, chief engineer and program manager for small-block engines. The high-strength aluminum pistons are shaped like those in supercharged engines, with a high-compression pop-up. another factor contributing to the high compression is maximum in-cylinder cooling from the direct fuel injection and extensive air-fuel mixing dynamics. The high-flowing intake and exhaust ports are twisted to direct air for peak tumble. Intake and exhaust valves have swapped sides, which gives slightly better flow and better enables the spark plug to be centralized for peak ignition efficiency.
Chevy claims its naturally aspirated LT1 is a match for some top turbo engines on the market. BMW's 4.4 liter, twin-turbo V-8 produces 400 hp and 450 lb-ft. It weighs 503 pounds and stands 29.6 inches high. With 50 more horses, the LT1 weighs 465 pounds and is just 25.3 inches tall.
More to come later