While 1970 was a great year for thumpin' engines and 11:1 compression – nobody was building supercharged engines for the street. In 2013, Chevrolet introduced the supercharged Corvette ZR1 making 638 hp. But that was no flash-in-the-pan event. This was followed by the 11:1 (yes, the compression is back!) LT1 - a direct-injected small-block. It seems fitting that Chevrolet's next step in performance would be to stuff a supercharger on top of that direct injected engine – and that's exactly what they did.
The LT4 (should we call it LT4-B?) is firmly rooted in the LT1 architecture and is basically a boosted version of the LT1 with only slightly reduce static compression (from 11:1 to 10:1) and a slightly smaller Eaton supercharger bolted on top. The engine will be released with the 2015 Corvette sometime later this year as the ZO6 and will also incorporate variable valve timing (VVT) as well as Active Fuel Management (AFM) which is the cylinder deactivation function. Because this information was released early, there are no set-in-stone numbers, but Chevy engineers promise no less than 625 hp (LS9 was 638 hp) and the LT4's torque will be at least 635 lb-ft, which looks to obliterate the LS9's 604 lb-ft achievement - and with less boost (9.5 vs 9.7 psi). The engineers also say that because this blower is shorter and smaller in displacement, it will spin up quicker and will benefit from a revised intercooler located below the blower that is also more efficient.
The dry sump will benefit from larger cooler capacity in anticipation of the heat the LT4
Interesting technical tidbits that have been released for the production LT4 include titanium intake valves, forged pistons, stainless steel exhaust manifolds, a revised dry sump system, machined connecting rods, and an aluminum balancer. Most of these revisions point to either increased durability or reducing reciprocating weight. All that means is the engine will rev accelerate that much quicker because by reducing the mass the engine has to accelerate, much more power can make it to the flywheel. And speaking of the drivetrain, Chevy will match this LT4 with brand new 7seven-speed manual and eight8-speed automatic transmissions.
Power density is a term used by engineers to encapsulate the effort of increasing power from a smaller package. The LT4's integrated supercharger is only 25mm (1 inch) taller in the rear than its normally-aspirated LT1 cousin. For perspective, it weighs 20 pounds less and it 85 mm (3.34 inches) shorter than the LS9 with nearly the same power – that's the definition of power density. The advantages are impressive for a production engine, but the future of this engine as swap potential will depend mainly on how easy it is to integrate this direct injection engine in an early chassis. Swaps that will use the engine in its stock configuration should not be difficult, but time will tell how this all plays out. We anticipate it won't take long for car crafters to figure out how to extract even more power from this combination. If anybody asks, this certainly must be the golden age of horsepower.
Corvette Power Curve 1953 to Present
|1953 ||235ci Blue Flame 6 ||150|
|1957||Fuel Injected 283ci||283|
|1962||Fuel Injected 327ci||360|
|1967||3x2 Carbureted 427ci||435|
|1996 ||LT1 350||300|
|1996 ||LT4 350||330|
|2013 ||LS9 6.2L Supercharged||638|
|2014||LT1 6.2L ||460|
This photo shows the new LT4 snuggled into the 2015 Corvette chassis. Note the dry sump ta
This is a view of the LT1's hypereutectic piston and rod assembly. The LT4's piston is for
This is the combustion chamber view from the LT1. Likely, the LT4 chamber will be configur