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Old 07-15-2019, 06:46 AM   #1
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Default Leaked GM LT7 Twin Turbo V8

Last week it was reported that the base model of the upcoming mid-engine Corvette C8, set to be called Stingray, will be powered by the 6.2-liter LT2 engine that will make around 500 horsepower.

And now, less than a week before its unveiling, information about an upcoming GM twin-turbo engine, dubbed LT7, that is earmarked for a future, high-performance variant of the Corvette C8, potentially the C8 Corvette Z06.

You may have seen these CAD images of the LT7 engine before, but thereís now some info to go along with the photos. So, GM will switch from blowers (superchargers) to snails (turbochargers) in its range-topping Corvette models. But donít let the LT7 moniker mislead you: the engine portrayed in these GM CAD images is not based on GMís fifth-generation Small Block / push-rod LT engine family, which includes the familiar LT1 (for the C7 Stingray), LT4 (for the C7 Z06), and LT5 (for the C7 ZR1). Instead, the LT7 is based on GMís new Dual Overhead Cam (DOHC) V8 engine architecture initially introduced by the 4.2L Twin-Turbo V8 LTA, otherwise known as Blackwing.

Donít expect to see or even hear about this new Twin Turbo LT7 V8 engine during the Corvette C8 reveal next week, since that event will be dedicated to the base model mid-engine Corvette, aka the C8 Corvette Stingray. Instead, this here LT7 will go into what we expect to be the C8 Corvette Z06, which is at least another 16 months out, if not more.

Current information about the LT7 is sparse, but we have uncovered that it will have a larger displacement than the 4.2-liter Blackwing LTA. Sources state that the LT7 will make more than the 650 horsepower generated by the supercharged 6.2L LT4 V8 in the C7 Z06, and well more than the high-output version of the Blackwing LTA, which is rated at 550 horses and 627 pound-feet of torque. Itís currently unclear whether the LT7 will share the same block as the LTA, or if the two engines will only share the same overall engine design/configuration, and not size.

The CAD images also show that the turbochargers are not mounted in the ĎHot Ví design of the Blackwing. Instead, they are placed on either side of the Vee, below the cylinder banks. As such, the twin throttle bodies, intake manifold, and entire induction system differ from those of the Blackwing. Imagine that the head design varies as well.

Another point of interest is the cooling setup. Since this powertrain is for a mid-engine car, it doesnít have a conventional front-mounted intercooler. On top of that, the DOHC Blackwing architecture utilizes water-to-air charge cooling, making the overall packaging of the cooling system very different from anything else GM has shipped in the past. Then again, a mid-engine sports car is already entirely different than anything in GMís current portfolio.

Itís worth noting that, when GM introduced the Blackwing V8 for the Cadillac CT6-V, originally called the CT6 V-Sport, the automaker made it a point in saying that the engine would be exclusive to Cadillac, through and through. But something seemed off; it didnít make sense that todayís General Motors, an organization laser-focused on pinching pennies and optimizing its business in any way it can, would dedicate the colossal amounts of human, financial, and production resources to bring to market an engine on an entirely new engine architecture just to use it exclusively in a low volume product offering like the CT6-V, especially when that model might not even stick around in the near future.

As such, it would make sense that the engine architecture behind the Blackwing V8 Ė as opposed to the engine itself Ė would be utilized across other high-end, high-performance vehicles within the GM portfolio. A higher-output variant of the Blackwing for a future C8 Corvette Z06, in the form of the LT7, fits that bill perfectly.

Itís also worth noting that the 4.2L Twin-Turbo V8 Blackwing LTA is hand-assembled at the GM Bowling Green plant in Kentucky Ė the one and only home to the Corvette. Hence, the assembly line is almost begging for the addition of a more potent variant of the Blackwing V8 for a future, higher-output version of the C8 Corvette. Whether that model will be called Z06, or something else, is a story for another time.
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