Can Hennessey deliver on its horsepower promises for the 2020 C8 Corvette?
Hennessey recently announced that it is working on building higher powered variants of the 2020 C8 Corvette. While Hennessey threw out some big numbers in its release, it is unclear if it actually has a plan in place to achieve those assertions, based on currently available information on the new Corvette.
Hennessey claims that it will offer a variety of upgrades for the new Corvette, including a stainless-steel exhaust system, a 700-horsepower supercharger system, and a 1200-hp twin turbo system. Exhaust systems should not be difficult to achieve, and it is not surprising that Hennessey will have one ready soon, but the bigger power increases seem a bit further away, especially when the new Tremec dual clutch gearbox is considered.
The Tremec TR-9080 debuting in the new Corvette is rated for a maximum of 590 lb-ft of torque. The stock configuration of the Corvette produces 495 horsepower and 470 lb-ft of torque, so considering the linear nature of those numbers, a 700-hp supercharged variant is likely to produce in excess of 600lb-ft of torque and exceed the rating of that gearbox.
Hennessey states that it will “incorporate an upgraded and fortified factory dual clutch transmission” for these upgrades, so it is possible that it’s working on some upgraded components, but it did not reply to an email asking for details on how it is going to accomplish it.
Tremec is likely working on stronger variants of its DCT for more powerful future trims of the Corvette, but it is unclear how the current TR-9080 could be upgraded to handle more torque, especially when you consider how the spiral bevel differential is integrated into the transaxle and the unitary cooling method deployed for both the gearbox and differential.
According to Hennessey’s release, the 1200-hp twin-turbocharged variant of its kit will be built on top of an upgraded LT2 V-8 engine with upgraded engine internals that include forged steel connecting rods and forged aluminum pistons with a 10.0:1 compression ratio. This makes sense in a turbocharged application to prevent detonation and lowers it by 1.5 from the standard 11.5:1 compression ratio of the LT2. It also sounds like Hennessey took a hint from Chevy, as that is also the compression ratio used by the supercharged LT4 engine in the C7 Z06.
Upgrades such as bigger brakes and Penske dampers are also listed in the Hennessey release, along with carbon fiber aero pieces. Images included with the release appear to show some of these aero pieces, including a very odd inlet on the roof of the car. Hennessey may have taken inspiration from the C8.R race car, which has such an inlet on the bottom of the hatch in order to feed cool air to the engine, but in the Hennessey image it appears that it might actually be detrimental to the car and shows no clear path of how it would connect to the intakes for the turbochargers.
The design of the inlet of the race car takes advantage of the aero of the hood and the “reverse mohawk” roof design to push air to the bottom of the hatch and force cooler air into the intake. The Hennessey design appears to interrupt that path of airflow and might actually even act to create more drag and slow the car down. We also asked Hennessey for details on this design but did not receive a reply.
It is almost inevitable that we will see highly modified versions of the Corvette as soon as deliveries start, and although Hennessey has a history of modifying Corvettes, at this time it is unclear exactly how it will accomplish the big power claims it is promising.