Hennessey Performance has started benchmarking on the dyno in preparation for an 850-hp upgrade kit.
It is an open secret that Hennessey Performance Engineering is working on the S650 Mustang Dark Horse to deliver a whopping 850 horsepower. To set parameters, the Texas-based aftermarket tuner strapped a 2024 Mustang Dark Horse on the dyno to see how much it packs from the factory before the upgrades begin.
Ford claims the Mustang Dark Horse can squeeze out 500 hp and 418 lb-ft of torque from its fourth-generation Coyote 5.0-liter V8, but that's at the crank and doesn't factor in driveline losses. This example is optioned with the Dark Horse handling package and a 10-speed automatic transmission instead of the six-speed Tremec manual.
The results on the dyno were quite impressive - 428 whp at 6,800 rpm and 379 lb-ft of torque at 5,000 rpm. Those numbers are higher than a dyno run of the S650 Mustang GT could muster in a dyno run courtesy of Middle Motorsports, registering only 408 hp and 351 lb-ft at the wheels.
To achieve 850 hp, Hennessey will equip the natural-aspirated V8 with a supercharger. Dubbed H850, the tuner will integrate a high-flow induction system, bigger fuel injectors, and an upgraded fuel pump. It will also feature an HPE software upgrade to make the 70% power increase target a reality.
The Hennessey S650 Mustang Dark Horse will also be installed with performance upgrades a dyno won't pick up, such as a new carbon fiber splitter, side skirts, and rear wing. As an option, the build will be offered with unique 'Heritage' graphics, as seen in the photos below.
The 850-hp supercharger upgrade package and a three-year/36,000-mile limited warranty will be available in both the 10-speed auto and six-speed manual versions. Hennessey is slated to begin production in the fourth quarter of this year.
Upon completion, the H850 Dark Horse would be at par with the highly limited Mustang GTD on paper, which will boast a bored 5.2-liter supercharged V8 with approximately 800 hp.