Hennessey strapped a 2.9-liter supercharger to the Mustang GT's 5.0-liter V8, and then attached a high-induction intake system and a new, axle-back exhaust system. There are also changes to the fuel injectors, fuel pump, and coilpack. Finally, Hennessey optimized the Mustang GT's engine management software. Alongside 804 ponies, torque is up to 648 pound-feet. For those keeping track at home, the HPE800 adds 369 hp and 248 pound-feet of torque – basically an entire sportscar's worth of performance – under the hood.
The result is staggering performance. Hennessey claims 60 miles per hour arrives in just 3.1 seconds, and if you line up at a drag strip, you'll cover the quarter-mile in 10.7 seconds. All in, the HPE800 will do roughly 208 mph. We'd like to know how Hennessey came up with those numbers – the company says "Performance figures are with experienced driver under ideal track conditions" – because getting 804 hp and 648 lb-ft of torque to the ground through road tires can't be easy. Hennessey gave the HPE800 Michelin Pilot Super Sport tires, but at just 275/30/20, the contact patch isn't dramatically different than the 275/40/19s on the Mustang GT Performance Package. The Pilot Super Sport is a good tire, but is that enough rubber on the ground to cope with that much power?
Other changes for the limited-edition Hennessey include a lowered suspension with KW Variant 3 coilovers and carbon-fiber aero aids, including a new front splitter, rear spoiler, and side sills. And naturally, there are plenty of reminders that you're driving something special – Hennessey adds its own floormats, embroiders its name into the headrests, adds a tasteful exterior graphics package, and attaches its name and the HPE800 designation to the rear decklid.
The HPE800 package is available on all combinations of the Mustang GT – coupe, convertible, automatic, or manual. Hennessey hasn't released prices for this extremely rare Mustang, but we'd expect it will demand a pretty penny.