Watch The Dodge Challenger SRT Demon’s 840-HP V8 Engine Scream On the Dyno

Watch The Dodge Challenger SRT Demon’s 840-HP V8 Engine Scream On the Dyno

It had to be factory-tested on a setup originally designed for NASCAR engines.

The candles have been lit, the incantation is nearly complete, and the Dodge Challenger SRT Demon is about to be summoned by dealers nationwide. But before that happens, take a moment to appreciate the extreme testing done on the 840-horsepower supercharged V8 engine in order to sharpen the knife of a car that, in the words of The Drive editor Mike Guy, “hates humans.”

To wring out every last bit of power from the Hellcat’s existing 6.2-liter engine, the tiny crack team of FCA SRT engineers worked in near-total secrecy to redesign over 60 percent of the internals, including the cast-iron block, high-strength alloy pistons, powder-forged connecting rods, and crankshaft. They also rigged up the car’s special air intake chiller system and rigged the whole thing to run on 100-octane gas. Parts suppliers were given the bare minimum details to work with, sometimes just a target figure, and internal simulator work helped piece everything together.

Of course, testing a screaming V8 engine that’s being covertly developed poses its own set of challenges. The SRT crew was able to do most of the work in their own building down the road from FCA’s main campus in Michigan, but they still needed to use the larger facility’s engine dyno setups to dial everything in. In order to keep the banshee’s howl from giving everything away, tests were originally conducted on nights and weekends.

Later, a more clever solution emerged—altering the dyno display screen to always read 707 horsepower, so anyone walking by would think they were just testing a plain-Jane Hellcat engine. There was more than one problem, though. Despite using a setup at FCA’s headquarters that was originally designed for NASCAR engines, they were still limited by the building’s fuel delivery system, which almost couldn’t keep up with the engine’s insane 1.36-gallons-per-minute appetite at full blast.

The video above shows one of these tests, and pay attention to the numbers at bottom left (and the red-hot exhaust pipes). Those 840 horses get all the attention, but it’s the Dodge Demon’s sky-high torque figures that get it off the line for that vaunted nine-second quarter-mile run. At a relatively tame 4500 RPM, the engine is already putting out almost 660 horsepower and 770 lb.-ft. of torque.

Also, in the video shown above, if you click “show more” option you`ll be seing some crazy numbers and detailed specs:

Displacement: Supercharged 6.2-liter V-8

Construction: Deep-skirt cast iron block; aluminum alloy heads with hemispherical combustion chamber

840 bhp (626 kW) @ 6,300 rpm; 770 lb.-ft (1,044 N•m) @ 4,500 rpm with Direct Connection Controller and unleaded 100 octane minimum fuel

808 bhp (603 kW) @ 6,300 rpm; 717 lb.-ft (972 N•m) @ 4,500 rpm with Premium 91 octane fuel

Production site: Saltillo Engine Plant, Ramos Arizpe, Mexico
62 percent new content compared with Hellcat V-8: engine block; crankshaft; pistons; connecting rods; supercharger
Cylinder heads machined on dedicated Demon/Hellcat CNC machines

Engine block is deck plate honed to minimize bore distortion
Every Demon and Hellcat engine is dyno tested for 42 minutes under load up to 5,200 rpm before being shipped to assembly plant in Brampton, Ontario

More air: Largest functional hood scoop opening (45.2 square inches) and triple-inlet air box (903.1 cubic inches). High flow, low restriction inlet system designed to deliver cool air into the supercharger.

Air-flow rate: 1,150 cubic feet per minute

SRT Power Chiller™: Redirects air conditioning refrigerant from cabin to chiller unit; reduces charge air temperature by 18 degrees Fahrenheit


Twin screw, 2.7 liters per revolution

Rotors 1.1 inches longer compared with Hellcat

Maximum boost pressure 14.5 psi compared with 11.6 psi for Hellcat

Dual water/air heat exchangers integrated into supercharger housing

Electric pump flows up to 11.9 gallons per minute

Engine internals:

Forged alloy steel crankshaft with 90.9-millimeter stroke and revised balancing
Induction-hardened crank bearing surfaces; individual journal optimized main bearing clearances
Forged high-strength alloy pistons; 30-micron increased piston to bore clearance
Powder forged connecting rods; upgraded shank and big end; revised ultra-high tensile fasteners
Flow doubled on piston cooling oil jets
Revised design valve springs
33 percent increase in oiling for valve springs and rocker tips – lubrication and cooling
Single-groove collets on valve stems for improved stability
Fuel injector pressure increased 27 percent
Oil pan and windage tray optimized for high acceleration – tested up to 1.8 g


TorqueFlite 8HP90 eight-speed automatic
Upgraded automatic transmission torque converter increases torque multiplication 18 percent
Torque converter stall speed increased 11 percent
In Drag Mode, transmission minimizes torque cut during gear changes – 400 millisecond shifts


Limited-slip differential
230-millimeter ring gear in high strength alloy, heat-treated aluminum differential housing
3.09 final drive ratio for maximum acceleration
20-percent thicker prop shaft made of high strength, low alloy steel tube; high strength steel stub shafts
Upgraded halfshafts with 8-ball Cross-Glide inner and outer joints; larger diameter barshafts with 41-spline count; high alloy steel inner and outer stub shafts

Nitto drag radial tires achieve up to 40 percent more launch force