Everything You Need to Know About the Dodge Demon’s 840HP V8

When news broke of the 2018 Dodge Challenger SRT Demon it was practically earth-shattering. Not only was it the highest horsepower V8 (obliterating the Hellcat’s claim), but it was the fastest production car ever made and the first to actually pull the front wheels at launch. Simply put, the Demon is an enthusiast’s dream. It comes fully equipped with the capabilities we typically spend thousands of dollars on in the aftermarket to accomplish. And now today, we have a closer look at the components that make that a reality.

Demon V8 Quick Facts

Output on 100-octane: 840hp at 6,300rpm, 770 lb-ft at 4,500rpm

Output on 91-octane: 808hp at 6,300rpm, 717 lb-ft at 4,500rpm

Production Site: Saltillo Engine Plant, Ramos Arizpe, Mexico

Construction: Supercharged 6.2L V8 with deep-skirt cast iron block, aluminum alloy heads with hemispherical combustion chamber

Starting at the top of the engine, the Dodge Demon’s powerplant uses a twin-screw supercharger that displaces 2.7 liters per revolution. The rotors are 1.1 inches longer than the Hellcat. Boost is 14.5 psi compared to the Hellcat’s 11.6 psi. The blower uses dual water-to-air heat exchangers integrated into the housing and an electric pump that churns 11.9 gallons per minute. It is further aided by the SRT Power Chiller, which redirects air conditioning refrigerant from the cabin in order to drop the charge air temperature by 18 degrees Fahrenheit. Better still, it uses the largest functional hood scoop (45.2 square inches) and triple-inlet air box (903.1 cubic inches) to move 1,150 cubic feet of air per minute.


In total, 62 percent of the Demon’s engine is new compared to the Hellcat V8 including the supercharger, engine block, crankshaft, pistons, and connecting rods. The cylinder heads are essentially the same, and are machined on dedicated CNC machines. The deep-skirted cast iron block is deck plate honed to minimize bore distortion as you’d see in a race engine shop. Here is a list of all the internal changes to the Demon V8:

  • Forged alloy steel crankshaft with 3.58-inch (90.9 mm) 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 valvesprings
  • 33 percent increase in oiling for valvesprings 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

Dodge says that every Demon and Hellcat engine is dyno tested for 42 minutes under load up to 5,200 rpm before being shipped to the assembly plant in Brampton, Ontario. A few other fun fact:

  • During a quarter-mile run, the Demon V8 ingests 173 cubic feet of air. That’s equivalent to the lung capacity of 816 humans.
  • 800 feet into a quarter-mile run, the Demon V8 would empty all the air in the cabin of the Dodge Challenger SRT Demon – 105 cubic feet
  • Demon V8 cooling system rejects 258 kW of heat at rated power – that would boil 1 quart of water at room temperature in 1.2 seconds. The heat rejected is equal to 250 electric toasters.
  • At rated power, high-octane fuel flows at 1.36 gallons per minute. Typical shower head flows at 2 gallons per minute
  • On each power stroke, piston and connecting rod is loaded with 11 tons of force – equivalent of 5 2018 Dodge Challenger SRT Demons. This happens more than 50 times a second at 6,300 rpm.

About the author

Scott Parker

Scott dreamed of being in the automotive media in high school, growing up around car shows and just down the street from Atco Raceway. The technology, performance capability, and craftsmanship that goes into builds fuels his passion.
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