Demon’s in the Details
The devil was, indeed, in the details when FCA asked its powertrain engineers to build a Demon to unleash at the New York auto show. Here’s how they produced it.
PONTIAC, MI – If you can, imagine 816 runners lined up on a racetrack, running full tilt for a quarter-mile. The air they collectively sucked into their lungs – 173 cu.-ft. (4.8 cu.-m) of it – is just enough to feed the intake of the supercharged V-8 under the hood of the Dodge Challenger SRT Demon on a ¼-mile (0.4-km) sprint.
Take a breather. Then consider, if you will, that at its rated output of 840 hp and 770 lb.-ft. (1,044 Nm) of torque, the 6.2L monster powering the Demon drinks 1.36 gallons (5.1 liters) of fuel per minute, not much less than a showerhead at full stream.
Triple-inlet air box.
Meanwhile, the Demon’s cooling system bleeds off enough heat – 258 kW – to boil water in 1.2 seconds. Dodge says it’s the equivalent of 250 electric toasters.
All of that energy rockets the street-legal (but not dragstrip-legal) Demon to 60 mph (97 km/h) in 2.3 seconds (on 100-octane racing fuel) and through the ¼-mile in 9.65 seconds, generating 1.8 g of accelerative force.
Enough of the stats and performance claims – it’s how the engineers tuned the already potent 707-hp, 640-lb.-ft. (868-Nm) Dodge Hellcat V-8 to reach Demon heights that offers insight into Dodge’s tuner thought process.
“How do we get more power?” asks Chris Cowland, director-Advanced and SRT Powertrains. “It’s fairly simple with a gasoline engine: Lots of air into the engine – and lots and lots of fuel to match it.”
Demon’s revised valves, springs.
Starting at the air-induction end, Cowland and his core crew of engineers beefed-up the twin-screw supercharger, adding 1.1-in. (28-mm) longer rotors vs. the Hellcat to push 2.7 liters of air per revolution (up from 2.4 liters), increasing boost pressure from 11.6 psi (0.8 bar) to 14.5 psi (1.0 bar).
Air comes in through a 45.2-sq.-in. (0.53-sq.-m) hood scoop and a giant, triple-inlet air box to allow air flow at 1,150 cu.-ft. (32.6 cu.-m) per minute. Unique to the Demon is use of the car’s air-conditioning system to knock 18° F (10° C) degrees off the intake temperature, boosting power by 15 hp, Cowland says.
Fuel comes in via twin in-tank fuel pumps capable of pushing high-flow, multiport injectors to a maximum of 7 bar (102 psi), a 27% increase vs. the Hellcat fuel system.
Demon’s beefier piston and rod.
To handle all that extra explosiveness and a 6,300-rpm redline, aluminum cylinder heads are stiffened, the valvetrain is redesigned for stability and valve-spring and rocker oil cooling is boosted 33%. Intake valves are two-piece hollow-stem while exhaust valves are sodium cooled.
The cast-iron engine block gets revised four-bolt steel main-bearing caps and stronger head bolts capable of handling cylinder pressures reaching 135 bar (1,958 psi). The crankshaft, crank bearings, pistons and connecting rods all see increased strength and reduced tolerances, while piston oil-cooling flow is double that of the Hellcat engine.
The rest of the drivetrain, from the torque converter to the tires, is significantly upgraded to handle the Demon’s prodigious power – but that’s for another story.
[email protected] @bobgritzinger
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