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When a Hellcat just isn't enough: the 840-hp Dodge Challenger SRT Demon, which parent company FCA said uses the most-powerful V8 ever installed in a production vehicle (image: FCA).

Musclecar Godzilla: Dodge Reveals 840-hp Challenger SRT Demon

After months of teasing and a high-profile tie-in with the Fast & Furious film franchise, FCA's Dodge division revealed its 2018 Challenger SRT Demon, a drag racer-in-street-clothes featuring an 840-hp variant of the now-famous 6.2-L supercharged OHV V-8 that the company boldly claimed makes the Challenger Demon the quickest production car in the world.

Revealing the Demon at an event on the eve of the 2017 New York auto show, Tim Kuniskis, head of passenger cars–Dodge, SRT, Chrysler and FIAT, for FCA North America, catalogued the Demon’s list of claimed firsts or record-setting accomplishments, most delivered by the car’s heavily-revised Hemi V8. Kuniskis said the Demon is the world’s fastest production vehicle to accelerate through the quarter mile, doing so in 9.65 s at a trap speed of 140 mph (225 km/h); the industry-standard metric of 0-60 mph (97 km/h) acceleration is dispatched in 2.3 s, which he claimed also is the world’s best, although that figure is bound to be disputed.

The Challenger SRT Demon, Kuniskis continued, goes from 0-30 mph (48 km/h) in 1 s flat and thanks to its prodigious 770 ftlb (1044 Nm) of torque—further augmented by special launch-enhancing powertrain techniques—is “the only production car ever to do a wheelie” at launch.

Hellcat engine on steroids

The Challenger SRT Demon comes quickly on the heels of Dodge’s Hellcat models that debuted the a 707-hp version of the supercharged 6.2-L Hemi V-8 that immediately was immortalized in musclecar circles—but the company is quick to point out the Demon’s performance upgrade comes from more than a mere supercharger boost increase. There are more than two dozen significant component engine upgrades in the move from 707-hp Hellcat to 840-hp Demon, Dodge said.

Increased boost is a chief factor, however: the Demon’s 6.2-L variant uses a 2.7-L supercharger in place of the Hellcat’s 2.4-L unit, generating a boost-pressure increase from 11.6 psi to 14.5 psi. The Demon’s engine redline also is hiked to 6500 rpm from the Hellcat’s 6200-rpm limit.

Meanwhile, intake of air also receives more attention: a larger airbox gets air from three paths, chief among them being the special “Air Grabber” hood duct, which Dodge claims is the largest functional hood scoop of any production car. Intake air also is routed from a new “Air Catcher” headlamp on the driver’s side and an inlet near the wheel liner. The engine is fed as much as 1,150 cu. ft. of air per minute, an 18% increase compared to the Hellcat V-8, an intake volume—you guessed it—claimed to be greater than any production vehicle.

But it doesn’t stop there. The Challenger SRT Demon features an all-new and production-vehicle first “Power Chiller” to reduce intake-air temperature by as much as 45 deg. Charge-air coolant, which first is cooled by ambient air that passes through a low-temperature radiator, then flows through the Power Chiller; the double-chilled coolant then is delivered to the supercharger’s heat exchangers.

The Power Chiller’s extra cooling capacity comes from diverting the air-conditioning refrigerant from the SRT Demon’s interior to a chiller unit mounted near the low-temperature circuit coolant pump. This combines with an After-Run Chiller that is designed to keep cooling fan and low-temperature cooling circuit functioning after the engine is shut down, reducing heat soak; the 8.4-in. Uconnect screen in the center stack can be configured to track supercharger coolant temperature, informing the driver “when the supercharger is at the optimum temperature for another run,” said Dodge in a release.

The Demon’s 6.2-L supercharged V8 also has two dual-stage fuel pumps (compared with a single dual-stage pump for the Hellcat V8) and the engine also is fitted with higher-strength pistons and connecting rods, a high-speed valvetrain and an upgraded lubrication system. Dodge said these modifications help the engine sustain higher output and pressures while meeting FCA US LLC’s stringent durability requirements.

Kuniskis told Automotive Engineering the Demon engine retains the same 9.5:1 compression ratio of the Hellcat engine, but higher cylinder pressures generated by the Demon engine enable more-aggressive spark advance. Dodge does admit, however, that the maximum power and torque figures are derived when using 100-octane unleaded gasoline. Fueling with readily-available 91-octane premium unleaded drops output to 808 hp and 717 lbft (972 Nm). A button on the dash is engaged to reap maximum horsepower when 100-octane fuel is onboard.

The Challenger SRT Demon is fitted exclusively with the same 8-speed automatic transmission already used in Dodge’s Hellcat models, but a new operating regime called TransBrake, designed to lock the output shaft to keep the car stationary while the driver increases engine revs to as much as 2,350 rpm without overpowering the brakes. The result, said Dodge, is 15% more available torque at launch.

The TransBrake design works in collaboration with yet another new driveline feature that Dodge said is a world first: Torque Reserve. When engine speed exceeds 950 rpm, Torque Reserve closes the supercharger bypass valve, effectively preloading the supercharger with boost and manages fuel flow and spark to individual cylinders to balance engine rpm with torque.

The two driveline management systems mean the engine is working with as much as 8 psi of boost at launch and up to 120% more launch engine torque. Using the steering-wheel paddle shifter to initiate launch, the driver can see full torque delivery to the rear wheels just 150 ms after launch. It all can shave as much as a tenth of a second off the quarter-mile run, the company said.

Oddball lightweighting

Dodge also said the 4280-lb (1941-kg) 2018 Challenger SRT Demon can be made nearly 200 lb (91 kg) lighter—but that weight savings comes largely from the customer’s choice to voluntarily delete equipment such as the sound system and the entire back seat. And also the front passenger seat, as it turns out.

Kuniskis acknowledges not many customers will choose to delete the seats—particularly when Dodge charges $1 each to order them. But the front passenger seat and belt weighs 58 lb (26 kg), the rear seat and belts amounts to a 55-lb (25-kg) load and 16 speakers yanked from the audio system amounts to 24 lb (11 kg), all comfort niceties that can hamper those quarter-mile bursts.

But Dodge SRT engineers did find several interesting places to shave weight for which the customer won’t have choice, including truck trim pieces (20 lb), smaller, hollow anti-sway bars (19 lb), 16 lb for lighter-weight wheels and open-end lug nuts and even 4 lb saved by using a manual adjust tilt-and-telescope steering column.

Production of the 2018 Challenger SRT Demon is said to be 3000 units in the U.S. and 300 units in Canada for a single model year. The car will be built at the company’s Brampton, Ontario, Canada assembly plant starting this summer and dealer deliveries will start in the fall.

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