2018 Dodge Challenger SRT Demon: All About The Engine

Let’s get down to brass tacks here: The long awaited, much anticipated 2018 Dodge Challenger SRT Demon is all about that engine. Sure, the suspension and braking have been worked over as much as they could, and although the new Demon handles and stops better than it has a right to, this car exists for one reason.

It’s all about that Hemi engine.

Straight Line Power

Look, I love Mopar products. Always have and, failing some huge metaphysical test in the future, I always will. They have a sort of American style akin to a World War II fighter plane. They get to the end of that quarter mile like nothing else on the planet. The handling and braking are . . . well, let me put it this way: Remember the first time you ever nailed the brakes on a B-Body for the third time? Put a little grey in your hair, didn’t it? To be 100 percent frank, Mopar is about going, not about stopping. Or handling all that much if you get right down to it. Sure, sure, you can tweak them here and there, but they’re never going to out-sprint a GTI around an AutoX course or be winning any rally stages. Shoot, even a wizard like Dan Gurney couldn’t make the things work as Trans Am cars.

Ah, but that engine, any Mopar engine. What a plant! What a mill! What a lump! It’s the engineering equivalent of a Claymore mine: Brutal, simple, reliable, and everso effective. Nurse, hand me the scalpel, my socket set, and that big pry bar. It’s time for some analytical biology.

More than 1 ton (2,500 pounds) is transferred from the Challenger SRT Demon’s front wheels to the rear ones at launch. The upgraded torque converter for the TorqueFlite 8HP90 eight-speed automatic transmission increases torque multiplication by 18 percent. Meanwhile, Nitto drag radial tires achieve up to 40 percent more launch force. Photo: FCA US LLC.

New Hemi Era

The particulars of the engine situated ‘neath that huge, be-scooped hood are well known by now: A supercharged 6.2-liter Hemi V8 with a deep-skirt cast iron block, aluminum alloy heads, and hemispherical combustion chambers. This is good for 840 horsepower (6,300 rpm) and 770 lb-ft. of torque (4,500 rpm) running on unleaded 100 octane fuel. Sure, it’s a little less if you can only get 91 octane juice (a measly 808 horsepower and 717 lb-ft. of torque and who can live with that little?) but still, any of those figures are outputs more associated with ocean-going tugs than something land-dwelling.

Versus the Hellcat Hemi plant, 62 percent of the Demon engine is new. The engine block, crankshaft, pistons, connecting rods, and supercharger are all new. The heads are manufactured and machined on dedicated Demon/Hellcat CNC machines. The deck plate for the block is honed to minimize bore distortion (natch) and every Demon engine is dyno tested for 42 minutes under load up to 5,200 rpm before being shipped to the assembly plant in Brampton, Ontario. Yeah, Canada. Who’d a thought, eh?

The triple-inlet air box for the 2018 Dodge Challenger SRT Demon (right) is larger when compared to the 2017 Dodge Challenger SRT Hellcat. 800 feet into a quarter-mile run, the Demon can empty the equivalent of all the available air in the cabin of the car, about 105 cubic feet. Likewise, during a quarter-mile run, the Demon ingests the lung capacity of 816 humans. Photo: FCA US LLC.

Massive Lungs

The new Hemi lump breaths like a marathon runner, thanks to the world’s largest functional hood scoop with an opening of 45.2 square inches. This triple-inlet air box (903.1 cubic inches total) provides higher flow and less restriction for the inlet system, feeding cool air into the supercharger at an air-flow rate of 1,150 cubic feet per minute. That’s approximately the volume of a 26-foot moving truck every 60 seconds.

All this air gets passed over the SRT Power Chiller which redirects air conditioning refrigerant from the cabin to the chiller unit, dropping the charge temperature by 18 degrees Fahrenheit. Clever! From there, the incoming air gets fed into the supercharger, a twin screw unit good for 2.7 liters per revolution or about 50% more displacement than a Miata engine. And that’s just the blower remember. Maximum boost pressure is 14.5 psi, up from 11.6 psi when compared to the Hellcat.

Valves for the 2018 Dodge Challenger SRT Demon use single-groove collets for improved stability during higher engine demands, along with redesigned valve springs and top retainers. Photo: FCA US LLC.

Beefing Up

That much boost puts an amazing level of strain on the engine internals, so everything within the mill has been seen to as well. The crankshaft, with a 90.9-millimeter stroke and revised balancing, is forged alloy steel with induction-hardened crank bearing surfaces. The individual journals have optimized main bearing clearances and the high-strength alloy pistons are forged as well. There’s been a 30-micron increase to the piston bore clearance. The connecting rods have been powder forged with upgraded shanks and bigger ends. The flow has been doubled on piston cooling oil jets and even the fasteners (y’know, the nuts and bolts and stuff) are revised ultra-high tensile bits.

Speaking of revised, the valve springs get a 33 percent increase in oiling for the springs themselves along with the rocker tips for increased lubrication and cooling. There are single-groove collets on the valve stems for improved stability. The fuel injector pressure has increased 27 percent because this thing drinks like a sailor on leave and, like all good drag racing motors, the oil pan and windage tray have been optimized for high acceleration, good for proper oiling up to 1.8 gs.

Street Legal Insanity

This all seems normal and fine and good to me. And then I realize: “This is for a street engine!!” This all seems normal and fine and good if your name is Keith Black and you’re standing next to the strip late one Saturday afternoon. But noooooooooooo, this engine was dropped in a street car. And they’ll sell it to anyone with the motor skills to write a fiscally solvent check. Anyone. Even people like (Heaven forefend), me!

Tony Borroz has spent his entire life racing antique and sports cars. He means well, even if he has a bias towards lighter, agile cars rather than big engine muscle cars or family sedans.

Photo: FCA US LLC.

Photos & Source: FCA US LLC.

About The Author

Tony Borroz grew up in a sportscar oriented family, but sadly, it was British cars. His knuckles still show the marks of slipped Whitworth sockets, strains to reach upper rear shock bushings on Triumphs, and slight burn marks from dealing with Lucas Electric "systems." He has written for a variety of car magazines and websites, Automoblog chief among them. Tony has worked on popular driving games as a content expert, in addition to working for aerospace companies, software giants, and as a movie stuntman. He currently lives in a secure, undisclosed location in the American southwestern desert.

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