2018 Dodge Challenger SRT Demon deep dive: a study in obsession and insanity

“You guys are crazy.”

That’s what Fiat Chrysler Automobiles CEO Sergio Marchionne told Tim Kuniskis, head of passenger car brands at FCA, and Chris Cowland, director of advanced and SRT powertrain engineering, when they first pitched the Dodge Challenger SRT Demon.

After learning about all the engineering work that went into this street-legal drag monster, we agree.

The Demon is to the Challenger what the ACR is to the Dodge Viper—the ultimate expression of the Challenger’s DNA. Understanding that explains some of the breathtaking engineering SRT put into this car. Under intense secrecy and compartmentalized development, Kuniskis and Cowland drove the Demon forward, rebuilding the most important parts of the Challenger SRT Hellcat to surge down dragstrips in a way no warrantied, street-legal production car can.

Purpose-built powertrain

The powertrain is an evolution of the Hellcat’s with some truly revolutionary changes. This is still a 6.2-liter supercharged V-8, but instead of 707 horsepower and 650 pound-feet of torque it can produce up to 840 hp and 770 lb-ft, because there’s more everything. But all these changes are in the name of three goals—getting air into the engine, cooling that air down, and figuring out how to get the most from each gram of fuel.

Shoving more air into the engine is where all the sexy changes were made, starting with the Demon’s gaping hood scoop. SRT claims it’s the largest functional scoop on the market, spanning 45.2 square inches. But if the Demon’s hood scoop is its mouth, the 14.8-liter air box are its lungs, inhaling 173 cubic feet of air over a typical quarter-mile sprint. That’s the lung capacity of you and your 815 closest friends. A larger filter with 72 percent more area funnels the air to a bigger supercharger.

That wondrous supercharger sounds like a million piccolos being played through the blades of an industrial fan; it displaces 2.7 liters compared to the Hellcat’s 2.38. Inside its aluminum casing, the fan blades are 1.1 inches longer, force-feeding air to the engine at 14.5 psi of pressure, 2.9 psi higher than the Hellcat.

But getting the air into the engine is only part the battle. A new SRT Power Chiller repurposes the Demon’s standard air conditioning to cool the charged air by 18 degrees Fahrenheit before it enters the combustion chamber. The system alone is responsible for 15 hp.

Once the air is in the combustion chamber, it mixes with more fuel. SRT increased the fuel pressure to 700 kilopascals, a 27-percent increase over the 550 kpa in the Hellcat. At full chat, twin fuel pumps force gas through larger fuel lines and out of the injectors at a rate of 1.36 gallons per minute. For comparison, a high-efficiency shower head has a flow rate of 1.5 gpm.

A highlight of the Demon’s impressive fuel system is the optional Direct Connection Controller. Part of the Demon Crate, this powertrain control module allows the engine to run on 100-plus-octane race fuel, unlocking the full 840 hp and 770 lb-ft of torque. On typical pump gas, there’s still 808 hp and 717 lb-ft of torque, but since the Demon Crate costs a mere dollar, virtually every Demon should be able to run on race gas. SRT recommends Sunoco 260GT or VP 101 race gas.

Even if you mix gas, the Direct Connection Controller will take care of you, monitoring the knock sensors to guarantee the octane level is appropriate. If it drops too low, no High Octane mode for you.

The Demon’s heart uses eight forged, high-strength pistons to charge into the iconic hemispherical combustion chambers at 2,600 g. SRT ditched the fuel-saving Multi-Displacement System—because why the heck wouldn’t they?—and increased the overall engine speed from 6,200 rpm to 6,500 rpm.

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