Chris Cowland, Chrysler’s director of sophisticated and SRT powertrain, not too long ago came clean with the engineering secrets behind the 707-hp 6.2-liter Hellcat V-8. In case you just stirred from suspended animation, this Dodge Challenger SRT engine is the most potent powerplant ever sold to consumers for road use by any American manufacturer.
Revelation 1: Whilst this Hemi is a cousin to 5.7-, 6.1-, and 6.4-liter Chrysler-constructed V-8 engines, the Hellcat is, for all intents, a new design sharing only basic architecture—such as a 103.9-mm bore—with its predecessors.
Far more than 90 % of the components (by value, not components count) are new. The cast-iron block has thicker webs and bigger cooling passages to help the added energy and pressure. The induction-hardened forged-steel crankshaft gives the desired 90.9-mm stroke. The powder-forged steel connecting rods have cracked bearing caps for more safe clamping. New forged-aluminum pistons withstand a lot more than 21,000 pounds of combustion pressure. The 24-mm wrist pins have a diamondlike coating for minimal friction.
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Revelation 2: Whilst the uninformed may possibly deem an iron cylinder block to be yester-tech, Cowland insists it is the perfect material for this application provided the intense loading. While a fresh aluminum style may possibly save a couple of pounds, package dimensions would certainly be larger due to aluminum’s drastically lower stiffness. The hard-functioning, quick-spinning Hellcat crankshaft is nicely supported by the iron block’s deep side skirts and twenty bolts securing the 5 main-bearing caps. A meaty closed upper deck resists cylinder-bore distortion.
Revelation 3: Even though the heat-treated A356 aluminum cylinder heads do not have hemispherical combustion chambers, they do carry massive 54.3-mm (2.14-inch) intake valves and 42.-mm (1.65-inch) exhaust valves. Both have hollow stems to save weight the exhaust stems are sodium-filled to dispense with excess heat.
Revelation 4: IHI Turbo America (formerly Warner-Ishi) manufactures the entire 80-pound supercharger—aluminum housing, aluminum rotors supported by steel shafts, and the twin air-liquid intercoolers—in a Shelbyville, Illinois, plant. A 1-way clutch on the blower’s input shaft prevents the higher-inertia rotating elements from back-driving the engine in the course of lift-throttle conditions. A lot more potent than a street sweeper, this blower can move 30,000 liters of air per minute. IHI earned this enterprise in a fly-off against 2 other supercharger suppliers.
Revelation 5: Spinning the twin-screw IHI supercharger is a substantial engineering feat. Washers securing the 10-rib drive pulley to the crankshaft are infused with industrial diamonds to provide adequate clamping friction. Driving the blower 2.36 occasions crankshaft rpm to provide 2.4 liters of air per revolution consumes 80 horsepower. The asymmetrical supercharger rotors spin at various speeds thanks to their interlocking configuration and 3:5-ratio phase gears at the back of the blower. At the 6000-rpm engine horsepower peak, the rotor spun by the belt from the crankshaft turns at 14,160 rpm even though its mate spins at 23,600 rpm.
The rotors are coated with a Teflon material that aids sustain the tight clearances needed to avert airflow leaks. In the event of accidental get in touch with, the soft coating abrades instead of the aluminum rotor material. Gears and rotor bearings are lubricated by a sealed-for-life splash program containing synthetic oil. Durability was confirmed by canting the blower at 47 degrees from horizontal and running it at diverse speeds and loads for 300 test hours.
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Revelation 6: Noise generated by the supercharger is engineered to please the obvious Hellcat users: folks with a stout performance bent. During idle and part-throttle driving, the bearing, gear, rotor, and airflow ruckus falls below the audible threshold. Kick the gas and you hear a subtle whine mixed in with the louder intake and exhaust sounds. No artificial noise is added by means of the car’s sound program.
Revelation 7: To cool the intake air and maximize its density, a 250-watt (1/3-horsepower) thermostatically controlled electric pump moves 45 liters of coolant per minute through the 2 heat exchangers (intercoolers) built into the flanks of the supercharger and the 2 radiators positioned at the front of the car. The aim is to lessen the temperature of the intake air to much less than 140 degrees Fahrenheit so the water and antifreeze mixture is maintained at about 100 degrees F.
Revelation 8: The fuel lines are .5 inch in diameter to quench Hellcat’s thirst for gasoline, although the air-fuel ratio is regulated by employing each speed-density and mass airflow calculations (doubling up was required to satisfy onboard diagnostics needs). Though direct injection was regarded as, appropriate higher-pressure delivery pumps with the needed capacity do not exist.
The 8 fuel injectors positioned in the intake runners provide up to 630 cc of gasoline per minute (or a single pint every single 6 seconds). The injector orifices are drilled at a 20-degree angle to aim the 17-degree cone of atomized fuel at the back side of the intake valve. Delivery is almost continuous to make certain that adequate fuel to support 707 horsepower is delivered. The heat of the intake valve vaporizes the microdroplets of gasoline before they enter the combustion chambers. 2 air intakes are supplied in the Hellcat Challenger: one particular at the center of a driver’s-side lamp located in the grille, the other at the bottom of an underhood filter housing.
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Revelation 9: A higher-capacity engine oil cooler is common Hellcat equipment. The factory-fill lubricant is Pennzoil Ultra Synthetic oil in a 0w40 viscosity grade. A total of 6 heat exchangers live at the front of each Challenger SRT powered by this engine.
Revelation 10: The Hellcat V-8 is offered with a option of a Tremec TR-6060 6-speed manual transmission or a ZF/TorqueFlite paddle-shifted 8HP90 8-speed automatic. Each are upgraded for this application and equipped with lubricant coolers.
A twin-disc 8.2-inch clutch feeds torque to the manual ’box. Launch manage is provided with both transmissions to support novices burn significantly less rubber and waste minimal time off the line. The automatic begins in second gear in launch mode. Thanks to the wide ratio spreads and tall prime gears, the Challenger SRT achieves up to 22 mpg in EPA highway tests. Sadly, its 13 mpg in city driving benefits in a $ 1700 gas-guzzler tax penalty.
BONUS Revelation: Each Hellcat V-8 receives a 42-minute dyno run at the Saltillo, Mexico, manufacturing plant for break-in. Maximum rpm is 5200 at 90-% load.
Chris Cowland was generous in sharing his expertise but anxious to move forward with the next project: The unconfirmed 800-hp supercharged V-10 under development to give the Dodge Viper sufficient venom to bite each the feisty Challenger and Charger SRT Hellcats.
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