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What Does "Hemi" Engine Mean?

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What Makes the HEMI V8 Hellcat Engine So Potent?
 
Ever wondered what makes the 6.2-litre supercharged HEMI V8 Hellcat engine the most powerful production engine in the world? Recently the Director of Advanced & SRT Powertrain at Chrysler, Chris Cowland, publicly revealed some long held secrets about why it’s so potent.

The 6.2-Litre HEMI V8 Hellcat Engine is a Brand New Design

Delivering 707 horsepower and 650 lb-ft torque, the 6.2-litre HEMI V8 Hellcat engine is a brand new design with only its basic framework resembling earlier 5.7-litre, 6.1-litre and 6.4-litre V8 engines built by Chrysler. In this case only the 103.9 mm bore is the same as that used in earlier engines. Over 90 percent of the 6.2-litre HEMI Hellcat engine components are new, and from the thicker webs and bigger cooling areas in the cast-iron block that support more power, to more secure clamping provided by connecting rods with cracked bearing caps, they all add up to extra powerful performance. New pistons from forged aluminum can handle combustion pressure exceeding 21,000 lb, and minimal friction is achieved through new 24-mm wrist pins with a coating that’s diamond-like.

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Cast Iron Block Provides Hard-Working Hellcat Engine with the Best Support

Some may say that the iron cylinder block is an outdated technology, but the Chrysler engineer insisted that cast iron is a perfect material for the intense loading in the Hellcat engine. Since the crankshaft in the Hellcat spins so fast and works so hard, it requires the support of main bearing caps secured by 20 bolts and deep side skirts of the iron block.

How the 6.2-Litre HEMI V8 Hellcat Engine Handles Excess Heat

It’s a combination of 42 mm exhaust valves and large 54.3 mm intake valves carried in the cylinder that help to handle heat, as well as the A356 aluminum cylinder heads being heat-treated. While the sodium-filled in the exhaust stems also emit excess heat, both the intake valves and exhaust valves also reduce weight by having hollow stems.

Rotating Components of Supercharger Prevented from Back-Driving the Engine in all Conditions

The entire supercharger, consisting of the twin air-liquid intercoolers, aluminum rotors with steel shafts and aluminum housing and totaling 80 lb, is manufactured by IHI Turbo America at a plant in Shelbyville, Illinois. The high-inertial rotating components never back-drive the engine even in lift-throttle conditions, due to the one-way clutch on the blower’s input shaft. The blower can transfer 30,000 litres of air in a single minute.

How the Twin-Screw IHI Supercharger is Made to Spin

In an historical engineering feat, the twin-screw IHI supercharger spins by a process involving a particular configuration. The 10-rid drive pulley is secured to the crankshaft by washers with industrial diamonds giving enough friction to clamp sufficiently. Delivering 2.4 litres of air per revolution by driving the blower 2.36 times crankshaft rpm takes a full 80 horsepower. Different spin speeds of the supercharger rotors which are asymmetrical is achieved through their interlocking and 3:5 ratio phase gears at the blower back. When the rotor spun by the crankshaft belt spins at 14,160 rpm at the 6000 rpm engine peak, the other rotor spins at 23,600 rpm.

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Especially Loud HEMI V8 Hellcat Engine Noise is Created Through Masterful Engineering

While no artificial noise whatsoever is added in any of the vehicle’s sound system, the supercharger makes noise on purpose to please drivers with a passionate performance drive. When the car is driving with part throttle or idling, the airflow sound, rotor, gear and bearing are not really heard. But as soon as the driver hits the gas, the louder intake, sounds from the exhaust and a whining sound all meld together to create a powerful growl.
 
Cooling Expertise Keeps the HEMI V8 Hellcat Engine Cool

The intake air density is maximized and cooled through the use of a 250-watt electric pump that’s controlled by a thermostat. Passing through two heat exchangers in the supercharger flanks and the two car radiators, 45 litres of coolant is moved per minute to reduce temperature. A mixture of antifreeze and the water is kept at around 100 degrees F.

Gasoline-Thirsty Hellcat Engine Quenched by Adequate Fuel Injectors

With fuel lines that have a diameter of .5 inches and an air-fuel ratio kept in check through mass airflow and speed-density calculations, the Hellcat’s thirst is quenched and enough gasoline is injected to it. Up to 630 cc of gas are delivered through eight fuel injectors that are located in the intake runners. What provides an almost continuous delivery of gasoline are the orifices in the injectors that are drilled at a 20-degree angle.

Hellcat Oil Coolers Are High Capacity

At the front of every Challenger SRT with a Hellcat V8 engine are six heat exchangers that it powers. Part of standard Hellcat engine equipment is engine oil cooler that is high capacity, and Pennzoil Ultra Synthetic oil with a viscosity grade of Ow40 is the lubricant used.

A Choice of Transmissions Offered with the Hellcat V8 Engine

Either the Tremec TR-6060 manual transmission with six speeds is offered with the Hellcat V-8 engine, or the ZF/TorqueFlite 8-speed automatic. Both come equipped with lubricant coolers and are upgraded.

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