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Supercharged 6.2 Hemi: “HellCat V8”

Modern Hemis 5.7 Hemi • SRT 6.1 and 6.46.4 Truck Hemi • Supercharged “HellCat”
Classic Hemis 426 HemiOld Hemi History • 392 Crate HemiDevelopmentPlane Hemi

The supercharged 6.2 Hemi is due to be shown early in calendar year 2014, with an estimated (by us) 640-680 horsepower. It will have MDS (with the automatic transmission, not the manual) and will use a clutched pulley for the supercharger. This engine, used only by SRT, will be available alongside the much less expensive 6.4 Hemi, which is also due for an update.

supercharger

We have been told by several sources that the internal target is 700 hp, and while we don’t believe the target will be reached when they get around to publishing SAE net figures, it’s beginning to look as though it’ll at least be in the mid-600s for horsepower. It will be hooked up to a manual transmission in Dodge Challenger, and an eight-speed automatic in Challenger and Charger; we’re estimating a peak of 640 pound-feet to stay within the 900 Nm capacity of the 8HP90.

hellcat log

“fargo59” wrote that it shares heads with the Apache SRT 6.4 Hemi engine. which may also indicate a large bore, short stroke design (6.4 is 4.090” bore, 6.1 was 4.055”). A 4.090” bore with a 3.58” stroke would be 376 cubic inches, or 6.16 liters. “A 6.4 with a forged 5.7 crankshaft would give the right dimensions and be relatively easy to work; a shorter stroke is also going to give the idea rod to stroke ratio and make it a high revving engine.” Cams are also reportedly similar to the 6.4 design.

392 Hemi

“Danno” wrote, “Air comes in through the front of the blower, and is compressed upwards, goes through runners, makes a 180° turn, and goes straight down through the four heat exchangers (one for each pair of cylinders), then into the intake ports. The fog lights have been replaced by vents for the low-temperature oil/coolant radiators; an opening in the wheel well lets the air flow out. One side is an oil cooler the other side is coolant. The coil covers say ‘supercharged HEMI.’”

The engine is slated to appear in the 2015 Charger, 2015 Challenger, and possibly a new SRT Ram 1500. The intent is to compete against ZL1, ZR1, GT500, and Z28. (Thanks, Danno, oh2o, JRS200x, AutoTechnician.)

How fast will the HellCat go?

ZF’s eight-speed automatic, to be coupled to HellCat, has a stunning range: its first gear has a low 4.71:1 ratio, while its top gear is a high 0.67:1. That automatic is the key to giving the V6 Charger its V8-like acceleration, along with 31 mpg on the highway.

Meanwhile, the fastest Mopar ever made (other than Viper and perhaps Tomahawk) was the Dodge Charger Daytona, which broke the 200 mph barrier in 1970, thanks to the hot 426 Hemi V8 and a great deal of time in wind tunnels. Can the new Charger and Challenger beat that time?

The Charger Daytona’s drag coefficient was a stunning 0.28, which is still quite good over four decades later — better, indeed, than current Chargers or Challengers. 2015 Chargers and 2015 Challengers might not reach that level of slip, but with the supercharged HellCat engine and the superb gear range of the eight-speed automatic, they probably won’t need to.

Forum member “AutoTechnician” wrote, “The power required to overcome aerodynamic drag increases with the cube of the speed (e.g. 20 mph requires eight times the power as 10 mph to push through the air.) It looks like it's going to require about 500 hp just push the Challenger through the air at 200 mph, using published drag and frontal area specs. Factor in mechanical losses, rolling resistance, etc... and you're easily well over 600 hp required at the crankshaft to do 200 mph. Keep in mind that the 638HP ZR1 can only do 205 mph.”

The efficient ZF transmission may help SRT; an open question is the HellCat’s power, now predicted at 640-680 hp.

With currently-used P245/45R20 tires (wider tires are expected) and a final drive ratio of 3.06, when the engine nears the current Hemi redline of 6,400 rpm (let’s say, when it’s at 6,200 rpm), the car should be going 208 mph, ignoring wheel slip, aerodynamic drag, and other limiting factors which are always present. (If they were not, all cars would have much higher top speeds.)

The eight speed drops the top gear from 0.83 to 0.67, while raising first gear from 3.59 to 4.71. That means the SRT people can play around a lot more with axle ratios, and puts seventh gear into play. SRT is probably playing with axle ratios right now, trying to find the best way to maximize performance (there’s only so much traction at launch); it looks as though the extra power from the Hellcat will push it over 200 mph.

The question may well change from “Will Dodge break its 44-year speed record?” to “Will it be Charger, Challenger, or Viper that becomes the fastest Chrysler of all time?”

Why call it “HellCat”?

The HellCat is named after a Grumman World War II fighter plane, used mainly on aircraft carriers; many of its 2,000-hp Pratt & Whitney engines (also used on Corsair and Thunderbolt) were made by Nash, the car company that later joined with Hudson to form AMC, which was purchased by Chrysler in 1987.

Hellcat fighterAround 12,200 Hellcats were made in a little over two years. They destroyed 5,223 enemy aircraft, more than any other Allied naval planes; the Hellcat’s overall kill-to-loss ratio was around 19:1, beating every Japanese aircraft by at least 4:1. Only 270 were downed by aerial combat during the war (most of the planes that were lost, fell to training accidents or transport problems).

In 1943, Admiral D.C. Ramsey sent a letter to workers at Nash:

The new Hellcat fighters powered by Pratt and Whitney engines have proved their superiority to the Japanese Zero ... In one of the engagements in the Solomons, the Hellcats tore into 14 Zeros and shot down eight without loss to themselves. The other 11 Hellcats encountered 19 Zeros and destroyed six with a loss of only one plane. The pilots reported, “The Pratt and Whitney engine [many of which were built by Nash] performed admirably with no blower difficulties and few exhaust stack failures.”

In the attack on Wake the Hellcats shot down more than 30 Jap aircraft in combat and destroyed approximately the same number on the ground. As far as is known the Zeroes failed to down a single Hellcat.

“HellCat” is only an internal project code; other names include Hurricane (four cylinders), Eagle (5.7 Hemi), and Apache (6.4 Hemi). 

Modern Hemis 5.7 Hemi • SRT 6.1 and 6.46.4 Truck Hemi • Supercharged “HellCat”
Classic Hemis 426 HemiOld Hemi History • 392 Crate HemiDevelopmentPlane Hemi

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