Every Dodge Challenger gets a significant makeover for 2015, and one version goes completely, supersonically 707-horsepower insane. That nutty one is the SRT Hellcat: a supercharged exaggeration of the resurrected Challenger that's been in production since 2008. It's not only the most powerful Dodge ever made, it's the most powerful production muscle car made. Ever.
On regular Challengers the styling updates for 2015 are inspired by the 1971 Challenger; the grille features spilt elements and the taillights are now separate LED units. And the interior sees dramatic improvements with loads of added features. But the Hellcat gets its own hood with a large scoop and vents, skips the split elements in the grille for better cooling and has a hole inside the left inner headlight to feed cold air to the beastly 6.2-liter supercharged Hemi V8.
Source
http://www.edmunds.com/dodge/challenger/2015/road-test.html