Images: Roush Performance

Ever since Ford reintroduced the 5.0 liter V8 into the Mustang GT, speed shops across the world have been busy squeezing more and more horsepower from less displacement than GM and Chrysler’s muscle cars. Roush has been at the forefront of tuning the new 5.0, and that tradition continues in 2015.

The 2015 Roush Stage 3 Mustang will officially start off with 670 hp and 545 lb-ft of torque, just 5 ponies less than the maximum tune level Roush offered last year. Does that mean Roush has even more horsepower on tap for the 2015 Mustang? We wouldn’t doubt it. After all, the 2013 Stage 3 that we tested started out with just 570 horsepower, with additional tunes and Roush parts available taking it up to 675 ponies. With the 2015 Stage 3 starting at 670, that leaves the door open for additional power packages (known as Phases in the Roush world) taking it over 700 horsepower and beyond.

How’d they do it? Well once again, Roush has stuck with what it knows works, utilizing a 2.3 liter Eaton TVS supercharger to boost the Mustang GT’s horsepower by about 50% over stock. A quad-tip exhaust with optional Roush active exhaust system, R7 aero kit, and other upgrades take it from mere supercharged GT into the realm of a Jack Roush supercar.

Prices start at $21,995, in addition to the $32,300 you’ll have to lay out for a base Mustang GT. From there, options and additions can take the price well past GT500 territory, though the Roush is a much rarer sight. Roush builds the cars before they’re delivered to customers, so Roush is the actual manufacturer. With Ford forgoing a supercharged Shelby for the 6th gen Mustang though, it’s up to Roush to carry the flame of straight-line performance in a package that handles as well. We’ll be getting our hands on a RS3 soon for evaluation, stay tuned.