How much horsepower does a Roush supercharger add to a Mustang GT?
In general terms, a Roush supercharger kit can push a Mustang GT into the high 600s to 800s horsepower, and in some configurations even higher, depending on the specific kit, octane fuel, and supporting upgrades. The exact gain varies by model year, engine setup, and tuning.
The question hinges on which Roush kit you choose and how you plan to run the car. Roush Performance offers several blower options for the 5.0-liter Mustang GT, each designed to deliver different levels of power, driveability, and reliability. Below is a look at the main options and what they’re designed to achieve, followed by a discussion of typical horsepower targets and the factors that influence final numbers.
Roush supercharger options for the Mustang GT
Roush categorizes its Mustang GT blowers into several performance tiers. The following list covers the primary offerings commonly described for street/strip use, though exact specs can evolve with new model years and product updates.
- Roush Phase 1 Supercharger Kit
- Roush Phase 2 Supercharger Kit
- Roush Phase 3 Supercharger Kit
- Roush Stage 3 Mustang Package (high-boost, extreme-tuning option)
Choosing among these options depends on how you intend to drive the car—daily usability, weekend fun, or track-focused performance—and how much supporting hardware you’re willing to install, such as fuel system upgrades and cooling solutions.
How these kits translate to real-world power
The horsepower you’ll see comes from the combination of the blower size, boost target, intercooling, fuel system capacity, and the tune. Broadly speaking, the kits are designed to push a modern Mustang GT well beyond stock horsepower figures, with higher-tier kits aiming for the upper end of the range when paired with appropriate fueling and intercooling. The most aggressive configurations can approach or exceed 800 horsepower at the crank on 93 octane, and can surpass that on race fuel, depending on setup and tuning.
It’s important to note that dyno results vary, and final numbers depend on several variables, including the vehicle’s year and baseline horsepower, atmospheric conditions, octane, and how thoroughly the car is prepared to handle the increased boost (fuel injectors, pump, exhaust, cooling, transmission hardware, and other supporting mods).
Factors that influence horsepower gains
Before you install a Roush blower, it helps to understand why two cars with the same kit and octane can produce different numbers. The following factors commonly affect the final horsepower figures achievable with a supercharged Mustang GT:
- Fuel octane rating and the fueling system’s capacity (injectors, pump, and return lines)
- Intercooling efficiency and overall cooling capability
- Engine year and baseline horsepower
- Boost targets and sensor-based tuning strategies
- Supporting modifications (exhaust, intake, intake manifold, transmission, and drivetrain)
- Altitude and ambient temperature
Prospective buyers should work with an authorized Roush dealer or a qualified tuner to select the kit that matches their goals and to ensure the vehicle is properly configured for safe, reliable operation under boost.
Summary
Roush’s Mustang GT supercharger lineup is designed to deliver substantial power gains, with more modest, street-friendly setups and very high-boost options for enthusiasts seeking top-end performance. Typical street configurations place total output in the broad 700–800+ horsepower range, with the most aggressive Stage 3 builds capable of reaching into the 800–900+ horsepower territory on race fuel. Real-world results depend on the exact kit, supporting upgrades, fuel, and tuning, so consultation with a certified installer is essential.
