How Much Horsepower Will a Supercharger Add?

A well-matched, intercooled street supercharger typically adds about 30–50% more horsepower on pump gas, which translates to roughly +40–120 hp on many 4‑cylinder engines, +80–150 hp on V6s, and +120–300+ hp on modern V8s; higher gains are possible with more boost, better fuel, and supporting upgrades. The exact increase depends on boost level, fuel octane, intercooling, tuning quality, engine size and strength, and the type of supercharger used.

What Determines the Horsepower Gain

How much power you’ll actually see from a supercharger is governed by a set of technical and practical variables that either unlock or limit the benefit of the extra airflow. Understanding these helps set realistic expectations before you buy a kit or schedule a tune.

• Boost pressure: More psi increases the pressure ratio and potential power, but also heat and engine stress.
• Fuel quality: Higher octane (and blends like E85) allow more timing and/or boost before knock, yielding larger gains.
• Intercooling: Efficient air-to-air or air-to-water coolers recover power by reducing intake temperature.
• Supercharger type and efficiency: Roots/twin-screw deliver strong low-end torque; centrifugal units build power with rpm and often parasitize less power at cruise.
• Engine baseline and condition: Displacement, compression ratio, cam timing, and volumetric efficiency all influence results.
• Tuning: Conservative vs. aggressive ignition/fuel strategies significantly change peak numbers and reliability.
• Parasitic drag and drivetrain losses: Driving the blower costs power; wheel-horsepower (whp) will be lower than crank numbers.
• Altitude and climate: Higher elevation and hotter ambient temperatures reduce absolute power.

Taken together, these factors explain why two seemingly similar cars can end up with very different dyno sheets even at the same boost level.

Typical Real-World Gains by Engine Category

The following ranges reflect common, intercooled, pump‑gas street setups (roughly 6–10 psi) with quality tuning on otherwise stock or lightly modified engines. Figures reference approximate crankshaft gains; wheel gains are typically 10–20% lower depending on drivetrain.

• 1.5–2.5L 4‑cylinder (120–220 hp stock): +40–120 hp at 6–9 psi; ends up around 180–320 hp.
• Performance 2.0–2.5L 4‑cylinder (200–250 hp stock): +60–120 hp at 7–10 psi; ends up around 260–370 hp.
• 3.0–3.6L V6 (230–320 hp stock): +80–150 hp at 6–8 psi; ends up around 310–470 hp.
• 5.0L class V8 (400–480 hp stock): +120–250+ hp at 6–10 psi; ends up around 520–730+ hp.
• 6.2L class V8 (420–495 hp stock): +130–280+ hp at 6–9 psi; ends up around 550–770+ hp.
• Truck 5.3–6.2L V8 (355–420 hp stock): +120–220 hp at 6–8 psi; ends up around 475–640 hp.
• Electric e‑superchargers (48V assist units): modest, transient gains—typically torque fill rather than large peak hp increases.

These are streetable, conservative expectations. Built engines, higher octane or E85, higher boost, and aggressive tuning can push beyond these ranges, while emissions-legal or tow-safe calibrations may sit toward the low end.

Examples from Popular Platforms

To ground the ranges in familiar applications, here are representative outcomes reported by major supercharger kit providers (assuming intercooled kits, healthy engines, and quality tunes). Actual results vary by fuel, dyno type, and calibration strategy.

• Ford Mustang 5.0 (≈450 hp stock): commonly 650–750 hp at 7–10 psi (TVS/twin-screw or centrifugal).
• Chevrolet LS3 6.2 (≈426–430 hp stock): about 550–620 hp at 6–8 psi.
• Hemi 5.7 (≈370 hp stock): roughly 500–600 hp at 6–8 psi.
• Subaru BRZ/GR86 2.4 (≈228 hp stock): roughly 280–330 hp at 7–9 psi.
• Mazda MX‑5 ND 2.0 (≈181 hp stock): typically 220–260 hp at 6–9 psi.
• Honda K20/K24 (≈200–205 hp stock): around 280–350 hp at 9–11 psi, with higher figures on E85.

These examples highlight the broad 30–50% gain pattern on pump gas, with platform-specific variations driven by fuel, intercooling, cam timing, and tuning headroom.

Quick Way to Estimate the Gain

While dyno testing is definitive, a back‑of‑the‑envelope estimate uses pressure ratio and an efficiency factor to approximate new horsepower at the crank.

• Find pressure ratio (PR): PR = (14.7 + boost psi) / 14.7. For 7 psi, PR ≈ 1.48.
• Choose an overall efficiency factor (η): 0.85–0.95 for a modern, intercooled kit and good tune; lower if non‑intercooled.
• Estimated new hp ≈ baseline hp × PR × η.
• Example: 450 hp engine at 8 psi, η = 0.92 → 450 × 1.54 × 0.92 ≈ 638 hp (≈+188 hp, ~42%).
• Wheel horsepower will be lower due to drivetrain loss (often 10–20% depending on transmission and driveline).

This method won’t capture all real‑world variables (heat soak, parasitic draw, timing limits), but it aligns closely with results from well‑engineered kits.

Types of Superchargers and How They Shape Gains

Different supercharger architectures deliver power differently across the rev range and have distinct efficiency and parasitic characteristics, which affect both peak numbers and driving feel.

• Roots/TVS: Instant boost and strong low‑rpm torque; great drivability and midrange; slightly higher parasitic loss at cruise.
• Twin‑screw: Similar to Roots in feel with improved adiabatic efficiency; strong across the band; popular on V8s.
• Centrifugal: Boost rises with rpm; often best peak hp per psi and lower parasitic draw; feels turbo‑like at the top end.
• Electric e‑superchargers: Short‑duration, low‑boost assist to fill lag; limited effect on peak hp in aftermarket stand‑alone use.

If your priority is instant torque and towing or street punch, a positive‑displacement (Roots/TVS/twin‑screw) unit shines. For top‑end numbers and track use, a centrifugal may deliver more peak hp per psi.

Supporting Mods, Reliability, and Legality

Unlocking safe and repeatable gains often requires upgrades beyond the blower itself. Skipping these can cap power or risk engine health.

• Fueling: Higher‑flow injectors and sometimes a fuel pump; E85 support if desired.
• Cooling: Intercooler, heat exchanger, and proper ducting; consider oil/transmission cooling on track cars.
• Tune: Professional calibration for ignition timing, fuel, knock control, and torque management.
• Ignition and plugs: Colder spark plugs and tight gaps to prevent misfire under boost.
• Driveline: Stronger clutch/torque converter and possibly axles or differential for large torque increases.
• Engine internals: Forged pistons/rods and lower compression for high‑boost or track abuse.
• Compliance: Check emissions legality (e.g., CARB EO numbers) if you need street legality.

With the right supporting parts and tune, a conservative 6–9 psi setup on a healthy stock engine can be reliable for daily driving; pushing beyond that usually demands stronger internals and premium fuel.

Summary

Most well‑designed, intercooled supercharger kits add about 30–50% more horsepower on pump gas—roughly +40–120 hp on a typical 4‑cylinder, +80–150 hp on a V6, and +120–300+ hp on a V8—while higher gains are achievable with more boost, better fuel, and engine upgrades. Results vary with boost level, fuel, intercooling, blower type, tuning, and drivetrain losses. Plan supporting mods and a quality tune, and use pressure‑ratio math for a quick estimate before you buy.