The Dodge Challenger is a beloved muscle car that blends modern engineering with the raw spirit of American performance. For owners seeking to elevate their driving experience beyond factory specifications, supercharger kits are among the most effective modifications. The difference between an 8-psi and a 10-psi kit is not just a number; it represents a shift in power delivery, reliability considerations, and overall driving character. This guide provides a detailed look into how much horsepower these two common boost levels add, what affects those gains, and what you need to consider before installing a supercharger on your Challenger.

Supercharger Basics: How Boost Translates to Horsepower

At its core, a supercharger is an air compressor driven by the engine's crankshaft via a belt. By forcing more air into the combustion chambers, the engine can burn more fuel, creating a larger explosion and thus more power. Boost pressure, measured in pounds per square inch (psi), indicates how much additional atmospheric pressure the supercharger forces into the intake manifold relative to ambient pressure.

A rough rule of thumb is that every 1 psi of boost adds approximately 6-8% more horsepower on a naturally aspirated engine, though this varies widely based on engine efficiency, displacement, and tuning. For the Dodge Challenger, which comes with several engine options (3.6L V6, 5.7L HEMI V8, 6.4L HEMI V8, and the supercharged 6.2L Hellcat), the baseline power level and the engine's mechanical tolerance significantly influence final gains.

Expected Horsepower Gains for 8-psi and 10-psi Supercharger Kits

While dyno results can vary by 10-20 horsepower depending on temperature, fuel quality, and specific kit design, here are realistic ranges for the two most popular engine platforms in the Challenger lineup.

8-psi Supercharger Kits

An 8-psi kit is considered a “street-friendly” boost level. It is often chosen for its balance of power increase and retained reliability, especially on engines that are not built with forged internals (like the 5.7L and early 6.4L HEMIs). Typical gains are as follows:

  • 5.7L HEMI (375 hp stock): +80 to +110 horsepower, resulting in around 455–485 whp. Torque gains are equally impressive, often exceeding 470 lb-ft.
  • 6.4L HEMI (485 hp stock): +100 to +130 horsepower, pushing output to 585–615 whp. Many owners report a 120–140 lb-ft torque increase.

The lower boost pressure allows for safer operation on pump gas (91–93 octane) without aggressive timing pull, making it a reliable setup for a daily driver.

10-psi Supercharger Kits

A 10-psi kit represents the upper limit for pump-gas reliability on many long-stroke HEMI engines without forged rods and pistons. This pressure delivers a more pronounced shove in the mid-range and top-end. Expected gains:

  • 5.7L HEMI: +130 to +160 horsepower, often reaching 510–540 whp. At this boost, the 5.7L’s smaller displacement means the supercharger has to work harder, generating more heat.
  • 6.4L HEMI: +150 to +190 horsepower, with whp figures of 635–675 whp. With proper cooling and fuel system upgrades, some have seen over 700 whp on 10 psi.

It is critical to note that 10-psi kits typically require a fuel system upgrade (larger injectors, higher-flow fuel pump, or a boost-a-pump) and often an intercooler to manage intake air temperatures. Even then, knock sensors may force timing retard on low-quality fuel, reducing gains.

Factors That Influence Actual Horsepower Gains

The numbers above are averages. Real-world results depend on a handful of variables that every Challenger owner should understand before ordering a kit.

Engine Condition and Displacement

An older high-mileage engine with ring wear will not hold cylinder pressure as well as a fresh motor. Larger displacement engines (6.4L) have more air volume to compress, so they respond more linearly to boost. Smaller engines (5.7L) require higher boost to make the same horsepower but generate more heat and stress per psi.

Supercharger Type and Efficiency

Not all superchargers create boost equally. Twin-screw and roots-type blowers (like those from Whipple or Kenne Bell) produce heat-soaked air more quickly than centrifugal superchargers (like ProCharger or Vortech). A less efficient blower at 10 psi may produce the same density of air as a highly efficient blower at 8.5 psi. Always look at the intercooler design and heat exchanger capacity.

Fuel Quality and Tuning

Octane rating is the single most important variable in forced induction. On 93 octane, an 8-psi kit can often run at peak timing without detonation. On 91 octane (common in western states), timing may be pulled, costing 15–25 horsepower. A 10-psi kit on 91 octane will likely require an ethanol blend (E85) to realize full potential, or at least a methanol injection kit.

Supporting Modifications

Simply bolting on a supercharger is rarely the whole story. Exhaust backpressure, intake restriction, and drivetrain losses all play a role. Common supporting mods that maximize gains include:

  • Long-tube headers and a 3-inch exhaust: Reduce backpressure and increase flow, allowing the supercharger to spool more freely.
  • Cold air intake (for centrifugal kits): Lowers intake air temperature by 10–20°F.
  • Fuel system upgrades: Large injectors (e.g., 1,000 cc/min), a boost-referenced fuel pressure regulator, and a stronger pump.
  • Heat exchanger/intercooler upgrade: Especially critical for 10-psi roots-type blowers; larger reservoirs and dual fans help maintain consistent IATs.

Comparing 8-psi vs. 10-psi: Real-World Driving Feel

Horsepower numbers don’t tell the whole story. The way the power is delivered differs significantly between the two boost levels.

Throttle Response and Low-End Torque

An 8-psi roots-style blower will feel extremely responsive off-idle, giving the impression of a much larger naturally aspirated engine. Acceleration from a stop is immediate. A 10-psi centrifugal setup, by contrast, builds boost linearly with RPM, so the hit comes at 4,000+ RPM—like a strong nitrous shot on the top end. Both are fun, but the character is distinct.

Intake Air Temperatures and Heat Soak

At 8 psi, heat is manageable. With a good intercooler, IATs can stay within 20°F of ambient during a hard pull. At 10 psi, the elevated compressor speed generates more heat, and heat soak becomes a real problem after consecutive pulls (e.g., autocross or drag racing). Many owners of 10-psi cars install a larger heat exchanger or a water-methanol injection system to keep detonation at bay.

Reliability and Engine Longevity

8 psi is generally considered safe for stock internals on the 5.7L and 6.4L HEMIs. The pistons and rods in these engines are cast, not forged. Ten psi pushes the cylinder pressure close to the limit; a lean spike or aggressive timing can cause ring land failure or rod bending. The 6.4L Apache engine has stronger rods than the 5.7L Eagle, but the pistons remain cast. For a daily driver that sees occasional track use, 8 psi is the safer bet. For a dedicated race car or a car built with forged internals, 10 psi is a natural step.

Case Study: Dyno Results from a 2019 Challenger 6.4L Scat Pack

To illustrate the difference, consider a stock 2019 Challenger Scat Pack ( 6.4L HEMI, 485 hp SAE) equipped with a Whipple twin-screw supercharger using a 4.00-inch pulley for 8 psi and a 3.75-inch pulley for 10 psi. On 93 octane with a conservative DynoJet tune:

  • Stock baseline: 406 whp / 412 lb-ft
  • 8 psi (4.00” pulley): 531 whp / 538 lb-ft – gain of 125 whp
  • 10 psi (3.75” pulley): 595 whp / 602 lb-ft – gain of 189 whp

The jump from 8 to 10 psi increased whp by 64 horsepower. Note that this is with a highly efficient twin-screw blower; a less efficient roots style would see smaller gains and higher IATs.

Selecting the Right Kit for Your Goal

Your choice between 8 and 10 psi should align with your intended use, budget, and willingness to perform supporting upgrades.

8-psi Kit – Best For:

  • Daily drivers that see occasional spirited driving
  • Stock engines without forged internals
  • Minimal supporting modifications (stock fuel system may be adequate on 5.7L)
  • Budget-minded builds (less expensive belt, smaller injectors, simpler tune)

10-psi Kit – Best For:

  • Track-focused cars that see frequent high-RPM use
  • Engines with forged rods and pistons, or those built by shops like Hemi Performance
  • Owners willing to upgrade fuel system, cooling, and maybe run E85
  • Drivers who want a dramatic, raw power increase and don’t mind heat management

Common Pitfalls and How to Avoid Them

Many first-time supercharger buyers focus only on the peak horsepower number. Here are three mistakes to avoid:

  1. Ignoring fuel system capacity. At 10 psi, stock fuel pumps often cannot maintain pressure. This leads to lean conditions and engine damage. A Fore Innovations triple-pump hat is a common upgrade for high-boost Challengers.
  2. Skipping a wideband O2 sensor and tune. Even the best hardware is worthless without professional tuning. A dyno tune by a HEMI specialist like High Horse Performance ensures the air-fuel ratio stays in the safe window (11:5 – 12:1 for gasoline).
  3. Not upgrading the belt system. High boost forces the supercharger to consume more parasitic power, and belts can slip. A larger crank pulley or a dedicated belt wrap kit (like the Griptec system) prevents slippage above 10 psi.

Installation Considerations

Both 8-psi and 10-psi kits require similar installation effort, but the margins for error shrink at higher boost. Key steps include:

  • Fuel pump and injectors: Must be upgraded for 10 psi on 6.4L and for any boost on 5.7L.
  • Intercooling: For roots/twin-screw kits, a larger heat exchanger and reservoir are strongly recommended at 10 psi.
  • PCV system: Boost can pressurize the crankcase, leading to oil leaks. A catch can and crankcase vent are necessary.
  • Spark plugs: Colder heat range plugs (e.g., NGK 6510) are required to prevent pre-ignition.

Final Verdict: Which Boost Level Should You Choose?

The answer depends on your appetite for risk and your intended driving style. For the majority of Challenger owners who want a reliable, fun, and streetable upgrade, an 8-psi supercharger kit offers the best balance of gains (100–130 extra horsepower) and mechanical simplicity. It transforms the car without requiring constant fuel system attention or worry about detonation.

For those chasing the highest horsepower numbers on a built engine—or who simply cannot resist the lure of 700+ whp—a 10-psi or even higher boost level with proper supporting mods will deliver an unforgettable experience. Just be prepared to invest an additional $3,000–$5,000 in fuel, cooling, and engine management to do it right.

No matter which path you take, a supercharged Challenger remains one of the most exhilarating muscle cars you can build. The key is to plan your build around realistic expectations and the specific engine in your garage.