The 707-horsepower Dodge Charger Hellcat delivers brutal acceleration and a supercharged V8 soundtrack straight from the factory. Yet for many owners, that raw power is just a starting point. The aftermarket has responded with bolt-on modifications that can push output well beyond the 800-horsepower mark without requiring an engine teardown or days in the shop. This guide covers five proven upgrades that offer the best balance of horsepower gains and fast installation times. Each part can be fitted with basic hand tools, often in a single afternoon, making them ideal for enthusiasts who want more performance without sacrificing daily drivability or tying up their car for weeks.

Before we dive into the specific mods, it's helpful to understand why the Hellcat responds so well to these upgrades. The 6.2-liter supercharged Hemi engine comes from the factory with a conservative tune and restrictive intake and exhaust systems designed to meet noise and emissions regulations. By freeing up airflow and optimizing the engine management, you can unlock a large amount of untapped potential. The modifications below have been chosen for their power-per-installation-time ratio, meaning you get maximum results for the least amount of wrenching.

1. Cold Air Intake System

Replacing the stock air intake with a cold air intake is the single most cost-effective way to improve your Hellcat's breathing. The factory air box draws air from inside the engine bay, which is typically hotter than ambient temperature. A cold air intake relocates the air filter to a cooler area and uses a larger, less restrictive filter element. This allows the supercharger to ingest denser air, which directly translates to more combustion pressure and higher power output.

What to Expect in Terms of Gains

Most cold air intakes for the Hellcat claim gains of 15–25 horsepower on a dyno. Real-world results vary depending on ambient temperature and the specific intake design, but almost every owner reports noticeably sharper throttle response and a more aggressive intake sound. The sound alone can make the car feel faster, but the measurable gains are real when combined with other mods.

Installation Time and Difficulty

Installation is straightforward, requiring only basic hand tools such as a socket set and screwdrivers. Most kits are direct bolt-on replacements with no cutting or drilling. Expect to spend 30–60 minutes from opening the hood to completing the swap. The process generally involves removing the factory air box and inlet tube, then installing the new intake assembly and filter.

Top-tier options include K&N, aFe Power, and Roush. All three offer high-quality filters and mandrel-bent tubes that flow significantly better than stock. Pay attention to whether the kit includes a heat shield—this prevents hot engine air from being pulled in and maximizes the cold-air benefit.

  • Improved airflow: Reduces restriction for the supercharger inlet
  • Enhanced throttle response: Less lag when you hit the gas
  • Simple installation: Requires no tuning or mechanical experience
  • Audible supercharger whine: The intake sound becomes much more prominent

2. High-Performance Exhaust System

The stock exhaust on the Charger Hellcat is designed to keep noise levels within legal limits and to fit the car's underbody packaging. It uses several mufflers and resonators that create back pressure, especially at higher RPM. A high-performance cat-back or axle-back exhaust system reduces that restriction, allowing the engine to expel exhaust gases more freely. This lowers the load on the supercharger and helps the engine spin up more quickly.

Power Gains and Sound

Expect 10–20 horsepower at the wheels, depending on the system and whether you retain the factory catalytic converters. More importantly, the exhaust note transforms from a subdued rumble into an aggressive, race-inspired roar. Hellcat owners who want a louder presence without being obnoxious can choose systems with removable resonators or adjustable mufflers.

Installation Time and Considerations

Most cat-back systems are bolt-on and use factory hanger locations. Installation typically takes 1–2 hours with a lift or jack stands and basic tools. The biggest challenge is often removing the rusty factory bolts and hangers, so a penetrating lubricant is helpful. Be aware that some systems require cutting the factory exhaust if you choose a full system that includes the mid-pipe.

Weight Reduction

Aftermarket exhausts are usually made from T304 stainless steel or even titanium, which is lighter than the stock steel components. This can shave 20–40 pounds off the rear of the car, improving rear traction and overall weight distribution. While not massive, every bit helps in a 4,400-pound sedan.

  • Increased horsepower and torque: Noticeable gains in the upper midrange and top end
  • Weight reduction: Lighter materials improve handling and acceleration
  • Aggressive sound: Unlocks the V8's natural exhaust note
  • Bolt-on installation: No welding required for most cat-back kits

3. ECU Tune (Engine Calibration)

The Dodge Charger Hellcat's engine control unit (ECU) is calibrated conservatively from the factory to protect the drivetrain and meet emissions standards across all markets. An aftermarket tune reprograms the fuel, ignition, and boost maps to extract more power from the same hardware. This is the single biggest power adder among the five mods, often adding 50–80 horsepower with no physical changes to the engine.

How an ECU Tune Works

Modern handheld tuners like the DiabloSport i3 or HP Tuners' MPVI2 plug into the OBD-II port and allow you to upload a custom calibration file. The tune modifies parameters such as air-fuel ratio, spark advance, cam timing, and supercharger bypass operation. The result is a smoother, more aggressive power curve and a noticeable increase in peak output. Some tuners also offer transmission tuning for firmer shifts and quicker response.

Installation Time and Safety

Uploading a tune takes about 15–30 minutes. The device connects to the OBD-II port, reads the stock file, and then writes the new calibration. It's critical to use a reputable tuner who has experience with Hellcat engines. A poor tune can lead to detonation or high exhaust gas temperatures that damage the engine. Look for tuners like Hemi Tuner or RIPP Superchargers who provide custom tunes for your specific mods.

Warranty Considerations

Flashing the ECU can void your powertrain warranty if detected by the dealer. Many handheld tuners allow you to revert the car to its stock calibration before dealership visits, but the ECU keeps a "flash count" record. Some owners choose to buy a second ECM to swap in for stock operation. Weigh the warranty risk against the performance gain before proceeding.

  • Significant power gains: 50–80 wheel horsepower without hardware
  • Customizable: Can be tailored for 93 octane, E85, or specific mods
  • Improved drivability: Smoother throttle response and transmission behavior
  • Quick installation: Done through the OBD-II port in under 30 minutes

4. Upgraded Supercharger Pulley

The factory supercharger pulley is sized to produce a specific amount of boost, typically around 11.6 psi from the IHI unit. By installing a smaller pulley (larger diameter on the crank side or smaller diameter on the blower side), you increase the supercharger's rotor speed, which forces more air into the engine. This mod can push boost into the 13–15 psi range, resulting in 30–50 horsepower gains in conjunction with a proper tune.

Installation and Required Supporting Mods

Replacing the supercharger pulley is a straightforward job that requires a pulley puller tool (often available for rent at auto parts stores) and a set of sockets. The process takes 1–2 hours. However, this mod absolutely requires an ECU tune to adjust fuel delivery and ignition timing for the higher boost levels. Running a smaller pulley without a tune risks detonation and engine damage.

Potential Downsides

Increasing boost also increases heat and stress on the supercharger and engine internals. The Hellcat's forged rotating assembly can handle more power, but heat soak becomes a concern on hot days. Many owners pair the pulley upgrade with a larger heat exchanger or an ice tank to keep intake air temperatures in check. Additionally, higher boost may require upgrading the fuel system if you target the upper limits.

A common upgrade is to go from the stock 2.70-inch supercharger pulley to a 2.62- or 2.50-inch unit. The 2.62-inch pulley is a safe choice for daily drivers running 93 octane fuel, while the 2.50-inch pulley is better suited for race gas or E85. Always verify that your tuner recommends the specific pulley size and have the tune ready before you install it.

  • Significant boost increase: Adds 2–4 psi of supercharger pressure
  • Relatively simple swap: Requires a pulley puller but no major disassembly
  • Requires a tune: Mandatory to ensure safe air-fuel ratios and ignition timing
  • Heat management needed: Larger heat exchanger recommended for sustained performance

5. Performance Spark Plugs

While often overlooked, spark plugs play a vital role in the efficiency and power output of a supercharged engine. The Hellcat comes from the factory with iridium-tip spark plugs that are gapped to .030 inch. Under higher boost and more aggressive timing from an ECU tune, the standard gap can cause misfires or weak combustion. Performance spark plugs, such as those from NGK or Denso, feature a finer electrode and a tighter gap to ensure reliable ignition under extreme conditions.

Gains and Real-World Benefits

Swapping plugs alone will not net a large horsepower increase—perhaps 5–10 pound-feet of torque in the midrange—but the real benefit is reliability. Properly gapped platinum or iridium plugs reduce the risk of misfires, especially at high RPM, and help maintain consistent combustion under heavy load. This mod is also an enabler for other performance upgrades; if you plan to tune the car or run a smaller pulley, fresh performance plugs are almost mandatory.

Installation Time and Difficulty

Replacing spark plugs on the Hellcat V8 is more involved than a typical four-cylinder, but it's still a DIY-friendly job. You'll need to remove the supercharger inlet tube and possibly the strut tower brace to access the passenger-side plugs. The driver side is easier. Total time is about 1–1.5 hours for a first-timer. Make sure you use a torque wrench to tighten them to the factory spec (approximately 18 lb-ft).

The two most popular choices are NGK LFR7AIX (iridium) and Denso IKH24 (iridium). Both are pre-gapped from the factory to .028–.030 inch, which is ideal for the Hellcat's boosted application. Some tuners recommend a tighter gap of .026 inch for cars running higher boost. Always check the gap before installation, even if they are labeled as pre-gapped.

  • Improved combustion efficiency: Better spark guarantees complete fuel burn
  • Enhanced reliability: Reduces misfires under high boost and high RPM
  • Enabling mod: Needed for safe operation of ECU tune and pulley upgrade
  • Simple process: Can be done in under two hours with basic tools

Putting It All Together: Order of Mods and Tips

If you plan to do multiple mods, the optimal order is: cold air intake → performance spark plugs → exhaust → supercharger pulley → ECU tune. Installing the spark plugs and intake first ensures the engine is breathing well and igniting cleanly before you add boost and a tune. The exhaust can be done at any point before the tune, but many tuners prefer that you have all hardware in place so they can calibrate the fuel and timing maps accordingly.

Consider investing in a wideband oxygen sensor gauge to monitor air-fuel ratios, especially after adding the pulley and tune. This provides peace of mind and helps prevent tuning mishaps. Also, keep in mind that the factory transmission and drivetrain have their limits. Beyond 800 wheel horsepower, you may need to upgrade the driveshaft, axles, or torque converter for reliability.

Final Thoughts

These five modifications offer the best power-per-hour investment for the Dodge Charger Hellcat. Whether you pick one or all five, each upgrade is designed for quick installation with basic tools, letting you get back on the road faster. The cold air intake and performance exhaust are excellent starting points for immediate gains and sound. Adding a tune and supercharger pulley will unlock the car's true potential, while fresh spark plugs keep everything running safely under the added stress. With a weekend's worth of work, you can transform an already ferocious sedan into a genuine street monster that rivals purpose-built sports cars.