The Jeep Grand Cherokee SRT is already a formidable machine, blending everyday luxury with track-ready performance. Yet for many owners, the desire to unlock more power is irresistible. With a modest budget of around $1,200, you can realistically add over 50 horsepower through a combination of smart, bolt-on upgrades and software tuning. This guide details the five most effective modifications to achieve that goal while maintaining reliability and daily drivability. Each upgrade has been chosen for its impact per dollar, ease of installation, and compatibility with the 6.4L HEMI V8 found in 2012–2023 SRT models.

1. Cold Air Intake System

Replacing the restrictive factory airbox with a cold air intake system is the most straightforward way to improve airflow. The stock intake is designed for noise suppression and cost efficiency, not maximum performance. A quality aftermarket intake uses a larger, less restrictive filter and a smooth mandrel-bent tube to deliver cooler, denser air directly to the engine. This can yield gains of 10–15 horsepower on the Grand Cherokee SRT, depending on the brand and ambient conditions.

Look for systems that include a heat shield to isolate the filter from engine bay heat. Brands like K&N, aFe, and Volant offer direct-fit kits with washable filters that last the life of the vehicle. Installation typically takes under an hour with basic hand tools, and no tuning is required. Beyond horsepower, you’ll notice sharper throttle response and a more aggressive intake growl when you step on the gas.

Cost for a premium cold air intake ranges from $300 to $450. Combined with proper maintenance, this upgrade provides a strong foundation for all subsequent modifications.

2. High-Performance Exhaust System

The factory exhaust on the Grand Cherokee SRT is designed to meet noise regulations and packaging constraints, which creates significant backpressure. Swapping to a cat-back or axle-back exhaust system reduces restriction, allowing the HEMI to exhale more freely. This alone can add 10–15 horsepower, but the real benefit comes when paired with other intake and tune upgrades.

Options range from full stainless steel cat-back systems (starting around $600) to modular axle-back sections that replace just the mufflers. Brands such as Borla, Corsa, and MagnaFlow produce systems specifically for the SRT. Look for mandrel-bent tubing and TIG-welded construction to ensure durability and consistent flow. Many systems also reduce weight by replacing heavy factory mufflers with lightweight performance chambers.

Expect to gain a deeper, more refined exhaust note without excessive drone. For maximum performance, consider pairing the exhaust with a set of aftermarket headers, though that would exceed the $1,200 budget and require tuning. Within the budget, a quality cat-back is the sweet spot.

3. ECU Tune (Performance Calibration)

An ECU tune is arguably the single most impactful upgrade for the money. The factory engine control unit leaves significant power on the table due to conservative timing, lean air-fuel ratios, and torque management limits. A custom or handheld tuner recalibrates these parameters to match your specific modifications and fuel quality. Gains of 20–30 horsepower are common on the 6.4L HEMI with just a tune alone.

Handheld devices like the DiabloSport i3 or HP Tuners interface allow you to flash a tune in minutes. Many tuners offer pre-loaded “canned” tunes for stock vehicles or for those with intake and exhaust upgrades. For the best results within the $1,200 budget, you can also purchase a custom remote tuning session from respected specialists like Hemifever or Flyin Ryan Performance. These tunes are tailored specifically to your vehicle and often include optimizations for fuel economy, transmission shift firmness, and throttle mapping.

Cost for a handheld tuner ranges from $300 to $500. Custom tuning adds another $150–$300 but is highly recommended if you have multiple bolt-on parts. A tune also allows you to raise the speed limiter and remove torque management for a more aggressive launch feel.

4. Upgraded Fuel Injectors

Once you increase airflow and modify the engine calibration, the stock fuel injectors can become a bottleneck. The 6.4L HEMI in the SRT uses injectors rated around 36 lb/hr. For moderate power gains (50–60 HP), these are generally sufficient. However, if you plan to run higher ethanol blends like E85 or push past 500 horsepower at the crank, upgrading to larger fuel injectors is essential.

Injectors in the 42–52 lb/hr range from reputable manufacturers like FiveO Motorsport or Injector Dynamics provide ample headroom. They also improve fuel atomization, leading to more complete combustion and reduced carbon buildup. Installation is straightforward on the HEMI: remove the fuel rail, swap injectors, and reinstall. The tune must be updated to account for the increased flow rate, which is why this upgrade is often done in conjunction with step 3.

Budget $250–$400 for a set of six high-performance injectors. Combined with the intake and exhaust, these injectors ensure your engine gets the fuel it needs at high RPM without leaning out. For the $1,200 total budget, many builders will allocate funds for a set of injectors and a tune, skipping a more expensive exhaust.

5. Performance Spark Plugs

While spark plugs are a maintenance item, upgrading to performance spark plugs can improve ignition reliability under the higher cylinder pressures created by other modifications. The factory plugs are adequate for stock power, but when you add intake, exhaust, and a tune, the spark quality becomes more critical. Plugs with a fine-wire iridium or platinum tip offer improved spark propagation and longevity.

Popular choices for the 6.4L HEMI include NGK Laser Iridium (part number 6510) or Denso Iridium TT. These plugs feature a tapered ground electrode that requires less voltage to fire, reducing misfire risk at high RPM. They are also pre-gapped and designed for high-performance applications. Replacing plugs is a DIY-friendly job on the SRT, taking about an hour with a spark plug socket and extension.

Cost is minimal: roughly $60–$80 for a complete set of six. While the horsepower gain from plugs alone is negligible (1–2 HP), they ensure that the other upgrades deliver full potential. Combined with the other four modifications, this small investment in ignition reliability helps maintain consistent power across the rev range.

Bringing It All Together: A $1,200 Power Package

To stay within the $1,200 budget, here's a realistic combination that yields over 50 horsepower:

  • Cold air intake – $350
  • Axle-back exhaust – $500 (or cat-back if you find a deal)
  • Handheld tuner + custom tune – $450
  • Performance spark plugs – $80
  • Total: $1,380 (slightly over, but you can substitute a less expensive intake or skip the custom tune for a canned tune to hit $1,200)

If you’re handy, you can install everything yourself, saving labor costs. This setup will push your Grand Cherokee SRT from the factory 475 horsepower to well over 525–530 at the crank, with a corresponding increase in torque. The vehicle will feel noticeably quicker, especially in mid-range punch and top-end pull.

For those wanting the most reliable 50+ HP gain per dollar, prioritize the tune and intake. The exhaust and plugs round out the package. Always perform these upgrades on a healthy engine with fresh oil and coolant. Regular maintenance ensures the parts work as intended.

Additional Considerations & Pro Tips

Before purchasing, research whether your specific model year (especially 2012–2015 vs 2016+) requires different calibration strategies. The 2018+ Grand Cherokee SRT Trackhawk has a supercharged 6.2L, so these upgrades apply specifically to the naturally aspirated 6.4L SRT. Verify that any tuner you buy supports your ECU’s protocol (DiabloSport and HP Tuners cover most years).

Also consider a portable wideband O2 gauge (around $200) if you plan to do custom tuning. It allows you to monitor air-fuel ratios in real-time, ensuring safe operation. While not mandatory, it adds peace of mind when pushing the limits.

Finally, upgrade your vehicle’s cooling system if you track the SRT. The factory heat exchanger can be overwhelmed with repeated high-load runs. For street use, the upgrades listed are perfectly adequate.

Conclusion

Increasing the horsepower of your Grand Cherokee SRT by over 50 HP on a $1,200 budget is entirely achievable with the five upgrades outlined above. A cold air intake, performance exhaust, ECU tune, larger fuel injectors, and improved spark plugs work synergistically to unlock the 6.4L HEMI’s true potential. Each component has been proven on countless builds and is available from reputable suppliers. With basic mechanical skills and a weekend of work, you can transform your daily driver into a more exhilarating performance SUV—without breaking the bank or compromising reliability.