Understanding Cummins Turbocharger Upgrades: A Comprehensive Guide

Upgrading the turbocharger on your 5.9L or 6.7L Cummins engine is one of the most impactful modifications you can make. A properly sized turbo increases airflow into the engine, allowing more fuel to be burned efficiently, which directly translates to higher horsepower and torque while improving exhaust gas temperature (EGT) management. However, choosing the right turbo isn't just about peak power numbers—it's about matching the boost characteristics to your specific driving needs, whether that's daily commuting, heavy towing, or competitive sled pulling.

The 5.9L and 6.7L Cummins engines have different factory turbo setups, fuel systems, and bottom ends, which means a turbo that works perfectly on a 5.9L may not be ideal for a 6.7L without modifications. In this guide, we'll break down the top five turbo upgrades on the market, explain their strengths and trade-offs, and help you decide which one delivers the maximum power for your application.

Key Considerations Before Upgrading Your Turbo

Before diving into specific turbo models, it's essential to understand a few foundational concepts. The turbocharger's compressor and turbine sizes determine how it performs across the engine's RPM range. A larger turbo can flow more air at high RPM but will spool slower (lag), while a smaller turbo spools quickly but may choke at higher boost levels. For a Cummins engine, the ideal turbo provides quick spool for responsive low-end torque (critical for towing) while still having enough top-end flow to support high horsepower goals.

Other factors to consider include your fuel injector size, the condition of your lift pump, and whether you plan to use performance tuning (a tuner or custom ECM flash). The turbo must be matched to the fuel system: too much airflow without enough fuel can cause lean conditions and high EGTs, while too little airflow with high fuel delivery leads to excessive smoke and potential engine damage.

We've curated a list of five proven turbo upgrades that cover a wide range of power goals, from mild 400 hp street builds to 800+ hp competition setups. Each turbo has been tested extensively in the diesel performance community.

1. BorgWarner S300SXE Turbo

The BorgWarner S300SXE series has become a staple in the Cummins performance world. Known for its robust construction and advanced SXE (Superior Extended Range) aerodynamics, this turbo family offers excellent efficiency across a broad operating range. The S300SXE uses a billet compressor wheel with a patented "extended tip" design that improves airflow and reduces backpressure compared to earlier S300 models.

  • Benefits: Increased airflow (up to 75 lb/min on larger variants), reduced spool time thanks to the efficient turbine housing, and excellent durability even at sustained high boost levels (35-50 psi typical). The SXE line includes multiple trim options (such as 62mm, 63mm, and 66mm compressor wheels) so you can tailor flow to your specific injector and fuel setup.
  • Compatibility: Fits both 5.9L and 6.7L Cummins engines with the appropriate adapter plate or T4/T6 turbine housing. Some models require a modified exhaust downpipe. We recommend checking exact measurements for your chassis.
  • Ideal Use: Great for street-driven trucks that see light towing, daily commuting, and occasional spirited driving. The S300SXE 62mm is a popular "daily driver" choice that can support 500-550 hp with supporting mods, while the larger 66mm variant works well for 600-650 hp builds.
  • Spool Characteristics: The S300SXE spools noticeably faster than older S300 models due to the SXE wheel design. In a 5.9L Common Rail engine, you can expect full boost by 2200-2400 RPM depending on turbine housing size.

For those looking to push beyond 700 hp, the BorgWarner S400SXE series is also available, but the S300SXE remains the sweet spot for most enthusiasts. You can learn more about BorgWarner's SXE technology on their official site: BorgWarner Turbo Systems.

2. Holset HE351CW Turbo

The Holset HE351CW is the factory turbo found on many 2007.5-2010 6.7L Cummins trucks, but it also fits earlier 5.9L engines with minor modifications. While stock turbos are often replaced for more power, the HE351CW can actually be upgraded to flow more than its factory rating. Many diesel enthusiasts use this turbo as a "budget upgrade" because it can be sourced used for a fraction of the cost of aftermarket units.

  • Benefits: Excellent low-end torque and quick spool-up due to its compact turbine housing. The HE351CW has a 60mm compressor wheel (inducer) and a 9-blade turbine design that provides good response. With a simple boost elbow adjustment and exhaust brake compatibility, it's very streetable.
  • Compatibility: Designed primarily for the 6.7L Cummins, but with the correct T3 flange adapter, it can be used on 5.9L 24V engines (both VP44 and Common Rail). Note that the 5.9L exhaust manifold configuration may require a spacer or different turbine housing.
  • Ideal Use: Perfect for daily driving and moderate towing demands up to around 450-500 hp. The HE351CW is not intended for high-rpm racing; it's optimized for spool and low-end grunt. Many truck owners pair it with a mild tuner (like a Smarty or EFI Live) to wake up the 6.7L without sacrificing reliability.
  • Limitations: On higher fuel systems (over 500 hp), the HE351CW will become a restriction, causing high drive pressure and elevated EGTs. It also tends to run hot at high boost levels (above 38 psi) for sustained periods.

If you're building a budget-minded street truck or work truck that still needs towing power, the Holset HE351CW is a solid choice. For detailed installation guides, check out Holset's official resources or aftermarket forums like TurboDieselRegister.

3. Fleece Performance Cheetah Turbo

Fleece Performance Engineering is a well-known name in the diesel aftermarket, and their Cheetah turbo line is legendary among enthusiasts who want to push boundaries. The Cheetah uses a proprietary billet compressor wheel and a custom turbine housing designed to reduce backpressure while maximizing flow. It's available in multiple sizes (62mm, 66mm, 72mm, and even 80mm) to suit anything from a street sleeper to a competition sled puller.

  • Benefits: High horsepower potential (some Cheetah models are rated for 800+ hp), exceptional spool time for their size due to advanced aerodynamics, and a stainless steel exhaust housing that resists cracking under high heat loads. Fleece also offers optional ported or wastegated configurations for precise boost control.
  • Compatibility: Available for both 5.9L and 6.7L Cummins engines with T4 or T6 turbine inlet flanges. Fleece provides detailed fitment guides and often includes gaskets and hardware. The Cheetah is a direct bolt-on for many models, though a larger downpipe may be needed for the 66mm+ versions.
  • Ideal Use: Best suited for racing (drag or sled) and heavy towing applications where high horsepower and torque are required. The Cheetah is also popular in "compound turbo" setups. For a single turbo street application, the 62mm or 66mm Cheetah works well up to 650 hp with proper fueling and intercooling.
  • Performance Notes: The Cheetah's billet wheel design is more sensitive to debris and oil contamination than cast wheels, so a quality air filter and clean oil are essential. It also tends to whistle loudly at lower RPM—something many owners enjoy.

Fleece Performance offers a wealth of technical data on their sight: Fleece Performance Engineering. We recommend matching the Cheetah turbo to your injector size (e.g., 75% over injectors for the 66mm) to avoid excessive smoke.

4. Industrial Injection Silver 62 Turbo

Industrial Injection (II) has been a leader in diesel turbochargers for decades, and their Silver 62 turbo has earned a reputation for delivering substantial power gains without sacrificing reliability. The Silver 62 features a CNC-machined 62mm billet compressor wheel and a heavy-duty turbine wheel, all housed in a ported shroud compressor cover for better surge control.

  • Benefits: Enhanced throttle response due to its lightweight billet wheel and improved fuel efficiency compared to a stock turbo because of better compressor efficiency. The Silver 62 also runs cooler EGTs than many larger turbos when towing because of its efficient flow range.
  • Compatibility: Works with both 5.9L and 6.7L Cummins engines. Industrial Injection offers different turbine housing sizes (typically 1.0 or 1.10 A/R) to tailor spool characteristics. On the 6.7L, it bolts directly to the stock exhaust manifold with the included adapter. On the 5.9L, you may need a different turbine housing flange.
  • Ideal Use: Suitable for daily driving and occasional topping. The Silver 62 is an excellent upgrade for trucks that need to tow a trailer a few times a week but also want to have fun on weekends. It supports power levels up to around 500-550 hp with standard injectors and a tuner.
  • Build Quality: Industrial Injection uses premium bearing systems (journal or ball bearing depending on option) and balances each turbo on high-speed equipment. The result is a turbo that lasts longer than many competitors in demanding conditions.

One of the standout features of the Silver 62 is its ease of installation—the unit is designed to be a "drop-in" on most 6.7L trucks without major modifications. You can view application-specific data on Industrial Injection's website: Industrial Injection Turbo Systems.

5. Garrett PowerMax Turbo

Garrett Motion (formerly Honeywell Turbo Technologies) is a name that needs no introduction in the forced induction world. Their PowerMax turbocharger line is engineered specifically for diesel performance, using advanced GTX-R series compressor wheels and dual ball-bearing cartridges. The PowerMax turbos are known for their exceptional efficiency and quick spool, making them a favorite among high-performance diesel builders.

  • Benefits: High boost potential (capable of 50+ psi), excellent reliability thanks to the ball bearing core that reduces friction and improves oil flow, and a broad efficiency map that allows the turbo to perform well across a wide RPM range. Garrett's PowerMax also features a lightweight titanium turbine wheel on some models for reduced rotational inertia.
  • Compatibility: Fits both 5.9L and 6.7L Cummins engines with the appropriate T4 or T6 flange. Garrett specifies power ratings—e.g., the PowerMax 62mm is rated for 550-650 hp, while the 68mm can handle 800+ hp. Installation typically requires a custom intake tube and downpipe.
  • Ideal Use: Perfect for performance builds that demand maximum efficiency and quick response, such as daily drivers that also see track time or towing applications where driver control and low EGTs are paramount. The PowerMax is often used in high-end competition vehicles including drag racers and tuner trucks.
  • Technology: Garrett's "GTX-R" compressor wheel design uses extended tip technology for improved flow. The dual ball bearing center housing eliminates the need for a heavy thrust bearing, reducing oil consumption and allowing for faster spool.

The PowerMax is more expensive than many other options, but the performance and reliability justify the cost for serious enthusiasts. Visit the Garrett Motion website for detailed maps and tuning recommendations.

Selecting the Right Turbo for Your Specific Goals

Now that we've covered the five top candidates, let's discuss how to choose the best one for your unique situation. The best turbo for a daily-driven towing truck is different from the best turbo for a 2,500 rpm sled puller. Here's a checklist to help narrow down your choice:

Define Your Horsepower Target

Be realistic about power goals. A 500 hp truck requires different fuel and intercooling than a 700 hp truck. Choose a turbo that has room to grow but doesn't sacrifice drivability for a power number you may never hit. For example, the BorgWarner S300SXE 62mm is great for 400-500 hp street trucks. If you plan to run big injectors and a high-flow CP3 pump, step up to the Industrial Injection Silver 62 or a Fleece Cheetah 66mm.

Consider Your Driving Conditions

If you tow heavy loads regularly, prioritize low-end spool and EGT management. The Holset HE351CW or BorgWarner S300SXE (smaller housing) will provide quick response and keep exhaust temperatures in check. For racing or high-speed pulls, a larger turbo like the Fleece Cheetah 72mm or Garrett PowerMax 68mm will offer greater top-end flow even if it spools slightly later.

Review Supporting Modifications

An upgraded turbo without proper fueling is like a big straw in an empty cup. Ensure your fuel injectors, lift pump, and CP3/CP4 pump can deliver enough fuel to match the air the turbo provides. Also, upgrade your charge air cooler (intercooler) if it's stock, as increased boost will produce higher intake air temperatures. A larger downpipe and exhaust system (at least 4-inch) are also necessary to prevent backpressure.

Budget Considerations

Turbo prices range from $500 (used Holset HE351CW) to over $2,500 (Garrett PowerMax or Fleece Cheetah). Factor in installation costs if you're not doing it yourself, as well as the cost of supporting parts. A properly matched budget turbo can outperform a top-tier unit if the rest of the system is not optimized.

Installation Tips and Best Practices

When installing a new turbo on your Cummins, always follow these guidelines to ensure long life and optimal performance:

  1. Check oil supply and drain: Ensure the oil feed line is not restricted and the drain line flows freely. A blocked drain can cause oil to leak past the seals. Consider installing an oil restrictor if using a ball-bearing turbo.
  2. Prime the turbo before starting: Disconnect the fuel pump relay and crank the engine for 10 seconds to allow the turbo to get oil before it spins at high speed. This prevents dry start damage.
  3. Upgrade the intake: Use a high-flow air filter and larger intake tube (4-inch or larger) to reduce restriction and keep the turbo well-fed.
  4. Adjust boost and fueling: Work with a reputable tuner to dial in boost levels and fuel delivery. Over-boosting with a stock fuel system can cause smoke and high EGTs. A boost controller or boost elbow can help set peak boost.
  5. Monitor critical parameters: Install gauges for boost pressure, EGT, and transmission temperature. These are essential for tuning and protecting your engine.

Conclusion

Upgrading your Cummins turbocharger is one of the most effective ways to unlock serious power and efficiency improvements. Whether you choose the robust BorgWarner S300SXE, the budget-friendly Holset HE351CW, the high-performance Fleece Cheetah, the reliable Industrial Injection Silver 62, or the technologically advanced Garrett PowerMax, each turbo offers distinct advantages tailored to different driving styles and power goals.

Remember that the turbo is only one part of a complete system. To maximize the return on your investment, ensure your fuel system, intercooler, exhaust, and engine tuning are all aligned with your turbo choice. Always consult with diesel performance experts or a trusted builder before making a purchase, as they can provide specific recommendations based on your truck's year, configuration, and intended use. By selecting the right booster for your needs, you'll achieve maximum power while maintaining the everyday drivability that makes the Cummins platform legendary.