Choosing the right turbo for your diesel truck is one of the most important decisions you can make when upgrading your engine. Whether you’re looking for more power, better towing performance, or improved efficiency, turbo selection directly impacts how your truck performs in real-world driving conditions.
The challenge many truck owners face is understanding how different turbo sizes, compressor maps, and housing designs affect power delivery, spool time, and overall drivability. Picking the wrong turbo can lead to excessive lag, poor fuel economy, or even engine damage. This guide breaks down everything you need to know about selecting the right turbo for your diesel truck.
Understanding The Role Of A Turbocharger
A turbocharger’s job is to provide (generally speaking) or increase (upgrade mindset) airflow into the engine, allowing it to utilize more fuel and generate more power. However, not all turbos perform the same way. The key factors that determine how a turbo behaves include compressor (intake side) and turbine (exhaust side) wheel sizes, housing dimensions, and airflow characteristics.
The size of the compressor wheel, measured by its inducer and exducer diameters, affects how much air the turbo can move and how efficiently it does so. A larger compressor wheel generally supports more power but takes longer to spool up, meaning there’s a delay in boost production. This is why selecting the correct size is crucial, as an oversized turbo can make a truck feel sluggish at lower RPMs.
Smaller turbos prioritize quick spool-up, making them ideal for towing and daily driving. When hauling a trailer, cattle, or equipment, you don’t want to wait for the boost—you need an instant response to maintain control and keep the power on tap. A smaller turbo achieves this by producing boost sooner, keeping power available in the RPM range where most towing happens.
On the other hand, larger turbos are designed for higher horsepower and torque output, typically at higher RPMs. These setups shine in performance applications where maximum airflow and power at the top end are the priority. However, they take longer to build boost, making them less responsive in low-RPM, heavy-load scenarios unless other modifications compensate for the slower spool.
That said, with the right supporting modifications, either turbo size can be adapted to different needs. Gear ratios, torque converters, camshaft profiles, and cylinder head work all play a role in shaping how a turbo performs. A well-matched setup can allow a larger turbo to behave more responsively, or a smaller turbo to deliver strong mid-to-high RPM power without excessive heat buildup. Choosing the correct combination is key to getting the performance you need without sacrificing drivability
How A/R Ratio and Turbo Size Impact Performance
One of the most misunderstood aspects of turbo selection is the A/R ratio, which refers to the area-to-radius ratio of the turbine housing. A smaller A/R ratio results in quicker spool time, making the truck more responsive at lower RPMs. A larger A/R ratio allows for greater exhaust flow at higher RPMs, supporting more horsepower but often increasing turbo lag.
A smaller turbine housing with a conservative A/R ratio is ideal for daily-driven trucks that need low-end response. On the other hand, trucks built for high-horsepower applications benefit from larger turbine housings that keep exhaust flow unrestricted at high RPMs.
For example, the BorgWarner S364/76/0.90 AR and S364/76/1.0 AR are the same turbo size but feature different exhaust housings. If you’re considering this turbo size for towing, you could opt for the larger A/R housing for increased exhaust flow—assuming you have supporting mods to compensate—or go with the smaller housing for quicker spool-up and better low-end response.
The type of driving you do should heavily influence your turbo choice. For a daily driver or work truck that sees a lot of stop-and-go traffic, quick spool time is essential. Smaller turbos or variable geometry turbos (VGTs) work well in these cases because they provide an instant boost without excessive lag.
If towing is a priority, a mid-sized turbo with a balanced A/R ratio offers a good mix of low-end torque and high-RPM efficiency, ensuring that the truck has enough power to handle heavy loads without excessive EGTs. Performance builds aiming for maximum horsepower often require large-frame single turbos or even compound turbo setups to deliver big power while maintaining some level of drivability.
A common mistake many truck owners make is assuming that a bigger turbo automatically means better performance. While a large turbo can produce high peak horsepower, it often comes at the cost of spool time and low-end response.
If the turbo is too large for the fuel system and airflow demands of the engine, it can lead to inefficiency, excessive EGTs, and poor drivability. Many trucks, especially daily-driven ones, benefit more from a properly sized turbo that optimizes power delivery across the entire RPM range rather than chasing high peak numbers.
On the flip side, if the turbo is too small for the engine's fuel system and airflow demands, it can work harder than intended, leading to overspeeding. When a turbo spins beyond its efficiency range, it can cause excessive heat, premature wear, or turbocharger failure. A smaller turbo may also struggle to keep EGTs in check under heavy loads, as it lacks the airflow capacity to efficiently clear exhaust gases. This is why selecting a properly matched turbo is crucial.
Popular Aftermarket Turbo Options
Cummins- For Cummins engines, Smeding Diesel offers a range of high-performance turbochargers, including their SX-E and drop-in replacement turbos, which provide excellent airflow and improved spool-up for both daily drivers and high-horsepower applications. Fleece Performance’s Cheetah series provides a drop-in VGT option with improved spool-up and better airflow, making it a great choice for daily-driven trucks. Fleece also offers options for 2nd and 3rd Gen 5.9's that don't utilize a factory Variable Geometry Turbo (VGT) with more drop-in ready non-VGT offerings.
BD Diesel’s Screamer turbo is another solid upgrade, delivering increased airflow while maintaining good drivability. Industrial Injection’s Phatshaft and Silver Series turbos are well-regarded for their durability and towing performance, while ATS’s Aurora 3000 and 4000 turbos are designed to enhance throttle response and low-end power.
Duramax—Duramax owners have several solid turbo upgrades to choose from. Industrial Injection offers a variety of performance turbos, including drop-in replacements and larger frame options for higher-power builds. Fleece Performance’s Cheetah series provides a drop-in VGT upgrade with improved spool and flow, making it a great choice for those who want more power without sacrificing drivability.
Garrett’s PowerMax turbos deliver increased efficiency and airflow while maintaining a factory-like fit. Duramax Tuner offers Stealth turbos, designed to maximize performance while keeping a stock-like appearance. BD Diesel’s Screamer turbo is another excellent upgrade, providing better spool-up and increased power while maintaining drivability.
Smeding Diesel also produces high-quality turbochargers, with options for daily-driven trucks and high-performance applications. Whether you’re towing heavy or chasing bigger horsepower numbers, there’s no shortage of proven turbo upgrades for the Duramax platform.
Powerstroke- Powerstroke engines have a range of aftermarket turbo options tailored for different needs. KC Turbos offers several popular upgrades, including their Stage 1 and Stage 2 turbos for better spool and increased airflow, as well as their Whistler Series for those who want a more aggressive setup.
Garrett’s PowerMax turbo is a well-known drop-in replacement that improves efficiency and response. BD Diesel’s Thruster turbo provides a solid balance of performance and drivability, particularly for the 7.3L Powerstroke. H&S Motorsports offers turbos designed for performance, focusing on optimizing power and efficiency.
BD Diesel’s Screamer turbo is perfect for an upgraded option with quick spool and impressive power gains. Calibrated Power’s turbo options are engineered to enhance the overall driving experience, with solutions designed for various levels of power and performance. No Limit Fabrication also provides custom turbo kits that allow for high-horsepower applications while maintaining reliability.
Supporting Mods A Turbocharger Can Benefit From
When upgrading to a larger turbo, there are several optional upgrades you can consider to further improve turbo performance and spool-up. If your truck has a turbo that feels too big or is reacting slowly, these upgrades can help you optimize the setup and get the most out of your turbo.
Tuning Solutions: An ECM update is one of the best ways to improve turbo spool performance. A well-tuned ECU can adjust fueling and timing, reducing turbo lag and improving throttle response for quicker spool times. A properly updated tune for your specific turbo size and driving style is key to getting the most efficient performance.
Larger Injectors: Upgrading to larger injectors allows for more fuel to match the increased airflow of a larger turbo, helping to reduce turbo lag and improving overall throttle response. When appropriately sized, this ensures that your engine gets the right air-to-fuel ratio for smooth power delivery.
Upgraded Fuel System: A high-flow fuel system, including a larger lift pump, can help guarantee that fuel delivery matches the demands of a larger turbo setup. This upgrade can help prevent fuel starvation and reduce lag.
Torque Converter: A high-stall torque converter can help with quicker spool times by reducing the load on the engine and allowing it to reach higher RPMs faster. This is particularly helpful in eliminating turbo lag and improving overall performance.
Intake & Exhaust Mods: Upgrading to a high-flow cold air intake system and optimizing your exhaust (such as installing a larger downpipe or high-flow exhaust) can improve airflow, which allows your turbo to spool faster. The less restrictive the intake and exhaust, the quicker your turbo will be able to build boost.
Cylinder Head Mods: Porting your cylinder heads or upgrading to larger valves and heavier springs can help further reduce airflow restrictions. This is an optional upgrade, but it can significantly enhance spool time, especially with larger turbos that demand higher airflow.
These upgrades are all optional but can be a great way to improve turbo performance and reduce lag if you're dealing with a setup that feels sluggish or underwhelming. By maximizing fueling and airflow, you can ensure your turbo spools quicker and provide better overall performance.
Final Thoughts
Choosing the right turbocharger for your diesel truck is a balancing act. While larger turbos can unlock incredible power, it’s essential to consider how they’ll perform across the full range of driving conditions. Too big of a turbo can cause lag and poor drivability, while too small of a turbo might limit your top-end performance. The key is finding the right size for your needs and pairing it with supporting modifications to achieve smooth power delivery, quick spool-up, and optimal performance.
Ultimately, the goal is to match your turbo to the type of driving you do most often. Whether you're towing, daily driving, or building a performance monster, the right turbo combined with thoughtful upgrades like tuning, fuel system improvements, and intake/exhaust modifications can unlock a significant boost in power and efficiency without sacrificing drivability.