The BorgWarner S400 turbocharger is the workhorse behind more high-flow diesel builds than almost any other frame on the market. If you’re pushing a Cummins, Duramax, Powerstroke, or a Class 8 truck engine past its factory power ceiling, chances are an S400 is either already bolted on or on your short list. This is the turbo that bridges the gap between reliable OEM boost and serious 700-plus horsepower territory, and it does it with a T4 mount, a big compressor wheel, and airflow numbers that make smaller frames look like toys. Here’s the technical breakdown fleet mechanics and owner-operators actually need: what the S400 flows, where it fits, and how to spec one right the first time.
What Makes the S400 a High-Flow Frame
The S400 series is BorgWarner’s large-frame turbo built on a 3.5-inch (roughly 88mm) turbine housing bolt pattern with a T4 flange and a 5-inch V-band compressor outlet on most variants. It’s designed for engines in the 5.9L to 15L displacement range, which is why you’ll see it on everything from heavily modified 24-valve Cummins pickups to Detroit, Caterpillar, and Cummins ISX over-the-road trucks.
What separates the S400 from smaller S300 units is raw airflow capacity. Compressor wheels in the S400 family range from about 71mm inducer up to 83mm and beyond, supporting anywhere from roughly 55 lb/min to over 110 lb/min of airflow depending on the specific spec. That range covers a single-turbo street truck all the way to the atmosphere charger in a compound setup.
Common S400 designations you’ll run into:
- S400SX3 – 75mm inducer, popular single-turbo choice for 6.7L Cummins and Duramax builds
- S400SX4 – 75mm to 83mm inducers, higher flow, common in compound top-mount and big single applications
- S475 / S480 / S483 – shorthand naming based on inducer size, all sitting on the S400 frame
- S400 with SXE billet wheels – extended-tip billet compressor wheels for improved efficiency and spool
For a broader look at how BorgWarner positions this frame against its other lines, our Borg Warner Turbochargers Performance, Reliability and Fitment Guide covers the full lineup.
S400 Compressor Specs and Airflow Reference
Picking the right S400 comes down to matching the compressor wheel and turbine A/R to your target power and RPM band. Undersize it and you’ll choke top-end. Oversize it and you’ll lag badly and drown low-end torque. Here’s a practical reference for the most common single-turbo specs.
| Spec | Inducer | Approx. Max Airflow | Realistic HP (single) | Best Fit |
|---|---|---|---|---|
| S472 | 72mm | ~68 lb/min | 550-650 hp | Daily-driven 5.9/6.7 Cummins |
| S475 | 75mm | ~78 lb/min | 650-750 hp | Sled pull / heavy tow street truck |
| S480 | 80mm | ~90 lb/min | 750-850 hp | Race / large single builds |
| S483 | 83mm | ~100 lb/min | 850-950 hp | Competition, high-RPM |
Turbine housing A/R matters just as much. On the S400 you’ll commonly see 0.90, 1.00, 1.10, and 1.32 A/R T4 housings. A tighter 0.90 spools quicker and suits towing and street use, while a 1.10 or 1.32 opens up top-end for high-RPM competition engines at the cost of low-end response. For a tow rig, err tighter. For a dyno queen, go bigger.
S400 Fitment Across Diesel Platforms
Because the S400 rides on a standard T4 foot and V-band housings, it drops into a huge range of applications with the right manifold or mounting kit. Here’s where mechanics are running them:
Cummins 5.9L and 6.7L
The S400 is a favorite single-turbo swap for both the 12-valve and 24-valve 5.9L, and the 6.7L. It typically requires a T4 exhaust manifold and a 4-inch downpipe. On stock-appearing compound setups, the S400 serves as the atmosphere charger feeding a smaller high-pressure unit like an HX35 or Holset primary. If you’re weighing the smaller Cummins options first, our Cummins ISB 5.9L Turbocharger Guide: HX35 vs HE341VE is worth a read before you jump frames.
Duramax LB7 through L5P
S400 single-turbo kits are widely available for the Duramax, usually paired with a new up-pipe and downpipe setup. The 75mm to 80mm range hits the sweet spot for these engines when built for 700 to 850 horsepower.
Powerstroke 6.0L, 6.4L, and 6.7L
On the 6.4L, the S400 shows up frequently as a compound upgrade or single-turbo conversion. The factory 6.4L runs a sequential two-turbo arrangement, and understanding how that works before you swap is important. See our breakdown on the Ford 6.4L Powerstroke High-Pressure vs Low-Pressure Turbo difference.
Class 8 and Medium-Duty
Cummins ISX, Detroit Series 60, and CAT C-series engines use S400-frame turbos from the factory in many configurations. When these come as wastegated or actuator-controlled units, the actuator becomes a critical wear item. For medium-duty and bus applications running related Cummins hardware, our Cummins ISL HE400WG guide covers the wastegated side of that world.
Actuators and Wear Parts You’ll Need
Not every S400 is a free-floating open turbo. Many OEM S400-frame and closely related large-frame turbos use pneumatic actuators to control wastegates or variable geometry. When an actuator fails, you get overboost, underboost, or erratic boost control that throws codes and kills fuel economy. Swapping the actuator is far cheaper than replacing the entire turbo, and PT Turbo stocks the correct units.
For Garrett-based large-frame and VGT applications, the Garrett Pneumatic Actuator 757979-5102 is available from PT Turbo for $240.94. For heavier-duty Garrett units that demand a higher-capacity actuator, the Garrett Pneumatic Actuator 445963-0040 runs $465.52 and handles the larger diaphragm loads found on bigger commercial turbos.
On the Mitsubishi side, which shares service overlap with many light and medium-duty diesel turbos, the Mitsubishi TD03 Pneumatic Actuator 49S3118761 is $104.33, and the Mitsubishi Pneumatic Actuator 4918918935 comes in at $83.99. Keep the right actuator on the shelf and you avoid a downpipe-off disaster becoming a week-long parts wait.
New vs Remanufactured S400: What’s Right for Your Build
A brand-new BorgWarner S400 is the obvious call for a competition build where you want the latest billet wheel technology and zero unknowns. But for a fleet truck, a work rig, or a replacement on a proven combination, a quality remanufactured unit saves real money and delivers the same reliability when it’s done right. PT Turbo has been rebuilding turbos to OEM tolerances for over 45 years, and every reman unit is balanced, tested, and backed.
| Factor | New S400 | Remanufactured S400 |
|---|---|---|
| Typical cost | $1,400 – $2,400+ | 30-50% less than new |
| Lead time | Often in stock | Often in stock or fast rebuild |
| Latest billet wheel tech | Yes | Depends on core |
| Best for | Race, max power, new builds | Fleet, work trucks, replacements |
| Warranty backing | Manufacturer | PT Turbo tested and warranted |
Browse available options on our remanufactured turbochargers page, or if you’ve got a good core, our turbocharger rebuild service can restore your existing S400 to spec with new bearings, seals, and a balanced CHRA.
Installation and Setup Tips That Save Turbos
An S400 will outlive the truck if you install it right. The failures we see on the bench almost always trace back to a handful of avoidable mistakes.
- Prime the bearings. Before first start, pre-fill the oil inlet and spin the shaft by hand. Dry startups kill journal bearings fast.
- Check your oil drain. The S400 needs a large, unrestricted, downhill oil return to the pan above the oil level. Restricted drains push oil past the seals every time.
- Clock the housings correctly. With V-band housings you have freedom to clock the compressor and turbine. Get the oil drain vertical and clear your other components before final torque.
- Match the downpipe. A 4-inch minimum downpipe keeps backpress
Cross-Reference & Superseded Part Numbers
The turbochargers covered in this article match or supersede the following OEM and manufacturer part numbers. If you are searching by part number, these are the units stocked by PT Turbo for this application:
14969880029 • 167735 • 167736 • 169011 • 169012 • 171699 • 171701 • 171701BW • 171702 • 171702BW • 171703 • 171923 • 171924 • 171925 • 171926 • 171933 • 173044 • 173385 • 174215 • 174827 • 174828 • 174829 • 174830 • 174832 • 174833 • 174834 • 176140 • 176141 • 176651 • 176652 • 176653 • 176654 • 176655 • 176656 • 176806 • 176807 • 177101 • 177248 • 177249 • 177285 • 177286 • 177287 • 177288 • 178164 • 178193 • 178194 • 178247 • 178370 • 178781 • 178782 • 178923 • 179172 • 179175 • 179179 • 179183 • 179352 • 179589 • 179600 • 316686 • 316699 • 316700 • 317943 • 317950 • 318096 • 318293 • 318295 • 318714 • 318715 • 319192 • 319193 • 319460 • 319494 • 474827 • 474828 • 474829 • 474830 • 474832 • 474833 • 474834 • 477285 • 477286 • 477287 • 477288 • 478164 • 479514-RMN • 53047109901-BILLET • 53047109904-BILLET • 56407100002 • 56409880016 • 56409880017 • A4720901480-RMN • NEW-FTR-TWN-TRB • RMN-BRG-V2S-TWN • RMN-BRG-V2S-TWN-GR-TO • RMN-BRG-V2S-TWN-NO
Can’t find your number above? Contact PT Turbo — our team has been matching part numbers since 1978.
Further reading: Learn more about BorgWarner.
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