S400 Turbo Guide: Sizes, Specs, Flanges & Fitment

The S400 turbo is the workhorse of the big-power diesel and drag racing world. It is BorgWarner's 400-frame turbocharger family — the platform behind most 1,000+ horsepower Cummins, Duramax, and Power Stroke builds, and the size class that defines what "big single" means in the diesel performance market.

This guide covers what an S400 actually is, how the sizes are named, what separates a T4 from a T6, and exactly which flanges, clamps, housings, and drains you need to make one bolt to your build. Black Sheep Industries manufactures S400 fitment hardware in-house and builds the True North Turbos TNT4R 400-frame turbocharger line in Canada.

What Is an S400 Turbo?

"S400" refers to BorgWarner's 400-frame turbocharger series — most commonly sold today as the S400SX and S400SX-E. The number does not describe the compressor size. It describes the frame: the center housing rotating assembly (CHRA), bearing system, and the physical envelope the compressor and turbine wheels live in.

Within that one frame, manufacturers offer a wide range of compressor wheels. That is why you will see S464, S467, S472, S475, S476, S480, S483, S485, and S488 — all of them are S400-frame turbos, and all of them share the same core architecture, oil feed and drain geometry, and mounting hardware.

The S400 originated in heavy-duty commercial diesel applications — Detroit Diesel, Cummins ISX, and similar over-the-road engines — before the performance aftermarket adopted it as the default single-turbo upgrade for high-horsepower builds.

What Does the Number After "S4" Mean?

The two digits following the frame designation refer to the compressor wheel inducer diameter in millimetres. An S467 has a 67mm compressor inducer. An S480 has an 80mm inducer. An S488 has an 88mm inducer.

Larger inducer means more airflow and more horsepower potential — but also more rotational mass, later spool, and higher exhaust energy required to get the wheel moving. Sizing an S400 is a trade between how much power you want and how early you want it.

S400 Turbo Sizes and Power Ranges

Every S400 uses the same frame, so stepping up in size does not change your mounting hardware — only the airflow. Here is how the common sizes map to real-world power on a well-built diesel:

Size Compressor Inducer Typical Application Approx. Power Range
S464 / S467 64–67mm Street, towing, sled pull entry, first big single 700–850 WHP
S472 72mm Street/strip, compound top charger 850–950 WHP
S475 / S476 75–76mm The most popular all-around S400 size 950–1,050 WHP
S480 80mm Serious drag and pulling builds 1,050–1,200 WHP
S483 / S485 83–85mm Dedicated race, large-displacement 1,200–1,300 WHP
S488 88mm Top of the 400 frame 1,200–1,400 WHP

Power figures are directional and depend heavily on displacement, fuel system, head studs, tune, and turbine housing selection. A 6.7L Cummins and a 5.9L will not make identical numbers on the same turbo.

Above 88mm you leave the 400 frame entirely and move into 500-frame territory — see the TNT5R 500-frame turbochargers for 92mm and larger.

Shop S400-Frame Turbochargers

S300 vs S400: What Is the Difference?

This is the most common question builders ask before committing to a manifold and downpipe, and the answer matters because the two frames are not interchangeable.

  • Frame size. The S300 is a smaller 300-frame turbo, typically 57–66mm on the compressor. The S400 is physically larger in every dimension.
  • Power ceiling. An S300 generally tops out around 600–700 WHP. An S400 starts near there and runs to 1,400 WHP.
  • Spool. The S300 spools noticeably earlier, which is why it remains the better choice for towing and daily driving.
  • Mounting. Different turbine flange footprints, different exhaust outlets, different oil drain sizes. Moving from S300 to S400 means new manifold, new downpipe hardware, and new drain fittings.
  • Compound setups. Many high-power builds run both — an S400 as the atmospheric charger feeding an S300 or stock-frame turbo.

If your target is under 700 WHP and the truck tows, an S300 is usually the smarter pick. If you are chasing four-digit power, the S400 frame is where you start.

S400 T4 vs T6: Choosing a Turbine Flange

The turbine inlet flange determines how the turbo mounts to your exhaust manifold. S400 turbos are available in both, and the choice affects manifold selection, flow capacity, and downpipe hardware.

T4 Flange

  • The most common S400 mounting standard, available divided or undivided
  • Wider manifold availability across Cummins, Duramax, and Power Stroke platforms
  • Uses a 4.62" half-marmon exhaust outlet
  • Ideal for street/strip builds up to roughly 1,100 WHP

T6 Flange

  • Larger flange footprint with more turbine inlet area
  • Better flow at high power, less prone to cracking under heavy load
  • Uses a 5.75" marmon exhaust outlet
  • Preferred for 1,100+ WHP, sled pulling, and dedicated race applications

Neither flange changes the compressor or the power the turbo can make on its own. It changes the manifold you need and how much turbine-side restriction you carry at high flow. Pick based on your manifold and your power target, not on size alone.

S400 Flanges, Clamps, and Fitment Hardware

This is where most S400 swaps stall. The turbo bolts up, and then the downpipe, the compressor outlet, and the oil drain all need parts that are not in the box. Black Sheep Industries machines this hardware in-house so you are not sourcing four parts from four suppliers.

Exhaust Outlet — T6 Marmon (5.75")

S400 T6 turbos use a 5.75" marmon-style exhaust outlet. You need a matching downpipe flange and a quick-release clamp.

Exhaust Outlet — T4 Half Marmon (4.62")

S400 T4 turbos use a 4.62" half-marmon outlet. The same flange also fits Garrett G-Series 42 and 45 turbochargers.

Compressor Outlet Discharge

The compressor discharge on an S400 uses a V-band connection to your charge pipe. Sizing depends on your intercooler piping.

Full breakdown, with measuring instructions and a complete SKU table: S400 Turbo Flange Guide — Marmon, Half Marmon and V-Band Fitment

Oil Drain

S400 drain flanges are sized by the bolt circle on the turbo's center housing drain pad — commonly 35mm, 65mm, or 100mm. Measure your center housing before ordering; the millimetre figure does not refer to the port size. For large-frame turbos, run a 12AN port rather than 10AN.

Undersized or restrictive drains are one of the most common causes of turbo seal failure on big singles — oil has to leave the center section by gravity, and a restricted return will push it past the seals.

Full breakdown, with routing rules and a leak diagnosis table: S400 Turbo Oil Drain Guide — Sizing, Routing and Why Turbos Leak

Complete Fitment Checklist

  • Turbine inlet: T4 or T6 manifold to match your turbo
  • Exhaust outlet: 5.75" marmon flange + clamp (T6) or 4.62" half marmon flange + clamp (T4)
  • Compressor discharge: V-band flange + clamp sized to your charge pipe
  • Oil feed line and restrictor appropriate to your bearing type
  • Oil drain flange matched to your center housing bolt circle (35mm, 65mm, or 100mm), 12AN drain hose, and return fitting
  • External wastegate and dump tube if running a divided or open housing
  • Turbo blanket for underhood heat management
  • Turbine and compressor housing gaskets — see replacement o-rings and gaskets

S400 Turbine Housings and A/R

Turbine housing selection has as much effect on how an S400 drives as compressor size does. The A/R ratio controls exhaust gas velocity into the turbine wheel: a smaller A/R spools earlier but restricts at high RPM, a larger A/R gives up low-end response for top-end flow.

Common S400 turbine wheel and housing combinations include 83/74, 87/82, 96/88, and 103/92, in A/R ratios from roughly 0.90 to 1.45.

Picking an A/R

  • 0.90–1.00: Earliest spool. Street trucks, towing-adjacent builds, sled pulling where response off the line matters.
  • 1.10–1.25: The balanced middle. Most street/strip S400 builds land here.
  • 1.32–1.45: Top-end flow. Drag racing and high-RPM applications where you can afford the lag.

S400 Turbos by Platform

Cummins 5.9L and 6.7L

The 5.9L 12v and 24v Cummins and the 6.7L are the most common S400 hosts. A T4 S467 through S476 is the standard first big single on a built 5.9L; 6.7L builds chasing four digits typically run T6 S480 and up. Both require an aftermarket T4 or T6 manifold and full drain hardware.

See also: 6.7 Cummins Turbo Upgrades

Duramax LBZ, LMM, LML, and L5P

Duramax S400 swaps almost always use a T4 or T6 kit with a dedicated manifold and up-pipe setup. Because the Duramax retains a valley-mounted turbo location, S400 conversions require more fabrication than a Cummins swap — plan for a full kit, not just a turbo.

See also: 6.6L L5P / L5D Duramax Turbo Upgrades

Power Stroke 6.0L, 6.4L, 6.7L, and 7.3L

The 6.0L Power Stroke is a very common S400 platform — the factory VGT is a known weak point, and an S400 conversion kit is a durability upgrade as much as a power upgrade. 7.3L builds typically pair an S400 with an intercooler and fuel system upgrade to see the benefit.

Compound Setups

An S400 is frequently used as the atmospheric (low-pressure) charger in a compound arrangement, feeding a smaller S300 or factory-frame turbo. This preserves low-end response while giving you the airflow ceiling of the 400 frame — the standard approach for trucks that need to tow and race.

Choosing the Right S400 for Your Build

First Big Single, Street Driven

S467 or S472 on a T4 flange with a 0.90–1.10 A/R. You give up some peak power for spool you can actually use on the street.

Street/Strip, 1,000 WHP Target

S476 on T4 or T6, 1.10–1.25 A/R. This is the most common configuration in the diesel performance market for a reason — it does everything reasonably well.

Drag and Pulling, 1,200+ WHP

S480 through S488 on a T6 flange, 1.25–1.45 A/R. Fuel system, head studs, and a built transmission are prerequisites, not options.

Compound Top Charger

S472 through S480 depending on the bottom charger. Match the S400 to the manifold pressure your high-pressure turbo will actually see.

Not sure? Send us your build details through the Turbo Spec Form and we will spec it with you.

Why Buy S400 Hardware From Black Sheep Industries

  • S400 flanges, clamps, and drains machined in-house — not resold imports
  • Flange and clamp sold together so fitment is right the first time
  • 304 stainless and aluminum options for every major flange
  • True North Turbos 400-frame turbochargers designed, assembled, and balanced in Canada
  • Priced in CAD with US customs and duties covered
  • Direct support from people who build these setups, not a call centre

S400 Turbo Resources

Frequently Asked Questions

What is an S400 turbo?

An S400 turbo is a BorgWarner 400-frame turbocharger. The designation refers to the frame size — the center housing, bearing system, and physical envelope — not the compressor wheel. S464, S467, S472, S476, S480, S485, and S488 are all S400-frame turbos with different compressor wheels.

How big is an S400 turbo?

The number after S4 is the compressor inducer diameter in millimetres. S400-frame turbos commonly range from 64mm to 88mm on the compressor. All of them share the same frame, oil drain geometry, and mounting hardware regardless of compressor size.

How much horsepower can an S400 turbo support?

Depending on compressor size, an S400 typically supports 700 to 1,400 wheel horsepower. An S467 sits near the bottom of that range and an S488 at the top. Actual output depends on displacement, fuel system, tune, and turbine housing selection.

What is the difference between an S300 and an S400 turbo?

The S300 is a smaller 300-frame turbo that generally supports up to 600–700 WHP and spools noticeably earlier. The S400 is a larger 400-frame turbo supporting 700 to 1,400 WHP. They use different turbine flanges, exhaust outlets, and oil drain sizes, so they are not interchangeable without changing hardware.

What size downpipe flange does an S400 use?

S400 T6 turbos use a 5.75" marmon exhaust outlet. S400 T4 turbos use a 4.62" half-marmon outlet. Both require a matching flange and quick-release clamp, which Black Sheep Industries sells together as a set.

What size oil drain does an S400 turbo need?

S400 drain flanges are specified by the bolt circle on the turbo's center housing drain pad — commonly 35mm, 65mm, or 100mm. Measure yours before ordering. For large-frame turbos use a 12AN port rather than 10AN, because a restricted gravity drain is a leading cause of oil pushing past the center section seals.

Should I run a T4 or T6 S400?

T4 is the more common standard with wider manifold availability and works well up to roughly 1,100 WHP. T6 offers a larger flange footprint and better flow at high power, and is preferred for 1,100+ WHP, sled pulling, and dedicated race builds.

Will an S400 work as a compound turbo?

Yes. S400-frame turbos are commonly used as the atmospheric charger in compound setups, feeding a smaller S300 or factory-frame high-pressure turbo. This preserves low-end response while providing the airflow ceiling of the 400 frame.