S475 Turbo

The S475 turbo sits at the centre of the BorgWarner S400 frame family — large enough to support serious power targets, yet balanced enough for trucks that see daily highway miles between track events. Whether you're building a 6.7 L Cummins street/strip truck or stepping up from a mid-frame S300, this guide covers everything you need to select the right 75 mm turbo configuration, match your housing A/R, confirm fitment dimensions, and avoid the installation surprises that trip up first-time S400 builders.

For a full overview of the S400 frame family and how all the inducer sizes compare, see our S400 turbo guide.

What Is an S475 Turbo?

An S475 turbo is an S400-frame turbocharger built around a 75 mm compressor inducer. The designation follows BorgWarner's straightforward S400 naming convention: "S4" identifies the frame family — the S400 series — and the two digits that follow indicate the compressor inducer diameter in millimetres. A 75 mm inducer means S475. A 72 mm inducer means S472. The logic is consistent across the lineup.

The S400 frame itself occupies the middle tier of BorgWarner's performance turbo hierarchy. It is a genuine step up from mid-frame S300 units in terms of flow capacity and physical size, while remaining more compact and accessible than the larger S500-series turbos used in purpose-built competition applications. For street/strip diesel trucks in the 1,000–1,200+ HP range, the S400 frame — and specifically the S475 configuration — is where most serious builders land.

When people refer to a Borg Warner S475, they are describing a turbocharger that uses the S400 centre housing and rotating assembly architecture, with a compressor wheel that measures 75 mm at the inducer. That 75 mm compressor is the defining characteristic of the S475 designation and the specification that separates it from every other size in the S400 family.

Is Every S475 a BorgWarner Turbo?

Not necessarily, and this distinction matters before you purchase. BorgWarner's OE compressor maps are the authoritative source for 75 mm inducer performance data — if you are working with published maps or spec sheets, BorgWarner's documentation is the reference standard.

However, the aftermarket for S400-frame turbos is substantial. Numerous suppliers produce centre housings, rotating assemblies, turbine wheels, and complete turbocharger units that use the same general S400 frame architecture. These aftermarket configurations may feature different cartridges, turbine wheel profiles, bearing systems, or compressor-wheel geometries that do not map directly onto BorgWarner OE data.

In practical terms, this means that when you see an S475 listed by an aftermarket supplier, the compressor inducer diameter should be 75 mm — but the compressor map, turbine wheel dimensions, and housing options should be verified against that specific supplier's specification sheet, not assumed to be identical to the BorgWarner OE configuration. If you are selecting a turbo for a specific power target and fuel strategy, confirming the complete specification of the unit you are purchasing is the right first step.

S475 Turbo Specs at a Glance

The table below summarises the core S475 turbo specs for the most common configurations. Specifications can and do vary by cartridge and aftermarket supplier. Treat these figures as a reference baseline, and confirm compressor-wheel dimensions, housing A/R, inlet flange, outlet configuration, and oil-drain specifications against the individual unit before purchasing.

Specification Common Value / Range
Compressor inducer diameter 75 mm (2.95")
Common turbine exducer — primary 96 mm (3.78")
Common turbine inducer — primary 88 mm (3.46")
Turbine exducer — alternate 92 mm (3.62")
Turbine inducer — alternate 83 mm (3.27")
Turbine housing A/R range (street/strip) 1.10 – 1.25
Common turbine inlet configurations T4 divided, T6 divided
Oil drain bolt centre 50.8 mm (2.00")
Oil drain port size 12AN
T4 exhaust outlet 117 mm / 4.62" half-marmon
T6 exhaust outlet 146 mm / 5.75" full-marmon
Supported power range 1,110 – 1,230 HP (crank)

Compressor Wheel Specifications

The 75 mm compressor inducer is the specification that defines the S475 designation. It is not a nominal or approximate figure — it is the measurement that distinguishes an S475 from an S472 on one side and an S476 or S480 on the other.

As a 75 mm turbo, the S475 generates a compressor map that sits noticeably above the 72 mm S472 in terms of peak flow capacity while remaining more responsive than an S480 in the lower and mid rpm ranges. This positioning makes the S475 turbo specs particularly relevant for high-output diesel builds where top-end airflow and acceptable street manners both matter.

It is worth restating: compressor-map data for aftermarket 75 mm wheels will not be identical across all suppliers. BorgWarner OE map data covers the original compressor wheel design. Aftermarket wheels of the same inducer diameter may have different exducer measurements, blade geometry, or trim specifications that shift the map. If compressor-map efficiency at a specific pressure ratio matters to your build, request the actual map from your supplier rather than relying on the OE published data as a substitute.

Common Turbine Wheel Combinations

The most widely used turbine wheel combination for the S475 pairs a 96 mm (3.78") exducer with an 88 mm (3.46") inducer. This is the primary configuration you will encounter in street/strip diesel builds and the combination most S475 housings are designed around.

A less common alternative uses a 92 mm (3.62") exducer paired with an 83 mm (3.27") inducer. The smaller turbine wheel reduces the swept area that exhaust gases must drive, which translates to quicker spool response under the same conditions. This configuration is typically selected for lighter vehicles or applications where spool time is weighted heavily in the build priorities, and where the modest reduction in peak turbine flow capacity is an acceptable trade-off.

The turbine wheel selection has a meaningful effect on spool behaviour and exhaust flow characteristics. Builders choosing between the two configurations should evaluate their engine displacement, manifold design, vehicle weight, and power target together — the turbine wheel is not an isolated variable.

Common Turbine Housing Options

For street and strip applications, S475 turbine housing A/R choices typically range across 1.10, 1.15, 1.18, and 1.25. These four values cover the meaningful range of exhaust-velocity and spool trade-offs for most diesel performance builds, and they are the options you will encounter most frequently from reputable suppliers.

Housing configurations are available in two primary turbine inlet formats:

T4 divided housings are the most widely available option for S475 builds. The T4 turbine inlet flange is a common standard in diesel performance, and T4 divided housings are produced by a broad range of suppliers with good manifold compatibility across Cummins, Power Stroke, and Duramax platforms.

T6 divided housings are used in higher-flow applications where maximum exhaust volume is required. T6 refers to the turbine inlet flange and housing configuration — a larger inlet geometry than T4 — and it becomes relevant as builds push toward the upper edge of the S475's supported power range.

It is important to be precise with terminology here. When builders talk about "bolt pattern" in the context of S400 turbine housings, they are specifically referring to the turbine inlet flange, inlet gasket, and turbine housing configuration — not the exhaust outlet. T4 and T6 describe inlet configurations, while the exhaust outlet dimensions (discussed in the fitment section below) are a separate measurement.

S475 Turbo Horsepower Range

The S475 turbo supports a realistic crank power range of 1,110 to 1,230 HP. This is the turbocharger's capability range — it describes the airflow capacity of the compressor wheel and turbine configuration, not a guaranteed output figure for any specific vehicle.

S475 turbo horsepower potential is substantial, but it requires a complete build to realise. A 75 mm compressor wheel moving enough air to support 1,200+ HP at the crank needs a matching fuel system, intercooler, engine internals, and exhaust path to operate in that range. In the majority of builds, practical output is limited by one of those surrounding systems before the turbo itself becomes the constraint.

This is actually an argument in favour of the S475 for many builders: the turbo has headroom beyond what most supporting systems can readily use, which means the compressor is rarely the first thing that needs to be revisited as a build evolves.

What Limits an S475 Build?

Compressor map efficiency becomes a consideration at the high end of the power range. At elevated boost pressure and airflow, a compressor wheel can move into less efficient regions of its map, generating additional heat and reducing the density advantage of the compressed charge. This is not unique to the S475 — it affects every fixed-geometry compressor — but it is worth understanding when targeting the upper end of the supported range.

Turbine flow restriction becomes more apparent above a 1.25 A/R housing. Turbine housings with tighter A/R values (lower numbers) accelerate exhaust gas velocity more aggressively, which improves spool response but creates a restriction at high exhaust flow rates. Builds pushing toward or above 1,200 HP need housing selection to reflect that exhaust volume requirement.

Engine displacement matters as well. Engines larger than 6.7 L produce exhaust volumes that require adequate housing flow to avoid backpressure that works against the turbo's efficiency. At the same time, the turbine must receive sufficient exhaust energy to drive the compressor — the relationship works in both directions.

Intercooler capacity, fuel delivery, and engine internals are where most S475 builds reach their actual ceiling first. A stock or mildly upgraded fuel system on a Duramax LML, for example, will limit power output well before the turbo runs out of compressor map. The same applies to intercooler core sizing, injector capacity, and the mechanical limits of engine components that were not designed for four-digit horsepower. The S475 is frequently not the weak link.

Power Goals and Housing Selection

A/R selection interacts directly with power targets, and the relationship is worth understanding before committing to a housing.

For builds in the lower portion of the S475's supported range — and for trucks where street driving means spool response matters more than peak flow — a tighter A/R such as 1.10 or 1.15 prioritises exhaust gas velocity and earlier boost onset. The turbine sees higher gas speed, driving the compressor wheel sooner, but at the cost of some flow capacity at the top end.

For builds targeting the upper end of the 1,110–1,230 HP range, a more open housing in the 1.18–1.25 range reduces turbine restriction and allows the exhaust system to breathe more freely at peak power. The trade-off is a slightly later boost onset, which most high-power builds are calibrated around.

When a build is genuinely targeting the region above 1,200 HP with significant exhaust volume, a T6 divided housing becomes worth evaluating. The T6 inlet configuration flows substantially more than a T4 at peak demand, and for builds where maximum exhaust flow is the priority, it removes a potential restriction that a T4 housing would otherwise introduce.

No specific A/R guarantees a specific horsepower result. The housing is one variable in a system that includes the compressor, turbine wheel, manifold, engine displacement, and boost target. Select the A/R that fits the complete combination.

S475 Turbo A/R Guide: Choosing 1.10, 1.15, 1.18 or 1.25

A/R — the ratio of a turbine housing's cross-sectional area to the radius from the housing centre to the centroid of that area — is the most important tunable variable in turbine housing selection. For an S475 turbo, the relevant A/R range for street and strip use runs from 1.10 to 1.25, and the right choice depends on your engine, manifold, vehicle weight, and power target working together.

Selecting S475 turbo A/R isn't a matter of picking the "best" number in isolation. A 1.10 housing on a 6.7 L Cummins making 1,000 HP will behave very differently on a 6.7 L making 1,200 HP with a high-performance exhaust manifold and stout intercooler. The housing is part of a system, and it should be selected as part of that system.

As a practical starting point: match tighter A/R values to builds where spool response is a stated priority or where exhaust energy is modest relative to turbo size. Match more open A/R values to builds where maximum peak flow and top-end power are the priority and where supporting systems are built to operate at that level.

When a T4 Housing Makes Sense

T4 divided turbine housings are the most accessible choice for the majority of S475 builds. They are widely available across multiple suppliers, well-supported by manifold options for Cummins, Power Stroke, and Duramax platforms, and compatible with the full 1.10–1.25 A/R range.

Choose a T4 housing when:

  • Your existing manifold or planned manifold uses a T4 turbine inlet flange
  • Vehicle packaging makes a T4 housing the more practical fit
  • Spool response is a meaningful priority alongside peak power
  • The build target falls comfortably within the mid-range of the S475's supported power band

Before ordering, verify turbine inlet flange compatibility between the housing and the manifold. "Bolt pattern" in this context refers to the turbine inlet flange, the inlet gasket, and the turbine housing mating surface — confirm all three match before a housing is selected. A T4 divided housing has a divided inlet that maintains exhaust pulse separation, which supports spool response on pulse-tuned manifolds; this is worth confirming with your manifold supplier or build notes.

When a T6 Housing Makes Sense

T6 divided housings are the appropriate choice when maximum exhaust flow is the primary requirement — specifically, builds where peak output is targeted above 1,200 HP and where a T4 housing would introduce measurable turbine restriction at peak demand.

The T6 turbine inlet configuration is larger than T4, accommodating greater exhaust volume without the flow restriction that a T4 housing begins to present at the upper end of the S475's range. This distinction is specifically about the turbine inlet configuration — the T6 inlet is a separate consideration from the T6 exhaust outlet, which is a larger full-marmon outlet connection (discussed in the fitment section).

Choose a T6 housing when:

  • The build targets the upper range of S475 horsepower capability
  • The manifold is designed or confirmed for T6 turbine inlet fitment
  • Exhaust outlet connections and downpipe hardware have been selected for a T6 outlet

Verify manifold fitment and exhaust outlet hardware compatibility before ordering a T6 housing. The T6 exhaust outlet uses a 146 mm (5.75") full-marmon connection, which requires T6-specific clamps and a downpipe designed for that outlet diameter. If your exhaust system is built around a T4 outlet, a T6 housing requires corresponding changes downstream.

S475 Spool Characteristics: Compared With S472 and S480

The S475 occupies the middle ground of the S400 family in more than just inducer diameter — it is genuinely the intermediate choice in terms of spool behaviour. A 72 mm compressor inducer (S472) builds boost earlier but runs out of compressor capacity at a lower power ceiling. An 80 mm inducer (S480) supports greater peak airflow but asks more of the engine and exhaust system before it comes on song.

The S475 sits between those two points in a way that most serious street/strip diesel builds find usable. The spool characteristics of any specific S475 installation, however, depend substantially on A/R selection, engine displacement, exhaust manifold design, and the complete vehicle combination — not on the inducer diameter alone. General descriptions of spool behaviour are useful for comparative context; they should not be treated as precise predictions for a specific build.

S475 vs S472

Moving from an S472 to an S475 adds compressor flow capacity in exchange for a modest delay in boost onset. On a 6.7 L Cummins under typical conditions, the difference in spool response between a 72 mm and 75 mm compressor becomes noticeable above approximately 2,800 rpm — below that threshold, the two turbos behave more similarly than the inducer diameter difference might suggest.

For street/strip builds, this trade-off is frequently acceptable. The S475 supports a meaningfully higher power ceiling than the S472, and the additional response window it requires is narrow enough that most builds can manage it through boost control calibration, manifold design, or A/R selection. If a build is specifically optimised for response on a modest engine and power target, the S472 remains the sharper tool; if the build intends to push beyond what a 72 mm compressor can comfortably support, the S475 is the natural next step.

S475 vs S480

The comparison between an S475 and an S480 reflects the same logic, applied in the other direction. Under identical conditions, an S475 reaches target boost approximately 300–500 rpm sooner than an S480. For a street-driven truck, that window represents meaningful real-world responsiveness — the difference between a turbo that's on-song in traffic and one that requires a longer pull to build meaningful boost.

The S480 operates an 80 mm compressor inducer, which expands the compressor map beyond what the S475 offers and supports a higher peak airflow ceiling. For builds genuinely targeting output beyond the S475's range, the S480 is the correct next step. For builds within the S475's documented capability range, the spool advantage is a meaningful reason to stay with the 75 mm wheel rather than stepping up to 80 mm.

For a side-by-side comparison of all S400 inducer sizes, see our S400 turbo guide.

S475 vs S476: Why 1 mm Matters

The S476 uses a 76 mm compressor inducer. The one-millimetre difference between a 75 mm and 76 mm compressor wheel is small enough to sound inconsequential, but in practice, builders do not treat the S475 and S476 as interchangeable — and for good reason.

A 1 mm change in inducer diameter shifts the compressor map in a measurable way. The inducer area scales with the square of the radius, so even a 1 mm diameter change represents a meaningful difference in the geometric capture area of the compressor. This translates to a different compressor map — different pressure ratio curves, different flow characteristics, and different peak efficiency islands. If a builder has selected an S475 based on a specific compressor map, substituting an S476 changes the map the build is calibrated against.

This matters most when a tune or fuel strategy has been developed against a specific compressor map, or when a power target has been evaluated against the documented flow range of a 75 mm compressor. Swapping between S475 and S476 is not a plug-and-play substitution.

Cartridge, Compressor Cover and Map Considerations

Some aftermarket centre housings and cartridge systems allow compressor wheel changes within the same housing body. The mechanical possibility of swapping a 75 mm wheel for a 76 mm wheel within the same centre housing does not make the two turbos equivalent from a calibration or performance standpoint.

The compressor cover — the housing that surrounds the compressor wheel and forms the compressor scroll — is designed for a specific wheel diameter. Changing the wheel without changing the compressor cover to match means the wheel-to-cover clearance and scroll geometry are no longer optimised for the installed wheel, which can reduce efficiency and alter the compressor map from what either the S475 or S476 data would predict.

Compressor maps are size-specific. If a build is specified to an S475 compressor map, confirm that the turbo being purchased includes both the correct 75 mm compressor wheel and the compressor cover matched to that wheel diameter. Purchasing an "S400" unit without confirming the complete compressor specification — inducer diameter, exducer, and cover — introduces uncertainty that a one-size-fits-all S400 frame description does not resolve.

Is an S475 Turbo Right for Your Truck?

For street/strip diesel trucks in the 1,000–1,200+ HP range, the S475 is the most commonly selected S400 configuration — and for good reason. The 75 mm compressor wheel delivers enough peak flow to support serious power targets while maintaining spool characteristics that are manageable on a vehicle that sees regular road use. It is not a single-purpose competition turbo that requires a drag strip to wake up, nor is it a conservative choice that runs out of map before the rest of the build is ready.

The balance of spool response and top-end flow that defines the S475 turbo is particularly relevant for trucks used across multiple contexts: a daily-driven Cummins that pulls a trailer on weekends and runs at a track event a few times per year, or a Duramax that needs to function reliably in traffic while delivering power that most vehicles will never see. The S475 is not a compromise in those contexts — it is the purpose-built choice for exactly that use profile.

Housing A/R, manifold selection, and supporting system quality all affect the final result. No turbocharger produces identical results across all platforms and builds. But the S475 gives most diesel street/strip builders the right platform to work from.

S475 Turbo Cummins Applications

The 5.9 L and 6.7 L Cummins engines are the most common documented applications for the S475, and the pairing makes straightforward sense. Both engines produce the exhaust energy and displacement volume to drive an S400-frame turbo effectively, and both are commonly built into the power range the S475 supports.

For an S475 turbo Cummins build, the practical considerations are:

  • Manifold design determines T4 or T6 turbine inlet compatibility and influences spool response
  • A/R selection should reflect the engine displacement, boost target, and how the truck is used
  • Fuel system capacity is frequently the first limit reached on 6.7 L Cummins builds, particularly at and above 1,000 HP
  • Intercooler core sizing needs to match the compressed charge volume a 75 mm wheel produces at target boost
  • Engine internals — rods, pistons, head studs — are practical ceiling components at the upper end of the power range

The 5.9 L Cummins, with its smaller displacement, may show slightly quicker spool response with an S475 than the 6.7 L under equivalent conditions, and may also see the fuel system as a limit somewhat earlier. Both are exceptional platforms for S400-frame builds when the supporting systems are matched to the turbo's capability.

For platform-specific manifold options and Cummins turbo components, see our Cummins turbo components collection.

Power Stroke Applications

The 6.0 L and 6.4 L Power Stroke platforms are documented S475 applications, though they present some installation considerations that deserve attention upfront.

Both engines can support the power range the S475 targets, and both have aftermarket manifold options that accommodate T4 turbine inlet fitment. The 6.4 L in particular, with its twin-turbo factory configuration, requires manifold and plumbing changes to accommodate a single large-frame S400 unit — a conversion that is documented in the platform community but requires careful planning around oil drain routing, exhaust outlet connection, and charge air plumbing.

Before ordering an S475 for a Power Stroke application:

  • Confirm oil-drain bolt centre and port size compatibility (see the fitment section)
  • Verify turbine inlet flange compatibility with the intended manifold
  • Confirm exhaust outlet diameter and clamp requirements for the downstream piping
  • Match the A/R selection to the build's power target and intended manifold design

For Power Stroke-specific manifold and fitment guidance, see our Power Stroke turbo fitment resources.

Duramax Applications

LBZ, LMM, and LML Duramax trucks are well-represented in S475 build documentation, and the S400 frame is a natural fit for these platforms at serious power levels.

One recurring note in LML Duramax builds is worth highlighting here: the factory CP4 high-pressure fuel pump is a documented reliability concern in high-power applications, and fuel delivery frequently becomes the practical power ceiling before turbo capability is reached. This is not unique to the S475 — any turbo upgrade that significantly increases air delivery will stress the fuel system to match — but it is a platform-specific consideration that deserves honest evaluation before a build is specified.

For LBZ and LMM trucks with CP3 injection systems, fuel delivery is a more robust starting point, and these platforms more readily support the upper range of S475 horsepower targets given appropriate injector and pump modifications.

Across all three Duramax variants, intercooler capacity and engine internal durability are meaningful constraints as power targets approach the top of the S475 range. A build evaluation should include the complete fuel system, intercooler, head hardware, and engine durability as co-equal considerations alongside turbo selection.

For Duramax-specific turbo and supporting component guidance, see our Duramax turbo upgrades collection.

S400-Frame Fitment and Installation Measurements

S400 turbos are large-frame units. Before one is ordered, several fitment dimensions need to be confirmed — not estimated, not assumed from photographs, and not borrowed from mid-frame S300 specifications. The measurements that matter are precise enough that a calliper is the right tool, not a visual comparison.

This section covers the fitment specifications that most retail and forum content omits or understates. Getting these numbers wrong before a build is an inconvenience. Getting them wrong during installation is expensive.

Oil Drain Bolt Centre and Drain Port Size

The S400 oil-drain bolt centre measures 50.8 mm (2.00"). This is the distance between the centres of the two drain bolt holes on the oil-drain flange.

Mid-frame S300 turbos use a 50 mm (1.97") bolt centre. The difference is 0.8 mm — less than a millimetre — which looks identical to the eye and cannot be reliably distinguished by feel or visual inspection. If you are measuring an existing drain flange or attempting to determine whether a housing is S300 or S400 frame, use a calliper. A reading of 50.7–50.9 mm indicates an S400-frame unit; a reading of 49.8–50.2 mm indicates a mid-frame unit. Visual identification at this tolerance is not reliable.

The S400 drain port is 12AN. This is a larger fitting than the 10AN hardware common in S300 installations. A 10AN fitting is undersized for an S400 drain port and will create a restriction in the drain circuit that can cause oil to back up into the turbo centre housing — a condition that accelerates bearing wear and contributes to seal failure. If your existing drain line uses 10AN hardware, it needs to be replaced with 12AN fittings before an S400-frame turbo is installed.

For S400 oil drain fittings and 12AN turbo drain hardware, see our turbo installation components collection.

Oil Drain Length Is a Separate Clearance Measurement

Oil drain length — the distance from the turbo drain flange to the first bend or connection point — is an independent measurement that is separate from bolt-centre spacing and port size. These three specifications describe different aspects of the drain system and each must be confirmed separately.

Available drain-length options for S400-frame installations are:

  • 35 mm (1.38")
  • 65 mm (2.56")
  • 100 mm (3.94")

The correct drain length for a specific installation depends on the physical clearance between the turbo's drain flange and surrounding components — the block, oil pan, cross-members, and any other structure in the drain routing path. This measurement is determined by the vehicle and installation, not by the turbo specification. Measure the available clearance in the actual engine bay before selecting a drain length, and confirm that the selected drain provides adequate clearance for the drain line to maintain a continuous downward slope to the pan. Gravity drain circuits do not tolerate uphill routing.

S400 T4 and T6 Exhaust Outlet Dimensions

The exhaust outlet configuration is the final fitment dimension to confirm before selecting exhaust components or a downpipe.

S400 T4 exhaust outlet: 117 mm (4.62") half-marmon
S400 T6 exhaust outlet: 146 mm (5.75") full-marmon
T6 clamp reference: 99502-0588

The marmon clamp connection style is common in S400 and larger turbo applications. Half-marmon and full-marmon describe the clamp and flange configuration geometry — these are not interchangeable with each other or with V-band clamp styles without adapter hardware.

Before selecting a downpipe or exhaust connection, confirm:

  1. Whether the housing uses a T4 or T6 exhaust outlet
  2. The outlet diameter (117 mm for T4, 146 mm for T6)
  3. Whether the clamp and downpipe flange match the outlet style (half-marmon or full-marmon)
  4. That the correct clamp is on hand — the T6 full-marmon connection uses clamp 99502-0588

These dimensions cannot be visually estimated from product photographs with sufficient accuracy. Verify against the specific housing specification before ordering downstream components.

How to Choose an S475 Turbo Configuration

The right S475 configuration is the one matched to your vehicle, manifold, supporting systems, and power target — not the most popular option or the highest-flowing housing available. Use the framework below to work through the selection systematically before committing to a specific configuration.

Start With Your Manifold and Turbine Inlet

The manifold determines your turbine inlet flange before anything else. An S475 is available in T4 and T6 turbine inlet configurations; the housing you select must match the manifold you are running or planning to run.

If the build is starting from an existing manifold with a T4 turbine inlet, a T4 housing is the direct match. If the manifold is being selected as part of the build, the turbine inlet choice is open — and that decision should reflect both vehicle packaging constraints and the power target.

T4 is the practical choice for most street/strip builds: widely available, well-documented for common platforms, and well-suited to the A/R range most S475 applications use. T6 is the appropriate choice when the build specifically requires the higher exhaust flow that a T6 inlet configuration supports, and when the manifold and exhaust outlet hardware are matched to T6.

Match A/R to Your Intended Use

Once the turbine inlet is confirmed, A/R selection narrows the field further. The 1.10–1.25 range covers most S475 street/strip applications:

  • 1.10 and 1.15: Appropriate where spool response is a significant priority. Smaller A/R values increase exhaust gas velocity through the turbine housing, driving the wheel sooner. Best suited to lower-displacement engines or builds where the power target falls in the lower-to-mid range of S475 capability.
  • 1.18 and 1.25: Appropriate where peak flow is weighted ahead of earliest possible spool onset. More open housings reduce turbine restriction at high exhaust volume, which benefits builds operating near the top of the S475's supported range.

Consider engine displacement, exhaust manifold design (pulse-tuned or log-style), boost target, and how the vehicle is primarily used. A track-only build can accept a slower spool; a truck that drives to work five days a week cannot.

No single A/R is universally correct for the S475. The right value is the one that fits the complete combination.

Confirm Supporting Systems Before Ordering

The turbo is the headline component, but it is not the only variable. Before placing an order, confirm:

  • Fuel delivery capacity — does the injection system support the fuel volume required at the target power level?
  • Intercooler sizing — is the core large enough to handle compressed charge volume at target boost and air temperature?
  • Engine internals — are rods, pistons, and head hardware suitable for the cylinder pressure a 1,100–1,200+ HP build generates?
  • Oil drain fitment — bolt centre (50.8 mm / 2.00"), port size (12AN), and drain length for the specific installation
  • Exhaust outlet hardware — T4 (117 mm / 4.62" half-marmon) or T6 (146 mm / 5.75" full-marmon, clamp 99502-0588) with matching downpipe

If you are uncertain about any aspect of the configuration — wheel combination, housing A/R, turbine inlet flange, or fitment measurements — contact us before ordering. Getting the configuration right the first time is significantly less expensive than addressing fitment issues after the fact.

Shop S475 Turbo and S400 Components

Black Sheep Industries carries S475 turbo configurations, S400-frame housings, and supporting installation hardware for builders across Canada and the United States. All pricing is listed in Canadian dollars (CAD), and US import duties are covered where applicable to your order — no surprise charges at the border.

Before adding an S475 to your order, use the fitment checklist from the section above to confirm:

  • Turbine inlet flange type (T4 or T6)
  • Housing A/R (1.10, 1.15, 1.18, or 1.25)
  • Exhaust outlet style and diameter
  • Oil-drain bolt centre, port size, and drain length

Wheel combinations and housing options vary by supplier and cartridge. The configuration details listed on each product page reflect that specific unit — confirm against your build requirements rather than assuming all S475 units share identical specifications.

Need help selecting an S475 configuration? Contact our team with your platform, current manifold setup, power target, and intended use, and we will help identify the right combination before you order.

Frequently Asked Questions About S475 Turbos

What horsepower can an S475 turbo support?

The S475 turbo supports a realistic crank power range of 1,110 to 1,230 HP. This represents the turbocharger's compressor and turbine flow capability — not a guaranteed vehicle output figure. In most builds, intercooler capacity, fuel delivery, or engine internal limits become the practical ceiling before the turbo's compressor map is fully utilised. Supporting systems must be matched to the turbo's capability for the build to reach the upper end of that range.

What are the common S475 turbo specs?

The defining S475 turbo spec is a 75 mm compressor inducer. The most common turbine wheel combination pairs a 96 mm exducer with an 88 mm turbine inducer; a less common alternative uses a 92 mm exducer / 83 mm inducer for quicker spool. Turbine housing A/R options for street/strip use typically run 1.10, 1.15, 1.18, and 1.25. The S400-frame oil drain uses a 50.8 mm (2.00") bolt centre, a 12AN drain port, and is available in drain lengths of 35 mm (1.38"), 65 mm (2.56"), and 100 mm (3.94"). Exhaust outlet dimensions are 117 mm (4.62") half-marmon for T4 and 146 mm (5.75") full-marmon for T6. Specifications can vary by aftermarket supplier; confirm the complete configuration before purchasing.

What is the best A/R for an S475 on a 6.7 L Cummins?

There is no single best A/R for an S475 on a 6.7 L Cummins — the right choice depends on the build's power target, manifold design, and use priorities. As a general framework: 1.10 or 1.15 suits builds where spool response is a stated priority and power targets fall in the lower-to-mid range of S475 capability. 1.18 or 1.25 suits builds targeting peak output where maximum turbine flow takes precedence over earliest possible spool onset. If the build is genuinely targeting output above 1,200 HP and the manifold supports it, a T6 housing becomes worth evaluating. Contact us with your specific build details if you need help narrowing down the right A/R for your combination.

What is the difference between an S475 and S476?

The S476 uses a 76 mm compressor inducer versus the S475's 75 mm. Despite a one-millimetre diameter difference, the two turbos are not interchangeable. The 1 mm change shifts the compressor map measurably — different pressure ratio curves, flow characteristics, and peak efficiency regions. Builders who have selected a specific turbo based on compressor map data should not substitute one size for the other. The compressor cover is also size-specific; fitting a 76 mm wheel into a cover designed for 75 mm (or vice versa) produces a configuration that does not match either turbo's documented map. Confirm the complete compressor specification — inducer, exducer, and cover — before purchasing.

Should I choose a T4 or T6 housing for an S475 street truck?

For the majority of S475 street/strip builds, T4 is the practical choice. T4 divided housings are widely available, well-supported across Cummins, Power Stroke, and Duramax platforms, and compatible with the full 1.10–1.25 A/R range. T4 housings are appropriate for builds targeting up to approximately 1,200 HP where manifold fitment or spool response is a meaningful consideration.

T6 becomes relevant when maximum exhaust flow is the primary requirement — specifically for builds targeting output above 1,200 HP where a T4 housing would introduce measurable turbine restriction at peak demand. T6 requires a manifold designed for T6 turbine inlet fitment and a downpipe matched to the 146 mm (5.75") full-marmon T6 exhaust outlet (clamp 99502-0588). If the rest of the build is not designed around T6 hardware, T4 is the appropriate starting point.