BorgWarner S400SX Turbine Housing – .90 A/R | T4 Inlet | V-Band Outlet | 87mm Turbine | 178787

Turbine housing only — does not include the turbocharger CHRA or compressor cover. Confirm this housing is compatible with your S400SX CHRA and compressor assembly before ordering.

T4 inlet flange — confirm your exhaust manifold uses a T4 (4-bolt) outlet before ordering. V-band outlet — confirm downpipe is equipped with a matching V-band flange or source a V-band adapter.

BorgWarner 178787 S400SX turbine housing with .90 A/R ratio, T4 exhaust inlet flange, V-band (VTF) turbine outlet, and 87mm turbine wheel inducer. Designed for high-flow diesel and large-displacement high-power gasoline applications. 15 lbs. Ships fast across Canada and the US.

S400SX Platform

The BorgWarner S400SX is one of the most widely used large-frame turbocharger platforms in diesel truck performance and high-power gasoline builds. The S400 frame accommodates large compressor and turbine wheel combinations that support power targets from approximately 600 hp through 1,500+ hp depending on wheel sizing and configuration. The SX designation indicates an extended-tip compressor wheel with higher aerodynamic efficiency than the standard S-wheel design, enabling the compressor to operate closer to its peak efficiency island across a broader flow range. The 87mm turbine is among the larger wheels in the S400SX lineup, suited to applications with high exhaust mass flow — large diesel engines, high-boost gasoline builds, or as the primary “big” turbo in a compound (twin) turbo system.

.90 A/R — High-Flow Turbine Housing

The A/R (area-to-radius) ratio is the single most important turbine housing specification for defining the turbocharger’s power band characteristics. A larger A/R ratio like .90 increases the cross-sectional flow area of the housing scroll relative to the turbine wheel, allowing higher exhaust mass flow rates to reach the turbine wheel before choking — this shifts the turbo’s peak efficiency toward higher engine speeds and higher flow rates, enabling greater peak power output. The tradeoff is slower spool-up compared to a tighter housing (e.g. .81 A/R), as the larger scroll volume requires more exhaust energy to build turbine speed. On large diesel engines and high-displacement gasoline builds where peak power is the primary objective and the engine generates sufficient exhaust energy at lower RPM, the .90 A/R is the correct choice for maximising top-end output. Buyers optimising for quicker response and a lower power band should evaluate a tighter A/R housing.

T4 Inlet Flange

The exhaust inlet uses a T4 (T04) 4-bolt square flange — the most widely used inlet flange in performance exhaust manifold design for diesel trucks and high-power gasoline builds. Confirm that your exhaust manifold or up-pipe features a T4 outlet pattern before ordering this housing. T3, T6, or divided T4 manifolds require a different housing or an adapter.

V-Band (VTF) Turbine Outlet

The turbine outlet uses a V-band clamp connection (VTF = Vent-to-Flange). V-band provides a secure, leak-resistant seal that can be rotated (clocked) to align the downpipe outlet in any direction without changing the housing, simplifying installation in tight engine bays. V-band connections are also faster to remove and reinstall for service than bolted flanges. Confirm your downpipe is fitted with a compatible V-band flange or source a V-band adapter to connect to a standard downpipe flange.

87mm Turbine Wheel

The 87mm inducer turbine wheel is sized for high exhaust mass flow applications. Matched appropriately to large-frame S400SX compressor wheel assemblies in the 74mm–83mm+ range for single-turbo builds targeting 700–1,200+ hp, or as the atmosphere-side turbine in a compound turbo configuration where it receives pre-compressed air from a smaller primary turbo. Confirm turbine wheel sizing compatibility with your CHRA when building or assembling an S400SX unit.

Turbine housing only — CHRA and compressor cover sold separately. Confirm CHRA, compressor wheel, and housing compatibility before assembly. Confirm T4 manifold flange and V-band downpipe fitment. Professional turbo assembly and installation recommended — incorrect assembly or installation can cause catastrophic engine damage. Ensure proper oil and coolant supply lines are in place before startup.

Specifications

• Brand: BorgWarner
• Part Number: 178787
• Platform: S400SX
• A/R Ratio: .90
• Inlet Flange: T4 (T04) 4-bolt
• Outlet: V-band (VTF)
• Turbine Wheel Inducer: 87mm
• Weight: 15 lbs
• Application: Universal — high-flow diesel and high-power gasoline builds