BORG WARNER 178790 S400SX TURBINE HOUSING 87MM 1.25 A/R T4 (TWIN-SCROLL)

Product Description

BORG WARNER 178790 S400SX TURBINE HOUSING — 87MM • 1.25 A/R • T4 DIVIDED
Go big on top-end flow without giving up drivability. This genuine BorgWarner AirWerks S400SX housing features a 1.25 A/R twin-scroll (T4 divided) volute sized for the 87mm S400 turbine—ideal for high-power singles and low-pressure chargers in compound setups. Cast-iron durability, proven pulse separation, and CPP Diesel tech support make it a bolt-on you can trust.

Fitment & Use

• Turbo Family: BorgWarner AirWerks S400 / S400SX (journal-bearing)
• Turbine Wheel: 87mm (S400)
• Inlet: T4 divided (twin-scroll)
• Outlet: 4.62" Marmon / V-band
• Best for: Big single S400 builds targeting strong top-end power; atmospheric charger in S300/S400 compounds with proper wastegate control

Cross-Reference / Alternatives (BorgWarner on CPP Diesel only)

• BORG WARNER 178787 — S400SX 87MM 0.90 A/R T4 (twin-scroll)
• BORG WARNER 178788 — S400SX 87MM 1.00 A/R T4 (twin-scroll)
• BORG WARNER 178789 — S400SX 1.10 A/R T4 (twin-scroll)
• BORGWARNER 177105 — S400 83MM 1.25 A/R T4
• BORGWARNER 177104 — S400 83MM 1.10 A/R T4

FAQ

Will 1.25 A/R T4 spool slower than 1.00–1.10 A/R?

Generally yes; the larger A/R favors top-end flow and lower drive pressure at the expense of some spool. If you’re street-biased, consider the 1.00–1.10 A/R options above; for big fuel and RPM, 1.25 A/R shines.

Is this housing divided (twin-scroll)?

Yes. The T4 inlet is twin-scroll to improve pulse separation and stabilize drive pressure when used with a divided manifold and paired runners.

What S400 turbos does it typically pair with?

Common matches include S472/S475/S476/S480/S482-based builds using the 87mm S400 turbine wheel. Always verify turbine wheel fit before purchase.

Legal for on-road use?

Not CARB legal. Intended for off-road/competition use where permitted. See Prop 65 notice below.

Specifications for BORG WARNER 178790