Garrett G42 Turbine Housing Kit Div T4 / V: Specs, Fitment, and Is It Worth It

The Garrett G42 Turbine Housing Kit Div T4 series provides three A/R ratio options for builders pairing a Garrett G42 Super Core with a divided T4 exhaust manifold. The G42 is Garrett's large-frame G Series platform, supporting Super Core power ratings from 1200 to 1585 horsepower across the original G Series and G-Series II lineups, and the turbine housing is purchased separately to allow inlet type and A/R ratio to be matched to the application independently of the Super Core selection. The Divided T4 series uses a four-bolt T4 flange in a divided (twin-scroll) configuration, which separates exhaust pulses from opposing cylinder bank groups through the turbine housing scroll to preserve pulse energy -- improving turbine efficiency and spool response compared to an open-scroll housing at the same A/R ratio. The G42 Div T4 series offers three A/R options: 1.01, 1.15, and 1.28. A companion O/V V-Band series covers the same 1.01, 1.15, and 1.28 A/R range on a V-Band manifold inlet. This guide covers the full G42 Div T4 turbine housing catalog, how to select between the three A/R ratios for a given power target and engine displacement, and how the G42 platform compares to the G40 for large-frame Garrett Performance Upgrade builds.

G42 Divided T4 Turbine Housing Specifications: Three A/R Options

The Garrett G42 Div T4 turbine housing catalog covers three A/R ratios, all with a Divided T4 inlet and V-Band downpipe outlet in standard rotation:

• 1.01 A/R (757707-0014): Tightest G42 Div T4 turbine area; provides the fastest turbine spool of the three G42 options by maximizing drive pressure at low exhaust flow rates; generates the highest turbine backpressure at peak RPM and is best suited to builds where rapid boost onset is the primary requirement and the power target is within the comfortable backpressure threshold of the 1.01 housing on the G42 turbine wheel
• 1.15 A/R (757707-0015): Mid-range G42 Div T4; the broadly applicable option across the G42 Super Core power range of 1200-1585 hp; balances turbine spool response with peak exhaust flow capacity for the displacement ranges most commonly used with the G42 platform; the starting point for builds where no data logging exists from a prior G42 installation
• 1.28 A/R (757707-0016): Widest G42 Div T4 turbine area; lowest turbine backpressure at peak exhaust flow; appropriate for very large displacement engines, high-RPM power bands, and builds where data logging from an existing G42 installation confirms the 1.01 or 1.15 housing is generating excess backpressure at the top of the RPM range

All three housings share the Divided T4 inlet and V-Band outlet configuration in standard rotation. The divided (twin-scroll) T4 inlet maintains separation between the two exhaust cylinder bank groups as exhaust gas enters the turbine housing scroll -- on diesel builds with six-cylinder engines and on gasoline builds using twin-scroll exhaust manifolds, the pulse separation preserved by the divided housing produces measurably faster spool than an open-scroll turbine housing at the same A/R ratio. The T4 flange is the standard diesel performance manifold bolt pattern for large single-turbo builds and is common across fabricated performance manifolds designed for the G42's power range.

The companion O/V V-Band series (757707-0011 through -0013) provides the same 1.01, 1.15, and 1.28 A/R options with a V-Band manifold inlet instead of the T4 flange. A builder whose exhaust manifold uses a V-Band discharge connection selects the O/V series; a builder with a T4-flanged manifold selects the Div T4 series. The A/R ratio selection guidance is identical between the two series -- only the manifold inlet connection differs.

Top Picks: Garrett G42 Div T4 Turbine Housings

For G42 builds on T4-flanged twin-scroll manifolds where spool response is prioritized, the Garrett G42 Turbine Housing Kit Div T4 / V-Band 1.01 A/R (757707-0014) is the tightest available option in the G42 Div T4 series. The Garrett G42 Turbine Housing Kit Div T4 / V-Band 1.15 A/R (757707-0015) is the mid-range selection suited to the broadest range of G42 applications across the 1200-1585 hp power range. The Garrett G42 Turbine Housing Kit Div T4 / V-Band 1.28 A/R (757707-0016) provides the maximum G42 Div T4 turbine area for high-displacement builds where peak backpressure data supports the larger housing. These housings pair with the Garrett G42-1200 Super Core Standard Rotation Super Core Assembly (860778-5004S) and the broader G42 Super Core lineup available in the Garrett G Series turbocharger catalog.

Match to the Build

• High-output diesel single-turbo build on a six- or eight-cylinder engine targeting 1000-1400 horsepower with a divided T4 manifold: The G42 Div T4 1.15 A/R (757707-0015) covers this range on large-displacement diesel engines with divided T4 manifolds; the 1.15 A/R balances turbine efficiency and peak flow for the displacement and power target combinations most common on the G42 platform; step to the 1.28 if data logging shows the 1.15 is limiting power at the top of the RPM range
• Diesel competition build targeting 1400-1585 horsepower where minimizing turbine backpressure at peak RPM is the priority: The 1.28 A/R (757707-0016) is appropriate at the upper end of the G42 power range where the engine's exhaust volume at peak output requires the largest available turbine flow area; on competition builds where spool time is less critical than extracting every horsepower at the RPM ceiling, the 1.28 removes the turbine-side backpressure constraint
• Street-driven diesel or gasoline build where boost onset matters as much as peak power: The 1.01 A/R (757707-0014) is appropriate when the build requires boost delivered earlier in the RPM range and the power target is within the comfortable backpressure range of the tighter housing; the divided T4 design already provides a spool advantage over an equivalent open housing at the same A/R
• Replacing an existing G42 turbine housing to adjust A/R after a power level or displacement change: The G42's modular design allows turbine housing replacement without removing the Super Core; a build that has changed its power target can step between the three Div T4 A/R options by purchasing the appropriate new housing; the V-Band downpipe outlet connection is unchanged across all three A/R options, so the downpipe requires no modification for a housing swap

Signs the Turbine Housing Is the Limiting Factor

• Drive pressure exceeding boost pressure at peak RPM under data logging -- the turbine housing is too small for the exhaust volume the engine produces at maximum output; excess backpressure creates a pumping loss that reduces net power and can cause head gasket stress on high-output diesel builds; stepping from the 1.01 or 1.15 to the 1.28 Div T4 reduces this condition when confirmed by a logged pull
• Power output leveling below the fuel and boost calibration's potential -- the engine approaching but not reaching its thermodynamic ceiling because turbine restriction is the final constraint at peak RPM; when air-fuel ratio, boost target, and fueling are on target but power stops climbing at the expected rate, turbine backpressure is the typical culprit on a properly sized G42 compressor
• Flange face distortion or warping at the T4 inlet from sustained high exhaust temperatures -- thermal cycling fatigue causing the flange face to lose planarity, producing an exhaust leak at the manifold joint; a warped flange reduces turbine efficiency by allowing exhaust gas to escape before entering the housing scroll; replacement with a fresh housing corrects the sealing surface
• Housing cracking at the V-Band outlet groove or scroll body on a high-cycle performance build -- thermal fatigue at stress concentrations in the housing causing structural cracks; a cracked housing must be replaced before exhaust leaks develop; any of the three Div T4 A/R options serves as the replacement matching the original A/R specification

Frequently Asked Questions

How does the G42 Div T4 housing compare to the G40 Div T4 for a 1200-horsepower build?

The G42 and G40 platforms overlap in the 1000-1250 hp range depending on Super Core selection, and the correct choice is determined by the engine's displacement and boost target against each platform's compressor map, not by the power number alone. A 1200 hp build on a large-displacement diesel engine with a wide power band typically fits the G42 compressor map more comfortably than the G40 at the same power target, because the G42's larger compressor wheel operates further from its surge line at the mass flow rates a large engine produces. The G42 Div T4 series starts at 1.01 A/R where the G40 starts at 0.85, reflecting the larger turbine wheel's inherently wider flow area -- the G42 at 1.01 provides comparable spool to the G40 at 0.85 on a large engine that generates the exhaust flow needed to drive the larger wheel.

Bottom Line

The Garrett G42 Turbine Housing Kit Div T4 series covers three A/R ratios from 1.01 to 1.28 for G42 builds on divided T4 exhaust manifolds in the 1200-1585 hp range. The divided twin-scroll design provides pulse-energy spool advantages over open-scroll alternatives at the same A/R. Start with the 1.15 A/R for a broad range of G42 applications; step to 1.01 for faster spool or 1.28 for lower backpressure based on the build's power target and data logging from the specific application.