Garrett G40 Turbine Housing Kit Div T4 / V: Specs, Fitment, and Is It Worth It

The Garrett G40 Turbine Housing Kit Div T4 series provides four A/R ratio options for builders pairing a Garrett G40 Super Core with a divided T4 exhaust manifold. The G40 is Garrett's mid-range G Series platform, covering builds in the 700 to 1250 horsepower range through its current Super Core lineup, and the turbine housing is purchased separately to allow inlet type and A/R ratio to be matched to the specific application. The Divided T4 series uses a four-bolt T4 flange in a divided (twin-scroll) configuration that keeps exhaust pulses from opposite cylinder banks separated through the turbine housing scroll, preserving pulse energy to improve turbine efficiency -- particularly at lower engine RPM where pulse separation has the greatest effect on spool characteristics. Four A/R ratios are available in the Div T4 series: 0.85, 0.95, 1.06, and 1.19. A companion Open/V-Band (O/V) series offers the same four A/R ratios on a V-Band manifold inlet for custom manifold and compound turbo applications. This guide covers the full G40 Div T4 turbine housing catalog, how to select the correct A/R ratio for a given engine and power target, and how this Garrett Performance Upgrade platform compares between Div T4 and O/V inlet configurations.

G40 Divided T4 Turbine Housing Specifications: Four A/R Options

The Garrett G40 Div T4 turbine housing catalog covers four A/R ratios, all with a Divided T4 inlet and V-Band downpipe outlet in standard rotation:

• 0.85 A/R (757707-0032): Tightest G40 Div T4 turbine area; fastest turbine spool on the G40 platform but highest turbine backpressure at peak exhaust flow; best matched to builds prioritizing low-RPM boost onset where peak power is not limited by backpressure from a tight housing
• 0.95 A/R (757707-0033): Mid-low range; a step up from the 0.85 with slightly reduced backpressure at peak flow while retaining fast spool characteristics; a starting point for builds on medium-displacement engines where spool response is a priority but the power target is above the 0.85's comfortable backpressure threshold
• 1.06 A/R (757707-0034): Mid-high range; balances turbine spool and peak flow for high-displacement single-turbo builds and high-output diesel applications; the most broadly applicable G40 Div T4 A/R ratio across the platform's 700-1250 hp power range
• 1.19 A/R (757707-0035): Largest G40 Div T4 turbine area; lowest turbine backpressure at peak exhaust flow; suited to very high displacement engines and builds where data logging confirms backpressure from the smaller housings is limiting peak power output

All four housings use a standard V-Band outlet for the downpipe and are standard rotation. The Divided T4 inlet is a divided twin-scroll flange -- the divided wall inside the housing separates the exhaust flow from the two cylinder bank groups through the turbine scroll, so each bank's exhaust pulse reaches the turbine wheel in sequence rather than mixing in the manifold. On diesel engines with inline six-cylinder configurations and on twin-scroll gasoline manifold builds, the pulse separation maintained by the divided housing produces measurably faster spool than an open (undivided) turbine housing at the same A/R ratio. The T4 flange pattern is the standard four-bolt diesel performance manifold interface and is common across fabricated performance manifolds for both diesel and gasoline builds designed for large-frame single-turbocharger use.

The companion O/V V-Band series (757707-0027 through -0030) offers the same 0.85, 0.95, 1.06, and 1.19 A/R options on a V-Band manifold inlet instead of a T4 flange. The A/R ratio selection guidance is the same between the two inlet series -- only the manifold connection type determines which series to buy. A builder with a T4-flange manifold uses the Div T4 series; a builder with a V-Band discharge manifold or compound turbo configuration uses the O/V series.

Top Picks: Garrett G40 Div T4 Turbine Housings

For builds requiring a tighter turbine area with priority on spool speed, the Garrett G40 Turbine Housing Kit Div T4 / V-Band 0.85 A/R Standard Rotation (757707-0032) is the smallest-area Div T4 option on the G40 platform. The Garrett G40 Turbine Housing Kit Div T4 / V-Band 0.95 A/R Standard Rotation (757707-0033) steps up one increment for builds where the 0.85 generates excess backpressure at peak power. The Garrett G40 Turbine Housing Kit Div T4 / V-Band 1.06 A/R Standard Rotation (757707-0034) is the mid-range selection suited to the broadest range of G40 applications. The Garrett G40 Turbine Housing Kit Div T4 / V-Band 1.19 A/R Standard Rotation (757707-0035) provides the maximum G40 Div T4 turbine area for builds where backpressure data supports the larger housing. These turbine housings pair with the Garrett G40-1150 Super Core Standard Rotation Super Core Assembly (860777-5002S) and other G40 Super Core options in the Garrett G Series turbocharger catalog.

Match to the Build

• High-output diesel single-turbo build on an inline-six engine targeting 700-1000 horsepower with a divided T4 manifold: The G40 Div T4 1.06 A/R (757707-0034) covers the 700-1000 hp range on inline-six diesel builds with T4 manifolds; the 1.06 A/R balances spool efficiency and peak flow across this range; step to the 1.19 if backpressure data shows the 1.06 is limiting power at the target RPM
• Diesel drag build targeting 1000-1250 horsepower where maximum peak power takes priority over spool speed: The 1.19 A/R (757707-0035) is appropriate for G40 builds at the upper end of the power range where minimizing backpressure at peak RPM is the priority; on a drag application where spool speed is less critical than peak flow capacity, the larger housing removes the turbine-side constraint at high exhaust flow rates
• Street-driven performance diesel where low-RPM boost onset is valued alongside high peak power: The 0.85 or 0.95 A/R housing is appropriate when the build requires boost earlier in the RPM range; the tighter turbine area generates higher drive pressure at low exhaust flow to accelerate the turbine wheel sooner, with the trade of increased backpressure at peak RPM
• Replacing an existing G40 turbine housing to adjust A/R after a power level change: The G40's modular design allows turbine housing replacement without disturbing the Super Core assembly; a build that has changed its power target can step to a different A/R by purchasing a new Div T4 housing; the V-Band downpipe outlet is unchanged across all four A/R options

Signs the Turbine Housing Is the Limiting Factor

• Turbine inlet pressure exceeding compressor outlet pressure at peak RPM under data logging -- turbine housing flow area too small for the engine's exhaust volume at maximum output; excess backpressure creates a pumping loss that reduces net power; stepping from the 0.85 or 0.95 A/R to the 1.06 or 1.19 reduces this condition when confirmed by a logged run
• Power output leveling off earlier in the RPM range than the fueling and boost calibration would predict -- the turbine housing limiting exhaust gas extraction before the compressor and engine reach their thermodynamic potential; when air-fuel ratio, boost target, and fuel delivery are all within range but peak power stops climbing at the expected rate, turbine backpressure is the likely constraint
• Turbine housing cracking at the V-Band outlet groove or at the divided wall junction inside the T4 flange -- thermal cycling fatigue from high exhaust gas temperatures and repeated heat cycles on a performance build; a cracked housing must be replaced before exhaust leaks develop at the V-Band joint; any of the four Div T4 A/R options serves as the replacement depending on the A/R specification of the original housing
• Warped or distorted T4 flange face producing an exhaust leak at the manifold joint -- thermal distortion from sustained high exhaust temperatures causing the flange face to lose flatness; an exhaust leak at this joint reduces turbine efficiency by allowing exhaust gas to escape before reaching the turbine wheel; housing replacement with a fresh flange face corrects the sealing surface

Frequently Asked Questions

How do I pick the right A/R ratio for my G40 build?

Start with the 1.06 A/R (757707-0034) if you do not have data logging from an existing G40 build to guide the selection -- it covers the broadest range of G40 applications without strongly biasing toward either fast spool or maximum peak flow. Use the 0.85 or 0.95 A/R when the build requires boost onset earlier in the RPM range and the peak power target is within the comfortable backpressure range of the tighter housing. Use the 1.06 or 1.19 A/R when the build targets the upper end of the G40's power range and backpressure data from a previous housing shows the tighter options were limiting peak output. The divided T4 design improves spool response across all four A/R ratios relative to an open housing at the same A/R, so the Div T4 series already provides better spool than an equivalent open housing before A/R selection is considered.

Bottom Line

The Garrett G40 Turbine Housing Kit Div T4 series covers four A/R ratios from 0.85 to 1.19 for G40 builds on divided T4 exhaust manifolds. The divided twin-scroll design improves pulse utilization and spool response across all four options. The 1.06 A/R covers the broadest range of G40 applications; step tighter for faster spool or wider for lower backpressure based on the power target, engine displacement, and data logging from the specific build.