Garrett G45 Turbine Housing Kit O/V V: Specs, Fitment, and Is It Worth It

The Garrett G45 Turbine Housing Kit O/V V-Band 1.15 A/R Standard Rotation (757707-0020) is a mid-range A/R turbine housing for the Garrett G45 high-output single-turbocharger platform, using an Open/V-Band exhaust manifold inlet and a V-Band downpipe outlet. The G45 is Garrett's mid-to-large frame entry in the G Series lineup, rated for approximately 1500 to 1600 horsepower in its current Super Core configurations, and it bridges the gap between the performance-oriented G35/G40 range and the very large-frame G55 platform. Like all G Series turbos, the G45 is sold as a Super Core assembly and a separately purchased turbine housing, which allows the builder to select the manifold connection type and A/R ratio independently for the specific application. The G45 turbine housing catalog offers eight configurations -- four A/R options in the Open/V-Band (O/V) inlet series and four in the Divided T4 (Div T4) inlet series. The 1.15 A/R O/V housing occupies the mid-range of the O/V series, balancing turbine spool efficiency against peak exhaust flow capacity for the displacement ranges and power targets that commonly use the G45. This guide covers the full G45 turbine housing catalog, how O/V and Divided T4 inlet types compare, and what builds are best matched to this Garrett Performance Upgrade platform.

G45 Turbine Housing Specifications: O/V and Divided T4 Inlet Series

The Garrett G45 turbine housing catalog covers two inlet types across four A/R ratios each:

Open/V-Band (O/V) Inlet / V-Band Outlet -- four A/R options:

• 1.01 A/R (757707-0019) -- tightest O/V turbine area; fastest spool but highest backpressure at peak exhaust flow
• 1.15 A/R (757707-0020) -- mid-range O/V; balances spool response and peak flow for a broad range of displacements
• 1.28 A/R (757707-0021) -- larger O/V area; lower backpressure at peak RPM, suited to higher-displacement builds
• 1.44 A/R (757707-0022) -- maximum O/V area; minimum turbine backpressure for very large displacement or high-RPM builds

Divided T4 (Div T4) Inlet / V-Band Outlet -- four A/R options:

• 1.01 A/R (757707-0023), 1.15 A/R (757707-0024), 1.28 A/R (757707-0025), and 1.44 A/R (757707-0026) -- same A/R progression as the O/V series in a Divided T4 manifold bolt pattern

The Open/V-Band (O/V) inlet uses a V-Band clamp connection at the turbine housing inlet instead of a bolt-flange manifold interface. This is common on custom-fabricated exhaust manifolds built with a V-Band discharge fitting, and on compound turbocharger outer housing configurations where the upstream charger feeds the G45 through a V-Band connection. The Divided T4 inlet uses a 4-bolt T4 flange in a divided configuration -- the divided (twin-scroll) design keeps the two exhaust cylinder banks separated through the turbine housing to preserve pulse energy from each bank's exhaust events, which improves turbine efficiency especially at lower RPM. The Div T4 is the standard inlet for diesel performance builds on platforms that use T4 exhaust manifolds, and for gasoline builds where twin-scroll exhaust manifolds are fabricated to exploit the pulse energy advantage.

All eight housings use a standard V-Band outlet for the downpipe connection and standard rotation (the turbine wheel spins in the conventional direction for a front-engine, rear-wheel-drive or four-wheel-drive single-turbo layout).

Top Picks: Garrett G45 Turbine Housings and Super Core

The Garrett G45 Turbine Housing Kit O/V V-Band / V-Band 1.15 A/R Standard Rotation (757707-0020) is the primary mid-range O/V turbine housing for G45 builds on medium-to-large displacement engines using a V-Band discharge exhaust manifold or a compound inlet configuration. It provides a broad operating range that works across a wide displacement span at the G45's 1500 hp-range power target. The Garrett G45 Turbine Housing Kit O/V V-Band / V-Band 1.01 A/R Standard Rotation (757707-0019) is the tighter alternative for builds prioritizing faster spool response over peak top-end exhaust flow. The Garrett G45 Turbine Housing Kit O/V V-Band / V-Band 1.28 A/R Standard Rotation (757707-0021) is the larger-A/R option for high-displacement engines or higher-RPM power bands where reducing turbine backpressure at peak output is the priority. For Divided T4 manifold applications at the same 1.15 A/R specification, the Garrett G45 Turbine Housing Kit Div T4 / V-Band 1.15 A/R Standard Rotation (757707-0024) provides identical turbine performance in the T4 flange inlet configuration. The turbine housing pairs with the Garrett G45-1500 Super Core Standard Rotation Super Core Assembly (888169-5005S) or other G45 Super Core options available in the Garrett G Series turbocharger catalog.

Match to the Build

• Single-turbo diesel or gasoline build targeting 800-1500 horsepower using a V-Band discharge manifold: The 1.15 A/R O/V housing is suited to builds where the exhaust manifold uses a V-Band outlet connection rather than a T4 bolt flange, covering engine displacements from approximately 4 to 7 liters depending on boost target and RPM range; the mid-range 1.15 A/R provides a balance between spool speed and peak flow that works across this displacement range without strongly biasing toward either low-RPM response or maximum top-end flow
• Compound turbocharger setup using the G45 as the large primary charger with V-Band discharge from the small secondary: In a compound configuration where a smaller high-pressure turbo feeds the G45 primary through a V-Band connection, the O/V inlet of the 757707-0020 accommodates the V-Band discharge from the secondary housing; the 1.15 A/R provides a good balance for compound builds where the primary G45 sees the combined exhaust flow from both banks and needs to spool across the secondary's operating range
• High-output diesel drag build on the G45 platform at its rated power ceiling: Diesel drag builds at 1200-1500 horsepower on the G45 with a twin-scroll or V-Band manifold use the 1.15 A/R O/V as a starting point, stepping to the 1.28 O/V if data logging shows turbine backpressure limiting peak power; the modular turbine housing purchase allows this A/R change without replacing the Super Core
• Replacing a turbine housing on an existing G45 build to adjust A/R for a power level or displacement change: The G45's modular design means A/R adjustments are made by purchasing a new turbine housing rather than a complete turbocharger; a build that has changed engine displacement or power target can step to a different A/R while retaining the same Super Core assembly

Signs the Turbine Housing Is Limiting the Build

• Turbine inlet pressure exceeding compressor outlet pressure at peak RPM under data logging -- the turbine housing flow area too small for the exhaust volume the engine is generating at maximum output; excess turbine backpressure creates a pumping loss that reduces power; stepping from the 1.01 or 1.15 A/R to the 1.28 O/V reduces this condition when confirmed by data logging
• Power output plateau below the build's fueling and boost potential -- the engine not reaching its thermodynamic output ceiling because turbine restriction is the limiting constraint at peak RPM; identifiable when other systems are not at their limits but power stops climbing at the expected rate; a larger A/R housing removes the turbine-side restriction and allows the build to reach its potential
• Exhaust manifold surface temperatures rising faster than expected under sustained high-output operation -- backpressure from an undersized turbine housing causing exhaust heat to back up into the manifold rather than flowing through the turbine efficiently; a larger A/R housing reduces this backpressure and the associated manifold temperature rise
• Cracking at the V-Band outlet flange or inlet V-Band groove on an existing turbine housing -- thermal cycling fatigue from repeated heat and cool cycles on a performance build; a cracked housing requires replacement before exhaust leaks develop at the outlet joint; the 757707-0020 is the direct O/V 1.15 A/R replacement for a G45 build with a worn original housing

Frequently Asked Questions

When should I choose O/V over Divided T4 on the G45?

Choose the O/V inlet when the exhaust manifold uses a V-Band discharge fitting rather than a T4 bolt flange. Custom fabricated manifolds for single-turbo gasoline builds and compound turbocharger secondary discharge connections commonly use V-Band, making the O/V series the correct choice. Choose the Divided T4 inlet when the exhaust manifold uses a T4 flange in a divided (twin-scroll) configuration, which is standard on diesel performance builds and fabricated twin-scroll gasoline manifolds. The A/R ratio options are identical between the two series -- the 1.15 O/V and 1.15 Div T4 housings provide the same turbine A/R and flow characteristics; only the manifold connection interface differs.

Bottom Line

The Garrett G45 Turbine Housing Kit O/V V-Band 1.15 A/R Standard Rotation (757707-0020) is the mid-range turbine housing for G45 builds on V-Band discharge manifolds at the 800-1500 hp range. It pairs with any G45 Super Core through the standard V-Band outlet and covers single-turbo and compound primary applications where the 1.15 A/R balances spool efficiency and peak exhaust flow. Step to the 1.28 O/V for higher-displacement or higher-RPM builds where backpressure data shows the 1.15 is the limiting constraint at peak power.