Garrett G55: Specs, Fitment, and Is It Worth It

The Garrett turbocharger G55-2250 is the largest unit in Garrett's G-Series super core lineup and one of the most capable single-turbo compressor assemblies available for diesel performance applications. At 94mm inducer and rated for up to 2,250 horsepower, the G55 super core is not a street-and-tow upgrade -- it is the top of the single-turbo power range for a fully built diesel engine on an aggressive fuel system. This guide covers the G55-2250 specs, the platforms it fits, the fuel system requirements to support it, and an honest assessment of who should buy it versus who would be better served by a smaller Garrett turbocharger from the same G-Series family.

G55-2250 Specs and Sizing

The Garrett G55-2250 super core (880547-5004S) is the compressor and turbine cartridge assembly only -- a super core does not include a turbine housing or compressor cover. The builder specifies those separately to match the engine's exhaust outlet and desired boost characteristics. Key specs:

• Compressor wheel inducer: 94mm
• Compressor wheel exducer: approximately 130mm
• Power rating: up to 2,250 horsepower
• Bearing type: Garrett journal bearing with oil-fed center section
• Configuration: super core assembly (CHRA) -- turbine housing and compressor cover sold separately
• Compressor map: optimized for high-flow diesel and gasoline applications at maximum build levels

The G55 fits at the top of Garrett's G-Series single-turbo lineup, which also includes the G25, G30, G35, G40, and G45. Each step up the lineup adds compressor wheel size, maximum flow capacity, and the engine displacement and power level it is optimized for. The G55 at 94mm is in the compound-high-pressure or maximum-single-turbo territory -- it is the right tool when nothing smaller will support the fuel system's output ceiling.

What Platforms the G55 Fits

Because the G55 is sold as a super core without housing, fitment is not determined by the super core itself but by the turbine housing and compressor cover the builder selects. This makes the G55 a universal assembly that can be adapted to any diesel or gasoline platform with the correct housing combination. Common diesel fitment applications include:

• Large-displacement Cummins builds (5.9L and 6.7L): Stage 4 and stage 5 competition builds running 400-plus-over injectors and a compound setup where the G55 serves as the primary drive turbo. The high-pressure position on a compound build for max-effort 5.9L and 6.7L Cummins engines is a common application for this compressor size.
• Built Duramax 6.6L: High-output LBZ, LMM, and LML builds on a fully modified fuel system. The G55 supports the airflow ceiling on a built Duramax injector and CP3 setup where a GT4094 or similar Duramax-specific upgrade has already been outgrown.
• Built 6.7L Power Stroke: Maximum-output Scorpion builds on 300-over-plus injectors where the factory compound system has been converted to a large single or compound with the G55 in the high-pressure position.
• Diesel drag racing and sled pulling: Competition-oriented applications where maximum compressor flow at a specific boost target is the primary design parameter. The G55 is well-suited to applications where the entire drivetrain has been built around the compressor map.

For street and tow builds or trucks running a daily tune, the G55 is substantially oversized. A smaller Garrett turbocharger from the same family -- the GT3794VA Stage 1 for the LBZ/LMM Duramax or the GT4094VA Stage 2 -- is the correct choice for street-driven builds because the compressor maps on those units are sized to produce efficient boost in the RPM and flow ranges a street truck operates in. The G55 at 94mm would be significantly outside its efficiency island at the boost levels a street truck runs, producing hot, inefficient boost where a properly sized unit produces dense, cool charge air.

Top Picks: Garrett G55 and Related Turbocharger Options

The Garrett G55-2250 94mm Super Core (880547-5004S) is the correct part for a maximum-output diesel build where the builder is specifying the turbine housing and compressor cover separately to optimize the build for a specific power target and boost curve. Garrett manufactures the G55 super core with the same precision bearing and seal standard as their OEM programs, built to tighter tolerances than most aftermarket competition alternatives at this compressor size.

For Duramax builders on the 2004.5-2009 LBZ and LMM platform who are not at the maximum-output build level, the GT3794VA Stage 1 and GT4094VA Stage 2 direct-fit kits are the appropriate Garrett upgrade path. These units include the turbine housing and all required hardware for a complete installation without custom fabrication. The Garrett PowerMax GTB1752V fills the same direct-fit role for the 2016+ Colorado and Canyon 2.8L Duramax. Each of these kits is a complete, platform-specific upgrade where the G55 super core is the assembly for builders who need maximum flow and are specifying housing and cover components themselves.

Browse the full turbocharger and actuator catalog for G-Series super cores, VGT actuators, and platform-specific turbo kits.

Match to the Build

Whether the G55 is the right Garrett turbocharger for a given build comes down to three questions: what power level is the engine targeting, what does the compressor map show at that boost and flow point, and does the fuel system support the airflow the G55 moves?

• Under 800 horsepower: The G55 is outside its efficiency island at power levels below 800 horsepower. A G35, G40, or G45 is a better fit depending on the application. Running the G55 undersized results in excessive charge air temperature, poor spool, and no performance advantage over a correctly sized unit.
• 800-1,400 horsepower single-turbo: The G55 is in its intended operating range. The fuel system must match: on a Cummins this means stage 5 injectors and multiple CP3 pumps or an equivalent high-volume fuel supply. On a Duramax it means a built CP3 setup with matched injectors at the same flow rate. The tune must be calibrated to the G55 compressor map specifically.
• Compound setup high-pressure position: The G55 works as the high-pressure unit in a compound arrangement on maximum-output engines. In this configuration a large atmosphere turbo feeds the G55, which then drives boost to the engine at the high-pressure stage. This setup is common in diesel drag and pulling classes where the compound arrangement fills the G55 efficiently across the RPM range.
• Turbine housing selection: Because the G55 is a super core, the turbine housing A/R ratio is the primary variable the builder selects to tune spool characteristics. A tighter A/R improves low-RPM response; a larger A/R supports maximum flow at the top end. Match the housing to the intended RPM range and boost target before committing to the housing selection.

Signs Your Current Turbo Has Outgrown Its Map

Builders upgrading to the G55 are typically coming from a smaller unit that is no longer meeting the engine's airflow demand:

• Boost pressure hitting a ceiling at wide-open throttle despite injectors and fuel system having headroom to push further
• Compressor outlet temperature climbing rapidly at full load -- the existing unit is working beyond its efficiency island
• EGTs rising faster than expected at high power levels, indicating insufficient air mass relative to fuel delivery
• The dyno sheet plateauing in a way that correlates with turbo inlet restriction rather than injector or fuel system limits
• A scan tool showing the intercooler outlet temperature climbing under sustained load rather than dropping or holding -- the charge air is entering the intercooler hotter than the intercooler can manage

Frequently Asked Questions

Does the G55 super core include a turbine housing and compressor cover?

No. The G55-2250 (880547-5004S) is the center section cartridge assembly only. The turbine housing and compressor cover are specified and sourced separately by the builder. This allows the builder to optimize the housing combination for the specific application, exhaust outlet, and boost target rather than being locked into a single housing configuration.

What oil feed and drain fittings does the G55 use?

The G55 uses standard Garrett journal bearing center section oil feed and drain port sizing. A -4AN oil feed line and a gravity-drain -10AN or -12AN oil return are typical installations. Confirm the exact port sizing on the specific super core assembly before plumbing -- Garrett publishes dimensional drawings for each G-Series model.

Is the G55 a good fit for a compound turbo setup?

Yes. The G55 is commonly used in the high-pressure position of a compound arrangement on maximum-output diesel engines. In compound configuration, the atmosphere turbo pre-compresses intake air before it enters the G55, which allows the G55 to operate efficiently across a wider RPM range than it would in a single-turbo configuration on the same engine.

Bottom Line

The Garrett G55-2250 94mm super core is the right Garrett turbocharger assembly for maximum-output diesel builds targeting 800 horsepower and above, where the builder is specifying housing components and the fuel system has been built to match the compressor map. For street and tow builds or platform-specific direct-fit upgrades on the LBZ, LMM, or 2.8L Colorado Duramax, the GT3794VA, GT4094VA, or PowerMax GTB1752V kits are the complete, correctly sized options. The G55 is a precision assembly for builds that genuinely need 94mm -- match the compressor to the engine, and the G55 will deliver everything Garrett designed it for.