Garrett G38: Specs, Fitment, and Is It Worth It

The Garrett G38-1000 turbocharger is a 62mm G-Series II supercore platform rated to 1000 horsepower, positioned between the G35 and G40 in Garrett's G-Series lineup. Where the G40 uses a 76mm compressor wheel to reach 1000-1250 hp, the G38 achieves the same 1000 hp ceiling with a more compact 62mm inducer -- a result of the G-Series II aerodynamic improvements that extract more flow and efficiency from a smaller wheel diameter. For builds where packaging a 76mm compressor frame is difficult, or where the goal is 1000 hp with faster spool than the G40's larger turbine section allows, the G38-1000 G-Series II is the more compact alternative that does not sacrifice the power ceiling. The G38 supercore pairs with Garrett's G38/GXR38 turbine housing kits available in V-Band/V-Band and divided T4/V-Band configurations across three A/R options. This guide covers the Garrett G38 platform specifications, how the turbine housing selection works, and what builds this Garrett turbocharger serves best.

Garrett G38-1000 Specifications and Platform Overview

The G38-1000 G-Series II is sold as a supercore -- the CHRA (center housing rotating assembly) paired with the compressor housing as a complete rotating assembly, ready to mate with a separately purchased turbine housing kit. Key specifications:

• Compressor inducer: 62mm billet aluminum compressor wheel
• Power rating: 1000 hp
• Generation: G-Series II CHRA with updated compressor aerodynamics, improved bearing preload, and wider efficiency island versus the first-generation G-Series design
• Turbine housing compatibility: G38/GXR38 turbine housing kits; available in O/V V-Band/V-Band (open V-Band compressor inlet, V-Band turbine outlet) in 0.85, 0.95, and 1.06 A/R; also available in divided T4/V-Band configuration in 0.85, 0.95, and 1.06 A/R
• Rotation: Standard rotation (counterclockwise from compressor inlet)

The G38 occupies a specific role in the G-Series lineup: it is the highest-powered single supercore available in a 62mm compressor frame. The G35-990 G-Series II tops out at 990 hp; the G38-1000 G-Series II raises the ceiling to 1000 hp in a 62mm package. The G40-1000 G-Series II also achieves 1000 hp but uses a 76mm compressor wheel that requires a physically larger turbine housing and produces a different spool characteristic. For a build where 1000 hp is the target and the smaller compressor frame provides a packaging or spool advantage, the G38-1000 G-Series II is the correct supercore.

Like the G35 and G40, the G38 is modular: the supercore is one purchase and the turbine housing kit is a second, separate purchase. No complete assembled turbocharger is sold for the G38 -- buyers select the housing A/R and inlet configuration independently from the rotating assembly. The turbine housing kits are shared with the GXR38 platform, which is Garrett's competition variant of the G38; the housing part numbers serve both the G38 and GXR38 supercores.

Top Picks: Garrett G38 Turbocharger Configuration

The Garrett G38-1000 62mm G-Series II Supercore Assembly (938272-5003S) is the single supercore option for the G38 platform -- there is only one power tier for the G38, unlike the G35 or G40 which offer multiple hp ratings. The G-Series II CHRA in the G38-1000 delivers the current-generation bearing design and compressor map that places the G38 at 1000 hp with a 62mm wheel, which is a meaningful aerodynamic efficiency improvement over what required a larger-frame turbo to achieve in earlier generations. A turbine housing kit must be ordered separately to complete the assembly.

For a V-Band exhaust manifold application, the Garrett G38/GXR38 Turbine Housing Kit O/V V-Band / V-Band 0.95 A/R (757707-0038) is the most versatile starting-point housing for a large diesel or gasoline single-turbo build at 1000 hp. The 0.95 A/R provides a balance of spool speed and top-end flow suited to large-displacement engines where the turbine needs to process high exhaust gas volume without restrictive backpressure at peak output. For a build with a T4-flanged exhaust manifold, the Garrett G38/GXR38 Turbine Housing Kit Div T4 / V-Band 0.95 A/R (757707-0043) provides the same 0.95 A/R in a divided T4 inlet configuration that mates to T4 exhaust manifold flanges common on diesel truck platforms. Browse the complete Garrett G-Series turbocharger catalog for all G38 supercore, turbine housing, and related G-Series options.

Match to the Build

• Large diesel single-turbo build at 900-1000 hp where a compact compressor frame is needed: The G38-1000 delivers the same 1000 hp ceiling as the G40-1000 G-Series II but in a 62mm compressor frame that packages more easily in tight engine bays; on diesel platforms where turbocharger mounting space is constrained but the build is targeting 1000 hp, the G38's smaller compressor housing is the correct choice
• Diesel build prioritizing faster spool at 1000 hp: A 62mm compressor wheel requires less exhaust energy to spin up than a 76mm wheel at the same boost target; for a large diesel build where low-RPM boost response matters alongside peak power, the G38 spools faster than the G40-1000 at the same turbine A/R, which improves throttle response and part-throttle boost delivery during towing or street driving
• Gasoline performance engine at 800-1000 hp: The G38 suits large-displacement gasoline builds where the compressor map covers the required flow at the engine's boost and RPM targets; gasoline applications typically select a tighter A/R housing than equivalent diesel builds to account for the higher RPM at which gasoline engines generate their peak exhaust energy
• Low-pressure position in a compound diesel turbo arrangement: The G38's 62mm compressor and available A/R range make it a viable low-pressure unit in a compound setup feeding a factory or smaller high-pressure turbo; the 0.95 and 1.06 A/R housings provide sufficient turbine flow capacity for the high mass flow rates a compound system processes at the low-pressure position

Signs the Existing Turbocharger Needs Upgrading to the G38

• Power output plateauing below 900 hp on a build that is fueled and calibrated for more -- the current compressor reaching its maximum mass flow before the engine's power potential is fully realized; if the existing mid-frame turbo is undersized for the build level, the G38-1000's larger flow ceiling corrects this without stepping up to the G40's larger physical frame
• Compressor surge at elevated boost on the existing turbo -- a rhythmic stutter or flutter under hard boost indicating the compressor map boundary being crossed; characteristic of a turbo undersized for the engine's demanded flow at a given pressure ratio; the G38's G-Series II compressor map provides substantially wider surge margin at 1000 hp flow rates than smaller-frame alternatives
• Excessive turbine backpressure limiting top-end power on the existing housing -- a turbine section that is too small for the engine's exhaust volume creating backpressure above peak power; the G38's 1.06 A/R option addresses this in a large single-turbo application by providing more turbine flow area without requiring a step to the G40's larger-diameter housing
• Physical wear requiring replacement on the existing large-frame unit -- the G38-1000 G-Series II provides a current-specification rotating assembly as a replacement when the existing unit reaches end of service life

Frequently Asked Questions

What is the difference between the G38 and G40 at 1000 hp?

Both the G38-1000 G-Series II and the G40-1000 G-Series II are rated to 1000 hp. The G38 uses a 62mm compressor wheel and the G40 uses a 76mm compressor wheel. The smaller G38 compressor spools faster at equivalent turbine A/R because it requires less exhaust energy to accelerate, which improves transient boost response. The G40's larger wheel flows more air at the same RPM, which extends the efficiency island at the upper end of the compressor map. For a street or tow diesel build where spool speed matters, the G38 has an advantage. For a high-RPM or maximum-effort build where peak flow ceiling is the priority, the G40 provides more headroom above 1000 hp with its G40-1250 variant.

Why do the G38 turbine housing kits say "G38/GXR38"?

The GXR38 is Garrett's competition-oriented variant of the G38 supercore. Garrett designed the turbine housing kits to be compatible with both the standard G38-1000 G-Series II supercore and the GXR38 competition supercore, so the same turbine housing part numbers serve both. The housing selection process -- A/R and inlet type -- is identical whether the supercore is the G38-1000 or the GXR38. This does not affect the G38-1000 build path; the G38/GXR38 turbine housing kits are the correct housings for the G38-1000 supercore.

Bottom Line

The Garrett G38-1000 G-Series II turbocharger delivers 1000 hp in a compact 62mm compressor frame that spools faster than the larger G40 at the same power target. It is a single-configuration platform -- one supercore paired with a separately selected turbine housing kit in the A/R and inlet type that matches the application. For builds targeting 1000 hp where packaging, spool speed, or the precision of a 62mm G-Series II aerodynamic design matters, the G38 is the G-Series option between the G35 and G40 that the catalog provides.