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The Specifications of a Garrett T25 Turbo

by Amanda Gronot

A "turbo," short for turbocharger, is a gas compressor in an internal combustion engine that allows the engine to take in more air, which means the engine has more oxygen for combustion and can therefore produce more power. Garrett specializes in producing turbos for all types of cars, from BMWs and Audis to racing cars. It manufactures small, medium, large, ball-bearing T-series and drag racing turbos. The T25 is a medium-size turbo.


The T25 Turbo has an oil- and water-cooled bearing system. It is the smallest ball-bearing turbocharger produced by Garrett, which means it uses balls to separate the moving parts of a bearing. It has an internal wastegate, which is a valve that diverts exhaust gases away from the turbine wheel in the engine, and an inlet flange, which is essentially a strengthening rib or rim. This turbo is best for smaller engines with up to 270 horsepower. There are three models of T25 Turbos: the GT2554R-471171-3, the GT2560R-466541-1 and the GT2560R-466541-4.

Compressor Dimensions

The GT2554R-471171-3 compressor has an inducer of 42 mm and an exducer of 54.3 mm. The "inducer" is where flow enters a wheel, which, for a compressor, means it is the "minor" diameter, and the exducer is the "major" diameter. This is reversed for the turbine wheel. The compressor has a "trim," or ratio between the areas of the inducer and exducer, of 60. The area/radius, or "A/R," which is a geometric relationship between different parts of the turbo housing, is 0.80. The GT2560R-466541-1 and the GT2560R- 466541-4 have an inducer of 46.5 mm and an exducer of 60.0 mm, with a 60 trim and a 0.6 A/R.

Turbine Dimensions

The turbine for all models of the T25 has a 41.7 mm exducer and a 53 mm inducer with a 62 trim and an A/R of 0.64.

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