GT Basics / Nomenclature
Today, Garrett has a wider selection of GT-series turbos available than ever before. As a result of this, please note that we have made a subtle modification to the GT nomenclature.
In our product catalog, all offerings are grouped according to their turbine wheel frame size. The frame size of a turbo or CHRA is dictated by its turbine wheel inducer diameter . The larger the turbine inducer, the bigger the frame size-- so any turbo in the GT42 family has a larger turbine wheel inducer than those in the GT35 family, and so on.
In the model name of each turbo or CHRA, you'll also notice two digits after the frame size. These two digits refer to the compressor exducer diameter, as measured in millimeters.
Let's use the GT4294 as an example. This unit has a GT42 frame size turbine coupled to a 94mm (exducer diameter) compressor wheel.
If there's an "R" on the end of a model name, this means the unit is ball bearing. So, a GT4294 is not ball bearing; whereas a GT4294R is ball bearing.
The biggest change related to the nomenclature is this: units which utilize a 53mm turbine wheel (as measured at the inducer) are now referred to as "GT25" frame size, while units employing the slightly larger 53.85mm turbine wheel are now referred to as "GT28" frame size.
For those familiar with our product range, this means that the unit formerly known as "the GT28R" (part number 466541-1) is now in the GT25R family. More specifically, it is now a GT2560R model.
A Guide To Garrett’s "GT" Model Numbers
* Positions "xx" refers to the frame size of the turbine wheel inducer.
o For example the "GT28" in "GT2860RS" refers to its turbine wheel frame size family. All GT28 units use a turbine wheel with 53.85mm inducer diameter
o As a rule of thumb, the larger the number, the larger the turbine wheel.
* Positions "yy" designate the compressor wheel exducer (major) diameter in millimeters
o The "60" in the GT2860RS example above has a 60mm compressor wheel exducer diameter.
o Note: Wheel sizes 100mm and over omit the "1" (hundreds digit)
o Example: the 02 in a GT4202 refers to its 102mm compressor wheel exducer diameter
* Positions "zz" may be used to designate special features of a particular turbocharger where applicable
o Example: GT2860RS
o "R" = this is a Ball Bearing unit
o "S" = used for units which require some differentiation from units in the same family
Compare a GT2860R to a GT2860RS. While both are ball bearing and externally similar, the GT2860RS is better suited for higher-flow applications than the GT2860R. In this case, the S reflects the higher-flowing nature of the GT2860RS