Garrett GT4508R Turbochargers

What the Garrett GT4508R is

The GT4508R is a Garrett GT45-series ball-bearing turbo with an oil and water cooled bearing system. Garrett’s archived pages rate it at 700 to 1,100 horsepower on engines of 2.0 to 8.0 liters (its 2015 catalog says 600 to 1,100), with a 108 mm compressor exducer, a 0.69 A/R compressor housing and an 87 mm, 85 trim turbine wheel; the compressor inducer is given as 81.6, 80.8 or 79.8 mm depending on the year. Its free-float turbine housings (1.01 to 1.44 A/R) have a T4 inlet and a 4 inch V-band outlet. It is no longer in Garrett’s current online catalog.

This page lists complete GT4508R turbos, a supercore, CHRAs and a gasket set. Garrett’s own guidance on turbine housings: a smaller A/R gives quicker boost response and more turbine power at low engine speed; a larger A/R lets the wheel flow more, with lower back pressure and more power at high engine speed.

Sources: Garrett GT4508R (archived 2006) · Garrett catalog volume 5 (2015, archived) · Garrett: Turbine Housings 101