Garrett G42-1200C Turbochargers

What the Garrett G42-1200 Compact is

The G42-1200 is one of Garrett’s G-Series turbos. It has a 10 mm ceramic dual ball bearing cartridge (the same as the GTX42), a 73 / 91 mm compressor wheel with 10 blades, and an 82 / 75 mm, 84 trim turbine wheel of Inconel rated for temperatures up to 950 °C, which Garrett says flows 10% more than the GTX42’s. Garrett rates it at 475 to 1,200 horsepower, calculated from compressor flow, on engines of 2.0 to 7.0 liters on its catalog pages (its G42 sell sheet says up to 8.0 liters). Its stainless turbine housings, with T4 or V-band connections in 1.01, 1.15 and 1.28 A/R, are free-float, for use with an external wastegate.

The Compact version (supercore 860778-5002S) has a compressor housing that Garrett says is 4 mm shorter axially and 29 mm smaller radially than the standard one, with a 0.90 A/R compressor housing instead of 0.85; Garrett gives its maximum speed as 118,000 rpm. This page lists Garrett’s complete turbo assembly kits with the compact housing and T4 divided or V-band turbine housings in 1.01, 1.15 and 1.28 A/R, the supercore and the CHRA. 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 G42-1200 Compact catalog page · Garrett G42 sell sheet (PDF) · Garrett: Turbine Housings 101

G42-1200C specifications

Wheel sizes are inducer / exducer, taken from the specification published for each part number. The turbine housing sizes are the ones on the listings above; the same turbo is sold with several.

On G Series turbos the number after the dash is Garrett's horsepower rating: a G30-660 is rated for up to 660 hp.