Garrett turbo oil restrictor GT25, GT28, GT30, GT35, GT40 AN-3

For: Garrett GT series ball bearings turbochargers

An oil restrictor is recommended for optimal performance with ball bearing turbochargers. Oil pressure of 40 – 45 psi at maximum engine speed is recommended to prevent damage to the turbocharger’s internals. In order to achieve this pressure, a restrictor with a 0.040” orifice will normally suffice, but you should always verify the oil pressure entering the turbo after the restrictor in ensuring that the components are functioning properly. Recommended oil feed is -3AN or -4AN line or hose/tubing with a similar ID. As always, use an oil filter that meets or exceeds the OEM specifications.

OIL LEAKAGE SHOULD NOT OCCUR ON A PROPERLY FUNCTIONING SYSTEM IF RESTRICTOR IS NOT USED UNLESS THE SYSTEM PRESSURE IS EXCESSIVELY HIGH.

Journal-bearings function similarly to rod or crank bearings in an engine – oil pressure is required to keep components separated. An oil restrictor is generally not needed except for oil-pressure-induced leakage. The recommended oil feed for journal bearing turbochargers is -4AN or hose/tubing with an ID of approximately 0.25”. Be sure to use an oil filter that meets or exceeds the OEM specifications.