Does my turbo require an oil restrictor?

Yes — all Kinugawa turbo install kits include an oil restrictor. The restrictor limits oil pressure entering the bearing housing, preventing seal failure, oil leakage, and premature wear. Orifice size varies by bearing type: 1.0mm for GT Ball Bearing series, 1.5mm for all TD series.

See also: What is the suitable oil pressure on a turbocharger?

Oil Restrictor Specs by Bearing Type

What Oil Pressure Does a Ball Bearing Turbo Require?

Ball bearing turbos require 40–45 psi at maximum engine speed. A 1.0mm–1.5mm orifice restrictor is sufficient for most applications. Always verify oil pressure at the turbo inlet after installation — do not rely solely on engine oil pressure readings. Use a -4AN feed line and an oil filter that meets or exceeds OEM specifications.

Do Journal Bearing Turbos Need an Oil Restrictor?

Yes. A restrictor maintains the hydrodynamic oil film that separates rotating metal components, reducing wear and preventing oil from being forced past the seals. Without it, excess pressure causes oil leakage into the compressor or turbine housing. All Kinugawa TD series journal bearing turbos ship with a 1.5mm orifice restrictor.

How Should the Oil Drain Be Installed?

Use a -8AN or -10AN drain line. The inner diameter must not be smaller than the drain port in the center housing — undersized lines cause oil to back up and leak past seals.

Gravity Feed Angle Rule

The oil drain outlet must follow the direction of gravity within ±15° when the vehicle is on level ground. If a gravity drain is not achievable in your application, install a scavenge pump to actively pull oil from the center housing.

The turbocharger axis of rotation must be parallel to level ground within ±15°. The oil inlet and outlet must be within 15° of perpendicular to level ground.