1.0mm Oil Restrictor Adapter AN4 This adapter allows you to easily create a custom oil restrictor by placing it between your AN adapter and AN fitting. Ideal for those looking to adjust oil flow without knowing the exact level of restriction from the start. Note : Oil restrictors are only intended for ball-bearing turbochargers. They are generally not recommended for journal-bearing turbochargers (some exceptions may apply). Instructions: Mount your AN4 oil inlet adapter on the turbo. Place the AN4 oil restrictor adapter onto the AN4 oil inlet adapter. Attach the AN4 oil line and tighten. The adapter is made of aluminum and seals like a washer between the two cones. Information Generally, the oil pressure for a car engine usually ranges between 4 and 7 bar, depending on the engine's design, oil viscosity, and engine temperature. A ball-bearing turbo should not exceed around 3 bar at maximum RPM. Smaller hole restrictor = Less flow = Lower pressure Larger hole restrictor = More flow = H