Is a restrictor required for your turbo?

From time to time it seems like some of our customers are confused about whether a restrictor is required for their turbo, so we’ll briefly discuss about it here. A restrictor adjusts the oil pressure it injects into the bearing system. Most of the cases we include a restrictor with our turbo whether it’s a journal bearing or ball bearing system turbo.

You’ve probably heard journal bearing turbos do not require a restrictor, however, with a restrictor that increases the injecting oil pressure, it ensures better lubrication, keeping the components separated by a hydrodynamic film, this greatly reduces the chance of oil leakage and smoke coming out of exhaust, consequently prolongs turbo life.

As for ball bearing system turbochargers, a restrictor is definitely required, if not, it often leads to oil leakage and premature wear of the components, finally cause failure of the turbo. When oil pressure is too low, it might not run through the ball bearing properly, when oil pressure is too high, it may result in oil leakage either from the compressor side or turbine side. With the structure of ball bearing, proper oil pressure is essential to keep the ball bearing function well. Using a 1mm diameter orifice restrictor controls the oil feed pressure at around 40-45psi, this ensures the bearing to be fully lubricated, therefore prolonging turbo life.

Keep in mind that besides a restrictor, carefully choosing appropriate oil feed lines and oil drain lines are imperative as well. Often times we use a -4AN oil feed lines with -10AN oil drain lines to maintain proper oil flow.