The use of turbo timers to shut the engine off some preset time after the ignition key is removed was needed in the old days. Early turbocharger bearing housings were only cooled by the lubrication oil of a running engine passing by the turbine bearing. If the engine was shut of when the turbine was still very hot excessive heat wick into the turbo bearing and seal area, cooking the oil to black carbon, causing bearing/shaft failure and heavy oil consumption. The newer (for over 15 years now) style turbo housings are water cooled as well as oil cooled. The original EJ20 Subaru turbo motor took advantage of water cooled bearings from the start and have never had this problem due to a unique design feature we will now explain. It is the reason you do not need to purchase a turbo timer.

The Subaru WRX engines have their water catch tank high on the engine above the turbocharger. It is that little can where you check the water level. When the engine is shut off the water continues to circulate via a physical property of water called a thermal siphon. Simply put, hot water rises up to the catch tank, being drawn from the relatively cool cylinder head water jacket up through the turbo housing. This nifty little idea works every time you turn off your engine.

One still needs to take a cool down lap at the track and perhaps should not stop at the top of a mountain pass to enjoy the view if you have been on the boost all the way up, but for the other 99% of the time there is no need to let the engine idle for a minute before shutting off ignition. Even when the engine is off, the cooling water will circulate past the turbine bearing housing.