The cure? Cool water. Turbocharger bearing systems that utilize water-cooled center housing sections have been found to be in perfect operating conditions at the end of an entire race season. The water-cooled center section is not for cooling the turbo while its running (normal oil cooling does a good job of that) but is intended for cooling the center bearing section after the hot engine is shut down. The coolant in the center housing carries the heat from the hot housing away from the bearing system, thus preventing the detrimental carbonizing effects of heat soak back. For less stringent applications, air-cooled centers are just fine. But for ball bearing applications, you must always run water cooling for long-term durability due to the low oil flow requirements (less bearing oil means less cooling effect). You may notice that many race cars are equipped with air-cooled ball bearing centers. But keep in mind that they replace (or rebuild) their turbochargers after every race, which is quite a costly proposition.
Take Home MessageJust remember, to prevent FOD failure, always run a good air filter. For you street guys, the cost of a slight inlet depression loss totally outweighs the cost of a new turbocharger! As far as preventing heat soak back failure, run a water-cooled center housing design where possible. Those with ball bearing applications must always run a water-cooled center housing system! In any event, always remember to let your turbocharged engine idle down for a few minutes after a hard session at the track. Following these simple rules will ensure that your turbocharger will live a long and happy life.