said by itguy05:said by Kearnstd:Never knew that about turbos. Though maybe its variable per car. I have the turbo engine in my 2012 Cruze and the manual never mentioned sitting there idling for a bit.
Depends on the car. I know with Ford's Ecoboost engines the turbo bearings (What get hot) are water cooled and do not need an idle down period. They circulate coolant around them and that will keep them cool when shut off.
From Ford directly:
"Designed for a life cycle of 150,000 miles or 10 years, EcoBoosts turbochargers feature water-cooled bearing jackets. This architecture is designed to prevent oil coking that could occur in previous-generation turbochargers. The new design means that EcoBoost drivers dont need to observe special operating precautions, such as idling the engine before switching it off."
Here is the real scenario that happens with turbos.
Turbos can spin in excess of 50,000+ RPM's. When it is spooled up "IE. making boost" the water does help keep the temps down and the oil keeps the bearing lubed (which is what helps keep it from destroying itself). But here is the kicker.
When you shut the engine off after acceleration and a quick stop, or rev the engine before just before shutdown (this is mostly for those with manual tranny's), the turbo keeps spinning until it stops after the engine is off. The speed at which the turbo was operating at before engine shutdown determines how long it will take the turbo impellers to stop spinning. "The slower the better" before shut off. When shut off and the turbo is still spinning down, not all cars are still circulating the coolant and/or oil to keep the bearings cool. This is where you run into short life spans. Even if your Ford has liquid cooled bearings does it still have a water pump circulating the coolant to the turbo, or a after oilier circulating oil to it? So it is still wise to wait a minute or several seconds before you shut the engine down, because not all cars have those function. My VW GTI has a secondary "timed" electric water pump just to pump the coolant to the turbo after shutdown. A nice feature but I still wait for the turbo to slow before shutting it off.