Turbo cars and start/stop technology?

I did a lot of research on how to look after turbo cars before I got the 335 and one of the things that were always advised was to leave the engine running at least 30 secs after a drive to let turbos cool a little since switching the engine off will cut the oil from them, so since I got the car I religiously leave it running 1-2 mins after a drive. My colleague at work has a 320d with start/stop, and it got me thinkig would that not make the life of the turbo a lot shorter with the oil being cut from it constantly in start/stop traffic probably while it's spinning too?

I did a bit of researching too, with the turbos being water and oil cooled, the ECU will continue to cool the turbo post shutdown with the electric water pump.

But even so it's no harm to do it, I drive easy for the last few minutes of my journey and let it idle for 30secs to a minute.

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Excellent, didn't know that! So that's why it has an electric water pump? And I thought they were just being awkward :D no harm in leaving it running a little bit though as you say.

Actually, that takes care of cooling but what about lubrication? Would the turbos not be spinning dry when the engine is switched off still? Do they have an electric oil pump top? So many questions!! Interesting stuff to know though :)

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Originally Posted by Peter-E36

Excellent, didn't know that! So that's why it has an electric water pump? And I thought they were just being awkward :D no harm in leaving it running a little bit though as you say.

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Electric water pump reduces parasitci load on the engine increasing performance and efficiency.

It also reduces heat soke after the engine is shut down as it continues to circulate the coolant being powered off the battery.

Quote:

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Originally Posted by Peter-E36

Actually, that takes care of cooling but what about lubrication? Would the turbos not be spinning dry when the engine is switched off still? Do they have an electric oil pump top? So many questions!! Interesting stuff to know though :)

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Turbos are "spun" by exhaust gas. There is no exhaust gas when the engine is not running.
Oil pressure is maintained long enough for impellers to spool down.

Thanks Doc :D

That answers that then! I was thinking it's a bit crazy to expect someone who's spending 80k on a new car to wait 2 mins everytime before switching off the engine! ....I'll still let it run a little though before switching it off just to be safe :p