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      11-30-2011, 12:50 PM   #1
CarAbuser
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Auto Start/Stop + Turbo Lifespan

I've noticed a lot of people saying that to prolong the turbo life the engine needs to be left running for a time after parking up.

I'm guessing this is to allow oil to circulate to cool the turbo. But since my car turns off the moment I take my foot off the clutch will this cause a reduction in turbo lifespan?
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      11-30-2011, 02:12 PM   #2
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I'm pretty sure the turbos are water cooled and the electric waterpump keeps running even whilst the car is off.
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      11-30-2011, 03:06 PM   #3
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Personally, I always turn off the Auto Start/Stop when I am in a traffic situation which requires me to put the car in neutral and take the foot off the clutch.

I'm sure BMW must have done plenty of R+D on the feature but I just don't get on with the idea of the engine turning off like that suddenly whilst it is hot and re-starting.

Maybe its just me worrying for nothing?!
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      12-01-2011, 03:01 AM   #4
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Yes, BMW have done plenty of research and it genuinely saves fuel, once you get used to it.

It used to be the case years ago that idling a while to keep up oil pressure as the turbo spooled down was necessary but you don't need to worry these days. The turbo is water-cooled, as mentioned, and the oil system has relief valves which can maintain pressure whilst the turbo spools down.
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      12-01-2011, 03:16 AM   #5
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Early Turbos used to need a timer or be allowed to run because when the turbine spindle stopped spinning, the very thin layer of oil between the spindle and the bearing used to cook and turn to flaky carbon. The next time the turbo spooled up, the carbon deposits circulated around the oil system and in time blocked the oil ways.

Now with water cooling the oil directly around the turbo stays much cooler and doesn’t boil.
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      12-01-2011, 03:29 AM   #6
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Not only that Del, but that was in the early days with mineral oil which, as you say, would soon boil at turbo temperatures if not circulated. Fully synthetic oil will not break down in the same way.
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      12-01-2011, 03:36 AM   #7
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Quote:
Originally Posted by xenon View Post
Not only that Del, but that was in the early days with mineral oil which, as you say, would soon boil at turbo temperatures if not circulated. Fully synthetic oil will not break down in the same way.
Agree Ian. hence my comment "Early Turbos"
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      12-01-2011, 04:08 AM   #8
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Thanks for the answers.
Kind of expected as much but it's reassuring to get confirmation.

I usually let the start/stop do it's thing with traffic lights but in start stop traffic I just keep it in gear.
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      12-06-2011, 06:23 AM   #9
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This is true of older turbo designs without active cooling beyond the oil used to lube the main bearing. For example my old Impreza needed a 'cool down' period of about a minute after hard driving to stop the oil in the bearing boiling off and creating a glaze of the bearing that eventually gums it up. However, newer turbo designs have added cooling and in some cases water cooling, so this isn't an issue.

Also you would hope that BMW would have thought of this when designing a car that stop/starts...

I'm on my second S/S 120d and there have been no turbo issues. I don't like the fact there is no water temp gauge in it, though. Luckily my M3 does have an oil temp gauge, this I like!
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