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how long do you let your turbo idle for? 700

About how long do most of you let your 740/760 TiC idle before shutting down? The manual suggests a couple minutes of cool down time. I usually let it idle for 1 minute before turning the car off. I know this is a stupid/useless kind of question but I was just curious.
--
1988 760Tic - 154,000, 1966 M-B 230 sedan - 98,000








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    how long do you let your turbo idle for? 700

    I always let my 944 Turbo idle for 2 minutes before final shutdown. It has a coolant circulating pump on it that cycles coolant through the turbo for 30 seconds after shutdown, AND I run synthetic. But I still give it that 2 minutes. Figure I saved enough time on my way that I can afford to sit once I'm there... ;)








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    how long do you let your turbo idle for? 700

    I never let mine "cool down".
    90 765 B230FT 186,000 original turbo bearing











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    how long do you let your turbo idle for? 700


    A common myth is that watercooled turbos do not need a cool down, but in reality they still have oil running through them to lube the shaft, so if you shut down to soon you still cook the oil that's held in the shaft, and oil does not continue to circulate after you turn off!

    You don't idle for the sake of cooling as such, you idle for the sake of keeping the turbo shaft lubed and to a degree cooled with cooler fresh oil.

    30 seconds is long enough if you have not been driving hard, 2-3min if your on the highway or thrashing or just driving fairly hard.
    Better safe than sorry I'd say, I give mine at least a min most times.
    --
    Veronica, my 85 760Ti








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      how long do you let your turbo idle for? 700



      There is also the common myth that the turbo keeps spinning for maybe a minute or more. If you take the intake hose off and look with a mirror while the engine is shut down you will find that it stops spinning within seconds since the inertia is kept to a minimum to make it spool up fast.Thus it does not need much oil after shut-down.








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        how long do you let your turbo idle for? 700

        Shaft wear happens when it is not getting enough clean cool oil, deposits build up on the shaft when you don't idle down after hard use.
        A hot turbo shaft plus hot oil is a bad thing, the heat soak factor of the turbo sitting with super hot oil in it the issue.

        If you have been running hot, the oil will be hot from both the engine and turbo (the turbo tranfurs a lot of heat to the oil), and on top of that the turbo gets super hot when it's been working hard, the whole idea of idle down time is to let both the turbo itself and the oil cool.

        In just 30 seconds of idling your engine can drop it's oil temp down quite a bit, which means less of a chance of super hot oil breaking down and coking up on the shaft of the turbo.
        Turbo shaft wear is what you are trying to reduce, and the cooler the oil is in the turbo, the less build up you will get every time you shut down.

        Watercooling does help all this, but really the watercooling is more for keeping the turbo cooler when it's running, not when it's shut down, it will cool the turbo down faster, but still does nothing for the actual oil, which is what you want to cool.

        --
        Veronica, my 85 760Ti








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    how long do you let your turbo idle for? 700



    With a watercooled turbo there is really no need for a cool-down period. The water will continue to circulate after the engine is shut down and prevent the heatsoak effect from overheating and coking the oil. This happens due to thermo siphoning. Using synthetic oil in a turbo is also a big help since it can take a lot more heat before turning into abrasive carbon in the turbo bearings.








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    Run synthetic and fageddaboudit. OTOH, 700

    when coming off the freeway hot onto a service station/gas stop or rest area on a road trip, I'll idle cool the car for four or five minutes...I've seen the exhaust header red hot!

    I've also chosen to just let the car idle while gassing up, lock the car with a second key in my pocket you darn betcha! Some of the newer cars won't let you run the engine with the gas cap off without setting an engine check code but I think the 700 series is ok with this. Also, the fuel fill is on the opposite side of the hot exhaust pipe so it's minimal risk. NJ won't let you do this because of their @#%#$% featherbedding law on pump jockeys (no self-serve!).








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    how long do you let your turbo idle for? 700

    I usually just drive the last few blocks to my house very subdued, not going into boost. Then, by the time I get home, it's had a chance to cool down.

    -Eric
    '89 765t 174k, "The Sieve"







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