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Thread: Turbo & turning off engine

  
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    Eddles's Avatar
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    Turbo & turning off engine

    I've got a '01 1.7 DTi MK4 Astra and a stupid question. Should I let the turbo spin down before turning off the engine, or it doesn't matter? If I should let the turbo spin down, how long should I wait until turning off the engine?

    Thanks for your time!

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    gazvan_86's Avatar
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    when i park up i give it 10secs or so just to let it stop.ok it might not do anything but hey,its kinda peace of mind ur looking after it that tad bit more
    streetbasser

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    If youve just been driving normally it shouldnt really matter, but if youve been on a high speed run or have just climbed a steep hill or any other type of driving when the engine has been working hard its advisable to let the engine idle for 20 seconds or more. If the engine is switched straight off when the turbo is very hot the temperature of the turbo actually increases quite dramatically as there is no cool air passing through it. This over a matter of time leads to the oil seals in the turbo baking hard and starting to leak oil, also the oil left in the turbo on switching off can burn and turn to carbon thus starting to block the oilways and eventually cause oil starvation. As I say though after normal driving it shouldnt really matter.

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    you should actually let the turbo cool down as the shaft sits on hydraulic bearings. Meaning if you kill the oil pump you will allow the hot shaft to rest on the bearing shells. (its either oil or air bearings, i cant remember)

    Causes wear and stuff, better to let everything cool down for 5 or so minutes.

    The guy above on about cooling air passing through it is speaking rubbish as thats only possible when mobile. Although he is right about the adiabatic temperature rise.

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    terex's Avatar
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    Im glad to see that Kingthechris agrees that the turbo needs to be cooled down before switching off however Im a little amused that he calls the cool air that it is drawn through the air filter and thus through the turbo when the engine is idling after a run (helping to cool it) as 'rubbish'. I think Kingthechris will find that so long as the engine is running air is passed through the turbo whether the vehicle is mobile or not.

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    Quote Originally Posted by terex View Post
    Im glad to see that Kingthechris agrees that the turbo needs to be cooled down before switching off however Im a little amused that he calls the cool air that it is drawn through the air filter and thus through the turbo when the engine is idling after a run (helping to cool it) as 'rubbish'. I think Kingthechris will find that so long as the engine is running air is passed through the turbo whether the vehicle is mobile or not.
    i think kingthechris will let you off with this one then . Apologies just the way you worded it.

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    thebigstu's Avatar
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    Always warm up and cool down I say

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    nry's Avatar
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    Depends who you believe...

    http://www.max-boost.co.uk/max-boost...eless_mods.htm

    "
    Turbo timers
    Total waste of space.
    Turbo timers are a remnant from days past, when all turbos were aircooled and synthetic oils were not around (or too expensive!)
    Switching off immediately after a full-boost run would then cause the oil pump to stop, and the oil remaining in the turbo bearing would carbonise and turn to a form of ash (coking was the term)
    Nowadays this cannot happen. The water jacket absorbs all the extra heat from the bearing, and then some. Therefore the oil temps don't exceed 120C even then, and synthetics tend to resist death until over 150C, so there is no benefit from the turbo timer, except unnecessary idling (that does the turbo seals no good, neither the camshafts)

    Idle is not good for turbos, water cooled turbos don't need any of this maintenance. Just roll smoothly after a full-boost run, if you're going to switch off immediately, that's all."

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    turbo timers are a waste of time. just dont be lazy and let it cool down before you turn off the ignition.

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    mattjk's Avatar
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    The water jacket takes the majority of the heat anyway, I'm pretty sure its in that article that John wrote on Max-boost. Always left mine to idle for about 10 secs before shutting off.

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