Hot Shutdown

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Gareth Wales
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Hot Shutdown

Post by Gareth Wales » Thu Nov 23, 2006 5:39 pm

What sort of time is reckoned to be adequate to avoid a hot shutdown of a turbo engine - I really can't see how a couple of minutes would be enough to allow "cooler" oil to circulate. But of course, I have no knowledge to support this. Neither do I know why a hot shutdown is injurious.

st gilles

Post by st gilles » Thu Nov 23, 2006 5:47 pm

It depends what you mean by hot shutdown....if you are coming into a services off the motorway and stop immediately having been on turbo for a few miles you will 'cook' the oil around the turbo and eventually have problems. If as most people do, you leave the 'fast' road and travel for a few miles at lower speeds without the turbo being on then you can turn it off when you arrive at your destination without waiting the 30 secs or so you would need at the M/way services as above.

jeremy
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Post by jeremy » Thu Nov 23, 2006 5:52 pm

I adjusted my end of journey or stop routine - so that I turn off the radio, shut the windows, undo my belt etc. then turn the engine off last as a matter of course.

The idea is to make sure the rotor is not spinning when the oil feed is cut - and of course that its nott so hot that the oil decomposes.

Stewart (oily!)
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Post by Stewart (oily!) » Thu Nov 23, 2006 5:54 pm

Hi Gareth, the main reason for a hot shutdown delay in a diesel engine is that after a brisk drive the turbocharger will very likely still be spinning after the car has come to a stop, were the driver to simply stop the engine at that point the turbine (which floats on an oil bearing) will be deprived of the oil it needs to prevent metal to metal contact and therefore rapid wear will occur. A period of idling will allow cool air to be drawn through the turbo, cooling it, the temperature issues you mention are less likely to be a factor in a diesel engine, petrol turbochargers run far hotter (incandescent red!) and spin far faster and can therefore cook the oil in the turbo bearings causing carbon buildup into the bargain and so need this precaution to a greater extent, I find that if I enter the parking ground where my garage is at tickover and drive to my parking space, remove seatbely, stereo fascia, etc etc then enough time has elapsed for me to safely stop the engine. Older caterpillar diesels recommended idling for a minute or so.
Stewart
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Gareth Wales
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Post by Gareth Wales » Thu Nov 23, 2006 6:02 pm

Excellent - thanks guys.