Allowing Turbo to cool off?

[Geekay]

The dealer said it is a good idea to allow the turbo on my new NS Di to cool for a minute before switching the motor off if had jsut had a prolonged run at the end of a long highway leg or if been worked hard in 4wd.
What do you think?

[matthewfnorbert]

if i have just done some gentle running prior to shut off then i just turn it off, if i know it has just been driven moderately hard in the minute prior to shutoff i will wait 30 sec or so.. oils are so much better now, so unless you have thrashed the living daylights out of it don't sweat it.. my oil analysis did not show any issues doing as above.

[simonfish]

I could be wrong, but I thought the idea of letting a turbo motor idle for a minute or two was so the turbo fan/spindle had a chance to cool down, rather than going from a couple of thousand rpm (or whatever they run at) to dead stop.

[Mike DiD]

If you have been working the engine hard - (driving over 80km/hr or going uphill) the exhaust system and the exhaust side of the turbo will be very hot.

If you shut off the engine in this state there is no longer any water or oil flow to take away this heat. Then the whole turbo body will get much hotter than it does while the engine is running causing the oil in the turbo to carbonise, eventually blocking the oil galleries.

[Walker]

Yes, Mike is right. I have been told before that although they are not standard on modern TD's, it is still a good idea to fit an aftermarket turbo timer. But I have always wondered about this, I would have thought that if they were necessary then manufacturer's would fit them????

[6G74]

I could be wrong, but I thought the idea of letting a turbo motor idle for a minute or two was so the turbo fan/spindle had a chance to cool down, rather than going from a couple of thousand rpm (or whatever they run at) to dead stop.

As Mike said, its to prevent excessive heat in the bearings of the turbo when you turn off the motor.

If you plan on keeping the car long term, sure its prolly a good idea, if not, or if its leased i dont see why you would bother.

As to why manufacturers dont do it, my only guess is that its gonna last past its warranty regaurdless.... so why spend more money....

[pjchris]

If you shut off the engine in this state there is no longer any water or oil flow to take away this heat. Then the whole turbo body will get much hotter than it does while the engine is running causing the oil in the turbo to carbonise, eventually blocking the oil galleries.

The current water cooled designs still circulate water even when the engine is off. The thermal current means that water heated in the turbo will rise out of the top and draw cool water in from below. Yes the oil flow will stop.

I still allow a short cool down, longer if I've been driving hard, though as I would rather be safe than sorry. Basically if I have been just idling around I will still unplug my iPaq, gather up my bags and other bits, and then only as I am leaving the car will I turn off the engine.

Peter

[MinniTheMoocha]

I have also heard that unless the motor is really hot you can in fact cause more soot build up in the engine because at idle you are cooling the motor rapidly?

So generally unless I have worked the car I switch off straight away.

[creamandchives]

RE: the fitting of Turbo Timers, the key reason that they are not fitted by the manufacturers is that they are illegal in Australia. This is due to the fact it is illegal to leave a car engine running with no driver or similar. My understanding anyway So hence you see a bit of after market fitting on rice boy cars, but you theoretically could be booked for it (or insurance issues, warranty issues, etc).

[dunkinx]

would the engine continue to run without the key in the ignition? I had an ordinary replacement key made, and the engine just cranks and wont start. which led me to the idea that the original key activates the ECU.

[Mike DiD]

I would assume that the key validation is only done on starting -once the engine is running, you could remove the key, provided the power remained on the engine electricals.

It's unfortunate that the law about having to turn the ignition off when leaving the car hasn't been updated to allow for modern technology. It'd be easy to have an interlock to provide the theft protection which is the intent of the law. As soon as the any gear was engaged while the turbo timer was running the engine, it would shut down the engine.

But don't hold your breath waiting - these laws are made by the same public servants who required that Hazard Flashers had to be disabled when European cars were first imported with them into Australia !