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[Auto Addict]

Is it true you should let a diesel turbo idle for 30 secs. before switching off?

[Andy B]

Is it true you should let a diesel turbo idle for 30 secs. before switching off?

It's not good for any turbo'd engine to turn it off straight away after 'enthusiastic' driving where the turbo has been in use. Letting it idle for a short time before turning it off allows oil to circulate the turbos bearing to remove heat from them

[Auto Addict]

Is it true you should let a diesel turbo idle for 30 secs. before switching off?

It's not good for any turbo'd engine to turn it off straight away after 'enthusiastic' driving where the turbo has been in use. Letting it idle for a short time before turning it off allows oil to circulate the turbos bearing to remove heat from them

Well, you live and learn, thank you

[chrisgixer]

So just like the rest of the engine?

[Auto Addict]

So just like the rest of the engine?

Looks like it.

[Andy B]

So just like the rest of the engine?

No ..... the oil in the rest of the engine isn't subjected to the same high temp as that around the turbo's bearings

[Auto Addict]

So just like the rest of the engine?

No ..... the oil in the rest of the engine isn't subjected to the same high temp as that around the turbo's bearings

You live and learn  - again

[chrisgixer]

So just like the rest of the engine?

No ..... the oil in the rest of the engine isn't subjected to the same high temp as that around the turbo's bearings

Maybe so, but that's relevant to a turbo, be it petrol or diesel. Why would a diesel turbo get special treatment any more than a petrol turbo.

I wouldn't give an engine any more of a chance to cool down after a thrashing or a pootle, but that's the nature of the speed limits and built up areas on the roads leading to my house.

Obviously after a track day that would "might" be different into pit lane.


But to say any turbo diesel must run at idle for an amount of time after a run would be ridiculous. IMO.

Let's face it if something is over heating, the quickest way to cool to down is to turn it off. Then apply un related cooling such as a fan. Hence the fans run after switch off.

No.....?

[henryd]

So just like the rest of the engine?

No ..... the oil in the rest of the engine isn't subjected to the same high temp as that around the turbo's bearings

Maybe so, but that's relevant to a turbo, be it petrol or diesel. Why would a diesel turbo get special treatment any more than a petrol turbo.

I wouldn't give an engine any more of a chance to cool down after a thrashing or a pootle, but that's the nature of the speed limits and built up areas on the roads leading to my house.

Obviously after a track day that would "might" be different into pit lane.


But to say any turbo diesel must run at idle for an amount of time after a run would be ridiculous. IMO.

Let's face it if something is over heating, the quickest way to cool to down is to turn it off. Then apply un related cooling such as a fan. Hence the fans run after switch off.

No.....?

I think what Andy is referring to is the spool down time for the turbo be it petrol or diesel,the turbo can be spinning at many thousands of rpm after a burst of acceleration and there is a risk that a sudden engine stop can leave the turbo still spinning without oil being pumped around the bearings

[Sir Tigger KC]

I've always understood that you should also let a TD idle for a while when started from cold so oil is pumped into the turbo. 

[hoofing it]

The turbo on a car engine will spool down almost instantly and the oil is pumped through the turbo bearings at some rate so if you should burst a oil feed pipe you end up with the sump contents on the road pretty fast.
If it were a bigger engine like a train of which ive driven at a railway preservation you always left the triple pump running for at least 2 minutes to let the turbo stop spinning

[Kevin Wood]

I think what Andy is referring to is the spool down time for the turbo be it petrol or diesel,the turbo can be spinning at many thousands of rpm after a burst of acceleration and there is a risk that a sudden engine stop can leave the turbo still spinning without oil being pumped around the bearings

Yes, and, in addition, the turbo will be very much hotter than any other part of the engine to which the oil circulates. Shut it down at this temperature and the residual oil in the bearing might get hot enough to scorch, leaving deposits on the bearing which will result in its' untimely demise. Leave it idling and it will continue to be cooled by the oil.

Probably only needs to be 30 seconds or so without load but, in a scenario where it comes from towing a caravan on a motorway, into a service station and engine off.. might be good practice to let it idle a little.

Some turbo cars have a water cooled turbo with either a thermo syphon or an electric pump that runs after the engine, but many have only an oil supply, which doesn't allow any flow after shutdown.

It goes without saying that petrol or diseasel is irrelevant, as the turbo is pretty much identical.

[Sir Tigger KC]

I guess also that turbos are generally mounted high up, so that the oil will drain out quickly. 

[Andy B]

So just like the rest of the engine?

No ..... the oil in the rest of the engine isn't subjected to the same high temp as that around the turbo's bearings

Maybe so, but that's relevant to a turbo, be it petrol or diesel. Why would a diesel turbo get special treatment any more than a petrol turbo.

I wouldn't give an engine any more of a chance to cool down after a thrashing or a pootle, but that's the nature of the speed limits and built up areas on the roads leading to my house.

Obviously after a track day that would "might" be different into pit lane.


But to say any turbo diesel must run at idle for an amount of time after a run would be ridiculous. IMO.

Let's face it if something is over heating, the quickest way to cool to down is to turn it off. Then apply un related cooling such as a fan. Hence the fans run after switch off.

No.....?

.....

It's not good for any turbo'd engine to turn it off straight away after 'enthusiastic' driving where the turbo has been in use. Letting it idle for a short time before turning it off allows oil to circulate the turbos bearing to remove heat from them

[chrisgixer]

So, 99 times out of 100, no, not necessary.

Unless your drive way is directly at the end of a motorway slip road after hard engine use.