I fully understand warming up a car but what are the reasons for cool down.
Is it to keep an oil supply to the turbo whilst is winds down or is it something completely diffenrent ?

Dont get too technical.........

Nik.

 

Oil is circulating round the engine and more importantly the turbo. As you know this will be very hot, especially if you have being driving hard. When you stop after hard driving leaving the engine running for approx 1 minute will allow any oil to leave the turbo and thus preventing it from turning to carbon and ultimatly frying your turbo.

Hope this helps!

 

Yeah agree with this. The turbo bearings get red hot with commited driving and are the number one reason for turbo failure. Running the engine off boost after a blast will allow oil to circulate through the turbo, drawing away excess heat, stopping the oil from getting fried and turning to carbon as stated by 16vmarc.

The biggest danger is coming off a high speed motorway blast into the services and then switching straight off. I usually take the last few miles home off boost and then let it idle for a couple of minutes.

 

Forgive me for being stupid but even when the engine is on tickover doesn't the oil still get pumped to the turbo ? Or is it only fed oil under use..............
Confused..............

 

All the time however it is as important to let it slow down as it is cool down - for instance letting it cool over the last few miles is wasted if you blip the throttle before turning off.

 

Yes youre right, but theres no pressure on the engine. No hard work is being done at this point.

 

The vf series turbos are water cooled, does this not eliminate the need to let the car idle?

 

get a turbo timer!

 

You still get a hot spot at the turbo because when you switch off both the oil & water are no longer being pumped past the area of the bearing to dissipate the heat.This means the oil stuck in the turbo bearings is static & cooks.

A bit like not turning your burger on a BBQ.Keep it moving & it cooks evenly,don't turn it & you get charcoal.

Mark

 

In a way yes.
The water coolant still circulates past the turbo when the engine is off.
This is by a clever bit of pipework.

dipster