Turbo Cooldown

[gazbutmk5gti]

yup the Borg Warner KKK K03s turbo is water cooled in the Mk5 GTI!!!!!

still doesn't mean u should rag it big time then just switch it off.

i tend to run no boost in the last mile of my journey and just cruise home!

what about oil supply when its still spinning away to itself when you turn the engine off

[bornfree]

although i'am no expert on petrol turbo engines,i work on turbo diesels from 4L high speed 100 hp to 27L 1300 hp at 1500rpm and we get turbo problems from engines being shut off from full load. one is heat which transfers from the turbine housing vaporizing the oil and destroying the seals, the other is lack of oil as the turbo is still spinning when the engine has stopped so it's running dry which destroys the bearings.it's possibly not as bad in a small engine like the golf as the turbine has less inertia therefore slowing quicker.but i always let my ed30 tick over for a couple of minutes before stopping .

bornfree

[gazbutmk5gti]

I've always done this on the many turbo charged cars I've had, its habit now. I know oil technology has really improved, but I still think its a good idea. Won't do any harm

[Saint Steve]

yes page 18 on that great link confirms it. 

[gazbutmk5gti]

confirms what

[NewGolf]

I'm guessing it proves you can turn the car off "hot" and not have to sit there for 1 minute on tickover. 

Cooling System
To prevent carbon build-up on the turbine
shaft in the turbocharger, an auxiliary
coolant pump provides additional coolant
circulation for a certain time after the
engine is shut off hot. The pump forces
the lower temperature coolant against the
normal direction of flow. The coolant flows
from the radiator through the turbocharger
to the engine block and back to the cooler.

[Teutonic_Tamer]

To be honest that's good practice with all engines, but more important on F.I cars.

Was that a typo?  Fuel injected engines are no different to carbed engines.  Or if you meant "forced induction" then again, not quite correct, because superchargers are very different to turbochargers.

[topher]

Forced induction... and it still applies to crank driven supercharged engines. Knock off a g-lader after a heavy run without cooling down and the seals won't last long!

[Teutonic_Tamer]

The Mk5 does this for you, there is an auxillary pump which forces water backwards around the coolant system - it is a sort of failsafe and does it for c.3mins after you switch off the ignition.

Erm, again, not quite correct.  Yes, the engine management does use an additional electric coolant pump, but this should NEVER be relied upon.

The crucial issue is the oil in the turbo bearings.  If you have been giving it a bit of a work out, and then immediately turn off the engine, the oil will rapidly coke up in the turbo bearings, and no amount of reverse flush coolant will stop that.

The best advice for turbo care (apart from the most crucial advice of the correct spec LongLife oil with a HTHS rating), is after a spirited run, try and use the last mile at a more sedate speed, and keeping the engine in the highest possible gear, with the least amount of throttle.  And when you do park up, let the engine idle for at least 30 seconds before turning off.

Never, EVER "blip" the throttle immediately before switching off, because you will have just sent your turbo spinning up to 180,000 rpm, and then immediately killed its oil supply.    Some sales twit did this at Woolsey Ipswich VW, and I nearly punched the cnut between the eyes! 

[Teutonic_Tamer]

yup the Borg Warner KKK K03s turbo is water cooled in the Mk5 GTI!!!!!

Not technically correct.  It is oil cooled, and the water then cools the oil.  Look at the BFO oil pipes going straight from the main oil gallery direct into the turbo bearings. 

still doesn't mean u should rag it big time then just switch it off.

i tend to run no boost in the last mile of my journey and just cruise home!

Agreed, good advice.