wross996tt

I know this has been debated before and mant people want to see actual data to get some sort of reliability estimate (of course for true reliabilty prediction it would require not only looking at failed turbos, but good ones as well, then perhaps fitting a weibull distribution and appropriate size and shape parameeters). This probably ain't going to happen. So here is what some of "the experts" say...After a period of driving when a turbocharger has been working hard (and turbo Porsche get pretty hot), it is important to let the engine run at idle speed for a period of time, allowing the compressor assembly to run down in speed and cool from the lower gas temperatures in both the exhaust and intake tracts. At the same time the lubricating oil from the engine is able to circulate properly so the turbine won't burn the lubricating oil that would otherwise be trapped within the charger with the turbine rotating at high speed. Idling allow the turbo itself to cool dramatically from operating temperatures. Shutting the engine down with cylinder heads and turbocharger at too high an operating temperature will cause the oil that is left on internal parts of these components to be cooked and turned into carbon. Carbon build up in cylinder components can cause stuck valves and rings causing high oil consumption. Carbon build up inside of a turbocharger lubrication section will cause seal failure, high oil consumption and eventual turbocharger failure.

http://en.wikipedia.org/wiki/Turbocharger

On second, just thought shut that puppy down right away. Its your car!

tkerrmd

Great answer Statman, thanks for taking the time to explain. Why didnt porsche idiot proof the turbo oil circulation by having it run independantly until cooled to a certain temp even if engine was turned off, doesnt the fans you here go on are for the same reason?

Kevin

The fact are if you do not cool or attempt to do a cool down everytime you turn your engine off you risk damage to your turbochargers. Not only do I see failed turbochargers from these cars, but I receive them for upgrades from 100 miles to 50K on them. Rarely do these units get 50K on them.

If you read your owners manual it says to take measures to idle your car.

AR you need to find a friend that has a turbo 911 and stick you hand under the engine right after the engine is turned off. The turbo's are hotter than the CATs. I did not say to idle the car for 5 minutes. If someone want good life out of there turbo's, they will try to idle the car. If you don't want to idle the car, plan for a rebuilt turbochargers by 20K.

wross996tt

Good question? German engineering (I'm sure the considered the pros/cons of such a feature and decided that if you are a P-car owner you are not an idiot and therefore do not need idiot proof devices...only to use your brain. Of course tthey also resisted putting cup holders in their cars...who drinks while they are actually driving?). The fans you hear are, I believe, tied to water temp., not oil or turbo temp. While of course they provide some cooling, they do not provide for cooling of the turbos which can only be accomplished by oil running through them. I can't remember the actual temp. delta that occurs in 2 minutes, but I know it is dramatic.

omega

kevin never heard from you about the aucuator shaft adjustment you built the k16s for me .. reprogramed and they are running gggggreat thanks steve...

ar38070

I see that you did not even attempt to answer any of my questions. Well I have 16k miles on my TT now. I track it 10-15 days a year. I guess I will know in 4k miles if my turbos blow up.

Kevin

What questions do you want me to answer. I see that you have a twin, so after you park it in your garage lay under the bumper and feel the heat radiating from the turbine housings. One good gauge on seeing how your turbochargers are fairing is to undo the plastic inlet pipe that go into the compressor housing. You can see your compressor wheel and check to see if you have any standing oil in the compressor housing. The compressor wheel should be a dark grey color, if it is brown, your are recycling oil through your intake tract.

The K16 or 24's aren't going to blow-up or come apart (the bearing and thrust systems is/are very good) they will just start to pass oil.

t urbo

Im a great believer in the 2 minute cool down but if it were a problem then why doesnt porsche tell you to let it idle before shutting off ? There is no mention of cool downs in the handbook in the UK.

Kevin

The owners manual does mention it on page 62 I believe.

t urbo

Not in the UK kevin. No mention at all.

t urbo

Maybe they dont mention it because 95% of turbos purchased in the UK are by Posers who never come out of second gear!