[Turbanator]

Originally Posted by ArTigor

while checking the engine bay saw some oil marks on the left side of engine head-block joint. Also there is soot deposit where the hose from intercooler meets the turbocharger, can this be signs of something bad?

Get the engine bay washed/ cleaned and then observe if there is any oil leakage.

Originally Posted by Indian2003

I never practice this idling rule
421,000 km must be ample evidence that the idling rule need not apply to eveybody.

+1, but I don't have any high mileage cars to support

If we see the implementation of stop/ start on most German cars, especially BMW, the moment we stop momentarily, like an intersection or to yield to oncoming traffic, the car will stop, and it does not matter whether we have driven 100 km or 10 km. (though I hate this implementation, that's a different topic)

However, these Auto-stop systems do factor engine temperature, so when the car is cold, the engine won't be cut off at a stop.

[shashanka]

Originally Posted by Indian2003

I never practice this idling rule and when I turn off the motorway I do some minutes of slow driving before I get home. I hardly redline the engine.
I can hear the turbo spinning when I pass 1850RPM and the speed then is 80 km/hour.
Even on the German autobahns when I stop for diesel, there is always a short distance to drive at slower speeds before I reach the pump.
421,000 km must be ample evidence that the idling rule need not apply to eveybody.

You are doing what is recommended for the good health of the turbo-charger! T/chargers fitted in automobiles have bush/sleeve bearings recieving oil from the main system. There is no separate lub. system for the turbo-charger. Since you are doing slow driving (or idling in case of other drivers) for a while before shutdown, that gives sufficient time for the bushes/sleeves to cool down to a temperature where boundary lubrication/spot welding conditions do not arise in the T/charger bearings, and you can safely shut down.

Slightly OT - In very large diesel engines (marine goliaths eg) with sleeve/bush/journal bearings in the t/chargers , a system followed earlier involved a header lub.oil tank which was kept filled to near 3/4 capacity by a supply from the main lub system and the o'flow would lead back to the engine sump. In case of a sudden failure of the main lub oil pump under full engine load & the st.by pump not starting on auto (as it should have) - this header tank would supply oil under gravity via a restricter orifice to the t/charger long enough to allow the turbo bearings to cool down below the critical temperature.

[Surya1]

Really informative!

All the more important for driving in colder regions.

On side note, where does VW group 1.5L TFSI/TSI engines stand?

[akshaysehgal]

Thanks, @GTO for this amazing thread. This is exactly what I was looking for!

I am almost angry I didn't read this before pushing my engine to the limits on the Yamuna expressway yesterday while returning from Agra and then immediately turning off the car in my parking!

Since reading this post, I have been trying to figure out if i20 N Line's (BI3) engine (1.0 L Kappa II T-GDi) has a water-cooled turbo or an oil-cooled one. I am guessing the latter but it's not really mentioned explicitly anywhere in my initial research.

[hani]

Originally Posted by Macfreak7

What I've noticed on my car is if I push hard with the A/C off and the engine oil temp goes up by a few degrees (to about 103-105), then turning the A/C on brings the temperature back down to about 99-100 pretty quickly. What gives?

I'm guessing this is because the A/C condenser fan is very close to the radiator and gives it a little bit of extra cooling

[itwasntme]

Originally Posted by Turbanator

If we see the implementation of stop/ start on most German cars, especially BMW, the moment we stop momentarily, like an intersection or to yield to oncoming traffic, the car will stop, and it does not matter whether we have driven 100 km or 10 km. (though I hate this implementation, that's a different topic)

However, these Auto-stop systems do factor engine temperature, so when the car is cold, the engine won't be cut off at a stop.

Very true. BMW's omission of a waiver from this 'feature' when the engine and turbo are very hot, is a very un-German thing to do . This is what the 330i Driver's Guide says.

There is no mention whatsoever of a hot turbocharger!

[Jeroen]

Originally Posted by itwasntme

Very true. BMW's omission of a waiver from this 'feature' when the engine and turbo are very hot, is a very un-German thing to do . This is what the 330i Driver's Guide says.

There is no mention whatsoever of a hot turbocharger!

It’s what I have been saying for the last ten years, if it’s not mentioned in the manual idling of the turbo prior stopping isn’t required. Fewer and fewer cars will require idling to cool the turbo. Who are you gonna trust? Internet wisdom or German engineering?

On start/stop type of cars, it is of course not required, or some logic would be programmed into the ECU.

What is interesting is that, apperently, a BMW engine can tell its fed high ethanol content fuel! I wonder what they consider high content, and how an engine determines a high ethanol content?

Jeroen

[ringoism]

Originally Posted by AnandB

My Kodiaq keeps the turbo on for a few minutes even after i turn off and go away. Doesn't happen everytime.

Originally Posted by Jeroen

It’s what I have been saying for the last ten years, if it’s not mentioned in the manual idling of the turbo prior stopping isn’t required. Fewer and fewer cars will require idling to cool the turbo. Who are you gonna trust? Internet wisdom or German engineering?

Old-school turbos were cooled and lubricated via only the oil feed line supplied by the engine's mechanical oil pump, hence the need for idling to cool it down. There are still quite a number of "old school" turbo cars being sold here. That said, my 1988 Mitsubishi had an oil/ water-cooled turbo which was supposed to run much cooler.


IIUC, the 2.0L TDI (EA288) as intro'd in 2012 in the Skoda Yeti and other VAG cars (must be same with Kodiaq), apparently has a secondary electric water pump which continues to circulate water through the turbo after shutdown - essentially eliminating the need for the driver to do that manually. Fans may also be kept on by the ECU, likely depending on various sensor analysis, in order to aid in this process of cooldown. Makes good sense and makes owning a turbo model a bit more "hands-off". Who needs one more thing to think about / adjust to? Ideally cars should adjust to us, not vice-versa.

-Eric

[firstguri]

Originally Posted by ringoism

IIUC, the 2.0L TDI (EA288) as intro'd in 2012 in the Skoda Yeti and other VAG cars (must be same with Kodiaq), apparently has a secondary electric water pump which continues to circulate water through the turbo after shutdown - essentially eliminating the need for the driver to do that manually. Fans may also be kept on by the ECU, likely depending on various sensor analysis, in order to aid in this process of cooldown. Makes good sense and makes owning a turbo model a bit more "hands-off". Who needs one more thing to think about / adjust to? Ideally cars should adjust to us, not vice-versa.

-Eric

Those are exactly the reasons because of which newer turbocharged cars can withstand start/stop system.

[Jeroen]

Originally Posted by firstguri

Those are exactly the reasons because of which newer turbocharged cars can withstand start/stop system.

Only partly, the main reason is the advance of material and production techniques of modern turbo’s which makes them much more resilient to this kind of operations. Also, turbo’s for the same reason have become much smaller and retain much less heat.

Jeroen

[firstguri]

Originally Posted by Jeroen

Only partly, the main reason is the advance of material and production techniques of modern turbo’s which makes them much more resilient to this kind of operations. Also, turbo’s for the same reason have become much smaller and retain much less heat.

Jeroen

Disagree. Metallurgy aside, the main issue with older oil cooled T/C's was coking of oil. Once the engine was switched off, the oil flow would stop and the oil remaining in T/C would start coking up. With newer water cooled T/C's and the ability of the cooling system to continue working even after engine's been switched off is primarily responsible for preventing this.

[Jeroen]

Originally Posted by firstguri

Disagree. Metallurgy aside, the main issue with older oil cooled T/C's was coking of oil. Once the engine was switched off, the oil flow would stop and the oil remaining in T/C would start coking up. With newer water cooled T/C's and the ability of the cooling system to continue working even after engine's been switched off is primarily responsible for preventing this.

Take an old turbo and a new turbo apart. Have a good look at how they are made and the bearings work.

You also need to take into account the old mineral lub oil and modern (semi) synthetic oils. They suffer far less from this coking of course, but it did require a different design of turbocharger.
Of course there is also a difference in what kind of bearings are being used. These days even on cars you will find journal and ball bearings. It’s the old journal bearings that were most susceptible to coking, due to design and production limits and of course whatever lub oil was available at the time.

Jeroen

[firstguri]

Originally Posted by Jeroen

Take an old turbo and a new turbo apart. Have a good look at how they are made and the bearings work.

You also need to take into account the old mineral lub oil and modern (semi) synthetic oils. They suffer far less from this coking of course, but it did require a different design of turbocharger.
Of course there is also a difference in what kind of bearings are being used. These days even on cars you will find journal and ball bearings. It’s the old journal bearings that were most susceptible to coking, due to design and production limits and of course whatever lub oil was available at the time.

Jeroen

Well you're not wrong about newer materials and bearing types or even the oils in use today. But Sir, metallurgy cannot prevent coking of oil. Similarly ball bearings will not prevent coking compared to journal bearings. Yes, synthetic oils will not comparatively coke up like mineral oils. If your point was that because of newer materials the thermal stresses are better handled thereby making the T/C's more hardy, then to an extent you'll be right. But then again the issue earlier was not that T/C's were breaking up! The issue was coking of oil and that has been addressed by better cooling management as taking away the heat is the only solution for preventing coking of oil.
Better materials and bearings have resulted in better performances. But that's another thing.

[Jeroen]

Originally Posted by firstguri

Well you're not wrong about newer materials and bearing types or even the oils in use today. But Sir, metallurgy cannot prevent coking of oil. Similarly ball bearings will not prevent coking compared to journal bearings. Yes, synthetic oils will not comparatively coke up like mineral oils. If your point was that because of newer materials the thermal stresses are better handled thereby making the T/C's more hardy, then to an extent you'll be right. But then again the issue earlier was not that T/C's were breaking up! The issue was coking of oil and that has been addressed by better cooling management as taking away the heat is the only solution for preventing coking of oil.
Better materials and bearings have resulted in better performances. But that's another thing.

Again, have a look at an old and a new one. Find two that have about the same rating. You will find, as a rule, the old one, far more bulky and heavier. Heat management is a function of design, I.e. what materials, how do shape certain parts, what oil do you use. I know your story is what many Internets are saying, but that is because lots of Internets are pretty generic in how they describe things. You need to look very specifically to find real research rather than a couple of Wikipedia-pagina. Or, be lucky and find somebody with more than Wikipedia knowledge on a car forum.

I am no specialist but I have worked closely with engine and turbo chargerdesigners and engineers in the past. Trying out all sorts of new stuff. feel free to see it differently, enjoy your car and turbo charger.

Jeroen
Currently no Turbo Charged engine's in my home fleet. Just got rid of the last one. Remaining are all NA and of course Supercharged! Need to get me one again to fiddle with..

[firstguri]

Originally Posted by Jeroen

I know your story is what many Internets are saying, but that is because lots of Internets are pretty generic in how they describe things. You need to look very specifically to find real research rather than a couple of Wikipedia-pagina. Or, be lucky and find somebody with more than Wikipedia knowledge on a car forum.

I am no specialist but I have worked closely with engine and turbo chargerdesigners and engineers in the past. Trying out all sorts of new stuff. feel free to see it differently, enjoy your car and turbo charger.

Jeroen

Well that's some prejudice linking my knowledge of T/C's with Wikipedia. My source of knowledge is my profession. Being a marine engineer, have studied the technicalities of turbochargers apart from also having overhauled them. Although the utilisation of turbochargers in marine field is a little different from automotive ones, but the basic principle remains the same. Hence I stated what I knew.
Current generation of T/C's no doubt utilise better materials and are hence even though lighter, are able to withstand the heat and stresses better, which further leads lower inertia and better performance. But that was exactly my point. Lighter turbochargers will result in better performances but will do nothing with regards to coking of oil. Of course to an extent better materials and design can dissipate more heat but you still need a cooling medium to take that heat away!