Turbochargers - Bearings, Cooling, General Info...

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john_pifer

john_pifer

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I'd like to get a discussion started on turbochargers. I've recently become more interested in them since I bought my new 2016 WRX, and, naturally, have found myself thinking about turbochargers more.

I feel like I have a pretty good baseline understanding of how turbine systems work, as I've long had a strong interest in aviation and have spent some time studying the operation of gas turbines. So, I'm looking more for detail in turbo operation.

As stated in the subject, my questions relate to the bearings and cooling, and just wanting to learn more about the operation of turbochargers in general - how to optimize their life, etc.

So, I've read that my 2016 WRX uses a Honeywell (Garrett) GT2259S:

https://www.turbobygarrett.com/turbobygarrett/turbocharger#GT2259

From the description, apparently it's oil-cooled only. I was wondering what kind of bearings it uses. On Garrett's page, the boxes for both ball-bearing AND journal bearings are checked...so, which is it? Does it use both types of bearings?

Would it be correct to say that "journal" bearings are hydrodynamic in operation, like the crankshaft main bearings and connecting rod bearings in an engine?

I remember reading, about 20 years ago, when I started getting interested in engines and performance cars, that it was a bad idea to immediately shut a turbocharged engine down, especially after highway driving or driving under load, due to the possibility of coking in the turbocharger due to oil sitting in the unit and getting cooked. Therefore many people would run turbo timers - basically a timer on the ignition to allow the engine to idle for a pre-determined period after the key was removed in order to allow oil and/or coolant to continue to flow through the bearings for a while with the engine at idle, in order to allow temps in the bearings to drop, hopefully enough that coking wouldn't occur.

Is coking still a problem with modern turbos and oils, or has the design of modern turbos and materials/specs used mostly accounted for that problem?

I know some turbocharged vehicles have water-cooled turbos (the new Fords?) and also have small electric pumps that continue to circulate some coolant through the turbo housing after engine shutdown... Obviously my Subaru, having an oil-cooled (only) turbo, doesn't have that feature, so I've been trying to let it idle for a couple of minutes after shutdown, to hopefully allow temps in the turbo to drop a bit.

After draining the FF, I plan on using PP 10W-30 due to very good NOACK (4.7%) and hopefully a bit less tendency to shear, though I know that'll happen with this engine, as well as being diluted with fuel (direct fuel injection).
 
Originally Posted By: john_pifer
From the description, apparently it's oil-cooled only.

Don't know if yours is set up like this or not...

Quote:
At any rate, the fix is simple and clever. Look at a Subaru turbo engine bay - something is missing from the radiator...... I'll save you the time: no radiator cap. That's because Subaru has made the highest point in the cooling system a small aluminum reservoir placed directly above the turbocharger who's coolant return is connected directly to it (and this is where the cap now resides.)

The reason is simple. Now, when you shut off the engine with a hot turbo, the coolant begins very quickly to boil. Obviously this hot coolant and steam rises quickly to the intelligently located mini-reservoir. This convection draws cool(er) coolant from lower in the system into the turbo and this process continues until the turbocharger cools sufficiently. In this way, even after shutdown with heat soak from the turbine section, the bearings never get much above the boiling temperature of coolant, protecting the oil from coking.


http://oppositelock.kinja.com/random-fun-car-fact-subaru-shutdown-turbo-cooling-514111544
 
The turbo has water cooling as do nearly all modern turbos.

Cool down happens when drive into your parking place as vehicle is not in boost typically unless you are a nut.

Subaru designs cooling with high spot so that natural convection keeps moving hot water away and draws cooler water into turbo cooling it.

My wife would laugh at me if I asked her to idle down her 2005 legacy turbo. It had 200k miles/conventional and works fine. Don't worry.
 
"Think of the backwards-caps bros out there now, who's WRXs run true and strong thanks to this simple innovation."

LOL! That's great
smile.gif
 
Originally Posted By: 5170
http://forums.nasioc.com/forums/showthread.php?t=2714154

Some would recommend against a resource conserving oil, prefering instead an ACEA A3 oil or an HDEO like RT6, for the 3.5+ HTHS.

Yes, I've been reading through the 2015+ WRX UOA thread for weeks now (it's over 100 pp long).

For now, I've come to the conclusion that the PP 10W-30 is an acceptable compromise for me when it's time to drain the FF, due to the fact that my car is stock and will see street use only. The price and convenience of obtaining the PP 10W-30 means I can change it frequently. I will get a UOA and, from that, I'll determine whether to go to something like M1 ESP 5W-30.

RT6 is out of the question due to high SAPS levels (this car is direct-injection only and is susceptible to intake tract deposits, which have shown a correlation to high-SAPS oils).

I just received the Mishimoto oil catch can system which I'll be installing shortly. I hope that will do a lot to mitigate intake tract deposits, on top of using Top-Tier premium fuel and using the right oil.
 
Originally Posted By: Quattro Pete
Originally Posted By: john_pifer
From the description, apparently it's oil-cooled only.

Don't know if yours is set up like this or not...

Quote:
At any rate, the fix is simple and clever. Look at a Subaru turbo engine bay - something is missing from the radiator...... I'll save you the time: no radiator cap. That's because Subaru has made the highest point in the cooling system a small aluminum reservoir placed directly above the turbocharger who's coolant return is connected directly to it (and this is where the cap now resides.)

The reason is simple. Now, when you shut off the engine with a hot turbo, the coolant begins very quickly to boil. Obviously this hot coolant and steam rises quickly to the intelligently located mini-reservoir. This convection draws cool(er) coolant from lower in the system into the turbo and this process continues until the turbocharger cools sufficiently. In this way, even after shutdown with heat soak from the turbine section, the bearings never get much above the boiling temperature of coolant, protecting the oil from coking.


http://oppositelock.kinja.com/random-fun-car-fact-subaru-shutdown-turbo-cooling-514111544




Interesting. I'll have to check mine and see if it has this.
 
I've read that Shannow knows quite a bit about bearings.

I'd love to hear his thoughts on turbo bearings.
 
Originally Posted By: john_pifer
RT6 is out of the question due to high SAPS levels


RT6 has SA level of 1.0%. From RT6 brochure:
Quote:
Shell Rotella T6 Energized Protection oil features Shell exclusive "Low-SAPS" additive technology


Granted, 1.0% isn't that low, but it's probably not far off from the PP 10w-30 that you are considering.
 
Originally Posted By: Quattro Pete
Originally Posted By: john_pifer
RT6 is out of the question due to high SAPS levels


RT6 has SA level of 1.0%. From RT6 brochure:
Quote:
Shell Rotella T6 Energized Protection oil features Shell exclusive "Low-SAPS" additive technology


Granted, 1.0% isn't that low, but it's probably not far off from the PP 10w-30 that you are considering.


Hmm... I'd heard it was high-SAPS. I've also heard that GF-5 oils are low-SAPS as compared to some other oils.

In any case, RT6 NOACK ain't that great.
 
i dont know on your car butg on big rig oil is cooled ,the air charge is cooled the oil transmission is cooled we got variable turbo charger
 
Would be interested in learning this as well.

My 2014 Ford F550 has a standard Variable Geometry Turbocharger. It is rumored that the early 2011-2012 models used ceramic ball bearings which would grenade into the engine. Ford apparently fixed that in later models with steel bearing...never confirmed any of this. Interested in learning more about this topic as well.

Last oil change I used an additive Archoil 9100 (friction modifier) which is suppose to help with lubricity. All I know is the turbo works very hard in my truck...maximizing its lifespan is of interest to me. Thanks again to all.

Best,
 
Originally Posted By: john_pifer
Originally Posted By: Quattro Pete
Originally Posted By: john_pifer
From the description, apparently it's oil-cooled only.

Don't know if yours is set up like this or not...

Quote:
At any rate, the fix is simple and clever. Look at a Subaru turbo engine bay - something is missing from the radiator...... I'll save you the time: no radiator cap. That's because Subaru has made the highest point in the cooling system a small aluminum reservoir placed directly above the turbocharger who's coolant return is connected directly to it (and this is where the cap now resides.)

The reason is simple. Now, when you shut off the engine with a hot turbo, the coolant begins very quickly to boil. Obviously this hot coolant and steam rises quickly to the intelligently located mini-reservoir. This convection draws cool(er) coolant from lower in the system into the turbo and this process continues until the turbocharger cools sufficiently. In this way, even after shutdown with heat soak from the turbine section, the bearings never get much above the boiling temperature of coolant, protecting the oil from coking.


http://oppositelock.kinja.com/random-fun-car-fact-subaru-shutdown-turbo-cooling-514111544






Interesting. I'll have to check mine and see if it has this.


It's water-cooled.
 
Probably water-cooled, and probably set up to be very conservative on the factory tune.

It sounds like you're on the right track. Use a synthetic oil, change it at a reasonable interval, and let the coolant circulate for a few minutes before shutting it down if you've just gotten off the highway or a stint of spirited driving. Most of the time that's going on surface streets at a steady low speed, so the turbo is no hotter than the rest of the engine when it shuts down. If your house is on top of a hill, then idling for a minute or two would be helpful. Otherwise just shut it down.
 
I ran a few old Garrett equipped Turbo Mopars up over 200,000 miles in the 90's.

You should have no issues.

Makes want to walk out to the Garage and see if the turbo charger on the Malibu is liquid cooled.
 
Originally Posted By: ls1mike
I ran a few old Garrett equipped Turbo Mopars up over 200,000 miles in the 90's.

You should have no issues.

Makes want to walk out to the Garage and see if the turbo charger on the Malibu is liquid cooled.


Like what, a LeBaron?
 
Originally Posted By: john_pifer
Originally Posted By: ls1mike
I ran a few old Garrett equipped Turbo Mopars up over 200,000 miles in the 90's.

You should have no issues.

Makes want to walk out to the Garage and see if the turbo charger on the Malibu is liquid cooled.


Like what, a LeBaron?


Yep, to be exact. A Shelby Lancer and a couple of different Dodge Daytona's.
 
Originally Posted By: ls1mike
Originally Posted By: john_pifer
Originally Posted By: ls1mike
I ran a few old Garrett equipped Turbo Mopars up over 200,000 miles in the 90's.

You should have no issues.

Makes want to walk out to the Garage and see if the turbo charger on the Malibu is liquid cooled.


Like what, a LeBaron?


Yep, to be exact. A Shelby Lancer and a couple of different Dodge Daytona's.


Man, those were all cool cars.
 
Originally Posted By: yvon_la
i dont know on your car butg on big rig oil is cooled ,the air charge is cooled the oil transmission is cooled we got variable turbo charger

Very few gasoline engines had a VGT turbo.

Also the reason turbocharges on diesels are different is because the EGT of a diesel is lower than that of a gasoline engine. This might allow diesel engines to only be cooled by oil flow, wheras gasoline engine typically have water cooling.

During much of the 1980s, a large number of gasoline engines had oil cooled turbos. That is why if you didn't wait 1-2 minutes before shutdown, the turbo would eventually build up sludge and then fail.
 
Originally Posted By: john_pifer
Originally Posted By: ls1mike
Originally Posted By: john_pifer
Originally Posted By: ls1mike
I ran a few old Garrett equipped Turbo Mopars up over 200,000 miles in the 90's.

You should have no issues.

Makes want to walk out to the Garage and see if the turbo charger on the Malibu is liquid cooled.


Like what, a LeBaron?


Yep, to be exact. A Shelby Lancer and a couple of different Dodge Daytona's.


Man, those were all cool cars.

I also had an 86 GLH. Man those cars were fun back in the day. Wish I had kept one of them.
 
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