Oil turbos vs oil & water.

[soundboy]

Besides the usual extra water lines. What are the benefits of using a oil cooled turbo alone vs a oil and water.

I was reading about how a turbo timer isn't needed with a oil and water setup because the water would cool the turbo even after the engine turns off.
Oil won't flow.

What about the temperature of the water system? Would this then allow the water system to run cooler but then again the same water would then need to cool the oil in the block.

Thoughts. Theories. All welcome

[daryl337]

You are very late to this discussion on this forum - but being from Trinidad I don't blame you for it.

The oil + water cooled do a better job for longevity of the turbo itself - it does not help the engine. In actuality, depending on the coolant flow path of the engine it can be a source of heat soaking issues.


Subaru for example recirculates their turbo coolant thru the engine - bypassing the radiator.

The result unfortunately is that the lower half of the block and cylinder head heat soaks relative to the other side.

Think of it as if an sr20det's coolant line recirculated the coolant back to that same side of the block only - you would end up heat soaking the one side of the block relative to the other. Coupled with a motor that runs MLS gaskets - and sits horizontally- they develop head gasket issues a lot. This issue specifically is noted for headgasket failures where the coolant begins to bypass.

There's a whole 'nother issue going on with their external oil leaks -

[Kingtal0n]

The colder you can get that turbo's compressor side in general the better for performance.

A colder center section (via water cool) is a great way to help make this happen.
But you can take other steps to further lower the compressor' temp, such as,
heat wrap your exhaust manifold & downpipe
turbo blanket
thermal coatings
reflective tape and heat shields

[zurud]

water cool turbo is mostly oem.. factory turbo should last 100k miles. its for people that use it for daily driver that just drive the car hard and shut it down immediately. It almost foolproof turbo.

[Croustibat]

Water cools the turbo when the water pump is actually stopped.

CHRA angling and heat difference creates a syphoon that circulates the water. If the turbo is not angled correctly, it will die fast (i remember the syphoon effect happens only when turbo is angled 10 to 20° )
It is the only moment watercooling is actually needed, because all the heat "stored" in the turbine and exhaust side heats the core way higher than it would be with the turbo running.

Today nearly all turbos are watercooled.

[rbfunz]

So explain how the coolant flows when the engine is off... Water pump sure isn't spinning.

[Kingtal0n]

apparently its possible


"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.

This simple innovation greatly simplifies the logistics of assertively driving your turbocharged car and has likely saved countless turbos from untimely deaths. Think of the backwards-caps bros out there now, who's WRXs run true and strong thanks to this simple innovation."
http://oppositelock.kinja.com/random-fun-car-fact-subaru-shutdown-turbo-cooling-514111544


but our cars have no such reservoir. So No clue if its true or not for us.

[Croustibat]

So explain how the coolant flows when the engine is off... Water pump sure isn't spinning.

I already explained it, thermal syphon :picardfp:

apparently its possible

[...]

but our cars have no such reservoir. So No clue if its true or not for us.

That "reservoir" position is not relevant. Ours is integrated at the top of our radiators.

Garrett explains it quite well:

https://turbobygarrett.com/turbobygarrett/sites/default/files/Garrett_White_Paper_01_Water_Cooling.pdf


They say approx 25° tilting is the best (quoted from http://www.turbobygarrett.com/turbobygarrett/oil_water_plumbing ), but also state 20° in the pdf above.

To minimize the effects of heat soak-back, water-cooled center housings were introduced. These use coolant from the engine to act as a heat sink after engine shutdown, preventing the oil from coking. The water lines utilize a thermal siphon effect to reduce the peak heat soak-back temperature after engine shut down. The layout of the pipes should minimize peaks and troughs with the (cool) water inlet on the low side. To help this along, it is advantageous to tilt the turbocharger about 25° about the axis of shaft rotation.

[Kingtal0n]

cool :D

learn something new, gota love forums and free information :cool:

[PoorMans180SX]

I was reading about how a turbo timer isn't needed with a oil and water setup because the water would cool the turbo even after the engine turns off.
Oil won't flow.


Turbo timers aren't really needed ever. If you're beating the crap out of your turbo car, let it idle for 30 seconds. Problem solved. If you're just driving it around, letting it idle longer isn't doing anything.


This simple innovation greatly simplifies the logistics of assertively driving your turbocharged car and has likely saved countless turbos from untimely deaths. Think of the backwards-caps bros out there now, who's WRXs run true and strong thanks to this simple innovation."
http://oppositelock.kinja.com/random-fun-car-fact-subaru-shutdown-turbo-cooling-514111544


That's ironic because Subaru turbos die all the time hahaha.

It's generally good to have a water cooled turbo, since the turbo is obviously crazy crazy hot, and the oil in the CHRA can only be helped by a little cooling water. But yes, it is mostly for shut down "oil coking" issues, which used to be a real problem back in the day when oil technology wasn't at the level it is today.