Differences between Oil & Water Cooled Turbo?
 

Edited so as to get the correct tale!

What a load of bollox, someones very confused or is telling porky-pies.

'Oil-cooled' = not water cooled, ie all cooling is by oil flowing through the bearings.
'Water-cooled' = oil does lubrication and water does cooling.

Water-cooled is always better. If you want to use an oil-cooled turbo (old truck turbo?) then you need to ensure that you have a good oil flow to the turbo and have a way of getting the heat out of it.

How many turbos do you have fitted anyway and what types are they? That might clarify where the confusion lies.

The cooling method has no effect on the spool rate. The choice of journal or ball-bearing might though (if you believe the sales hype). Ball-bearing turbos are always water cooled. Journal bearings can be water or oil cooled.

You will find virtually all turbo's are oil cooled, putting water on them doesnt do much good, it normally evaporates at the temps they run, oil takes much higher temps for it to evaporate, plus it has the added benefits of not rusting the metal and lubricates the bearings ;)

Tony:D

Right, I'm still no nearer finding out definitively if oil or water cooled but it looks like I have 2 Garrett GT25 or GT28's (not sure how to tell the difference as it doesn't say on the turbo). The G stands for roller bearing AFAIK. Supposedly USA spec turbo's?
Clear as mud I know!

It will be oil cooled.

Tony:D

what on earth are you on about? Please keep your misinformation to yourself. All turbocharged Impreza's come with water cooled turbos from the factory.

Are you trying to take up pslewis' job?

M8, sorry, should've mentioned it's a modded Noble M12.

I don't know about Noble M12s but to try and clear up any misconceptions on Subarus this might help.
The GC8 turbo is water cooled and it has an oil feed to lubricate the turbine shaft / bearings. Oil enters on the top side and feeds via a pipe under the turbo back to the sump. The water return pipe flows back to the header tank.
Typically, rally cars operate without the water cooling. I have operated several turbos without cooling water but ceased that practice as I believe it substantially reduces turbo life for the small gains. It will also result in much higher localised oil temperature.

The G doesn't stand for anything specific. The GT series of turbos is a series of turbos from Garrett comprising sleeve bearing and ball bearing versions. They are catagorised by more modern designs of turbines and compressors inherited after Allied signal got involved with Garrett. The GT25 or 28 turbo will be ball bearing cored if they are GT25R versions, and I suspect they are. Either way, water cooling is much prefered if you can do it, as it does extend turbo life, and can do away with the need for a turbo timer or similar. I am pretty sure that all the GT turbos are water cooled, and certainly all the ball bearing version are, as they have a restricted oil flow due to the bearing type.

As Harvey says, the benefits of water cooling, (longer life, self cooling after engine stop, decreased oil degradetion) far outway the benefits of oil only (reduced cost of turbo, easier to swap, which is why rally cars do it).

Paul

The Garret T25/T28 have feeds for water cooling, this cools around the main turbo housing, and an oil feed for bearing lubrication (possible extra cooling)

All bearings on all rotating compnents on any engine or turbo is oil cooled.

The casings, liners and heads are what is water cooled ;)

Arent the bearings encased in with water passages, and effectively, it is the water which is cooling the bearings (with oil providing lubrication - but also aiding cooling?)

The T25 and T28's as used in Nissan's are definitely water cooled.

These turbo's are not water cooled, to be water cooled you have to solely rely on the water to cool that part, ie a water cooled engine, normally alloy in construction, take away the water and the component fails very rapidly. On a turbo, you can take away the water and it still runs (the oil still takes most of the heat out of it), though it reduces the life it can still be efficient.
Also, you will find these turbos are water/air assisted, that is also more efficient.

Tony:p

If you remove the water cooling from a ball bearing garrett turbo, it will fail, the same with an IHI ball bearing turbo. Due to the bearings they have a restricted oil feed, not sufficient to properly cool the turbo.

Bloody dodgy design then ;)

Tony:D

LOL.. another classic quote. Love it :D

Tony.

its also true, you cannot run a turbo on water alone ;) so these will be water assisted, not just cooled.

Tony:)

Who said you could run a turbo on water alone then? :D

:rolleyes:. So if you use water to help cool an oil fed turbo in your mind it's not water cooled????

Because Tony B spoke we must no longer say our turbos are water cooled, so i must have a TD which is oil cooled but assisted by water and air.

FFS, you take the biscuit.

Tony.

PS can you tell me a turbo that isn't 'air assisted' in it's cooling.... anybody run one on their car in a vacuum???

PMSL :D

And people wonder how new forums members pick up such bad misinformation...

Paul,

I think that reply should have been prefaced with

People like Tony help to keep you in business, surely the more misinformation that gets spread about, the better :)

LMAO it's so true...braided brake lines, synthetic brake fluids, nasty fast road pads, Dump valves, induction kits, 5 inch tailpipe backboxes with 2.5" standard bore, boost controllers, fancy pulleys, sooper duper oil addatives, Fancy multi tip spark plugs.


All of which claim performance gains, but are mostly misinformation :D

The braided lines give confidence if not performance, but have to agree on the rest ALi-B :)

Jesus, it was originally an innocent enough question!!!;)
However......I now know a bit more(:):(?).
The turbo's are both Garrett (still not sure what number as none showing on the casings), & they are each fed by two separate oil lines, so one for lubrication & one for cooling. I'm advised to get a turbo timer sharpish as 5-10 minutes cooling time is required!
The original info that they are USA spec & roller bearing is also correct.
Not sure if I'm happy or not, the spool up is lightning fast with no noticeable lag but if that's at the expense of longevity it's a potential high price to pay.

LOL :p

No one mentioned air assisted until i did..... strange?
Right, there is no "real" water cooled turbo, simply because water doesnt cool the turbo enough.
There is one simple answer to this and all the "experts" have not yet explained it? any chance you want to?
I'll mention the word "physics".
I shall let you ponder that one for a while ;)

Tony

I'll mention the word "b0l*0x". There really is no point in being more eloquent...

Oh dear.

Water doesn't cool the turbo enough? Enough for what? How much does the water cool the turbo, and why isn't it enough?
One simple answer to this? What is 'this'?

Are you trying to be the new Mycroft?

Paul

Why would anyone mention air assisted.... all turbos are air assisted so does anybody really need to mention it. As i said do you know of any turbo that doesn't actually have air circulating around it.... maybe you've run a turbo in the vacuum between your ears????

LOL @ Physics... fooook off Tony :) You really do talk crap... why don't you explain it to us. There are some intelligent people all listening on this thread for your answer. I'm sure the Enginneers among us would be very interested in the answer. I'm dying to hear your theory on properties of water for cooling.

Tony.

Yeah, I may have been a bit iffy on that, my point was that they don't last as long and aren't as safe as the original rubber ones. Not sure how regularly they need to be changed as routine, but I know what happens when they aren't :(