Why doesn't anyone with single turbos run oil AND water cooled bearings?
 

I have never seen anyone with an aftermarket turbo on an rx7 running oil and water cooled bearings. Is it just not worth the effort to run the extra lines?

i have it... it depend on the turbo some have the option and some dont.. you done need it but i like having it

I know you don't need it, but some friends of mine were trying to convince me there is no reason not to have it. They are trying to tell me the cooling gains are well worth doing it. I'm just curious as to what those with some experience have to say.

By watercooling the center housing you dramatically reduce the stress put on the oil seals. It's super easy to run some coolant lines the turbo, and it can substantially increase its lifespan.

If you aren't ordering a kit, then you usually just have to ask for the water-cooled CHRA. It was no extra cost when I talked to Turbonetics...

Corky Bell highly recommends them in his book. The stock 2nd gen turbo has it too. 3rd gens don't?

All GT series turbo's are watercooled centersection, and cannot be run without water lines, if you run it without you will have bearing faliure very shortly afterwards.


-Sean

FD turbos are water cooled. The upper rubber coolant line (which tees into two separate lines to feed each turbo) is quite prone to failure...

Thanks for all the responses guys. Looks like I will be going water cooled also.

Does Chrysler Engineering count as being experienced?

http://www.thedodgegarage.com/turbo/sae_22_graph.gif

From SAE Paper 840252 (about turbocharging the 2.2l engine)

I would say that if turbo longevity was of any concern, water cooling is mandatory. And considering that rotaries are partially oil-cooled, I would want to spread the turbo cooling around to the oil and the coolant instead of just baking the oil. (Literally)

Mine is oil/water cooled.

Now thats what I wanted to see. Great info peejay!

i've got oil and water as well....

Yep oil and water cooled also. We have the lines from the factory, why not put them to good use instead of bypassing them.

Depends on the turbo design. Some are designed to run without coolant, while some require it. My 35/40 was water cooled, but my T66 is not. I don't have any numbers to back this, but I would think running coolant through a hot turbo would put more strain on the coolant system, possibly yeilding higher water temps.

If your cooling system is up to snuff it shouldn't matter. I'd rather spend a few hundred extra on a better radiator than replace turbos more often.

Better slightly higher water temps than MUCH higher oil temps and oil degradation. Since oil quality and temperature is so vital to a happy rotary, it seems almost like a no-brainer to want a water-jacketed turbo.

Isn't it give and take? Either way you are going to gain so much heat weather its in the oil or coolant, right?

Now if the turbo I want isn't water cooled is it worth an extra $80 to get it? Does it cost more to rebuild or anything? Heres the turbo I'm looking at currently:

http://store.yahoo.com/cheapturbo/t4b.html


For $79 it gives you a wet bearing housing and for $79 more than that a 360 degree thrust bearing. Sound good?

But without the water cooling, you are literally cooking the oil in the bearing, causing (vastly) decreased bearing life, as well as degrading the oil more rapidly and raising oil temps - and oil quality/temperature is *critical* to a rotary engine.

Race cars often run oil-cooled only turbos due to the fact it's one less seal to fail. With turbos being rebuilt/replaced on a regular basis, bearing life isn't an issue for them. On the street, hands down, go with a water cooled bearing. All of GReddy's offerings (Mitsubishi) are oil cooled only. I have a plain bearing GT40 that's oil cooled only as well. I think the ball bearing stuff is both but the plain bearing stuff is oil sans water.
Michel

Ball bearing GT turbo's have to be, if not there is a seal inside that will fail and you will literally have ball bearings come out the oil drain, I've seen it. You cannot run these without water. Ask me how I know;), personally I will go water cooled every time otherwise your just cooking your oil.

Quite right. As water begins to gas-bubble and detach from heated surfaces nearing 90C (~200F) reducing cooling surface, oil increasingly soaks the heated surface improving conduction, yet water being far better in conducting heat until this point, so we maintain a high flow. The oil is effective in dissipating heat beyond 230C (~450F), of course being tortured beyond 250C. In these oil-only turbos, I see huge oil cavities for bearing contact.

What external bolt-on gadgets can be used for adding a water jacket, without replacing the bearing body?