WarspeedFD

Could anyone tell me any advantage going oil cool vs. the oil and coolant other then cooler runnign turbo? Will there be more space for oil cool housing to mount?

I going to upgrade to a Turbonetics 60-1 and need to decied dry and wet housing.

peejay

"Wet" is the only way to fly.

Marcel Burkett

I'v been running "dry" for a while now without any problems , I use Mobil synthetic oil just in case . One other advantage is lower coolant temperatures , mine runs between 180 and 190 deg F normally , and thats with very "spirited " driving . On the very hot days it will only get up to about 195 .!! I also use the KOYO with a NPR mounted out front .

Railgun

Marcel, do you have a comparason of coolant temps between water cooling the turbo and not?

If you can water cool it, do it. Good rule of thumb.

WarspeedFD

Thanks for the valueable info guys!

peejay

Ah but what are your oil temps like... oil temps are extremely critical for rotaries, since the oil is about a third of the cooling system.

I retract my statement: Water cooled is the only way to fly, unless you need to be able to change your turbo in a very short period of time, like a 20-minute servicing time limit. Every little bit helps there, as do quick-disconnects, slotted holes, replacement of bolts with studs and vice-versa.... But for engines that are expected to keep the turbos for longer than a day or two, water cooling is the only way.

Remember how turbos used to have such a bad rap, "they last 60k and then you have to replace them", etc? That was before water cooled housings were common.

Carl Byck

I'm not disagreeing, exactly... BUT, oil cooled only is more readily available used, and if your coolant system is marginal(your temps exceed 210 with water cooled), then oil only can work fine.
Advantages;
- cooler CHRA should mean longer life
- acts as a heat exchanger balancing your oil and water temps(to a point) reducing the demand on both systems compared to dry.
Disadvantages;
-more expensive
-more complicated to plumb
-adds signifigant heat to coolant
-not readily available used
I would not agree with the statement that wet CHRAs automatically last longer, most big truck turbos are oil cooled only, these are for the long haul trucks logging hundreds of thousands of miles. If the CHRA was designed to be cooled by oil only I would expect it to last as long as its water cooled breathren. The key to a long lasting oil only set-up is synthetic oil, and maintaining clean oil, and oil supply fittings. Virtually all the dry failures I have read about or seen, are the result of coking, or failure to deliver enough oil to the turbo. I would say 90% of all the turbos supras run are oil cooled only. There are tons of these guys, and relatively few failures.

As always, if you build a solid system, it will last. If you are going dry, you need to be sure to have adequate oil cooling, and cleaning. If you are going wet, you need the above plus a coolant system up to the task. Pretty simple really. Consider that if you went from a wet factory set-up(most are), to a dry aftermarket set up(most are) w/out upgrading your oil system, that would be like upping the boost w/out adding fuel, yet plenty of people do it, thus the bad rap IMHO. All in all wet is probably more reliable due to the redundancy of the system(oil, and water), and the lower demands placed on each system, as compared to oil only.
Build it right, and it will last, do it half assed, and it will not.
Carl Byck

peejay

Diesels also run at significantly lower EGTs at anything but full power. I would imagine that would play a large factor.

OK let's dig up the picture I like to dig up every three months when this issue comes up. Just bear in mind that even synthetic oil starts to break down at roughly 175degC.

Carl Byck

In looking at that graph, the coolant gains no temperature during heat soak???? Sorry but that is not possible, you have coolant (a very small amount) sitting in a housing that according to your graph is roughly 300* C how is it possible that ~25lbs of metal heated to 300*C would not raise the temperature of a 1/4 cup of water????
Whose graphs are those? I suppose an IR pyrometer could easily dispell the myth of your graph. Simple go out for a spirited drive, come home, and measure the temp at the center of the CHRA (it will be close to the bearing temp), then, measure it 5-10 minute later. I am assuming that you have a water cooled CHRA. Do you really believe this graph?. Educate me if you may, but I do not believe that graph for a second. One more question, what part of the turbo is finned, the CHRA? Carl

peejay

The temperature readings are of the *bearing*, not the coolant. Additionally, don't discount the potential of convective coolant flow, after all that had been used in lieu of water pumps on engines for years.

If you still have a problem with the figures, write to Chrysler's engineering department - that graph is one of several from their SAE paper on developing their turbocharged 2.2l engine.

Carl Byck

What is their address? Chrysler turbo, that's a pretty reliable motor LOL. I'm sure they are accurate, probably out of context though. Probably a graph used to demonstrate how reliable they could make their motors

peejay

Actually, 150-200k is not uncommon on the stock engine/turbo. Even after wackos get hold of the car and crank the boost up just past "too much" and into "not quite sane" territory.

The only problem is the same as the problem with any other car: There are a great whopping shitload of people whose idea of maintaining their car is wiping the windshield off when they fill their gas tanks.

I know someone who was one of those - she had one car for 100k and in that time she did four oil changes, or rather she gave in to my nagging and allowed me to change the oil. (She has since changed her ways, good thing too, Buick V6's tolerate that kind of abuse but now she has this weird Scandinavian thing that probably wouldn't)

Ever drain shiny, silver-grayish, thin-as-water oil from the oil pan before? No? Then you maintain your car. You're not normal. Now picture the "normal" people running around with absolutely acidic coolant digesting their water pumps and radiators and water passages, with that nasty "oil" coursing through the oil passages of the bearings, the HLAs, the turbo bearings. Black gritty ATF. *And they keep chugging along*.

Now, if water cooling can make turbos live in the face of *that* kind of abuse, why are they a bad idea for *our* kind of abuse? Yes we generally keep up on our maintenance, but then again we're going way beyond the loads that Joe Putt-putt would put on his LeBaron or whatever.