Oil cooled Vs Oil/Water cooled turbos
 

What are the major differences between the two? What's best for daily driving? Or daily and occasional tracking?

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One is old outdated design

The other has oil and water

https://www.garrettmotion.com/racing...or-your-turbo/

Oil cooled turbos are typically journal bearing, ball bearing will almost exclusively be water and oil cooled.

You will get much better transient response (on/off gas pedal) from a ball bearing turbo, but honestly it's preference. I like journal bearing/oil cooled because they're cheaper, less things that can leak, and are easy to rebuild.

Some will say that ball bearing turbos spool faster, but hardly; it's the transient response they're talking about. Ball bearing water cooled turbo is certainly better for daily driving, for no reason other than temperature management

To be clear, oil is not intended to cool in a modern car, the ability to evacuate heat is a property of the oil that older designs took advantage of. A modern turbo with air flow maximized under full load can't evacuate heat from the metal fast enough with oil alone, or if it can cooks it in the process, and heat is what kills a turbo build if everything else is done right. Do a few pulls or keep it under load for a while and heat builds up, your IATs rise, knock starts to creep in, and bam, there goes a rod.

Water cooling has much more capacity for heat, and the thermal management system of your engine is designed to remove any heat as quickly as possible. Using it to cool a turbo means a few things benefit down the line. Oil is cooler which is important for our cars, and good for general oil longevity, whether that's breaking down one lap later or letting you stick with a lower weight option for a DD, or just not burning as much between changes. The air charge picks up less latent heat from the turbo before we even reach the intercooler, and if you're not radiating as much heat from the turbo into the engine bay your intake pipes don't transfer ambient heat into your charge. The turbo itself being cooler means smaller tolerances can be used safely which is what let the change from journal to ball bearing happen among other design tweaks and materials choices that a more stable operating temp allows (Like how @DarkPira7e mentioned transient response being better: Lighter components and less drag means less energy lost spinning the turbines)

I think in the end it's fine to be oil cooled, but you need to temper your expectations and have your supporting mods lined up. An oil cooler becomes 100% essential, and things like turbo blankets, hood louvres, and charge pipe insulation have more dramatic effects. Best choice is to spring for water cooled if you can get it.

The biggest difference is the need for cool down to keep the turbo from coking up. When installed properly you will still have coolant flow due to thermal heating of the coolant after shut down. This keeps the turbo temp from spiking after shutdown when oil flow quits.

Thanks for the info guys. With the types of synthetic oils we use these i think that an oil cooled turbo shouldn't be much of a concern right?

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Just make sure you do a cool down. You will be fine.

I would personally never use a oil only turbo when there are typical sized water cooled turbos that give the same performance results but have much better thermal control and reliability.


They use water cooling for a reason.

Alot of OEM HiPo cars have electric pumps that keeps the coolant flow going for a while after shut down.

Sound engineering principles, use them

All my turbos have been water and oil. I have never had a turbo oil problem. I don`t do idle cool downs on daily driving but I drive sensibly the last few blocks. At the track I do similar.

Synthetic oil has a higher heat tolerance than conventional oil before vaporization and oxidation, but it is like 600F vs 300F. The turbo will see exhaust temperatures much higher than that like 1200+F. Iron will start to glow red at 900F and that is fairly common on a turbo that is pushed hard even without high boost.

You may be thinking, I’ll just do more oil changes. That could work to reduce the potential for bearing wear or failure. Besides oil damage, you will see higher oil temps, which can lead to engine failure if oil pressure drops too much, so you will need a decent oil cooler. If that isn’t cutting it then higher weight oil will be an unideal bandaid. The other bandaid is to use a turbo timer or always make sure to idle the car for five minutes +/- depending on your driving before turning it off.

Love the inputs from you guys. I like the different perspectives. I'll definitely be going with a water and oil cooled turbo.

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I think this is something that a few people miss. If you drive a bit with low/no boost things can cool down fine. A hot turbo is glowing red, and a turbo that's cool enough to avoid vaporizing oil or coolant could still be hot enough to burn you. No need for any turbo timers or whatever if you can keep your foot under control.

I can’t do this. I have a short commute, so I drive it like I stole it to the garage.

OEMs don’t have turbo timers because water cooling post shutdown is designed into the car like these guys point out:

If a system can’t take advantage of thermal syphoning, nor does it have an electronic water pump that can be controlled post shutdown, then a long cool down is definitely needed.

They use water cooling because ball bearings only have a tiny oil flow, not because water cools better.


See above. Modern journal bearing turbos are still oil cooled.