Water vs Oil

[GQboy]

What is better , Water cooled or oil cooled turbos?

[steven101]

What is better , Water cooled or oil cooled turbos?

http://forums.turbobricks.com/archive/i ... t-132.html

[KiwiBacon]

All turbos are oil cooled. Water jacketing is just hot shutdown help.

Diesels don't need water jacketed turbos.

[NutterGQ]

All turbos are oil cooled. Water jacketing is just hot shutdown help.

Diesels don't need water jacketed turbos.

100% Right

[HotFourOk]

Mine has water cooling from the factory, so they must have thought it was beneficial.

[Guy]

All turbos are oil cooled. Water jacketing is just hot shutdown help.

Diesels don't need water jacketed turbos.

But they cant hurt either ... the cooler you can keep your oil, within reason the longer you oil will last.

[KiwiBacon]

All turbos are oil cooled. Water jacketing is just hot shutdown help.

Diesels don't need water jacketed turbos.

But they cant hurt either ... the cooler you can keep your oil, within reason the longer you oil will last.

Your coolant temperature and your oil temperature are quite similar, so your coolant won't be doing much cooling of your turbo oil.

[Guy]

All turbos are oil cooled. Water jacketing is just hot shutdown help.

Diesels don't need water jacketed turbos.

But they cant hurt either ... the cooler you can keep your oil, within reason the longer you oil will last.

Your coolant temperature and your oil temperature are quite similar, so your coolant won't be doing much cooling of your turbo oil.

Even if you are flogging the machine a bit and your egts are hitting 500 to 550 ?

[zagan]

Water cooled turbo will be better.

as water will remove the heat away quicker than oil.

[me3@neuralfibre.com]

It's only the core that is lubricated and cooled. The turbine and compressor are not cooled by the core in any significant fashion.
Oil is used for lubrication and cooling.

On shutdown oil drains away when oil flow stops, and can burn onto the shaft and bearings as the heat soaks from the hot turbine housing into the core that is no longer being cooled by oil flow.

Water cooled adds a water jacket around that oil cooled core. The water is present all the time, will thermosyphon to cool even after shutdown, will boil at 120deg (approx) and limit heating to this value until entire coolant boils dry - unliekly.

So - on hot shutdowns, a water cooled core is much less liekly to carbonise the oil around the bearings.

It has no effect on EGT's

The 2 arguments that I have heard are
a) Diesel's dont run the turbine housing at a high enough temperature for the heat soak to be a significant issue. (although tuning / driving may impact this)
b) Water cooled cores run less oil through them, as the assumption is the cooling is handled by the water. The (uncommon I hope) practice of running a water cooled core with only oil may be more problematic then just running an oil cooled core.

There is such a thing as an air cooled core. It uses air bearings and runs without oil. Lots of research, but nothing in production I am aware of. I think the turbopumps on some rockets are using these bearings.

Personally I prefer the water cooled core for insurance in the event I am careless and shut the turbo down hot. I dislike turbo timers and don't run one, prefering to be a little cautious. I believe many manufacturers run water cooled cars on petrol motors as cheap insurance against all the early problems in the 80's with hot shutdowns. Doesn't mean it's a bad thing.

Paul

[Guy]

It has no effect on EGT's

I never assumed it would have any effect on EGT's the reason I refered to EGTs was if you have been driving hard for a sustained period, heat soak in the housing may become an issue
When i was bogged on friday night my turbo core was around 220c as measured with a laser pyrometer (dosent everyone have one in their glovebox ?) These temps could not be good for the oil passing through the bearing. If it had cooling water passed through it as well I suspect the core would have stayed alot cooler and passed far less heat into the penrite HPR diesal flowing through there.

[Guy]

It has no effect on EGT's

I never assumed it would have any effect on EGT's the reason I refered to EGTs was if you have been driving hard for a sustained period, heat soak in the housing may become an issue
When i was bogged on friday night my turbo core was around 220c as measured with a laser pyrometer (dosent everyone have one in their glovebox ?) These temps could not be good for the oil passing through the bearing. If it had cooling water passed through it as well I suspect the core would have stayed alot cooler and passed far less heat into the penrite HPR diesal flowing through there.

[KiwiBacon]

I never assumed it would have any effect on EGT's the reason I refered to EGTs was if you have been driving hard for a sustained period, heat soak in the housing may become an issue
When i was bogged on friday night my turbo core was around 220c as measured with a laser pyrometer (dosent everyone have one in their glovebox ?) These temps could not be good for the oil passing through the bearing. If it had cooling water passed through it as well I suspect the core would have stayed alot cooler and passed far less heat into the penrite HPR diesal flowing through there.

Being bogged is the most extreme case for heating as you'll have next to no airflow through the engine compartment. Every other situation gives you more airflow to go with the high loads.
While the outer skin of the turbo core may reach 220 deg C, the parts in contact with the oil run cooler. Your oil is heated far more by circulation around the pistons, cylinder head and valves than it is by your turbo.
Did you also measure the turbine and compressor housings?

Water jacketed turbos don't have less oil flow than a non jacketed turbo. The bearing arrangement is identical.

When you idle a diesel, the engine blows lots of warm exhaust through the turbo, temps under 200 deg C which cools the turbo down fast.
But a petrol when idling is producing very little airflow and still at a very high temperature. This is why they have water jacketed turbos, they don't cool themselves very well.

If you have a water jacketed turbo, by all means hook them up. But it's not necessary.

[marko]

I don't know why people just use an oil accumalator on the turbo feed, even if you turn the engine off without letting it idle for a while, this device will send oil to the bearings and filter the oil aswel. Your turbo wil last forever.

[Ruffy]

I don't know why people just use an oil accumalator on the turbo feed, even if you turn the engine off without letting it idle for a while, this device will send oil to the bearings and filter the oil aswel. Your turbo wil last forever.

Agreed. Unfortunately oil cooling is one of the most overlooked modifications to performance engines.
An oil cooler will increase the longevity of your engine and turbo. Coupled with an accumulator your oil and your turbo will love you.

[zagan]

Unfortunately oil cooling is one of the most overlooked modifications to performance engines.

huh? all turbos use oil to help keep them working properly.

Most highly modded cars run water cooled turbos not just oil cooled.

just look at the compressor maps for your turbo and you'll find it's lowest RPM is probably around the 20,000rpm mark, maybe going up to 200,000rpm up at the top.

you need oil to keep stuff turning let alone cool it

[HotFourOk]

Unfortunately oil cooling is one of the most overlooked modifications to performance engines.

huh? all turbos use oil to help keep them working properly.

Most highly modded cars run water cooled turbos not just oil cooled.

just look at the compressor maps for your turbo and you'll find it's lowest RPM is probably around the 20,000rpm mark, maybe going up to 200,000rpm up at the top.

you need oil to keep stuff turning let alone cool it

I think he means a method to cool the engine oil, like a radiator for your oil located at the front of the vehicle.

[KiwiBacon]

I don't know why people just use an oil accumalator on the turbo feed, even if you turn the engine off without letting it idle for a while, this device will send oil to the bearings and filter the oil aswel. Your turbo wil last forever.

I don't think it'll help.

Oil starvation isn't the problem with a hot shutdown, it's heat. Even if the accumulator did continue to flow oil, with the shaft not turning it'd only cool the centre section of the shaft.
The edges and the bushings wouldn't get any oil flow so would still heat and coke up.

Also for an accumulator to release oil, you'd need to let air bleed into the top of it. A one-way valve on my oil feed that could gum up and let oil out is not something I want. You could use a gas charged accumulator, but this is more parts to solve a very simple problem.

[me3@neuralfibre.com]

I don't know why people just use an oil accumalator on the turbo feed, even if you turn the engine off without letting it idle for a while, this device will send oil to the bearings and filter the oil aswel. Your turbo wil last forever. :D

I don't think it'll help.

Oil starvation isn't the problem with a hot shutdown, it's heat. Even if the accumulator did continue to flow oil, with the shaft not turning it'd only cool the centre section of the shaft.
The edges and the bushings wouldn't get any oil flow so would still heat and coke up.

Also for an accumulator to release oil, you'd need to let air bleed into the top of it. A one-way valve on my oil feed that could gum up and let oil out is not something I want. You could use a gas charged accumulator, but this is more parts to solve a very simple problem.

Spot on Kiwibacon.
Further - Oil cooler would help if oil temp's were a problem, but often they arne't. Oil accumulator won't do much for heat soak.

Paul