# Using transmission fluid for controller cooling



## dcb (Dec 5, 2009)

gear oil is a lot more viscous than atf or glycol, and isn't much more dense than atf, so I would think it is harder to pump without offering more mass flow.

Not worth messing about with, keeping the controller happy is a top priority.


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## Moltenmetal (Mar 20, 2014)

Manual transmission fluid is generally an 80 wt oil- far too viscous for good heat transfer. Stick with glycol-water, which is less viscous, has a higher heat capacity and density and thermal conductivity- it wins on all four properties over any oil for heat transfer, and you don't need lubricity.

If you keep a closed system, corrosion isn't an issue. You'll be operating well below boiling so no worries there.

If you must use an oil, use a light weight mineral oil. Even ATF is heavier (more viscous) than you need.


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## Sunking (Aug 10, 2009)

Use what utilities and computer hackers use that is non toxic, Mineral Oil.


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## Matej (Dec 4, 2015)

Viscosity and heat transfer are what I assumed would be the main negatives.

I would employ a 12V pump made specifically for moving gear oil, used for cooling differentials and transmissions.
As for the heat transfer, I know it would never cool as well as glycol. In the end it comes down to whether it would be at least slightly more efficient than only air-cooling, or if it would be completely pointless.

Some manual transmission fluids are actually mineral oil-based, so that could be something for me to look into.


On the topic of mineral oils and computer cooling, has anyone experimented with full immersion cooling of controllers? Perhaps one could repurpose a small fuel cell and house the controller and mineral oil in it. Then use the fuel inlet and outlet to pass the oil through a radiator. Or just use the vehicle's original fuel tank filled with mineral oil.


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## Sunking (Aug 10, 2009)

Matej said:


> On the topic of mineral oils and computer cooling, has anyone experimented with full immersion cooling of controllers? Perhaps one could repurpose a small fuel cell and house the controller and mineral oil in it. Then use the fuel inlet and outlet to pass the oil through a radiator. Or just use the vehicle's original fuel tank filled with mineral oil.


Not myself personally, but PC Gamers have been doing it for at least 10 years. Toms Hardware Forum has tons of archives from 10 to 12 years ago. Enough so now manufactures of Tower Cases offer them already to go. They have even evolved with Water Ethylene Glycol models. However PC's are now antiques and dying off.


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## Matej (Dec 4, 2015)

Sunking said:


> Not myself personally, but PC Gamers have been doing it for at least 10 years. Toms Hardware Forum has tons of archives from 10 to 12 years ago. Enough so now manufactures of Tower Cases offer them already to go. They have even evolved with Water Ethylene Glycol models. However PC's are now antiques and dying off.


A few years ago I was going to build an immersed PC but in the end I decided against it, primarily because it seemed messy to maintain and replace components.
In the end I always end up sticking with air cooling for the sake of cleanliness and simplicity. I have a feeling I will do the same with the car.

PC's are dying off in most fields except gaming, where they are actually seeing a rise in sales while consoles are slowly dropping in popularity. This is kind of exciting, since that is where most PC progress happens anyway.


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## bigmotherwhale (Apr 15, 2011)

I believe fluid viscosity is inversely proportional to heat transfer co efficient, correct me if i am wrong there people, so you would reduce cooling effectiveness, the only reason you would do it is because you have a cooling loop that uses oil for a transmission or motor and want to make use of that already. Glycol cooling system is much more efficient at moving heat. however an oil based system does not corrode or degrade in the same way as a water based system, so the effectiveness stays the same for longer.

I made several full submersion pc systems using oil, my best find was baby oil as its non toxic readily available and relatively low viscosity. What put me off is that they were heavy, very heavy the wires acted as conduits for the oil and were difficult to seal and you get funny looks buying gallons of baby oil.


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## Sunking (Aug 10, 2009)

bigmotherwhale said:


> I made several full submersion pc systems using oil, my best find was baby oil as its non toxic readily available


Baby Oil is Mineral Oil with fragrance added. Most of the folks I knew who used oil cooling, used transformer oil that utilities use. I use to give it to them and we used it by the tanker truck loads and 55 gallon drums.


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## Sunking (Aug 10, 2009)

Matej said:


> PC's are dying off in most fields except gaming, where they are actually seeing a rise in sales while consoles are slowly dropping in popularity.


Very small market. The other thing is the gaming software manufactures do dot publish PC versions as the market is too small to justify the cost. It takes all their resources to just make versions for Sony PS4 and Microsoft Xbox. Some do not even bother with making both versions and exclusive to either Sony or MS. 

Having said that I do have a custom PC I built and still upgrade from time to time.


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## ken will (Dec 19, 2009)

Matej said:


> The routing would go as follows:
> Pump > Transmission > Radiator > Controller > Radiator >
> 
> The idea is to minimize the number of various fluids in the car. Instead of adding another separate circuit and fluid for the controller, why not make use of one that is already present.


As the transmission wears, little flakes of metal become suspended in the fluid. I don't think you want to send metal flakes to the controller.
I vote for separate circuits!


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## Matej (Dec 4, 2015)

ken will said:


> As the transmission wears, little flakes of metal become suspended in the fluid. I don't think you want to send metal flakes to the controller.
> I vote for separate circuits!


There would have been a magnetic filter right after the transmission and also after the pump (in case the gears in the pump chip or break).

However, it seems the consensus is that this would not be a worthwhile pursuit after all, so it is a no go.


On the other hand, a fully immersed controller is intriguing. Perhaps it would be worth experimenting with, if anyone has an old Curtis.
Having a car that smells of baby oil instead of exhaust fumes would be hilarious.


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## Sunking (Aug 10, 2009)

Matej said:


> Having a car that smells of baby oil instead of exhaust fumes would be hilarious.


Does not take electric motors to do that. Mineral oil, or really any vegetable or petro oil can be used as diesel fuel. In my career at a electric utility we had a small group of people that took used transformer oil and used it as diesel fuel. They also collected cooking oil from restaurants. In those days utilities and restaurants had to pay to have it hauled off. Today goes to the highest bidder using tax dollars to pay for it.


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## bigmotherwhale (Apr 15, 2011)

ken will said:


> As the transmission wears, little flakes of metal become suspended in the fluid. I don't think you want to send metal flakes to the controller.
> I vote for separate circuits!


The oil would flow through the cold plate cooling the power stage only, there would be no contact between the electronics and the oil.


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## Sunking (Aug 10, 2009)

bigmotherwhale said:


> The oil would flow through the cold plate cooling the power stage only, there would be no contact between the electronics and the oil.


Ditto. Stop and think about it. Imagine Water / Ethylene Glycol systems. Water and electricity do not mix. Granted you could submerge with oil, but that is not how it is done.


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## Matej (Dec 4, 2015)

Sunking said:


> Does not take electric motors to do that. Mineral oil, or really any vegetable or petro oil can be used as diesel fuel. In my career at a electric utility we had a small group of people that took used transformer oil and used it as diesel fuel.


The oil would not be burned, of course. But I assume one could still smell it through the vents if the controller was submerged in it.
I was actually going to run my car on biodiesel and waste oil before deciding to go electric.




bigmotherwhale said:


> The oil would flow through the cold plate cooling the power stage only, there would be no contact between the electronics and the oil.


I assumed he meant it could eventually clog up the cooling passages with gunk.


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## karmann eclectric (Mar 26, 2008)

I actually tried this for my Zilla, hoping to reduce weight and improve tranny efficiency by cooling with 80 wt manual tranny lube, but gave up after a couple of electric fuel pumps rated for diesel couldn't move the stuff. Heating the tranny fluid in an EV should yield benefits though, esp. in winter. With shorter duty cycles, no idling, and no heat transfer to speak of EVen from the clutch or torque converter, manual trannys in an EV rarely get warm.


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