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Yes, if the power we could put to the ground with an AWD setup were high enough, it would overcome any weight disadvantage.
Given the 'small' drive units have separate cooling loops for the motor and inverter it's possible you can manage temperatures better than the 'large' DU.

On our conversions we're separating out these two cooling loops and should have some data to report in the next couple of months :cool:
 

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Water temperatures are very cool. Here's a data point: Stator temp 171 degC, Inverter temp 43 degC, Water in 35 degC, Water Out 37 degC
How did you fill the system and bleed out the air? It sounds like you have a vapor lock in the cooling jacket.
 

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Would water wetter or another advanced coolant take more heat off for racing? The OEM solution isn't always best because it has to work in all conditions.
 

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I want to echo KENNY

How did you fill the system and bleed out the air? It sounds like you have a vapor lock in the cooling jacket.

Thinking about it he has GOT to be right - those temperatures cannot be right no engineer would design a system like that

You have an air pocket ! or even worse somebody has lost a rag
 

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Do you have any idea of the flow rate? Rate of heat removal from the motor is simply flow rate, multiplied by temperature rise, multiplied by specific heat capacity. It might be informative to know how much heat is being moved.

It is true that pumping froth is not likely to be effective, but I assumed that the system was bled properly. Has anyone seen the appropriate Tesla service procedure, or is service documentation all secret?
 

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Is it possible that you're getting boiling creating air pockets when you're running 150-170C? 50/50 Dexcool boils at 129.4C at 15PSI.

What oil/water heat exchanger are you running? Have you looked into Laminova exchangers? They're heavily used in F1, Koenigsegg, etc.

Great project!

JP
 

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Motor Cooling.
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The Tesla stator/rotor/power electronics are water cooled. Despite having a very high capacity cooling system and an ice reservoir, we were not able to keep the stator temperatures down. (There were no problems with inverter temperatures). This year, we will be experimenting with oil bath cooling of the stator/rotor air gap in addition to the water cooling. We will utilize a water/oil heat exchanger and a positive displacement gear pump to circulate ATF.
In the Tesla Small Drive Unit discussion, it became apparent that the motor is oil-cooled, with the oil then transferring heat to the water (antifreeze) cooling loop. I realize that this is a large drive unit, but I'm guessing that the cooling system is fundamentally the same; if it is, the oil flow and heat transfer is critical. Do you have oil temperatures at useful points, such as in and out of the heat exchanger?

It sounds like heat from the stator transfers poorly to the water because the oil cooling system (if it is like the small drive unit) is not sufficiently effective. That would mean that there is potential for improvement in both the oil-to-water heat exchanger, and in oil flow at lower motor speeds (because the oil pump is gear-driven at a speed proportional to drive unit rotational speed), without adding a cooling system.
 

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In the Tesla Small Drive Unit discussion, it became apparent that the motor is oil-cooled, with the oil then transferring heat to the water (antifreeze) cooling loop. I realize that this is a large drive unit, but I'm guessing that the cooling system is fundamentally the same; if it is, the oil flow and heat transfer is critical. Do you have oil temperatures at useful points, such as in and out of the heat exchanger?

It sounds like heat from the stator transfers poorly to the water because the oil cooling system (if it is like the small drive unit) is not sufficiently effective. That would mean that there is potential for improvement in both the oil-to-water heat exchanger, and in oil flow at lower motor speeds (because the oil pump is gear-driven at a speed proportional to drive unit rotational speed), without adding a cooling system.
Brian-

Could a Laminova oil-to-water heat exchanger be deployed inline? AFAIK, their HEs are the best in the game: http://www.laminova.se/products/oil-coolers

(I'm a supplier to Koenigsegg, which uses these HEs)
 

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Very interesting project!
Loved the racing footage, particularly how you pass several other races at once.
Gotta love all that torque.
Never lets you down,
Never gives up,
Never gonna run around and desert you... unless you are overheating or your batteries die, then it really makes you cry.

Something that also might help. I spoke with someone a while ago that was also putting his battery in high demands and had battery overheating problems.
Adding more does help, but you run into weight issues all over again.
What they did is have 2 packs. One on charge and the other in the vehicle.
When needed, the battery was swapped out.
I dont know how practical that may be for you, but they designed their vehicle around replacing the pack quickly.
Also, I have a few of the Kia Soul packs.
As for the newer leaf packs, they are very difficult to find. Lots of demand for them.
 

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Discussion Starter · #32 ·
I see there are lots of replys going back a couple of months that I haven't responded to.

I'm pretty sure that the water system has been bled properly. We have huge flow and V8 capable radiator. The problem is that the outer cooling jacket around the stator just can't remove heat fast enough. Under race conditions the stator temp goes up 12 to 20 degrees per lap.

There is no oil cooling inside the large drive unit. The stator windings are encased in epoxy. The outer surface is in contact with the cooling jacket. The rotor has cooling water running through the center (Tesla has a patent on this). The only access we have inside the motor is via the air gap, or the ends of the rotor/stator.

During our testing we ran ATF or de-ionized water in the air gap. Unfortunately, the added heating provided by the fluid shear forces added more heat than it removed. We also tried spraying deionized water once the temperatures exceeded about 120 deC hoping that as the water flashed to steam it would provide a cooling effect. No success there either.

We did have some success when combing water spray with large amounts of compressed air, but the practicalities of implementing this are high.

We also considered CO2 injection but were concerned by the high stresses caused by the temperature differentials and the problems with carrying large CO2 tanks in a race car
 

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Hi
Bringing this over from the Small Tesla motor discussions

If you are using the inbuilt pump you only get peak flow and cooling at max speed

I would suggest
Use a small tank - 4 litres? as a buffer - internally split but with a weir so that so that if one side pumps more than the other it simply spills

One pump going from the "hot" side to the radiator - and back to the "cold" side

The other pump going from the "cold" side to the motor and back to the hot side

Both pumps need to be quite meaty - the idea is that they are pumping at the same pressure as the internal pump used to at max speed

When you drive it for part of the lap it will be heating up because it can't move the heat fast enough
But for part of the lap it will be cooling

With the old motor pump the amount of cooling went up and down - with this set-up the cooling will stay at maximum - over the course of the lap you will reject more heat to the radiator than you used to

If the temperature keeps rising don't panic - as the system gets hotter it will be able to reject more heat - as long as it stays below the temperature that causes damage you should be OK
 

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Discussion Starter · #34 ·
Once again, the large drive unit has a different cooling system. The external water jacket and water to the center of the rotor are the only cooling mechanisms. There is no oil pump.
 

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Once again, the large drive unit has a different cooling system. The external water jacket and water to the center of the rotor are the only cooling mechanisms. There is no oil pump.
So what are you using for a water pump? - does it (or can it) run at full power all of the time?

And are you using a seperate water pump and a hot/cold well (tank) system for the radiator?
 

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Discussion Starter · #36 ·
We are using a Craig Davies electric water pump rated at 115 lpm. This runs at full speed all the time. As well as the radiator, we have an reservoir that holds about 20 litres. We can fill it with ice to pre-cool the motor to aboit 5 degC. This delays the time to power limiting by one or two laps. (Temperature rise per lap is in the range of 12-20 degC/lap).
 

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There is no oil cooling inside the large drive unit. The stator windings are encased in epoxy. The outer surface is in contact with the cooling jacket. The rotor has cooling water running through the center (Tesla has a patent on this). The only access we have inside the motor is via the air gap, or the ends of the rotor/stator.
Ah, so not like the small drive units. Thanks for the info, and sorry for the sidetrack. :)
 

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Could you press aluminum, copper or polycrystalline diamond fins through the epoxy to touch the wiring of the stator to become heat pipes to move the heat from the stator into the fluid outside of the epoxy?

I assume that aluminum or copper would not work because they are electrically conductive but polycrystalline diamond could be the perfect material to excavate heat from the stator to the fluid.

For context, most epoxies are going to have a thermal conductivity of less than 1.0 W/Mk, where as a polycrystalline diamond that touches both the metal of the stator and the coolant can have a thermal conductivity of up to 2,000+ W/Mk. Cheaper diamond plates are 1,000 W/Mk

Thus a few (dozen) of these 10x10mm diamond plates ($245 each) placed through the epoxy might make a big difference in getting the waste heat out of the motor...

https://e6cvd.com/us/application/all/tm200-10-0x10-0x0-3mm-pl.html

Bulk Resistivity (Rv): 1x1012 Ohm cm
Surface Resistivity (Rs): 1x1010 Ohm cm
Thermal Conductivity: >2000 Wm-1 K-1 @293 K
Thermal Diffusivity: >11.1 @ 300 K (cm2s-1)
 

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A green Tesla-powered Cobra race car just run the second-fastest time (of all 60 entrants) at the Knox Mountain Hill Climb. I'm guessing there can't be two of these cars in B.C... so congratulations! :)

Knox Mountain Hill Climb
(Look for car #101 and #701 - for the same car with two drivers - in GTO class)

It looks like the motor temperature rise can be tolerated for one minute and fifty-one seconds of hard climbing. :D
 
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