# Motor temperature and cooling



## DIYguy (Sep 18, 2008)

I'm not an authority on motor heat generation vs drag racing impact... but your suggestion is definitely of value. This method of cooling is effective for drawing away heat. There are heat recovery drain pipes that basically take flattened copper tubing and wrap it around the larger copper drain pipe so that when the bath water or dishwasher water is released down the drain, the heat energy is drawn through the copper by thermal conduction. 

I suppose there is some time lag to get the heat to the barrel of the motor... but there has to be some positive impact. Of course, if you are generating a great deal of heat in a short time, (like drag racing may do) then you may want to have both forced air and conduction cooling.

Sounds good to me! Would you then recirc the coolant through a radiator? Perhaps it could be used for cabin heat supplement in the cooler climates (for regular driving applications that is)??


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## Woodsmith (Jun 5, 2008)

For something as quick as a drag race you could use ice. Run the cooling coil from the motor to a reserviour full of ice. The heater water goes in the top and the chilled icewater comes out the bottom to return to the motor.

You may need to experiment to see how much ice you managed to melt per run.


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## DIYguy (Sep 18, 2008)

Woodsmith said:


> For something as quick as a drag race you could use ice. Run the cooling coil from the motor to a reserviour full of ice. The heater water goes in the top and the chilled icewater comes out the bottom to return to the motor.
> 
> You may need to experiment to see how much ice you managed to melt per run.


Yes, good idea. This method is often used for ICE's to cool the fuel. A small ice box with a copper coil to run fuel through. Increases density I believe and has a cooling effect as well apparently improving volumetric efficiency... Perfect for racing as it's a short term requirement. I suppose dry ice (CO2) could be used for longer durations....


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## bipole (Sep 8, 2009)

Thanks for your input guys. Do you think there would be enough heat available from the motor casing and the controller to supply comfort heat to the cabin? I was just opening up a broken ceramic heater to get the element out and thinking how inefficient this use of power would be.

As I see it, the major producers of waste heat in the car would be:

Brakes
Motor losses
Batteries
drive train losses
controller

The controller is easy, the motor, not difficult. Drive train and batteries are probably not worth going after. Brakes, not easily water cooled, but....

This leads me back to my desire for some motor braking. If the Kinetic Energy of the car could be transformed to a medium for cabin heating, that would be efficient and provide useful braking action. Of course I'm relating to series DC use, ignoring regen possibilities.

Motor braking probably deserves a new thread.


The other aspect of the motor cooling is the pre-chill, drag racing application. Yes, ice would be the most convenient thermal absorbent. I'm thinking this would buy a little time before thing go thermally bad on the run. Pro Stock drag racers use a large A/C unit to run chilled water through the engine in the pits.


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## DavidDymaxion (Dec 1, 2008)

I had thought that cooling the forced air could help -- put a block of dry ice where the evaporated C02 could be blown into the motor.

I have heard of Salt Flats racers water cooling the brakes by dumping the cooling water tank onto the brakes during the stop. For high speeds, cooling inlets and ducts hurt the aerodynamics, so air cooling is less favored.


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## CroDriver (Jan 8, 2009)

I asked a DC motor producer about liquid cooling of DC motors. He said that there's no point in cooling DC motors with liquid since you could only cool down the stator but the rotor is the critical point.

In this case you would have a cold stator and a melted rotor


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## Guest (Oct 13, 2009)

I disagree. I've gained quite a bit by just blowing forced air up the toot of a Netgain Warp9. And I've seriously considered this "water coil" concept around the outside. 

The power the motor puts out is a function of how much power you put in. It will do whatever it can do up to the point of burning up. That's entirely a function of how quickly it can dissipate heat. Anything you can do to get heat away from it is a plus, inside, outside, crossways.

I'm not a drag racer. But if you're not overtemping now, I would have to carefully weigh, and I mean that in a literal sense, the weight of the system you propose. I would think that every ounce of weight removed is worth a pound of power. A pump. A reservoir. The coolant. The copper. I can't imagine it being an advantage at the weight of what is required.

But I was amused to see a Tesla limp back to the pits after three laps and the company's quick response that it "wasn't designed for racing but as a daily driver." Who would spend $140K on a "sports car" with a sub 4 second 0-60 and want to hear that. It was entirely a cooling issue. It overtemped and went into limp mode. It is air cooled, and like the AC Power parent, inadequately so.

We are using a liquid cooled controller and AC motor on the 2009 Mini Cooper Clubman. By retaining the radiator and using a high end racing water pump with braided steel lines and AN connectors, we think we can get rid of the heat pretty famously, and potentially get more out of both components than they were quite designed for, or at least ensure they produce their maximum spec.

But my experience has been that shutdown/overtemp is a function of long freeway runs, long uphill freeway runs, etc. I just don't think it's going to matter much in 12 seconds.

I could live with being wrong on this. But if I were dragging, I would be all about weight reduction. If you could get those batteries to be 2/3 of the weight of the car, I think they'd move pretty briskly with you sitting on top.

Jack Rickard
http://evtv.me


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