Why do our cars have oil pumps?

[Dolemite]

I understand that it's for the gearbox... but why? Every other normal car has a much more complicated transmission & doesn't have a pump.

 

[iwannam3]

Every automatic has an oil pump. 1950s had 2 pumps, the one in the rear would let you push start the car. 25 mph or so.

the model 3 also has an oil filter that the S and X don't have. They had a lot of drive unit failures early so that is why I think they added a filter. The 3 may pump oil through an oil cooler in addition to the bearings.

 

[destructure00]

I understand that it's for the gearbox... but why? Every other normal car has a much more complicated transmission & doesn't have a pump.

Uhhh...auto transmissions have pumps.....

 

[ZOMGVTEK]

Every automatic transmission has an oil pump inside the housing that’s driven off the engine. For a traditional auto, oil pressure/flow is required to both operate some parts of the transmission as well as lubricate and cool. In the model 3, oil is used to lubricate, cool, hold/flush contaminants, and quite likely to also improve dimensional stability by stabilizing the temperature gradients across the assembly. It needs to be driven separately though, since it needs to operate over a much larger speed range than a conventional automatic. No doubt this could be done without a pump, like most EV’s, but the pump design affords significant advantages with the downsides of the cost, complexity, and likely lower reliability. The oil goes through a stacked plate heat exchanger, so without flow heat isn’t rejected into the coolant loop. It also is used to heat the battery, and with a pump this means it can be done without the vehicle moving. Plus, the pressure drop across a filter would be really challenging to overcome without the assistance of a pump. And the filter is a key element to ensure long service intervals and hopefully life.

 

[MP3Mike]

Even the Model S&X have a pump, it is just a mechanical one inside the motor. Of course the problem with it is that it only functions in forward. It doesn't lubricate the motor/gears when operating in reverse. So you can cause damage to the gearbox if you reverse a long distance. (It also doesn't have a filter like the Model 3 has.)

 

[Dolemite]

My b, I meant manual transmission, which has a lot more gubbins than the super simple gearbox in the Model 3. For those, splishy splashy oil is enough... but it sounds like Tesla decided the complexity vs. benefit of adding an oil pump was worth it.

The oil goes through a stacked plate heat exchanger, so without flow heat isn’t rejected into the coolant loop. It also is used to heat the battery, and with a pump this means it can be done without the vehicle moving. Plus, the pressure drop across a filter would be really challenging to overcome without the assistance of a pump. And the filter is a key element to ensure long service intervals and hopefully life.

So the heat exchanger dumps the heat from the gearbox oil into the coolant loop?

Not sure I completely understand what you mean by heating the battery without the vehicle moving - wouldn't it need to be warm from the car being driven, first? afaik the only active heating going on is from stalling the motor to generate heat in the coolant loop.

Also would you happen to know if the diff is part of the gearbox lubrication loop? It must be...

Even the Model S&X have a pump, it is just a mechanical one inside the motor. Of course the problem with it is that it only functions in forward. It doesn't lubricate the motor/gears when operating in reverse. So you can cause damage to the gearbox if you reverse a long distance. (It also doesn't have a filter like the Model 3 has.)

I'm guessing this isn't an issue with the Model 3 since the pump is a brushless motor?

 

[Bill Foster]

My b, I meant manual transmission, which has a lot more gubbins than the super simple gearbox in the Model 3. For those, splishy splashy oil is enough... but it sounds like Tesla decided the complexity vs. benefit of adding an oil pump was worth it.


So the heat exchanger dumps the heat from the gearbox oil into the coolant loop?

Not sure I completely understand what you mean by heating the battery without the vehicle moving - wouldn't it need to be warm from the car being driven, first? afaik the only active heating going on is from stalling the motor to generate heat in the coolant loop.

Also would you happen to know if the diff is part of the gearbox lubrication loop? It must be...


I'm guessing this isn't an issue with the Model 3 since the pump is a brushless motor?

Even some manual trans cars have oil pumps in their trans

 

[Dolemite]

I'll remember to include a 7-page disclaimer in my next thread

 

[73zdriver]

Yes and they do fail as mine did at about 2000 miles.. You will get a warning car is ok to drive and to schedule service. But it will limit your speed to a mere 50 to 55 mph. It where i live, the car was undriveable as speed limits are 65 i was a road block. Tesla towed to service center to fix it.

 

[bedoig]

To pump oil

 

[ZOMGVTEK]

So the heat exchanger dumps the heat from the gearbox oil into the coolant loop?

Not sure I completely understand what you mean by heating the battery without the vehicle moving - wouldn't it need to be warm from the car being driven, first? afaik the only active heating going on is from stalling the motor to generate heat in the coolant loop.

Also would you happen to know if the diff is part of the gearbox lubrication loop? It must be...

Yeah, the entire drive unit effectively gets flushed with oil best I can tell. That oil gets pumped through a heat exchanger and filter, so without the oil flow the heat isn’t going to be dumped to the coolant and it’s just whatever it can shed through the casing. The way the car heats the coolant is by heating the motors, but this heat won’t get to the battery without the oil being pumped through the heat exchanger while the coolant is also flowing past it. So this would mean with splash lube, the motor couldn’t be used to heat the battery while stationary since it’s isolated and only cools the oil inside the heat exchanger, not the motor itself. There’s no coolant passages on the motor like on S, it’s just oil. And yeah, driving backwards should be just fine in a 3.

 

[Dolemite]

Yeah, the entire drive unit effectively gets flushed with oil best I can tell. That oil gets pumped through a heat exchanger and filter, so without the oil flow the heat isn’t going to be dumped to the coolant and it’s just whatever it can shed through the casing. The way the car heats the coolant is by heating the motors, but this heat won’t get to the battery without the oil being pumped through the heat exchanger while the coolant is also flowing past it. So this would mean with splash lube, the motor couldn’t be used to heat the battery while stationary since it’s isolated and only cools the oil inside the heat exchanger, not the motor itself. There’s no coolant passages on the motor like on S, it’s just oil. And yeah, driving backwards should be just fine in a 3.

Great info... thanks. So it sounds like it's a misconception that the glycol loop has anything to do with directly cooling the motor and/or inverter on the Model 3? It all happens through the heat exchanger w/ the gearbox oil?

 

[MP3Mike]

Great info... thanks. So it sounds like it's a misconception that the glycol loop has anything to do with directly cooling the motor and/or inverter on the Model 3? It all happens through the heat exchanger w/ the gearbox oil?

But that heat exchanger is exchanging between the gearbox oil and the glycol loop. I'm not sure if the inverter is cooled by the oil or glycol but I would guess glycol.

 

[Dolemite]

But that heat exchanger is exchanging between the gearbox oil and the glycol loop. I'm not sure if the inverter is cooled by the oil or glycol but I would guess glycol.

Yeah I answered my own question - looks like glycol passes through the inverter & then into the heat exchanger:

 

[ZOMGVTEK]

I think the design is overall pretty great. The drive units are basically self contained systems that can dump heat externally when needed. Presumably they are designed to tolerate oil pump failures and still be able to operate comfortably short term. I would assume at least one design revision has occurred on the pump, so most likely they’re getting better. They are Tesla branded parts... The major downside is battery heating is very poor in very cold weather at high speed, since the motor casing sheds so much heat. You mostly need to be parked, or in a moderate climate, then it works well.

 

[Flatbat]

This might make it a bit clearer. My bold.

"Model 3 does not have an external high voltage coolant heater. All the heat that the HV Battery needs is provided by the powertrain, even when the car is parked. Both front and rear Model 3 drive units contribute to waste heat mode. During cold soak conditions, the Front Controller (VCFRONT) sends a request to the drive inverter(s) to produce the necessary power that is required to heat the coolant and therefore HV battery cells. Current is used to heat the stator, without changing the torque/speed output, which will heat the transmission fluid being pumped and heat transferred to the coolant being pumped thought the heat exchanger.

If the vehicle is driving, the motor control strategy changes to produce excess powertrain losses in order to provide heat to the HV battery. In the case that the car is parked in the cold and the HV battery needs to be heated up, the drive inverter provides the appropriate current to the motor to produce heat with zero torque/speed change."

 

[wrishel]

Every automatic has an oil pump. 1950s had 2 pumps, the one in the rear would let you push start the car. 25 mph or so.

the model 3 also has an oil filter that the S and X don't have. They had a lot of drive unit failures early so that is why I think they added a filter. The 3 may pump oil through an oil cooler in addition to the bearings.

There is also an oil pump for battery cooling.

 

[TomB985]

This might make it a bit clearer. My bold.

"Model 3 does not have an external high voltage coolant heater. All the heat that the HV Battery needs is provided by the powertrain, even when the car is parked. Both front and rear Model 3 drive units contribute to waste heat mode. During cold soak conditions, the Front Controller (VCFRONT) sends a request to the drive inverter(s) to produce the necessary power that is required to heat the coolant and therefore HV battery cells. Current is used to heat the stator, without changing the torque/speed output, which will heat the transmission fluid being pumped and heat transferred to the coolant being pumped thought the heat exchanger.

If the vehicle is driving, the motor control strategy changes to produce excess powertrain losses in order to provide heat to the HV battery. In the case that the car is parked in the cold and the HV battery needs to be heated up, the drive inverter provides the appropriate current to the motor to produce heat with zero torque/speed change."

This is how I understand it, did you get this from a source or are you restating information that was assumed from observation? Just curious if there's more reading I can do on this.

 

[Flatbat]

There is also an oil pump for battery cooling.

Not quite. There is a coolant pump for Battery cooling.

This is how I understand it, did you get this from a source or are you restating information that was assumed from observation? Just curious if there's more reading I can do on this.

It is a direct quote from the Theory of Operation section of the Tesla M3 Service Manual.

 

[TomB985]

Not quite. There is a coolant pump for Battery cooling.


It is a direct quote from the Theory of Operation section of the Tesla M3 Service Manual.

Got it, that makes sense. Where did you get your service manual from?