MASTER THREAD: Comprehensive Road-Course Modification Guide — Optimizing the 3 for the track

[Vines]

I can't imagine the heat pump would affect the drivetrain cooling.

I think that changing the cooling system might have changed the drivetrain cooling, those systems seem closely enough related to have some effect, positive or negative.

From what I understood, the ac compressor was part of the cooling loop, so there has to be some if marginal effect. Also, since Tesla was in there making changes to the cooling system its not impossible to think they improved drivetrain cooling.

 

[Adrian Cockcroft]

If you're getting 1.2G lateral on street tyres in any direction you're doing well. 1.4+ is possible with track tyres.
What are the actual tyre pressure values on lap 0 and lap 5? They look about 5psi apart but it's hard to tell with that graph.

Thanks for that. I was pushing it fairly hard in some of the corners. Gave up on spreadsheet and used R to convert the bar to psi (*14.5)
LF "1st Qu.:41.33 " "Max. :44.59 " RF "1st Qu.:41.33 " "Max. :46.04 "
LR "1st Qu.:41.33 " "Max. :44.59 "RR "1st Qu.:40.96 " "Max. :43.86 "

Has anyone else used R to build a summary function for the data files?

Will definitely drop the pressures next time. I've lost a few low profile rims to potholes in the past so I'm going to keep the street pressures on the high side.

 

[subieworx]

Thanks for that. I was pushing it fairly hard in some of the corners. Gave up on spreadsheet and used R to convert the bar to psi (*14.5)
LF "1st Qu.:41.33 " "Max. :44.59 " RF "1st Qu.:41.33 " "Max. :46.04 "
LR "1st Qu.:41.33 " "Max. :44.59 "RR "1st Qu.:40.96 " "Max. :43.86 "

Has anyone else used R to build a summary function for the data files?

Will definitely drop the pressures next time. I've lost a few low profile rims to potholes in the past so I'm going to keep the street pressures on the high side.

What tires and what size?

 

[subieworx]

I think that changing the cooling system might have changed the drivetrain cooling, those systems seem closely enough related to have some effect, positive or negative.

From what I understood, the ac compressor was part of the cooling loop, so there has to be some if marginal effect. Also, since Tesla was in there making changes to the cooling system its not impossible to think they improved drivetrain cooling.

They definitely could have upgraded the cooling to the drivetrain and we will just have to wait for details. A heat pump though by nature Of how it works wouldn’t help cool the drivetrain any further. I actually wouldn’t be surprised if the heat pump was disabled in track mode in order to prioritize cooling to the drivetrain. Heating the cabin with the heat pump would theoretically reduce cooling capacity to the drivetrain.

 

[MountainPass]

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Just a little teaser for you guys...

For those not on social media:

Stay cool! MPP's Drive Unit Oil Cooler is just around the corner. All the important details to come, but we thought you guys might like a sneak peak here first

#tesla #model3 #neverstoptuning #designedinhouse #domorelaps #model3performance #racing

 

[MasterC17]

So the heat pump by itself probably will have no affect on cooling, as the A/C was never the limiting factor (it cools the battery, not the D/U's). HOWEVER - the Model Y has a much larger radiator as the condenser was deleted. That may result in the refreshed Model 3 also having a bigger radiator. We shall see.

Now that MPP has made it public - I will be testing out the new drive unit oil cooler in less than two weeks!

 

[Adrian Cockcroft]

What tires and what size?

Stock M3P

 

[Dangerous Fish]

So the heat pump by itself probably will have no affect on cooling, as the A/C was never the limiting factor (it cools the battery, not the D/U's). HOWEVER - the Model Y has a much larger radiator as the condenser was deleted. That may result in the refreshed Model 3 also having a bigger radiator. We shall see.

Now that MPP has made it public - I will be testing out the new drive unit oil cooler in less than two weeks!

On the rear drive unit only? Does the front need it?

 

[MasterC17]

On the rear drive unit only? Does the front need it?

We believe the rear drive unit is the issue (permanent magnet). The front drive unit (induction) does not have the issue. If it were also PM, it would likely also have the issue.

 

[mattack4000]

If track mode's data is correct, the front inverter temp goes up like the rear ones. The ramp is just a little slower at the beginning and the overall temperature seems a little lower.

 

[MasterC17]

If track mode's data is correct, the front inverter temp goes up like the rear ones. The ramp is just a little slower at the beginning and the overall temperature seems a little lower.

That is correct, though the Inverter is not the "weak point" in the drive unit. The difference in how a permanent magnet motor and an induction motor are magnetized/create magnetism is the key to understanding their thermal limitations. That being said, cooling both motors certainly would not hurt, but that would drive up overall cost and complexity to the end user.

 

[mattack4000]

It wouldn’t hurt to have it for sure, but I am not sure how much of an impact it will really have. Half a lap? Can that one single cooler extend it by one lap?

 

[Dave EV]

It wouldn’t hurt to have it for sure, but I am not sure how much of an impact it will really have. Half a lap? Can that one single cooler extend it by one lap?

You typically get two benefits from adding an oil cooler which can help mitigate temperature rise.

1. More oil volume - now it takes longer to heat up the oil to the same temperature. Which leads to the question - how much oil is in the rear motor, and how much more do you need to add with the oil cooler? This by itself is helpful, kind of like how big brakes take longer to heat up.
2. Given that the rear motor has no cooler for the oil, adding a radiator and fan, even a small one, can make a big difference in how much heat you can shed. I am guessing that it's thermostatically controlled, so the fan turns off below a certain temperature, or at least can be manually controlled as you probably only want to run this on the track.

 

[Mash]

Airflow through the cooler is everything. Increased oil volume is not making much difference since it's not significant volume increase. That place doesn't have ventilation, so heat has nowhere to go. Efficiency of cooling is proportional to the delta of temperatures of air and the radiator. Adding a fan there helps to mix air and avoid hotter zones around it, but it's not remotely as effective as sitting in the stream of ambient air. What is the plan with that @MountainPass ?

I would assume that making aluminium plate with fins as a part of the undertray is the best radiator possible for the rear side without disrupting airflow under the car too much. With internal fins available then it's possible to use a fan blowing through the air cooler onto this plate. This way heat will be extracted out much better.

Another way is to make a large input and output ducts with 2 holes for them in the undertray and a fan pushing air through since naturally air won't go there.

 

[Dangerous Fish]

So, when we get the 'red battery' state in TM, this is the drive unit temperature.
Let's say the battery turns from red to green in 5 laps of a track. If we then do a slower lap, it comes right back down to green pretty quickly.
This corresponds to the Track Mode data where it's 'normal' state seems to be around 67% and the graphic starts to turn orange around 75% and gets to bright red >90%.

I've seen it get up to 98% but then when I slow down, it drops back to 67% within about 60 seconds.
This % value is not an oil temperature, it's the motor windings temperature, because that's where the stock sensors are and the oil temperature would take much longer to fall.

So what this is going to come down to is how much difference a larger volume of cooler oil circulating around the windings is going to make. The flow rate of the pump is supposedly really high, which would certainly help with this.

It may be better to try and increase the oil volume than cool a smaller volume down with fans and airflow. Both would be good, of course.
An oil temperature sensor would help. We could stick one of these on the dash and confuse people.

 

[subieworx]

Air flow is key as others have mentioned. You either need air flow to the unit itself or airflow to a remote cooler. With the entire bottom of the car being separated from airflow the drive units are going to get quite hot. Many performance cars have naca or similar style ducts formed into the flat bottoming to direct cooling air to specific parts of the drivetrain. I was surprised when I had my M3P on the lift and saw not one and at that time it was clear to me this was never designed to be a track car.

A air/liquid cooler will work well in this case, but it needs an inlet and exhaust to be effective. Otherwise it will heat soak and cease to perform any cooling. I think an additional liquid/liquid cooler would be a better alternative with a front mount heat exchanger, separate fluid reservoir and pump. It would also be interesting to remove the front and rear drive cover panels and run it on track to see the temp changes. The aluminum exterior of the motor housings are a huge heat sink and with air flow would help to shed heat.

 

[Dangerous Fish]

Air flow is key as others have mentioned. You either need air flow to the unit itself or airflow to a remote cooler. With the entire bottom of the car being separated from airflow the drive units are going to get quite hot. Many performance cars have naca or similar style ducts formed into the flat bottoming to direct cooling air to specific parts of the drivetrain. I was surprised when I had my M3P on the lift and saw not one and at that time it was clear to me this was never designed to be a track car.

A air/liquid cooler will work well in this case, but it needs an inlet and exhaust to be effective. Otherwise it will heat soak and cease to perform any cooling. I think an additional liquid/liquid cooler would be a better alternative with a front mount heat exchanger, separate fluid reservoir and pump. It would also be interesting to remove the front and rear drive cover panels and run it on track to see the temp changes. The aluminum exterior of the motor housings are a huge heat sink and with air flow would help to shed heat.

Airflow around the drive units is going to make little or no difference. Take the aero covers off and all you'll get is turbulence anyway.
The drive units may be aluminium but they are not designed to suck heat away from the oil inside. The heat needs to be carried away from the windings as quickly and efficiently as possible and then dumped somewhere.

 

[MountainPass]

I am looking forward to giving you guys more information later on. It kills me to read this discussion and not contribute.

 

[Mash]

Motor windings are low heat capacity. And since the car can survive full power for a few minutes - it's obviously no problem of cooling windings. But coolant and oil soak heat and cooling power drops. So cooling of coolant and oil have to solve it. Cooling body of drive unit is not very effective, but another option, just not a lot of surface area on a drive unit to effectively use it as radiator - small radiator is way more effective. Plus it's better to cool hottest part and body of drive unit is not that.

 

[subieworx]

I am looking forward to giving you guys more information later on. It kills me to read this discussion and not contribute.

Let us know! There are track days to attend and other cars to beat up on!