1/8 mile drag race findings

[SantaCruzOMB]

I've made 3 trips to the track recently in a '22 M3P and wanted to share what I've found and see what others have done to improve performance. I'm still on the 20" wheels and I'm going to experiment with tire pressure next time.

1. I ran a 7.43 with a passenger so weight seems to have a negligible difference. I probably won't bother buying lighter wheels or reducing weight anywhere else. My car also has a tow hitch that weighs at least 30lbs.

2. Heating the battery didn't seem to help. I leave the supercharger and get to the track at about 92% SOC and even though the battery is hotter my first runs aren't the quickest. I've tried setting the destination to a supercharger also to preheat the battery but didn't notice any benefit.

3. My quickest runs are usually around the 3rd pass (89% SOC). I usually leave by 82% and the performance doesn't drop off too much above 80%.

4. When people say a certain lane is quicker you can actually prove it since this car is so predictable. At my track the right lane is about 0.1 seconds quicker.

5. Even though it's Texas people are generally positive about an EV at the track. People know it's a Tesla but very few people seem to know what model it is. One guy asked if it was the "Played".

 

[mpgxsvcd]

I can unequivocally say that preconditioning the battery and optimizing both the SOC and battery temps does matter. The issue is that you aren’t really measuring the battery temperature. You are just guessing at it.

If you track the battery temperatures and the “Max Discharge” value with an OBD2 reader you would see that you aren’t anywhere near the full potential of the car at less than 90% SOC and a battery that has not been preconditioned right before the run.

Your 7.27 second 1/8 mile time is actually really good for 20” UberHeavy wheels. However, you can go faster than that with a properly setup car and especially if you go with some lighter weight 18” wheels.

I know people think that just supercharging beforehand heats the battery up enough. It actually doesn’t. That battery cools off VERY quickly even on 100 degree F days. The optimal temperature is sometimes above 130 degrees F.

The graph below shows how big a difference preconditioning can make.

Here is how fast it can go. However, most of the gains are after half track so it won’t show up as much in the 1/8.

 

[jackmott]

It is possible that when he was at the track it was hot enough that he was good no matter what he did. Texas was still real warm in Sept.

 

[mpgxsvcd]

It is possible that when he was at the track it was hot enough that he was good no matter what he did. Texas was still real warm in Sept.

The optimal Temperature is sometimes above 130 degrees F. It is a common misconception that hot ambient air temperatures are enough to give optimal performance. Preconditioning gets the battery WAY hotter than even the hottest ambient temperature we encounter in our daily lives.

 

[evroro]

Thanks for the data and feedback!

When doing drag runs, what's the best way to ensure the battery is at optimal temperature and conditions?
What tire pressures did you run, and what is optimal for best drag runs?

 

[mpgxsvcd]

Thanks for the data and feedback!

When doing drag runs, what's the best way to ensure the battery is at optimal temperature and conditions?
What tire pressures did you run, and what is optimal for best drag runs?

This video explains how to optimize the performance.

I have done additional testing on tire pressures and slip start based on feedback from that video. Neither of those things seemed to matter but I had good track prep so traction wasn’t and issue.

I tried 46 psi and 36 psi for the tires in several runs. They both produced similar times and similar trap speeds. However, I ABSOLUTELY could feel the difference for cornering. On a road course 30 something PSI seemed optimal compared to 40+ psi.

Slip start didn’t seem to do anything unlike Track Mode where you can literally watch the battery temps plummet.

Track Mode is the only thing that really drastically slows the car down. Heavy and large wheels slows it down somewhat too.

 

[tm1v2]

That slowness from Track Mode cooling is no joke, I can feel the difference after Track Mode has been on for a while in the twisties.

Which is mostly fine, there's still plenty of power left for that sort of driving, but I do wish we could disable the extra cooling in Track Mode. Especially for those, *ahem*, short passing opportunities.

 

[jackmott]

The optimal Temperature is sometimes above 130 degrees F. It is a common misconception that hot ambient air temperatures are enough to give optimal performance. Preconditioning gets the battery WAY hotter than even the hottest ambient temperature we encounter in our daily lives.

Sure, but say 100 deg ambient temperature plus driving to the track gets the battery pack to what? When I have done road trips here in Texas preconditioning only kicks in like 15 seconds from the charger, so it must be close?

 

[jackmott]

That slowness from Track Mode cooling is no joke, I can feel the difference after Track Mode has been on for a while in the twisties.

Which is mostly fine, there's still plenty of power left for that sort of driving, but I do wish we could disable the extra cooling in Track Mode. Especially for those, *ahem*, short passing opportunities.

Just the noise and wear and tear on the fans is annoying as hell too.

 

[SantaCruzOMB]

I know people think that just supercharging beforehand heats the battery up enough. It actually doesn’t. That battery cools off VERY quickly even on 100 degree F days. The optimal temperature is sometimes above 130 degrees F.

I figured it held the higher temp longer after charging. It makes sense that my 3rd and 4th runs are usually the quickest though. I don't have a way to monitor the battery temp but would a few back to back runs be enough to get it hot? I'll continue to set the navigation to a charger also but I've had mixed results. Sometimes it will start preconditioning and other times it doesn't. Maybe it was already hot enough from prior runs.

 

[mpgxsvcd]

Sure, but say 100 deg ambient temperature plus driving to the track gets the battery pack to what? When I have done road trips here in Texas preconditioning only kicks in like 15 seconds from the charger, so it must be close?

The battery pack doesn’t heat up as much from driving spiritedly as the motors do. I saw almost 90 degrees F in the motors after only two back to back 1/4 mile passes. The battery actually cooled down and it was about 95 degrees out here in the NC sun.

The preconditioning is finicky. That is why I wish they simply gave us a setting to heat up to optimal temps no matter what else is going on.

In my testing I saw preconditioning disabled as low as 42 degrees C and start as high as 49 degrees C. Optimal temps are above 52 degrees C.

This is why monitoring the temps through an OBD2 reader like the S3XY buttons is so important. You have no idea what the temperatures are without the reader. The range is quite large and motor temps seem to affect “Max Discharge” but to a lesser degree than battery temps.

The only consistent way to tell what my performance would be was through that “Max Discharge” value. If you get to 459+ KW “Max Discharge” then hold on. After 40+ mph the acceleration with 459 KW “Max Discharge” is significantly different. The only way to get to 459 KW “Max Discharge” is through preconditioning with a nearly full battery. I typically see 442 KW or less without preconditioning even after driving it in the hot sun for many miles.

 

[mpgxsvcd]

I figured it held the higher temp longer after charging. It makes sense that my 3rd and 4th runs are usually the quickest though. I don't have a way to monitor the battery temp but would a few back to back runs be enough to get it hot? I'll continue to set the navigation to a charger also but I've had mixed results. Sometimes it will start preconditioning and other times it doesn't. Maybe it was already hot enough from prior runs.

It is never hot enough from prior 1/4 mile runs. The optimal battery temp is above the hottest ambient temperatures you will encounter. The battery always cools down as soon as preconditioning stops.

Now, it isn’t like it instantly goes back to ambient temps on hot summer days. However, on cool fall days the inlet temperatures will fall fairly quickly.

That being said motor temps do affect performance and I don’t believe that is reflected in the max discharge value. I have seen my 2nd run be faster even with a slightly lower “Max Discharge” value. I believe the difference is that the motors were cold on the first run and needed to be slightly warmer but I don’t have any conclusive evidence for that.

I would also like to say that all of my testing was for 1/4 mile drag races where I stop for several minutes in between runs. This may not apply to continuous Road Course tracks. There heat in all of the components can build up very quickly from all of that continuous use. That is where Track Mode is a necessity. You have to cool everything down there to prevent damaging some components.

 

[mpgxsvcd]

The battery pack doesn’t heat up as much from driving spiritedly as the motors do. I saw almost 90 degrees F in the motors after only two back to back 1/4 mile passes. The battery actually cooled down and it was about 95 degrees out here in the NC sun.

The preconditioning is finicky. That is why I wish they simply gave us a setting to heat up to optimal temps no matter what else is going on.

In my testing I saw preconditioning disabled as low as 42 degrees C and start as high as 49 degrees C. Optimal temps are above 52 degrees C.

This is why monitoring the temps through an OBD2 reader like the S3XY buttons is so important. You have no idea what the temperatures are without the reader. The range is quite large and motor temps seem to affect “Max Discharge” but to a lesser degree than battery temps.

The only consistent way to tell what my performance would be was through that “Max Discharge” value. If you get to 459+ KW “Max Discharge” then hold on. After 40+ mph the acceleration with 459 KW “Max Discharge” is significantly different. The only way to get to 459 KW “Max Discharge” is through preconditioning with a nearly full battery. I typically see 442 KW or less without preconditioning even after driving it in the hot sun for many miles.

The first paragraph should have said 90 degrees C for the motor temps and 95 degrees F for the outside temps. It wouldn’t let me edit the post to correct it.

 

[tm1v2]

Sure, but say 100 deg ambient temperature plus driving to the track gets the battery pack to what? When I have done road trips here in Texas preconditioning only kicks in like 15 seconds from the charger, so it must be close?

@jackmott Preheating kicks in for you only 15 seconds before the Supercharger? Damn it's hot in Texas.

More like 30-60 minutes ahead for me I think...

 

[tm1v2]

Just the noise and wear and tear on the fans is annoying as hell too.

@jackmott Yes, but if I'm driving hard enough to justify Track Mode I can't really notice the fans anymore.

If my car were out of warranty I'd be looking into some kind of override for the cooling system. If MPP can force on Track Mode style max cooling with their Cooling Party Controller, it ought to be possible to forcibly disable said cooling. On this car I'm not messing with anything drivetrain or electronic while it has warranty coverage though.

 

[jackmott]

@jackmott Yes, but if I'm driving hard enough to justify Track Mode I can't really notice the fans anymore.

If my car were out of warranty I'd be looking into some kind of override for the cooling system. If MPP can force on Track Mode style max cooling with their Cooling Party Controller, it ought to be possible to forcibly disable said cooling. On this car I'm not messing with anything drivetrain or electronic while it has warranty coverage though.

If you are using track mode at an autocross you sit there in grid just generating noise (and cooling your battery too much).
If you use it on the street, you sit there generating noise even when stopped or cruising slowly to where you are driving hard. And you have to go into park to turn it on.

Its all very not "driver oriented" as is Tesla's way.

 

[SantaCruzOMB]

Update: The track was pretty crowded last night but I was able to get 5 runs. The only change was being more deliberate on pre-conditioning the battery and that gave me 15-20 minutes of heating before each run. In past results I rarely got the notification of preconditioning but last night I kept setting the gps destination over and over until I did. Remember to choose a supercharger and not a destination charger.

The results seem to be more consistent and slightly quicker. I'm most impressed about getting a 7.32 in the left lane which is notably slower than the right.

One of my runs was against a 2020 M3P with 18" Martian wheels and the battery improvements in the 2022 still allowed me to win with a 0.1 margin.

 

[mpgxsvcd]

Update: The track was pretty crowded last night but I was able to get 5 runs. The only change was being more deliberate on pre-conditioning the battery and that gave me 15-20 minutes of heating before each run. In past results I rarely got the notification of preconditioning but last night I kept setting the gps destination over and over until I did. Remember to choose a supercharger and not a destination charger.

The results seem to be more consistent and slightly quicker. I'm most impressed about getting a 7.32 in the left lane which is notably slower than the right.

One of my runs was against a 2020 M3P with 18" Martian wheels and the battery improvements in the 2022 still allowed me to win with a 0.1 margin.

View attachment 866471

Those are solid times for the UberHeavy wheels.