Model S on the Track - A Review

[mnx]

I went ahead and e-mailed ownership with the suggestion. If I don't get a satisfactory response, I'll try contacting one of their powertrain and battery cooling systems engineers I found on LinkedIN...

So I e-mailed JB, and heard back. It sounds like there is nothing that could be done firmware wise to help out with the continuous power output.

There are a number of components in the powertrain
that all have similar power limits (as designed!) and these are based on
hardware limits. With EV's today there are substantial cost and
performance penalties to design them for extremely high continuous power
ratings. In particular there are big tradeoffs in the battery system. We
aimed very directly at the high performance, street, operation for the
car knowing that we would sacrifice some capabilities on the track.

I guess I'll just enjoy my Model S as-is until Tesla produces something more capable on the track. (If anyone produces a track capable EV I'm sure it will be them.)

 

[pilotSteve]

Thanks mnx for emailing JB. As an engineer myself I find his answer very eloquent and exactly what I would expect from Tesla's first class design/engineering team!

In short, someday maybe we'll see the SHO (special high output) or whatever nomenclature version that is more racer friendly. Expect to pay +15k or more for it? Hopefully we'll see!

So I e-mailed JB, and heard back. It sounds like there is nothing that could be done firmware wise to help out with the continuous power output.



I guess I'll just enjoy my Model S as-is until Tesla produces something more capable on the track. (If anyone produces a track capable EV I'm sure it will be them.)

 

[brianman]

WTB limiter limiter... just for 20 minutes at a time.

 

[trygve]

This guy seems to be having full power for a while. Could be the extra cooling because of the high-speed track, long sweeping turns with partial throttle application or something else?

Anyway, what I would love was a setting for max power, both to be able to limit power for other drivers and also to be able to dial in optimal max power for a specific track/weather combination to prevent hitting the limiter. I'd rather drive on the track with a constant limit than suddenly hitting "a wall"

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This guy seems to be having full power for a while. Could be the extra cooling because of the high-speed track, long sweeping turns with partial throttle application or something else?

Anyway, what I would love was a setting for max power, both to be able to limit power for other drivers and also to be able to dial in optimal max power for a specific track/weather combination to prevent hitting the limiter. I'd rather drive on the track with a constant limit than suddenly hitting "a wall"

Forgot the link: http://www.carscoops.com/2013/06/tesla-model-s-driver-tries-willow.html

 

[mnx]

I agree, a consistent experience is what I'd really like if I can't have full power all the time! What do others think?

This guy seems to be having full power for a while. Could be the extra cooling because of the high-speed track, long sweeping turns with partial throttle application or something else?

Anyway, what I would love was a setting for max power, both to be able to limit power for other drivers and also to be able to dial in optimal max power for a specific track/weather combination to prevent hitting the limiter. I'd rather drive on the track with a constant limit than suddenly hitting "a wall"

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Forgot the link: http://www.carscoops.com/2013/06/tesla-model-s-driver-tries-willow.html

 

[Doug_G]

I agree, a consistent experience is what I'd really like if I can't have full power all the time! What do others think?

Engage Miata Mode!!!

 

[mnx]

Engage Miata Mode!!!

HAHA!

I was thinking more like "engage S85 mode".

 

[Discoducky]

Why not just fix/improve the weak link/bottleneck to the power limit? And what is it again? Heat I think is the most likely culprit. So why not have extra cooling for the hottest components. Guessing it is the motor/inverter assembly. After market should be able to solve this for $3 to $5K

 

[mnx]

Why not just fix/improve the weak link/bottleneck to the power limit? And what is it again? Heat I think is the most likely culprit. So why not have extra cooling for the hottest components. Guessing it is the motor/inverter assembly. After market should be able to solve this for $3 to $5K

Reading between the lines in JB's e-mail (quoted above in post 101) I took it to mean that the battery system in the Model S wasn't up for track duty even if thermal limits are hit elsewhere first...

It's all still speculation though.

 

[stopcrazypp]

Reading between the lines in JB's e-mail (quoted above in post 101) I took it to mean that the battery system in the Model S wasn't up for track duty even if thermal limits are hit elsewhere first...

It's all still speculation though.

First thing in the way is there's no way to get temp data for any of the components, so we don't even have an idea which general area is approaching its thermal limits (motor, PEM, or battery) much less the specific part of that area. The Roadster you can see through the VDS or the ODB port where the limits are.

But I do like the suggestion to have a settable power limiter. It'll be easy to implement in software and would be a great way to minimize this issue.

 

[JRP3]

Someone just needs to attach one of these to the heat exchanger and see if it makes a difference. http://www.teslamotorsclub.com/show...Track-A-Review?p=413651&viewfull=1#post413651
Who wants to be a guinea pig? Or just stick some temp sensors on the heat exchanger and see if power limits at a specific temperature. Slap one on the motor and inverter too while you're at it.

 

[mnx]

First thing in the way is there's no way to get temp data for any of the components, so we don't even have an idea which general area is approaching its thermal limits (motor, PEM, or battery) much less the specific part of that area. The Roadster you can see through the VDS or the ODB port where the limits are.

But I do like the suggestion to have a settable power limiter. It'll be easy to implement in software and would be a great way to minimize this issue.

Yeah, we really need the access code to get to the "service menus" or whatever they are called. Even if it is a read-only menu with access to things like temperature.

 

[FlasherZ]

Yeah, we really need the access code to get to the "service menus" or whatever they are called. Even if it is a read-only menu with access to things like temperature.

Not even the service centers are given this information anymore, from what I've been told. A bad apple spoiled the whole bunch and they basically pushed all functionality into the tech laptops.

 

[jat]

Engage Miata Mode!!!

Funny you say that -- after it starts limiting power, I do start driving it like a big, heavy Miata -- taking different lines through the corners to preserve momentum.

I went to the track (Atlanta Motorsports Park) yesterday with my new track tires (BFG g-Force Rivals), and they made a huge difference -- I was able to keep it floored from the apex of turn 12 to braking for turn 1, and added over 10mph to my top speed compared to stock 19" Goodyears. That also meant I burned through the battery much quicker as well, and power started limiting at about 5 laps instead of 8. By the end of a 25min session, it had limited power to only 100kW, which is the lowest I had ever seen it and it wasn't much fun to drive at that point (140kW was ok, you just changed your lines).

 

[trygve]

I don't know how big of an impact regen has, but I guess all of you drive with regen on low on the track? Regen will just heat up the battery even more, so should be avoided.

 

[Doug_G]

You want regen off, and not just for thermal reasons. The regen upsets the balance of the car when you're turning into a corner. In the Roadster you can't turn it off, and you really have to adapt your driving style to it. In particular you have to move from the brake to the accelerator very quickly but smoothly to neutralize the braking/acceleration. With the Model S you can simply turn the regen down and it becomes a non-issue.

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Funny you say that -- after it starts limiting power, I do start driving it like a big, heavy Miata -- taking different lines through the corners to preserve momentum.

Exactly. At Shannonville I went from braking early at the end of the back straight, to braking late, to going through with the accelerator on the floor.

The Model S has one advantage over the Roadster, though; it appears to cool down quicker. You can pull into the pit and sit for 5-10 minutes and head back out again with full power. The Roadster take much longer to cool down.

 

[brianman]

You want regen off, and not just for thermal reasons. The regen upsets the balance of the car when you're turning into a corner. In the Roadster you can't turn it off, and you really have to adapt your driving style to it. In particular you have to move from the brake to the accelerator very quickly but smoothly to neutralize the braking/acceleration. With the Model S you can simply turn the regen down and it becomes a non-issue.

I'm probably just "doing it wrong" but I haven't had have any trouble that I would associate with what you're describing, and I leave the setting on Standard.

 

[Doug_G]

I'm probably just "doing it wrong" but I haven't had have any trouble that I would associate with what you're describing, and I leave the setting on Standard.

One advantage of the Model S is that it's better balanced than the Roadster, with a nearly 50:50 weight distribution. The situation is worse for the Roadster due to its 60:40 rearward weight balance, so you really need to transfer weight onto the front tires to get it to turn in. So maybe this doesn't matter as much with the S.

 

[brianman]

@Doug_G - Point of clarification: I was referring to the regen setting portion of your post, not the rest. Sorry for the imprecision in my quoting skillz. I agree about the "moving foot from brake to accelerator quickly" as being an adjustment from ICE to TeslaEV; enough that I mentioned it to my instructors at the Ridge so that they were/will-be aware of the mental translation being applied to their instructions.

 

[jat]

I don't know how big of an impact regen has, but I guess all of you drive with regen on low on the track? Regen will just heat up the battery even more, so should be avoided.

I left regen on standard, though I don't really recover much energy from it since at the track you brake really hard initially and trail off. I didn't find any problem with regen upsetting the car, and in fact the regen braking serves the function of trail braking to keep weight on the front tires as I turn in. If you are using 100% of the traction budget for turning, then that will be an issue and you will have to press lightly on the accelerator to achieve neutral throttle, but as I'm not racing I'm not driving at the very limit of the car.