Optimizing track mode for snow driving

Hello everyone,

I've just returned from Winter Driving School, now that my MYP has track mode. I thought I would share the settings I came up to optimize track mode for high performance driving on snow (high performance here refers fine control, not outright speed).

Here's a video - see below for discussion of settings & analysis.

Before my MYP, I had Audi's and Subaru's that would let me turn off the stability program. That was much more effective in snow than an MY without track mode. I had hoped they'd eventually give us track mode, and that with it, my MY would be able to get into the same ball park for car control as my prior cars. I am happy to report that that is exactly what happened - but it was not a direct, or short path to that goal. If you just want to know the numbers I'll give the spoilers now. Read on if you're interested in why these ended up being the right numbers or in how we got to them.

Notes:

• These settings were with around 200 lbs of cargo in the trunk
• The track had a solid foundation of ice with several inches of snow that we wore through in several spots.
• These bias and regen settings are likely not optimal for either all-ice or all-snow, but they'd be fine as a starting point
• The stability setting is critical, and would be the same for any conditions

Settings:
Front/rear power bias: 30/70% (anywhere between 35/65 and 20/80 was acceptable)
Stability: -9
Regen: 75% on the skidpad, 30-40% on the slalom

IMPORTANT: Watch out for ABS on ice - with regenerative braking on even partially, if you trigger ABS, the car will keep doing ABS after you take your foot off the brake, b/c it still does ABS for regen-braking. That means you can't threshold-brake to get back your grip. Or at least to do it w/ regen on, you would have to actually press the accelerator to the point where the car wasn't braking anymore, reverse-modulate by lifting to brake more, and pressing to brake less. Crazy-making, that was too next-level single-pedal driving for my brain, I didn't try.

Ok, I'll jump directly to the biggest spoiler from all that: the -9 stability setting. It took a lot to get to this.

-10 does not work well because the MY has open differentials, and uses the brakes to force power from a slipping wheel to the other side of the differential (some call this EDL - Electronic Differential Locking). However, Tesla considers this part of "stability," and when stability is at -10, it's completely off. -9 is the magic number because it enables just enough EDL to reliably get wheels on both sides of an axel to spin together, without cutting out power or doing other tricks to stop you from sliding intentionally.

Here's how we came to all the above...

On the first day, my results were really frustrating - about 1/3 of the time, I could initiate controlled oversteer readily, and keep it controlled for 3-8 seconds. 1/3 of the time it wouldn't come easily, I'd have to slam the accelerator to get oversteer, and then it would be wild/uncontrollable. And 1/3 of the time the car just wouldn't do anything except just keep going slowly in whatever direction I was pointing it, with no understeer or oversteer, no matter how hard I pressed the accelerator.

I tried many combinations of settings that day, ranging from 50/50 to 20/80 bias, 30-80% regen, and -10, -7, and -6 stability. The other tweaks only had a minor impact on how often or how long I could maintain controlled oversteer, or how likely I was to wildly oversteer & spin out. There was no happy medium - always a split between too much, not enough, and always unpredictable.

We had a social event that evening, and I had a great super technical conversation and super constructive conversation with one of the instructors. We had several theories:

1. Maybe even with stability as low as I can put it, the car is still doing some stability control
2. Maybe there is a timer, and it's only willing to let me spin wheels wildly for a limited time
3. Maybe part of the problem is that when the details are just right, and open differential can still spin both wheels (like if they have exactly the same amount of grip and are going the same speed when you overpower them)
4. Maybe the built-in "Drift Mode" setting - which you can not edit, but you can see what settings it is using - has a hidden change that it does that is not available to me in the custom settings

So, we came up with the following experiments to answer the above questions, and he let me go out to the track early on day 2 to conduct them:

1. Get on some ice, point the car straight, and floor it for a long time. See if it eventually cuts power
   1. It did not
2. Same as above, but have observers on both side of the car - see if all four wheels are spinning at the same time
   1. They were not. Sometimes wheels on both sides of an axel would spin, other times it would go back & forth between one side and the other.
3. Turn on Drift mode, and see if I was maintain a continuous drift without it ending except by my choice
   1. I was
4. Duplicate Drift mode's settings in a custom setting group, and see if I was still able to maintain continuous drift (thus proving or disproving whether the built-in Drift mode has a special hidden setting)
   1. I was, and thus, it does not.

Armed with all of the above information, the instructors all concluded that the car still has some kind of traction or stability control going on, even when it's set to -10. I was not convinced. The one thing we didn't have an experiment for was to determine whether the inconsistent results were simply because an open differential has inconsistent behavior.

That is when I thought of trying -9. It was more of a hail-mary, I never believed it was going to work. My thinking was this:

• If an open diff sometimes will still spin both wheels, then maybe all the times I was able to cause oversteer, it is because in those cases, by chance, I got both wheels to spin.
• I had a feeling that the alternating spinning and stopping of wheels that they reported during the straight-line acceleration test was because as I moved forward (slowly b/c of all the slipping), a wheel that was once on ice would eventually find snow, and if the opposite wheel was then on ice, I'd expect the slipping to switch from one wheel to the other
• Maybe, with a lot of luck, if I add the smallest amount of stability programming that I can add, it will bring in just enough EDL to force both wheels to spin whenever one is spinning, but not so much as to prevent me from getting the car to slide.

Well it worked! We did one more test:

• Straight-line floored acceleration with observers on both sides, and front/rear bias at 50/50
  • All four wheels spun continuously until I took my foot off the accelerator!

After that, I tried 25/75 front/rear bias and hit the skid pad again. For the first time, I was able to "drift" in all-wheel-drive mode for as long as I wanted, and it worked every single time. We never did bother to figure out why Drift Mode also enabled this, even though it uses a Stability setting of -10. I think it is a combination of me already being moving and turning before flooring it, and turning off the front motor means the equation for keeping wheels on both sides of the read differential became much simpler.

 

[florida_man]

Fascinating thread, loved learning about how the stability control uses brakes to compensate for the open diff. I'm not surprised that the MY has an open diff, but I didn't know that for sure before this.

 

[avramd]

I started looking for some winter driving school around here after reading this thread. Found one that's taught on the same track I've been on 4 times this past summer. It's by the local BMW Car Club of America though, so I had to get a membership to be able to take the course. So I guess I'm now a proud member of a BMW club...without ever having owned a BMW.

Driving school is on 2/25. I can't wait! (hopefully our mountains of snow this winter haven't all melted by then)

Oh man, I'm so excited for you!!! And I'm humbled that my post inspired someone to take decisive action! Any chance they have snowmaking equipment at your track?

Yes, I'm right there with you - this one is put on by an Audi club, and while they do not require WDS participants to join the club, I think I probably will anyway b/c this was such a fantastic program, and they are really good people, so I want to be supportive and stay connected. And lets be honest, as much as I do love Molly (my Model Y), here is something I'm willing to declare as an absolute fact: Once the open supercharger network is sufficient for non-Tesla EV's to go cross country, and Audi is selling as many EV's as ICE cars, Audi EV Quattro will absolutely blow the doors off of anything Tesla will be willing to sell to the masses. So, I may become an Audi owner again in the not-inconceivably-distant future.

 

[avramd]

In case anyone here is interested, here's where I landed on new winter tires:

I'm pretty loyal to Nokian, so it was only ever a question of which stud-less Nokian, and in what size. Nokian has a series of EV tires that have a layer of foam built into them to help reduce road noise. They make R5's (and Hakka 10's) in the EV variant. However, my winter rims are 18", I subscribe to the belief that all other things held equal, narrower and taller tiers are better for snow. So I'm running 245/50-18's vs the OEM 255/40-19's. Molly is an MYP "Stealth" - no PuP, partly b/c I was afraid the bigger brakes might make it impossible to fit 18" winter rims.

So, the problem is that apparently there isn't an EV on earth that comes with this size tire from the factory. Nokian does not make their EV tires in anything close to my size - in fact they only make one 18" size period. I was willing to give up my winter rims, put R5 EV's on my OEM rims (OEM tires due to be replaced anyway), and get new summer rims later. However, there is almost zero stock of Nokian's EV tires anywhere in the US. The story I got from multiple dealers is that supposedly the factory that makes their EV tires is in Russia, or that the warehouse is, etc. So I had ordered a set of regular R5's. Then on a whim, I looked at the other sizes made, and found out that they make a 285/40-19 R5 EV. Sonovagon wouldntyaknowit, there was one set of four of them left in the entire US. For $1200 . We verified they would fit the OEM rims, thanks to their massive 9.5" width. And I had been thinking of getting over-wide tires for those rims anyway, to help protect from curb rash when parallel parking.

But OMG did I not want to spend $1200 putting fatter than OEM snow tires on my car so that I would then have to unload my winter rims AND buy a whole new set of summer rims. So, I chickened out, and stuck with the regular R5's for my 18's. The go on tomorrow.

Anybody interested in a good deal on some 18" Hakka 9's in MY diameter, with lots of tread and a little bit of stud left? Rims not included...

 

[dafuzztsu]

Love the detailed explanation and generous sharing of your R&D efforts. 10/10 will refer to this thread later.

 

[gx9901]

Oh man, I'm so excited for you!!! And I'm humbled that my post inspired someone to take decisive action! Any chance they have snowmaking equipment at your track?

Yes, I'm right there with you - this one is put on by an Audi club, and while they do not require WDS participants to join the club, I think I probably will anyway b/c this was such a fantastic program, and they are really good people, so I want to be supportive and stay connected. And lets be honest, as much as I do love Molly (my Model Y), here is something I'm willing to declare as an absolute fact: Once the open supercharger network is sufficient for non-Tesla EV's to go cross country, and Audi is selling as many EV's as ICE cars, Audi EV Quattro will absolutely blow the doors off of anything Tesla will be willing to sell to the masses. So, I may become an Audi owner again in the not-inconceivably-distant future.

I don't know if they have snowmaking equipment at the track. They do have a skidpad so perhaps they could at least make some ice surfaces if needed. I'm hoping for some snow before then, but we're getting a heatwave now (mid to high 30s, yippy kai yay!) so not sure if it'll happen.

As for Audi Quattro, the only experience I have with it is in my mom's fat etron. Is that considered a real Quattro system? The few times I drove it this winter it seemed pretty good, but it's all normal driving and I have no idea how to judge AWD performance in winter conditions.

 

[avramd]

There are different etrons - I think that just means that it's electric, it could be like a Q5 etron or an etron GT, and I'm sure there are others. I don't actually know what any particular one uses for a quattro system.

Audi in general is pretty good about ensuring maximum traction, and also letting owners disable stability assist. They do iterate on their AWD systems though, so not all of them are top-notch. The last time I had an Audi, they had Torsen limited-slip center diffs, and open front & rear diffs with EDL - electronic differential locking, which is the computer applying brakes to a spinning wheel to force power through the diff to the other wheel. It works very well in snow if you don't go crazy. If you over-do it, you'll overheat your brakes. it will sense that and stop you from damaging them by not doing EDL anymore until they cool off.

 

[gx9901]

By the way, this thread was named the "Thread of the Week" on the last TMC Podcast (episode 34).

 

[SmashMonkey]

Thanks OP! I'm new to Tesla and this thread is very interesting. I have tried autocrossing and tracking ICE cars in the past, but not Teslas. The first thing I thought of when reading this is left foot braking. Honestly, I'm not good at left foot braking at all. But instead of trying to balance under/over steer with 1 foot using throttle lift and regen, what about 2 footed driving? How do Teslas respond to brake pedal under throttle? Does the car cut power to the wheels when the brake pedal is depressed?

• Lift the throttle to shift weight to the front wheels, so they will have more grip
• Turn, with the extra grip, to steer the car to the correct side of the next cone
• Unwind the steering wheel so you are not turning anymore
• Only accelerate once you are going straight, b/c you're at the limit, and you don't have enough grip to accelerate while turning

 

[tm1v2]

Thanks OP! I'm new to Tesla and this thread is very interesting. I have tried autocrossing and tracking ICE cars in the past, but not Teslas. The first thing I thought of when reading this is left foot braking. Honestly, I'm not good at left foot braking at all. But instead of trying to balance under/over steer with 1 foot using throttle lift and regen, what about 2 footed driving? How do Teslas respond to brake pedal under throttle? Does the car cut power to the wheels when the brake pedal is depressed?

@SmashMonkey My 2013 S P85 and 2021 3P both complain when accelerator and brake are pressed at the time time. Despite the complaining they DO allow for at least some power with both pedals pressed though, e.g. I can drive at a steady speed with moderate pressure on the brakes. (Don't do that with anyone/anything in front of you.)

I've never cared for left foot braking for any kind of performance driving though (in any car), so I can't say if my Teslas would allow for that. The only reasons I've pressed both pedals at once are:
1) To bed or just quickly clean the brakes (e.g. if they're squeaky after a rain).
2) By accident (right foot pressing both pedals at once).

 

[avramd]

By the way, this thread was named the "Thread of the Week" on the last TMC Podcast (episode 34).

Whoa - no kidding! I will have to check that out!

Thanks for mentioning here.

 

[avramd]

Thanks OP! I'm new to Tesla and this thread is very interesting. I have tried autocrossing and tracking ICE cars in the past, but not Teslas. The first thing I thought of when reading this is left foot braking. Honestly, I'm not good at left foot braking at all. But instead of trying to balance under/over steer with 1 foot using throttle lift and regen, what about 2 footed driving? How do Teslas respond to brake pedal under throttle? Does the car cut power to the wheels when the brake pedal is depressed?

I cross-posted this write-up on Reddit, and somebody brought that up. S/he asked if track mode "breaks the link between the accelerator and the brake pedal?" I responded saying I wasn't aware of a link. S/he said: "You’ve never pressed the brake pedal & accelerator at the same time? Pressing both generates an error (screen & audio beep), puts motor power in a T/C-like timeout for maybe a 1/4 second (edit:minimum, continued holding of both continues to lock out the accelerator). It’s what makes taking advantage of left-foot braking a slamdunk choice for the Model 3.
What you described sounded like pressing both at one."

I didn't understand it, and didn't pursue it.

 

[avramd]

Anyone out there following this thread who is interested, I am going back to a 2nd WDS next weekend. If any of you have any experiments you'd like me to conduct, or anything you're trying to suss out, please share. No promises, but if something makes sense to me, I'll add it to my list to try out while I'm there.

Here's what I currently plan on doing:

• I have "stud-less ice tires" now (Hakka R5's); this is the #1 reason for going back, to see how much more grip they have, and if the increased grip is enough to combat the hyper-sensitive accelerator pedal. By the end of the last school, my primary challenge was that the smallest foot movements I could muster still overpowered the conditions
• I plan to drive with regular shoes or maybe even slippers, instead of clunky mud shoes
• I'm going to try bringing a couple sponges or other mushing things to put under the accelerator pedal. My hope here is that if it takes more effort to press the pedal, then it'll be easier to ask for smaller increments of power
• Based on another thread, I'm going to test out all three stop modes for braking on ice - Hold, Creep, and Roll. A couple people have the theory that Hold mode can cause the brakes to lock up before the car is stopped. I don't think that is the case, however on really slippery ice, I can imagine a situation where the car thinks it is stopped, but it isn't.
• I also plan to focus on "regenerative threshold braking," or perhaps we should call it "reverse threshold braking." For those who haven't done these kinds of schools, threshold braking is a technique to decrease stopping distance over-and-above what the ABS is capable of, by looking for just the amount of brake pressure that does not trigger the ABS. This involves lifting your foot slightly until the ABS stops firing, so the car spends more time braking with grip than slip. As noted above, Teslas will trigger ABS without the driver touching the brake pedal b/c regen braking is strong enough that it can cause wheel lock-up. Since your foot is already not on the brake pedal, there's no lifting to be done. The super counter-intuitive antidote for this is to press the accelerator a little once you feel the ABS kick in. By telling the car you want to go the speed you're already going, it will stop using ABS. Then you can lift again, but less, to "look for" the amount of regen braking that the surface can handle.
• MAYBE: Try real-time bias shifting; When the tail swings farther than I wanted it to, tap the display to shift power to the front wheels only; In theory, increasing front wheel power should reduce and even reverse the car's rotation much sooner than just waiting for the tail's inertia to run out. This may prove to be unsafe due to the need to take a hand off the steering wheel, and the inappropriate distraction of trying to hit just the right spot on a touch-screen with a free-floating arm in a rotating car.
• MAYBE: In-flight reverse shifting; Teslas have another, little-recognized, trick up their sleeves compared to ICE cars, instant switching between forward and reverse w/out taking hands off of wheel: When I over-rotate by mistake, or when approaching a slippery hairpin turn then perhaps deliberately over-rotate when coming off of the previous curve - once the car is facing the wrong direction, but still moving, shift into reverse and drive backwards for the moment, to influence control and direction. If it's just an accidental over-rotation, then I'd probably try to turn the 180º into a full 360º rather than stop and do a cumbersome/clunky K-turn to get back going the right direction. When facing a hairpin turn with a curve just before, it perhaps just spin into a 180ª on purpose, enter the hairpin in reverse, come to a stop and accelerate straight forward. Making it kindof a V turn. Getting the car's orientation change out of the way before the inertial direction change will enable me to use 100% of available grip for just the inertia change. This is fairly wild, and while it might work in principle, I suspect I'm nowhere near good enough to do it effectively. Also, the organizers might deem it unsafe for the sake of the school b/c it would make my inertia less predictable, and therefore harder to keep things safe between me and the other cars that are on the track with me.

 

[tm1v2]

@avramd Just a few notes based on what you wrote.

Hold mode - For M3P there is never Hold when in Track Mode. I'm guessing there is no Creep when in Track Mode either but I never use Creep anyways so I haven't tested that.

Accelerator map - I completely agree about the overly sensitive Sport map (on the M3P in my case). It gives way too much power for very little pedal travel. A lot of sporty or trying-to-be-sporty cars do this or have a mode like this these days, but I never like it, I find it gimmicky and it can make precise control more difficult than it needs to be. On my ICE cars with drive by wire I would program a very linear or progressive throttle map for easy modulation - while still allowing full torque demand when deep in the pedal of course.

For snow driving in this car maybe Chill is enough power? Normally I never want Chill, because if I suddenly want full power for any reason it's not available, but on complete snow & ice I imagine Chill could be enough. I haven't tried using Chill in Track Mode though, not sure if that is allowed.

How cool would it be if Tesla made a builtin touchscreen interface for custom accelerator maps? I'll keep dreaming...

I'll also mention that in Track Mode with regen set to 100%, it feels like more of the pedal travel gets mapped to regen, and acceleration becomes easier to modulate. However I recognize that 100% regen is probably bad on snow and ice given the rear bias.

 

[avramd]

For snow driving in this car maybe Chill is enough power? Normally I never want Chill, because if I suddenly want full power for any reason it's not available, but on complete snow & ice I imagine Chill could be enough. I haven't tried using Chill in Track Mode though, not sure if that is allowed.

Chill mode gets disabled when you enable Track Mode - I tried that.

I'll also mention that in Track Mode with regen set to 100%, it feels like more of the pedal travel gets mapped to regen, and acceleration becomes easier to modulate. However I recognize that 100% regen is probably bad on snow and ice given the rear bias.

That doesn't add up for me - when I think that through, here's what I come up with (please correct if I'm missing something): if more of the pedal travel was regen, then less would be for acceleration, so it would be more sensitive, not less?

 

[tm1v2]

Chill mode gets disabled when you enable Track Mode - I tried that.


That doesn't add up for me - when I think that through, here's what I come up with (please correct if I'm missing something): if more of the pedal travel was regen, then less would be for acceleration, so it would be more sensitive, not less?

I get what you're saying, but it doesn't actually feel more sensitive to me.

Maybe just because the acceleration part is deeper in the travel, that alone is enough to feel less jumpy than the regular Sport mapping?

I wish we could see and reprogram the actual power/torque demand function or tables involved.

 

[52 16 57 39]

I’ve been absent from TMC for a few months - and this thread is amazing!

Heading out to my P to customize my “new” snow settings. Thanks all!

 

[gx9901]

Since our snow has been melting away pretty good over the past few weeks, I was concerned that I’ll be doing the winter driving school on dry pavement. But it looks like we’re getting at least a foot of snow dumped on us over the next couple of days, so we should be good to go for winter driving school this weekend. Can’t wait!

 

[avramd]

Since our snow has been melting away pretty good over the past few weeks, I was concerned that I’ll be doing the winter driving school on dry pavement. But it looks like we’re getting at least a foot of snow dumped on us over the next couple of days, so we should be good to go for winter driving school this weekend. Can’t wait!

Good luck! Sadly for me, our WDS was postponed a week b/c the snow on the track has melted, and there isn't enough new snow in the forecast for this weekend. They moved it to next weekend - there is more snow forecast next week, no idea if it'll be enough or last long enough.

 

[gx9901]

Good luck! Sadly for me, our WDS was postponed a week b/c the snow on the track has melted, and there isn't enough new snow in the forecast for this weekend. They moved it to next weekend - there is more snow forecast next week, no idea if it'll be enough or last long enough.

Aw man, hopefully you guys get some decent snow for the WDS next week. Good luck to you as well!

 

[gx9901]

@avramd As I'm getting ready for the winter driving school this weekend, I've got a question for you regarding your experience with the car's range. What was your starting SOC, ending SOC, and how much track time did you guys get for the day?

I just got a copy of the schedule and it looks like we'll get six 25-minute sessions on the track with an instructor during the day. I've been to this track during the summer for HPDE and I always arrive with SOC at around 93%. For HPDE I can do about 4.5 out of 7 the 20-minute sessions we are allotted before I have to quit with about 13~15% SOC or risk not making it home. I imagine winter driving school won't drain the battery like HPDE so hopefully no issues lasting the entire day. But it will be a lot colder so I'm thinking starting SOC might be in the 85% range. Anyway, just trying to get an idea on what to expect. Thanks!