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:
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:
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:
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
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:
- Maybe even with stability as low as I can put it, the car is still doing some stability control
- Maybe there is a timer, and it's only willing to let me spin wheels wildly for a limited time
- 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)
- 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
- Get on some ice, point the car straight, and floor it for a long time. See if it eventually cuts power
- It did not
- Same as above, but have observers on both side of the car - see if all four wheels are spinning at the same time
- 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.
- Turn on Drift mode, and see if I was maintain a continuous drift without it ending except by my choice
- I was
- 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)
- I was, and thus, it does not.
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.
- 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!