Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Disappointing traction control - is it me?

StealthP3D

Well-Known Member
Dec 12, 2018
9,747
77,819
Maple Falls, WA
Exactly, most situations when in poor traction scenarios, all cars are struggling to maintain their best grip. You want to minimize ANY slippage at all times, if you can.

That's false. Every snow type has different needs but all of them have one thing in common:

If there is not a small amount of slippage under acceleration, you are not accelerating as fast as possible. This is true on dry and wet pavement as well. I've found my Performance Model 3 to be amazing in straight-line grip under acceleration, even on uneven surfaces like packed snow with patches of pure ice. The key is to not put your foot too deep into the accelerator. You will squirt forward like no one's business. I've noticed this on slippery wet pavement too. All four wheels will be scrubbing hard to maximize forward thrust.

It's also true to an even larger degree when considering threshold braking, especially on loose surfaces (including snow). Early ABS systems on dual-sport motorcycles were widely hated for their long stopping distances on sand and gravel. They were not stopping quickly because they were overly aggressive in avoiding lockup. An expert rider could stop in much shorter distances. New ABS systems have largely solved this problem by allowing "micro-lockup". The wheel doesn't fully lock-up but it is turning much slower than the forward speed.
 

StealthP3D

Well-Known Member
Dec 12, 2018
9,747
77,819
Maple Falls, WA
In my experience it is far from seamless. I'd like torque to all four wheels so I don't slip in the first place. If I accelerate from a stop while turning in the snow the car will yaw back and forth as it transfers power back and forth between the front and rear wheels. It's quite annoying and I don't believe it's faster than true AWD. I haven't driven it this season in the snow so maybe it has improved.

As I previously mentioned, this is because you are not modulating the throttle appropriately. The Tesla system is not a "mash and go" system - it's better. It's not difficult to do it properly and this difference gives the car more flexibility to be driven however the driver wants.

On the braking side of the equation, it is a "mash and stop" system. Your fastest stop will be pressing the brake pedal fully and holding it there. This is for obvious safety in panic stops.
 

Daniel in SD

Well-Known Member
Jan 25, 2018
6,856
9,734
San Diego
As I previously mentioned, this is because you are not modulating the throttle appropriately. The Tesla system is not a "mash and go" system - it's better. It's not difficult to do it properly and this difference gives the car more flexibility to be driven however the driver wants.
With full time AWD there is no need to modulate the throttle. I can simply apply a throttle level that does not result in wheel slip. If I apply too much throttle the car will slide sideways instead of a rotating. Many people find this behavior preferable. With the Model 3 system you must slip the rear wheels to get power to the fronts. Clearly even Tesla themselves doesn't think this is an optimal system since they use the exact opposite system on Raven vehicles and a true AWD system on older Model S/X.
 
  • Like
Reactions: camalaio

Fredneck

Member
Nov 8, 2019
478
-32
Pennsylvania
That's false. Every snow type has different needs but all of them have one thing in common:

If there is not a small amount of slippage under acceleration, you are not accelerating as fast as possible. This is true on dry and wet pavement as well.

Completely false. Anyone who knows anything about friction would know there is a static friction and a dynamic friction. The static friction coefficient is always higher than the dynamic friction for two solids. That's why you can walk on ice easily when it is very cold, but it becomes slippery when simply a bit below freezing. The pressure of your weight melts the ice just under your feet and creates a thin layer of water which does not have a different coefficient of static friction.

Once you break the adhesive connection between two surfaces the dynamic coefficient of friction takes over creating less force between the two objects. That's why once an object on a slope starts sliding, it takes something significant to get it to stop.
 
  • Love
Reactions: camalaio

StealthP3D

Well-Known Member
Dec 12, 2018
9,747
77,819
Maple Falls, WA
Completely false. Anyone who knows anything about friction would know there is a static friction and a dynamic friction. The static friction coefficient is always higher than the dynamic friction for two solids. That's why you can walk on ice easily when it is very cold, but it becomes slippery when simply a bit below freezing. The pressure of your weight melts the ice just under your feet and creates a thin layer of water which does not have a different coefficient of static friction.

Once you break the adhesive connection between two surfaces the dynamic coefficient of friction takes over creating less force between the two objects. That's why once an object on a slope starts sliding, it takes something significant to get it to stop.

You are ignoring that tires are molded from rubber has "give" to it and is composed of individual tread blocks that deform. I have more than enough real world performance driving and riding under my belt to know that my tires are slipping under the fastest acceleration (although, obviously, if they actually spin up, it's slower). I'm speaking of a very small amount of slippage where the wheel is turning slightly faster than the speed of the vehicle. There is a bit of "scuffing" going on.

You can rely on textbook definitions of static and dynamic friction, I'm gonna stick with what I know works. If you go to the dragstrip you can actually hear the "scuffing" I'm talking about coming from the tires of the fastest launches.
 

Fredneck

Member
Nov 8, 2019
478
-32
Pennsylvania
You are ignoring that tires are molded from rubber has "give" to it and is composed of individual tread blocks that deform. I have more than enough real world performance driving and riding under my belt to know that my tires are slipping under the fastest acceleration (although, obviously, if they actually spin up, it's slower). I'm speaking of a very small amount of slippage where the wheel is turning slightly faster than the speed of the vehicle. There is a bit of "scuffing" going on.

You can rely on textbook definitions of static and dynamic friction, I'm gonna stick with what I know works. If you go to the dragstrip you can actually hear the "scuffing" I'm talking about coming from the tires of the fastest launches.

You can wax poetic about tread "give" and your life experience, but you have nothing to cite that says slippage gives better acceleration than not slipping at the highest level of torque that doesn't slip.

The reason in the past they would allow some slippage is because a locked wheel was how they detected that the maximum level of adhesion had been reached or I should say passed. Once it slipped, that was too much and the braking force was backed off. In fact the earliest anti-lock systems simply modulated the brake pressure to allow some rotation of the wheels. Very crude, but better than fully locked wheels.

Now the trick is to get as close as possible to the max adhesion from a non-slipping wheel without actually letting it slip at all. Hard to do, so they get by with a small amount of slipping.
 

Saghost

Well-Known Member
Oct 9, 2013
8,217
7,010
Delaware
With full time AWD there is no need to modulate the throttle. I can simply apply a throttle level that does not result in wheel slip. If I apply too much throttle the car will slide sideways instead of a rotating. Many people find this behavior preferable. With the Model 3 system you must slip the rear wheels to get power to the fronts. Clearly even Tesla themselves doesn't think this is an optimal system since they use the exact opposite system on Raven vehicles and a true AWD system on older Model S/X.

Pretty sure the Ravens got the PMSR in the front because they were all AWD to begin with and there was no way to get 360 kW into the off the shelf Model 3 PMSR cores, which is necessary to make the Performance/Ludicrous S/X match their predecessors. I don’t think that decision considered strategy for driving on snow and ice as a factor at all.

I’m not an expert on the technology, but I’m having trouble coming up with any technical reason they can’t control the PMSR motor as quickly and seamlessly as they do the induction motors - it’s maybe a little more complex because they are synchronous and so you have to match the phase timing to the rotor and index it for the desired torque output, but near instantaneous control should still be possible.
 

StealthP3D

Well-Known Member
Dec 12, 2018
9,747
77,819
Maple Falls, WA
You can wax poetic about tread "give" and your life experience, but you have nothing to cite that says slippage gives better acceleration than not slipping at the highest level of torque that doesn't slip.

Yes, go to the dragstrip and listen to the tires of the cars with the best launches (as measured by the clock). You can hear the tires scuffing!
 

Incredulocious

LEAF → RAV4EV → Model 3 → Model Y
Mar 31, 2012
427
587
Scotts Valley, CA
To those of us who would like an AWD “snow” mode for our Model 3’s that keeps the front motor engaged to avoid rear slips, please submit another request to Tesla and send a tweet to Elon. It didn’t work last year, but let’s keep trying.
 

Daniel in SD

Well-Known Member
Jan 25, 2018
6,856
9,734
San Diego
Pretty sure the Ravens got the PMSR in the front because they were all AWD to begin with and there was no way to get 360 kW into the off the shelf Model 3 PMSR cores, which is necessary to make the Performance/Ludicrous S/X match their predecessors. I don’t think that decision considered strategy for driving on snow and ice as a factor at all.

I’m not an expert on the technology, but I’m having trouble coming up with any technical reason they can’t control the PMSR motor as quickly and seamlessly as they do the induction motors - it’s maybe a little more complex because they are synchronous and so you have to match the phase timing to the rotor and index it for the desired torque output, but near instantaneous control should still be possible.
That's my point. The part time AWD system is done only for efficiency. There is nothing else better about part time AWD.
 

mswlogo

Well-Known Member
Aug 27, 2018
6,121
4,733
MA, NH
With full time AWD there is no need to modulate the throttle. I can simply apply a throttle level that does not result in wheel slip. If I apply too much throttle the car will slide sideways instead of a rotating. Many people find this behavior preferable. With the Model 3 system you must slip the rear wheels to get power to the fronts. Clearly even Tesla themselves doesn't think this is an optimal system since they use the exact opposite system on Raven vehicles and a true AWD system on older Model S/X.

To be fair. You don't have to make rear slip to get torque to the front. I used to think that too. But with all the CanBus graphs and CANBus Videos, it's clearly not the case. But you may have to apply more throttle than circumstances may dictate (like my black ice curve example) to get the front torque and you actually have no idea how much throttle you actually need (unless monitoring your CANBus :)). And you do run the risk that you could slip the rear wheels in light (normal) acceleration (exactly the kind of light foot you should be using in slick conditions) before the front wheel get to business. So you could come to the conclusion that rear has to slip to get the front going. And it happens way too often. And like you said you should not have to throttle anything. I just push the throttle any way I please in the Raven X, and it just goes. Not spinning tires, nuttin. Light foot, heavy foot, throttle foot. Absolutely not a thing to think about, feel or sense.

The problem is the front only gets torque with acceleration, and a fair amount of it. And the rear can break loose before you apply enough acceleration. See Chart I posted above showing AP with 5 mph acceleration, the front never gets an ounce of torque. That's just not right.
 
  • Love
Reactions: camalaio

Daniel in SD

Well-Known Member
Jan 25, 2018
6,856
9,734
San Diego
To be fair. You don't have to make rear slip to get torque to the front. I used to think that too. But with all the CanBus graphs and CANBus Videos, it's clearly not the case. But you may have to apply more throttle than circumstances may dictate (like my black ice curve example) to get the front torque and you actually have no idea how much throttle you actually need. And you do run the risk that you could slip the rear wheels in light (normal) acceleration (exactly the kind of light foot you should be using in slick conditions) before the front wheel get to business. So you could come to the conclusion that rear has to slip to get the front going. And it happens way too often. And like you said you should not have to throttle anything. I just push the throttle any way I please in the Raven X, and it just goes. Not spinning tires, nuttin. Light foot, heavy foot, throttle foot. Absolutely not a thing to think about, feel or sense.

The problem is the front only gets torque with acceleration, and a fair amount of it. See Chart I posted above showing AP with 5 mph acceleration, the front never gets an ounce of torque. That's just not right.
Yes, it's completely backwards. On snow with crap all season tires (snow tires are not practical in Southern California!) you have to slip the rears in order to get torque to the front. Ideally you'd want to start at 50/50 at low throttle and send more torque to the back during hard acceleration.
Anyway, at least everyone understands how the car works now. Last year there were people insisting that it sent torque to front at low throttle.
 
  • Like
Reactions: camalaio

mswlogo

Well-Known Member
Aug 27, 2018
6,121
4,733
MA, NH
Yes, it's completely backwards. On snow with crap all season tires (snow tires are not practical in Southern California!) you have to slip the rears in order to get torque to the front. Ideally you'd want to start at 50/50 at low throttle and send more torque to the back during hard acceleration.
Anyway, at least everyone understands how the car works now. Last year there were people insisting that it sent torque to front at low throttle.

Popcorn is popping in the microwave, waiting for @StealthP3D response :)
 

camalaio

Active Member
May 28, 2019
1,483
2,106
Vernon, BC, Canada
That's false. Every snow type has different needs but all of them have one thing in common:

If there is not a small amount of slippage under acceleration, you are not accelerating as fast as possible. This is true on dry and wet pavement as well.

First of all, that is indeed mostly false (static vs. dynamic friction -- slippage implies dynamic friction, which is always less than static).

But again, my goal is not to get around "as fast as possible" in Winter! I want to arrive as confidently and safely as possible. I want no slippage, and if I can't get that, I want minimised slippage.

Maximum speed is simply not desirable for a daily driver on public roads in poor Winter conditions, which is the topic of this thread. How a Performance Model 3 behaves on a Winter race circuit is completely irrelevant to this discussion, and to most people's chances for arriving home from their commute safely and confidently.

I have a full winter on my Stealth P3D using Pirelli Sottozero II's and have driven my wife's LR RWD Model 3 on the OEM MMX 4's in the snow and ice a couple of times. I also love driving in winter conditions and have driven a wide range of FWD, RWD and AWD gas cars through winter storms (usually on curvy mountain roads but also across the prairies).

IMO, the Model 3 does very well in snow and ice although it does give the driver more leeway to put the power to the tires even when slip is detected. The "nanny" is very permissive. :D That said, there is a sweet spot with the throttle modulation when it's really slick that will keep you well connected (no one else in the car will be able to detect any slip). You just need to drive like you are on a very slippery surface. The traction control will assume you want to maintain traction (and it's very fast and seamless about kicking in). It's only when you use the accelerator to tell the "nanny" you want to play that she gives you more leeway. I love it! But when driven gently, even on extremely slick surfaces, the nannies are super fast reacting, so fast you might think they are not even active. But as soon as you get a little frisky with the throttle she lets you play.

I think a contributing factor to some people claiming the nanny is too permissive is related to the way the tread blocks will wear on a car with as much effortless torque as the Model 3 has. If you use the accelerator much on wet or dry pavement even moderately (this is the equivalent of flooring it at high RPM's on ordinary cars) the tread blocks will wear into a sawtooth pattern. Especially when using winter tires with their softer rubber compounds. This sawtooth wear pattern on the tread blocks from acceleration creates what I refer to as "directional traction". Specifically, it reduces traction on snow and ice under acceleration and increases it under braking.

I installed winter tires on my P3D yesterday afternoon (the same set I used all last winter) and the sawtooth wear pattern was rather pronounced. I really don't mind this at all because the AWD of the P3D has all the climbing (and accelerating) ability I need in the snow and ice and it actually improves emergency stopping on snow and ice (and control under braking on snow and ice). I noticed this same effect on my FWD Volvo S80 T-6 where it was more problematic because that car was below average in snow/ice hill-climbing ability even though it was above average at cornering on snow/ice. But here's the thing - My AWD Mazda CX-5 never developed this sawtooth wear pattern because it only had 155 hp. Even though I often drove it semi-rally style (pedal to the metal) it simply didn't have the torque to the wheels to get a pronounced sawtooth treadwear pattern. It had pretty good nannies but they seemed overly intrusive when trying to drive in a sporting style. They were very competent but no fun at all.

So, yes, treadwear patterns can affect your perception of how well a car maintains traction under acceleration on snow and ice.I have played with "Chill Mode" and setting regen on "Low" when driving through the winter wonderland that is the North Cascades with all of it's grades and switchbacks but have settled on leaving it in standard accel and regen mode because I don't see any advantage to the "softer" modes. "Chill Mode" is particularly bad to use in snow and ice because it adds a small time delay and reduces repeatability of throttle application. I absolutely hate it.

I've found normal regen to have very fast-acting traction control (it cuts/reduces regen when slip is detected) but it still leaves enough regen braking that the tires can form a wall of snow or slush in front of them which increases braking under those conditions. When I add additional friction braking and more slip is detected, the regen braking backs off even more. If it's slippery enough the regen braking will back off completely in order that directional control can be maintained. So I have no issue driving down steep hills with full regen and simply modulating the regen with the throttle (and the directional nannies are kicking in as needed to help maintain directional control as well).

I find the Model 3 is the easiest and most relaxing car to drive fast in the snow and ice, uphill or down, without losing control or feeling like I'm fighting the nannies. Yes, it's a bit "looser" than any other nanny equipped car I've driven but it maintains directional control better even when it's loose. And I absolutely hate the abrupt way that most car nannies cut power the instant they detect a tiny bit of slip. The fast-acting but not overly invasive TC is why I think the Model 3 works better. This is comparing it every other car, truck and SUV I've driven hard in the snow including a long list of Volvo's and AWD Subarus, AWD Mazda, FWD VW's and AWD Ford pickups. I'm not counting all the cars that were pre-nanny. That said, the AWD and Performance Model 3's have different software from each other and I've only driven the Performance and RWD Models in the snow and ice. So maybe the AWD (non-perf) is somehow different. But I doubt it.

Hmm. Your experience is significantly different from most others in this thread. I think most others have had regular AWD instead of Performance though. I wonder if it actually is different somehow?

I also have fairly new (this season) Winter tires. They've also been driven on fairly gently because I hate to burn through expensive soft rubber, so I don't think my problem is this "sawtooth" thing you mentioned (I also doubt it would be extremely noticeable to the point of necessitating this thread, but it's the first time I've heard of this phenomenon).

But I must point out what you are noticing for "very fast-acting traction control" is no more than "very fast updating stats on regen power". Regen does not have traction control. The reduction in regen power is only because less torque is being transmitted to the drivetrain because your tires are sliding. You won't fully lose steering ability thanks to the induction motor up front, which won't fully lock up with regen alone. This is probably the reality behind your statement regarding directional control, and nothing related to intentional backoff of regen strength.

Here's what I actually feel when I drive my Stealth 3 on very slippery surfaces:

When the rear tires begin to slip the tiniest amount under gentle acceleration it immediately reduces power to the rear while simultaneously applying power to the front in an amount equal to the rear reduction. This is so seamless I imagine many don't even detect it is happening at all. Then, if it detects front traction has broken it is very pro-active about reducing power enough to maintain steerage but it will allow the rear a somewhat generous amount of slippage, the amount being proportional to how deep you press the accelerator beyond the available traction limit. This all happens so fast it doesn't appear to be transferring power around at all, it just feels like the rear is a little loose. These observations are deducted from a lot of experience driving a lot of cars under such conditions (it happens too fast to feel the power being transferred front to back).



I can see how some might come to that conclusion. But, no, I can climb a hell of a lot faster on a snowy grade in my AWD P Model 3 than ANY other AWD I've ever driven (normalized for tire differences). It literally rockets forward in the slick! It's scary how quickly it can reach 60 mph on a sheet of clean snow/ice. The only way it could do this is with all four wheels clawing for maximum traction and being extremely fast reacting to changes in traction from microsecond to microsecond. There is absolutely zero doubt in my mind about this!

Here's a tip for the fastest acceleration in snow/ice: Don't mash the pedal all the way because the nanny will think you want to play as it will transfer too much power to the rear while maintaining perfect traction (and not much drive) from the front. It will actually be slower than rolling onto the throttle just enough to engage the traction control throughout your run. You don't have to be super-precise about it but don't give it far more throttle than it could hope to take. I had a motorcycle once that, due to it's lack of constant velocity carbs, required similar throttle control. For the fastest roll-on acceleration, it was necessary to roll on the throttle at a rate compatible with the amount of power the engine was capable of producing at any given rpm. Giving it more throttle than it could use didn't really cause it to obviously bog down but it didn't give you it's best either. This actually made it more fun to ride because it rewarded the rider for being one with the machine. The Performance Model 3 is the same and I have a hard time believing the regular AWD is not similar (but I don't know that).




I have ripped up the mountain corners and switchbacks (some of them very tight downhill off-camber turns) in track Mode and the important nannies are still there to save you. It's a VERY easy car to drive fast on snow and ice, even in Track Mode.



Sigh...This graph has zero relevance to this discussion (because the rear wheels were not slipping at all). The Model 3 does drive like a rear wheel drive car but only until it detects ANY slippage from the rear tires under acceleration. And it doesn't take much to start sending torque to the front. There is no way I could rocket to 60 mph so quickly in snotty, slippery and variable conditions if it were not sending prodigious amounts of torque to the front wheels. And, yes, with heavy throttle inputs in the slick it will send an excessive amount to the rear. I like this because it fixes what killed me about the nannies on every other car I've ever driven (that had electronic nannies), their overly heavy-handed and crude babysitting of the throttle. I've never used nannies that reacted as quickly to variable traction situations either.

You need to get out and drive your Performance Model 3 more in the snow and ice. You don't even need to turn on track mode to go fast. Track mode is tuned for pavement although it will still offer enough error correction in the snow and ice to keep reasonable people out of trouble. It's pretty obvious that Tesla's philosophy when they tuned the traction control was to protect the car from loss of control while simultaneously believing that humans basically know what they are doing. This is a powerful car so just realize that heavy-handed throttle control in the snow and ice is not necessarily going to give you what you want unless you are just looking for a little rear-end hooliganism. If you feel the back end break loose, easing off the throttle will actually transfer more torque to the front. Maximum torque to the front happens when you are always asking for a little more throttle than conditions would allow (without nannies).

I have much more limited experience with my wife's LR RWD in the snow and ice but I noticed the same thing - for maximum acceleration in slippery conditions you want to keep the throttle input closer to the range of available traction. Otherwise, the nanny will think you want to play. I find it very intuitive and empowering. Simple, practical and fun (if you want).

First, letting off the accelerator transfers no power to the front. That's entirely false, verified by various people with the Scan My Tesla app. If anything, backing off actually applies regen in the front while providing forward torque in the back still, which seems odd IMO. The car is also simply not designed to accelerate when you lift off the throttle, because absolutely no car would ever be designed to do the opposite of what the driver requested with their foot.

Second, the graph actually has all the relevance to this discussion. As the OP, I can absolutely make that claim as well because I know what I was bringing up.

My whole point is that the Model 3 relies on the rear losing traction before the front engages (or that's how it seemed, and indeed is now confirmed). I don't want to lose traction before I get more, I want to have all the traction available to control the car's vector at all times confidently and safely in a sure-footed manner.

I don't want to get to 60mph as fast as possible on ice on public roads. Heck, I don't ever want to reach 60mph on ice because that's just too fast to be able to control the vehicle if something unexpected comes up. Even if I had studded tires I wouldn't imagine driving that fast in terrible conditions.

Perhaps it was lost that this is a daily driver car for us. It needs to leave town via some curvy parkways and other roads, travel a highway with plenty of corners, turn off up a hill, navigate another section of curvy highways, then navigate a curvy road to get to work. Repeat in reverse to get home. Straight-line performance is not at all my priority. Even in the dry and grippy, I'm not rocketing to my destination as fast and aggressively as physically possible because even that isn't safe with all the dirt and crud on the roads.

As I previously mentioned, this is because you are not modulating the throttle appropriately. The Tesla system is not a "mash and go" system - it's better. It's not difficult to do it properly and this difference gives the car more flexibility to be driven however the driver wants.

On the braking side of the equation, it is a "mash and stop" system. Your fastest stop will be pressing the brake pedal fully and holding it there. This is for obvious safety in panic stops.

Surely forward motion can also be designed for safety in Winter conditions? Even if it's being a "Snow Mode" option like we've been talking about. Certainly beats everyone having to learn the very specific finesse required to drive a Model 3, which seems to also imply driving at reckless acceleration and speeds which aren't appropriate for icy public roads.

With full time AWD there is no need to modulate the throttle. I can simply apply a throttle level that does not result in wheel slip. If I apply too much throttle the car will slide sideways instead of a rotating. Many people find this behavior preferable. With the Model 3 system you must slip the rear wheels to get power to the fronts. Clearly even Tesla themselves doesn't think this is an optimal system since they use the exact opposite system on Raven vehicles and a true AWD system on older Model S/X.

Exactly this. No reason to decide that people that drive in Winter conditions should be slipping 4/12 months of the year as an intentional design.

You are ignoring that tires are molded from rubber has "give" to it and is composed of individual tread blocks that deform. I have more than enough real world performance driving and riding under my belt to know that my tires are slipping under the fastest acceleration (although, obviously, if they actually spin up, it's slower). I'm speaking of a very small amount of slippage where the wheel is turning slightly faster than the speed of the vehicle. There is a bit of "scuffing" going on.

You can rely on textbook definitions of static and dynamic friction, I'm gonna stick with what I know works. If you go to the dragstrip you can actually hear the "scuffing" I'm talking about coming from the tires of the fastest launches.

Drag strip physics and systems have absolutely zero relation to Winter driving conditions.

The additional acceleration given by the "give" and "stretch" and "flexing" and "loading" of the driven tires at a drag strip is a complex behaviour that requires a lot of available traction and power in order to reproduce.

You can have all the power in the world on ice, but you're not going to flex the tire in any meaningful way to pull a drag-style launch because the traction just isn't there. If you want traction on ice, get some road-wreckin' huge spikes put in your tires and let 'er rip.

I’m not an expert on the technology, but I’m having trouble coming up with any technical reason they can’t control the PMSR motor as quickly and seamlessly as they do the induction motors - it’s maybe a little more complex because they are synchronous and so you have to match the phase timing to the rotor and index it for the desired torque output, but near instantaneous control should still be possible.

I'm no expert either, but from where I sit I can see how a synchronous motor would be a massive PITA to control on a low-traction surface. That may be just it?

To be fair. You don't have to make rear slip to get torque to the front. I used to think that too. But with all the CanBus graphs and CANBus Videos, it's clearly not the case. But you may have to apply more throttle than circumstances may dictate (like my black ice curve example) to get the front torque and you actually have no idea how much throttle you actually need. And you do run the risk that you could slip the rear wheels in light (normal) acceleration (exactly the kind of light foot you should be using in slick conditions) before the front wheel get to business. So you could come to the conclusion that rear has to slip to get the front going. And it happens way too often. And like you said you should not have to throttle anything. I just push the throttle any way I please in the Raven X, and it just goes. Not spinning tires, nuttin. Light foot, heavy foot, throttle foot. Absolutely not a thing to think about, feel or sense.

The problem is the front only gets torque with acceleration, and a fair amount of it. See Chart I posted above showing AP with 5 mph acceleration, the front never gets an ounce of torque. That's just not right.

Nailed it (but I feel like this has been stated a dozen times by now :p). That's why it's "effectively RWD" in Winter conditions, because one should be driving with sufficient caution that the accelerator threshold to engage the front motor would be indicative of risky driving at best.
 

camalaio

Active Member
May 28, 2019
1,483
2,106
Vernon, BC, Canada
For those that can't get enough of this argument here's another 13 pages to read: "Full-Time" AWD Winter Mode
@StealthP3D and I are very persistent. I've got to stay off this forum. Haha.

Genuine lol at the first reply.

And then followed by "I hear so much praise for Tesla traction control that sometimes I worry if something is wrong with mine, or it's just me". Oof. I know that feel.
 

Saghost

Well-Known Member
Oct 9, 2013
8,217
7,010
Delaware
I'm no expert either, but from where I sit I can see how a synchronous motor would be a massive PITA to control on a low-traction surface. That may be just it?

Certainly the difference in performance between the cars is tied up in the difference in programming and hardware in the inverters, but whether it's an inherent limitation of the hardware or something that's fairly easy to fix with a firmware update (or somewhere in between) isn't at all obvious from what we know now.

I would have thought a synchronous motor on a slick surface was easier to manage - inherently self regulating to an extent.

If the wheels slip, the motor surges forward in the phase by twenty or thirty degrees of rotation (almost 10:1 gear reduction, so that's only a couple degrees of rotation of the wheels) - and so the torque delivered to the motor immediately drops because it's no longer lagging so far in phase. Unless the traction changed radically, the tires will presumably connect again at this new reduced torque level.

Then the controller presumably has to pushing the fields further ahead again to get the torque delivery the driver is calling for...

Of course, an induction motor is almost the same sort of thing, but for that motor it has to continue to spin faster to relieve the torque, so as soon as it hooks up, the torque levels rise again if the field rotation remains the same.
 

StealthP3D

Well-Known Member
Dec 12, 2018
9,747
77,819
Maple Falls, WA
To those of us who would like an AWD “snow” mode for our Model 3’s that keeps the front motor engaged to avoid rear slips, please submit another request to Tesla and send a tweet to Elon. It didn’t work last year, but let’s keep trying.

AWD isn't a cure-all and doesn't necessarily stop the wheels from slipping. Clean or polished ice can be incredibly slippery and EV's have lots of instantaneous torque. All the driver nannies in the world cannot prevent some slipping in some conditions. I have found my Model 3 to be very planted if I drive it more sensibly than I often do! ;)

I really think you should work on your fine throttle control and see how it can magically give you optimum torque front and rear without obvious slipping. I've explained how Tesla has mapped the throttle and the traction control together but you don't seem to be listening. It doesn't work like other cars I've driven (it's better because it's more versatile in that it can be driven in different modes just by how the throttle is modulated). Yes, it took a little playing around to understand it but, now that I do, it's very intuitive and it just plain works without having to select different modes.:)
 
  • Like
Reactions: joelliot

camalaio

Active Member
May 28, 2019
1,483
2,106
Vernon, BC, Canada
Certainly the difference in performance between the cars is tied up in the difference in programming and hardware in the inverters, but whether it's an inherent limitation of the hardware or something that's fairly easy to fix with a firmware update (or somewhere in between) isn't at all obvious from what we know now.

I would have thought a synchronous motor on a slick surface was easier to manage - inherently self regulating to an extent.

If the wheels slip, the motor surges forward in the phase by twenty or thirty degrees of rotation (almost 10:1 gear reduction, so that's only a couple degrees of rotation of the wheels) - and so the torque delivered to the motor immediately drops because it's no longer lagging so far in phase. Unless the traction changed radically, the tires will presumably connect again at this new reduced torque level.

Then the controller presumably has to pushing the fields further ahead again to get the torque delivery the driver is calling for...

Of course, an induction motor is almost the same sort of thing, but for that motor it has to continue to spin faster to relieve the torque, so as soon as it hooks up, the torque levels rise again if the field rotation remains the same.

How I think of it is this (and it may be entirely incorrect):

The synchronous motor here is likely very "coggy" to my understanding and wants to not spin if no power is applied. In order to make it spin, you have to be driving it at a very precise speed (synchronous). You can tell the difference in speed between the two powered wheels and see if one is spinning more than it should (implying slipping because of the open differential) but otherwise it's hard to tell if it's slipping or not. It's not just applying torque, it's basically selecting an exact speed (which I imagine is selected in the context of accelerator input and current speed).


AWD isn't a cure-all and doesn't necessarily stop the wheels from slipping. Clean or polished ice can be incredibly slippery and EV's have lots of instantaneous torque. All the driver nannies in the world cannot prevent some slipping in some conditions. I have found my Model 3 to be very planted if I drive it more sensibly than I often do! ;)

I really think you should work on your fine throttle control and see how it can magically give you optimum torque front and rear without obvious slipping. I've explained how Tesla has mapped the throttle and the traction control together but you don't seem to be listening. It doesn't work like other cars I've driven (it's better because it's more versatile in that it can be driven in different modes just by how the throttle is modulated). Yes, it took a little playing around to understand it but, now that I do, it's very intuitive and it just plain works without having to select different modes.:)

Your not-a-cure-all statement is not incorrect, but:
  1. If I have AWD, please let me use both the front and back axle so I, the driver, can utilise all available traction to minimise slippage.
  2. EVs have instant torque but extremely gentle throttle application (which would be fine in any other vehicle, including older Teslas) shouldn't result in high torque that causes the wheels to slip. The driver isn't asking for high torque with their foot.
Fine and reserved throttle control results in 0% power being applied to the front motor unless the rear is slipping, and that rear slippage could have been prevented if the front was already engaged.

To be fair, you've also explained throttle and traction control in ways that doesn't exist in reality which is why people aren't listening. There is no traction control for regen, but you claim there is. You claim backing off the throttle applies front motor power, but it does the opposite. You claim driving at 60mph (and accelerating there as fast as possible) is a sensible way to drive in winter because it gives you more traction. None of these are true, and why you're seeing resistance to your statements.

I have no doubt that the way you are driving is "fun", but I'm looking for safety and confidence instead.
 

Products we're discussing on TMC...

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top