Acceleration limitations on MXM4 tires for dual motor?

[zhu-]

Lately I've been watching my screen during launches from a stop and noticed I'm not getting max acceleration with the bar only reaching about ~80% for the first second. Acceleration feels same as before though I haven't always been watching the screen so not sure if this is recent or not.

I tested this in 80-90F sunny weather. My front tires have even threads of 7/32 on sides and center. Rear tires are 7/32 on the sides and 6/32 in the center with 40 psi all around. Is this a limitation of the MXM4 tires?

 

[SSedan]

So you can input the tire model into the car?

I will presume there was slip on the surface you are on traction control intervened. Tesla traction control is very good compared to any ICE I have driven, you might not notice the slippage happen.

 

[run-the-joules]

For whatever reason, the car never puts down max power from a stop or from very low speed, irrespective of traction. You could put on drag tires and get the same effect. This is why even a Leaf feels punchier off a stop… at least until you get to 15mph or so.

 

[run-the-joules]

So you can input the tire model into the car?

I will presume there was slip on the surface you are on traction control intervened. Tesla traction control is very good compared to any ICE I have driven, you might not notice the slippage happen.

Depends what you consider "good". I call Tesla's traction control aggressively bland-enforcing and intrusive.

 

[AlanSubie4Life]

Lately I've been watching my screen during launches from a stop and noticed I'm not getting max acceleration with the bar only reaching about ~80% for the first second. Acceleration feels same as before though I haven't always been watching the screen so not sure if this is recent or not.

I tested this in 80-90F sunny weather. My front tires have even threads of 7/32 on sides and center. Rear tires are 7/32 on the sides and 6/32 in the center with 40 psi all around. Is this a limitation of the MXM4 tires?

You were not traction limited unless the surface was really poor (you have an AWD, and even the Performance is not traction limited).

Remember that the power requirements are nearly ZERO around 0mph. Power is proportional to RPM for constant torque. (RPM*Torque)

In the P3D, I've never watched the bar during a launch for obvious reasons, but I wouldn't expect it to max out until I get to about 45mph, where max power is reached. (Exactly what this bar displays and whether it uses a linear scale...I have no idea...though recording a video of it during a launch would make it pretty easy to figure out since we know the power ramps roughly linearly up to 45mph. Your observations suggest the scale is logarithmic.)

 

[ZOMGVTEK]

I never watched the bar, but the AWD is almost never traction limited in a straight line. Even in heavy rain, and cooler temperatures. I find wheel slip and traction control to be very noticeable, and it’s ability to put down power in adverse weather conditions with over inflated eco tires is very good.

But yes, the power bar should gradually rise under nominal conditions assuming it really indicates power. Power rises linearly up to 40ish and maintains flat past that. You’d need effectively infinite current into the motor at 0mph to maintain constant power.

 

[AlanSubie4Life]

For whatever reason, the car never puts down max power from a stop or from very low speed, irrespective of traction. You could put on drag tires and get the same effect.

This is true (but you mean max torque). However, you reach peak torque (not power) after about 0.2 seconds, after the first ~8 inches of travel (for the Performance). From thereon out you are at peak torque until you reach the power peak. So that 0.2s time period wouldn't explain the meter observations in this case.

In any case, there isn't nearly enough torque available to break the MXM4s free (need something like 10% more torque from the Performance to start having an issue with MXM4s). The Model 3, regardless of variant, simply doesn't produce enough torque to the wheels to break them free in a straight line on a good surface (unlike similar HP ICE vehicles). Traction control doesn't really even need to think about operating.

 

[zhu-]

My tests were done on smooth clean roads and it felt the same as always so I guess that's just how it is. Thanks for the input!

 

[ZOMGVTEK]

If you go into a corner a bit too fast and hammer the throttle around the apex, the back will kick out and you can easily feel the traction controls response.

Now we just need someone to make a box for the AWD 3 that makes the stock traction control a bit more fun. It should probably be called a PartyBox or something...

 

[AlanSubie4Life]

If you go into a corner a bit too fast and hammer the throttle on the exit, the back will kick out and you can easily feel the traction controls response.

Now we just need someone to make a box for the AWD 3 that makes the stock traction control a bit more fun. It should probably be called a PartyBox or something...

MPP must be hoping that Tesla doesn't start providing a $2k Performance upgrade. (Fortunately for MPP, it's unlikely it would be priced that low...)

 

[ZOMGVTEK]

I’d pay $2k all day for the track mode button. I’d prefer if it had toggles to adjust the power from ‘chill’, to ‘standard’ and then ‘performance’.

 

[run-the-joules]

I’d pay $2k all day for the track mode button. I’d prefer if it had toggles to adjust the power from ‘chill’, to ‘standard’ and then ‘performance’.

I just want a button called "I am an adult" that lets me turn off traction and stability control.

 

[ZOMGVTEK]

I just want a button called "I am an adult" that lets me turn off traction and stability control.

While I agree, I suspect the drive units don’t have enough capacity to maintain long term reliability with the huge shock loading you can get with big wheel slip.

I think if you unplug a wheel sensor you effectively totally disable traction and stability. Presumably you’d loose the pseudo LSD. And the tuning appears to leave quite a lot to be desired without these systems. The axles have the wrong amount of power and you can’t do anything about it at this time. But if they had a distribution slider AND an ‘I’m an adult’ button, I’d buy it. This probably won’t happen though. I suspect for the overwhelming majority of people buying a 3, it’s the most powerful car they ever drove. Too many would end up in trees and living rooms.

 

[EV-by-the-Sea]

For whatever reason, the car never puts down max power from a stop or from very low speed, irrespective of traction. You could put on drag tires and get the same effect. This is why even a Leaf feels punchier off a stop… at least until you get to 15mph or so.

Part of me wonders (pure speculation) if it's self preservation intended to reduce stress on the axles.

 

[run-the-joules]

Maybe this is interesting, maybe it's not:

From my LR RWD, captured at 240fps. I believe this was before the supposed 5% power increase.

I'll try it again with a full charge and suction cup the gopro to the ceiling to get a nice stable video. You know, for science.

 

[run-the-joules]

The axles have the wrong amount of power and you can’t do anything about it at this time. But if they had a distribution slider AND an ‘I’m an adult’ button, I’d buy it. This probably won’t happen though. I suspect for the overwhelming majority of people buying a 3, it’s the most powerful car they ever drove. Too many would end up in trees and living rooms.

I've only got one motor, so I don't have to worry too much about distribution and yeah, for a lot of people this car is a huge step up in performance. It's quicker than my last one, but not by a huge margin. Much, much slower than my sportbike, though…

 

[AlanSubie4Life]

Maybe this is interesting, maybe it's not:

From my LR RWD, captured at 240fps. I believe this was before the supposed 5% power increase.

I'll try it again with a full charge and suction cup the gopro to the ceiling to get a nice stable video. You know, for science.

Good to see. Looks like the display is logarithmic or something similar. Which makes quite a bit of sense since you want to be able to see small power fluctuations for optimizing your driving, but when you're consuming 200kW vs. 300kW, who really cares...