Non-performance AWD acceleration

[RSL2020]

I have had my non-P AWD for 6 weeks now. One pattern I have noticed - under full throttle acceleration from anywhere in the 0-15 MPH range the car accelerates hard until about 40 MPH then has a bit of a torque dial back from 40-60MPH.

But, if I accelerate from the 30-40 MPH range the car screams like a banshee to whatever speed I let off.

Of course I have formulated my own hypothesis as to why this may be happening. I wonder if maybe, just maybe Tesla has placed a software mechanism of slowing the car to the advertised 0-60 time of 4.5 sec. So anytime thinks it is in a full throttle 0-60 run (where it may be timed) it kicks in a software nanny to limit torque.

Once the car is above the 20-30 MPH threshold then there is no advertised specifications to meet, thus it goes like heck.

Anyone else experiencing this?

 

[1.21GW]

Its a result of the torque curve of the electric motor. Constant torque from 0 rpm up to a certain speed, then it begins to taper off

 

[RSL2020]

Available torque should be the same in both the stated scenarios, which it isn't. I'm just fishing to see if others have similar experiences. If not, then its off the the SC.

 

[Daniel in SD]

Available torque should be the same in both the stated scenarios, which it isn't. I'm just fishing to see if others have similar experiences. If not, then its off the the SC.

I think it's a psychological phenomenon. I guess I should check with my Vbox but I'm pretty sure it's the same no matter what speed you start from.

 

[bd7349]

I think it's a psychological phenomenon. I guess I should check with my Vbox but I'm pretty sure it's the same no matter what speed you start from.

Interested to see what your Vbox shows in both scenarios.

 

[coleAK]

I think areodynamics also be having a greater impact? The faster you go the greater force the the air pushes you back

 

[Daniel in SD]

I think areodynamics also be having a greater impact? The faster you go the greater force the the air pushes you back

Aerodynamics don't do anything at legal speeds. It takes less than 15kW to maintain 60mph. The motors are more than 300kW total.

 

[coleAK]

Have you done the math to see that 15 kw can maintain 60mph? If so Under what conditions?

The drag is a function of velocity^2 so the graph is a upward curve not a line. So the faster you go the more effect it has. Calculating the drag in N (using 1.2 as air density and 0.23 as Cd and 2.6 m^2 as front SA) as a function of mph I get: 0 mph=0N 20mph=30N 40mph=108N 60mph=269N 80mph=459N 100mpg = 760N So somwhere in that 50-60-70 mph economy goes way down, that was the basis of the national speed limit of 55 mph in the 1980’s. Given the extremely low Cd of the model 3 the aerodynamic “wall” is somewhat higher.

efficiency and external forces are the same using gas or electric. In my LX 570 (Cd 0.35 ) I get ~20 mpg going 60 mpg and 18 mpg going 70 mph (10% reduction) This gets exacerbated when Pulling my camper (Cd ~0.7 and double the SA) due to the fact I’m essentially pulling a wall down the road. Going 60mph I get 10 mpg going 65 mpg I get 8 mpg a 20% reduction

Just doing very basic math (not the integrals) and making some liniar assumptions the listed 0-60 mph in 4.5 sec = that’s an average acceleration of 5.9 m/s^2 so for a 1800 kg car having a 269N force acting against it isn’t all that much but the drag force will significantly increase from there. double the speed to 120mph and it’s 910N. And none of this takes into considerstion any other external forces.

Also the best source I can find for the hp of the non perf AWD is 271 hp that is more like 200 kw than 300 kw.

 

[Daniel in SD]

Have you done the math to see that 15 kw can maintain 60mph? If so Under what conditions?

The drag is a function of velocity^2 so the graph is a upward curve not a line. So the faster you go the more effect it has. Calculating the drag in N (using 1.2 as air density and 0.23 as Cd and 2.6 m^2 as front SA) as a function of mph I get: 0 mph=0N 20mph=30N 40mph=108N 60mph=269N 80mph=459N 100mpg = 760N So somwhere in that 50-60-70 mph economy goes way down, that was the basis of the national speed limit of 55 mph in the 1980’s. Given the extremely low Cd of the model 3 the aerodynamic “wall” is somewhat higher.

efficiency and external forces are the same using gas or electric. In my LX 570 (Cd 0.35 ) I get ~20 mpg going 60 mpg and 18 mpg going 70 mph (10% reduction) This gets exacerbated when Pulling my camper (Cd ~0.7 and double the SA) due to the fact I’m essentially pulling a wall down the road. Going 60mph I get 10 mpg going 65 mpg I get 8 mpg a 20% reduction

Just doing very basic math (not the integrals) and making some liniar assumptions the listed 0-60 mph in 4.5 sec = that’s an average acceleration of 5.9 m/s^2 so for a 1800 kg car having a 269N force acting against it isn’t all that much but the drag force will significantly increase from there. double the speed to 120mph and it’s 910N. And none of this takes into considerstion any other external forces.

Also the best source I can find for the hp of the non perf AWD is 271 hp that is more like 200 kw than 300 kw.

Battery is about 75kwh. 300 miles at 60mph is 5 hrs. 75kwh/5hr=15kw. In reality you can go quite a bit farther than 300 miles at 60mph and much of the loss is not aerodynamic so it’s much less than 15kw.

 

[coleAK]

Battery is about 75kwh. 300 miles at 60mph is 5 hrs. 75kwh/5hr=15kw. In reality you can go quite a bit farther than 300 miles at 60mph and much of the loss is not aerodynamic so it’s much less than 15kw.

That is taking simplifying to the extreme. Using watts and time may work when calculating power consumption on something simple and fixed like a lightbulb but for something as complex as a Tesla is not close. Where do you get that the range is 300 miles traveling st 60 mph? I would be willing to bet at 60 mph in the real world you would get <300 miles. Basically making the assumption that you will be towed to 60mph then released, traveling in a straight line, fixed temperature, on a perfectly smooth dry road and in a vacuum or you are going to run the car on rollers.

 

[ulrichw]

That is taking simplifying to the extreme. Using watts and time may work when calculating power consumption on something simple and fixed like a lightbulb but for something as complex as a Tesla is not close. Where do you get that the range is 300 miles traveling st 60 mph? I would be willing to bet at 60 mph in the real world you would get <300 miles. Basically making the assumption that you will be towed to 60mph then released, traveling in a straight line, fixed temperature, on a perfectly smooth dry road and in a vacuum or you are going to run the car on rollers.

I think you lost track of the original argument: The point was to determine how much power the car is "robbed" of at 60 mph, and Daniel's arithmetic is quite appropriate for that (0-60 tests should be done level, no wind in a straight line).

FWIW, there's various corroborating information, too: The EPA model for the model 3 AWD (i.e., the model that was used to generate the EPA range ratings) suggests that the total drag (including static, linear and square drag - i.e., rolling resistance, wind resistance, and various internal friction) amounts to 98.78 lbs. force at 60mph. That translates to 11.8 kW.

I'd also be more than happy to take up your bet. At 60 mph I'm guessing you'll be significantly over the EPA rating. (I'm averaging 237 wH/mi on a mixed freeway/city street commute with cruise speeds in the high 60s to low 70s on the freeway and significant hills (about 1700 feet of undulations in a round trip)).

 

[coleAK]

Sorry I was just trying to make the point to the original question that there are many factors that would contribute to the perceived torque dial back. Thinking about it software is probably one of the larger factors. We all know that the engines and batteries are the same bemetween AWD and performance. I can’t imagine the differential gearing is different or any electric resistance is different so there has to be a software limiter that is governing it. It would be interesting to run a performance vs an AWD and see if they are close until that ~40mph point. Honistly I have only driven the car not on “chill” mode for 2 days and those 2 days I had new studded tires on so have a traction disadvantage unti late May’ish

Ok so I haven’t figured this out. Is there a Menu to see wh/mi?

 

[AlanSubie4Life]

Ok so I haven’t figured this out. Is there a Menu to see wh/mi?

This is approximate, it's probably not exactly correct, but should help you:
Left hand "quick access window" on the display, bottom section, sweep left or right (there are three different pages I think) to bring up the page with the lightning bolt (I think), click the lightning bolt, odometer shows up, then scroll to see the various odometers. By default it seems to show your efficiency since the start of your drive, but other trip meters are available through scrolling. They can be renamed as well (I've labeled one "Lifetime" as others have, and hopefully no one will reset it...).

 

[coleAK]

This is approximate, it's probably not exactly correct, but should help you:
Left hand "quick access window" on the display, bottom section, sweep left or right (there are three different pages I think) to bring up the page with the lightning bolt (I think), click the lightning bolt, odometer shows up, then scroll to see the various odometers. By default it seems to show your efficiency since the start of your drive, but other trip meters are available through scrolling. They can be renamed as well (I've labeled one "Lifetime" as others have, and hopefully no one will reset it...).

Thanks! Found it. Now I can understand more about cold weather consumption.

 

[AlanSubie4Life]

Thanks! Found it. Now I can understand more about cold weather consumption.

You're welcome. To correct my instructions above now that I checked how it actually works...:

Left hand "quick access window" on the display, bottom section, swipe to bring up the left-most page (there are three different pages), the page with an odometer, then scroll up/down to see the various odometers. By default the odometer seems to show your efficiency since the start of your drive, but other trip meters are available through scrolling. They can be renamed as well (I've labeled one "Lifetime" as others have, and hopefully no one will reset it...).

The lightning bolt was for charging settings, it's a different page and not relevant here.