So with our clearly statistically significant data set we can say with complete confidence that the Tesla Model S limiter is +3 mph relative to the advertised max speed.
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The real top speed of the Model S
- Thread starter TheAustin
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L@urens
Family, Racing, Karting, MTBing
Old thread, but found it interesting to look at range at (or near) top speed.
A German test shows that even when going 'flat out', normal traffic patterns will slow you down and you will not get below 125mi/200km range.
I've extended the line in the graph below, and at constant 120mph (193kmh) you should have a range of about 125 miles or 200km:
A German test shows that even when going 'flat out', normal traffic patterns will slow you down and you will not get below 125mi/200km range.
I've extended the line in the graph below, and at constant 120mph (193kmh) you should have a range of about 125 miles or 200km:
LuckyLuke
Model S P90DL
mnx
2018 M3P
Assuming drag grows with the square of speed and using the 80 mph point to calibrate creates the table below. This suggests that purely based on power the top speed would be 241 mph.
| Speed mph | Time h | Range mph | Power kW |
| 35 | 12.0 | 420 | 7 |
| 55 | 5.3 | 291 | 16 |
| 80 | 2.5 | 200 | 34 |
| 130 | 0.9 | 123 | 90 |
| 150 | 0.7 | 107 | 120 |
| 241 | 0.3 | 66 | 310 |
Clprenz
Member
My hopes: Saleen can improve cooling on motor. Also I think they could put some kind of two speed gear box, kick in at 90 mph or something.
Top speed: 175 mph
Top speed: 175 mph
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
It really was not about the torque, it was about incompetency.
Those magna and xtrac transmission "experts" were little more than techicians jugling gears i.e. adapting existing gearbox designs.
EV gearbox represents whole new can of worms and as such demands a much deeper engineering understanding than what was available to tesla around 2005.
A 2speed gearbox done right could still prove mighty beneficial. It is a must in a vehicle with some official towing capabilities.
I really can't see why a 2speed dual-clucth transmission could not work? Al gears always engaged, to change gear on clutch opens and the other closes. Use multi-plate clutch to smoothen transitions and voila.
Gearbox they were trying to use in roadster was a 'traditional' robotized manual transmison. Those meshgears just weren't up to the task.
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Johan
Ex got M3 in the divorce, waiting for EU Model Y!
OK good input! How about some form of CVT (continous varible transmission) like those Audi, Lexus and Honda have in some prouction cars? The Lexus Rx450h has that I think.
CVT would/could also work but they relatively suck from efficiency point of view.
It's usefulnes comes from alowing ICE to stay close to optimal RPM. What is lost in CVT is more than compensated by ICE being a bit more efficient.
Electric motor has much wider "optimal" RPM range hence much less profit from holding its RPM almost unchanged.
Dual speed transmission would be a bit less efficient than a reduction gearbox because of some additional always rotating parts (gears, clutches, bearings) but if it would allow electric motor to spin faster at lower speeds (same power at higer RPM means lower current and hence lower heatlosses) and also lower RPM at higer speeds - it would enable higher output power at speeds above ~80 mph.
Look at power/speed diagram:
MSP can output its maximum power between 42 mph and 72 mph, a 30 mph wide "max power window". Below 42 and over 72mph its max power (and efficiency!) drops.
A dual speed version could double the width of this "maximum power window" from 30 to 60mph - say from 27 mph to 87 mph.
Now when you go faster than ~72 mph, motor efficiency drops. With a dual gear setup it would retain maximum efficiency up to 87mph.
Now when you go slower than ~42 mph, the motor does not work optimaly. With a dualratio transmision it would work optimaly already at 27 mph.
I would not be shocked if future models "reintroduce" multiple ratio gearbox. Adequately engineered of couse.
Audi's CVT is a "real" CVT - it has one input and one output shaft, with a mechanism (belt) to transfer/multiply torque between them in "infinite" number of different ratios or steps. This could work in a EV but because of poor efficiency don't hold your breath
CVT in Lexus / Prius / Volt / hybrids has two inputs and one output - it is basicaly a torque summation device. It needs two indepentant motors to work and is as such unusable in a "single motor EV".
It's usefulnes comes from alowing ICE to stay close to optimal RPM. What is lost in CVT is more than compensated by ICE being a bit more efficient.
Electric motor has much wider "optimal" RPM range hence much less profit from holding its RPM almost unchanged.
Dual speed transmission would be a bit less efficient than a reduction gearbox because of some additional always rotating parts (gears, clutches, bearings) but if it would allow electric motor to spin faster at lower speeds (same power at higer RPM means lower current and hence lower heatlosses) and also lower RPM at higer speeds - it would enable higher output power at speeds above ~80 mph.
Look at power/speed diagram:
MSP can output its maximum power between 42 mph and 72 mph, a 30 mph wide "max power window". Below 42 and over 72mph its max power (and efficiency!) drops.
A dual speed version could double the width of this "maximum power window" from 30 to 60mph - say from 27 mph to 87 mph.
Now when you go faster than ~72 mph, motor efficiency drops. With a dual gear setup it would retain maximum efficiency up to 87mph.
Now when you go slower than ~42 mph, the motor does not work optimaly. With a dualratio transmision it would work optimaly already at 27 mph.
I would not be shocked if future models "reintroduce" multiple ratio gearbox. Adequately engineered of couse.
Lexus / Prius CVT is completely different from a CVT in an Audi.
Audi's CVT is a "real" CVT - it has one input and one output shaft, with a mechanism (belt) to transfer/multiply torque between them in "infinite" number of different ratios or steps. This could work in a EV but because of poor efficiency don't hold your breath
CVT in Lexus / Prius / Volt / hybrids has two inputs and one output - it is basicaly a torque summation device. It needs two indepentant motors to work and is as such unusable in a "single motor EV".
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mnx
2018 M3P
I doubt we'll see a two speed transmission in a Tesla product anytime soon. It's a solution in search of a problem... Sure it might be beneficial for some track driving, but the power limiting kind of makes that a moot point.
Perhaps it could show up as an option on Model E for folks who want to drive over 200km/h on the Autobahn. I'm not convinced it would make sense to do all the necessary R&D for an option that is selected on <10% of orders... (Just a guess).
It would be cool however to have a Tesla product with a higher top speed.
Perhaps it could show up as an option on Model E for folks who want to drive over 200km/h on the Autobahn. I'm not convinced it would make sense to do all the necessary R&D for an option that is selected on <10% of orders... (Just a guess).
It would be cool however to have a Tesla product with a higher top speed.
Tesla already have a solution for this - they have said that the Model X AWD system has different gear ratios for the two motors (primarily to improve efficiency: the claim is that AWD Model X is no less efficient than a RWD Model X would be). Hence most of the advantages of a 2-speed transmission without needing to shift.
Admittedly, they haven't actually said that this will affect the top speed (and it might possibly not if the front motor is the one with the higher ratio and is also smaller).
Admittedly, they haven't actually said that this will affect the top speed (and it might possibly not if the front motor is the one with the higher ratio and is also smaller).
I've made that chart from data Tesla Motors had published - a bit of explanation.
But having only single speed reduction gearbox means Tesla won't have a car with even half-serious towing capability in a car with >100 MPH top speed. Trouble is STARTING torque from stand-still and slow maneuvering - at 5 MPH Model S can only output about 25 kW / 35 HP.
This may sound "enough" but it may not be enough to pull a boat out of water. Forget about towing a trailer over some hilly terrain or expect power limiter to kick in and soon later to 'kill' the power altogether.
Dual motors with different reduction ratios sound as a good compromise. What is necessary though is a mechanical clutch to prevent the "low speed" motor to over-spin and self-destruct at high speed.
Such a mechanical clutch is also already at halfway to dual-speed transmission. Or maybe not because it is not under such tight timings - no problem if it needs a few seconds to engage while vehicle is slowing down.
We have a saying: "One who was bitten by a snake is fearful of a rope". Tesla almost failed because of multi-speed transmission and then came out with a single-speed reduction gearbox that is "good enough" to beat almost everyone around.
But having only single speed reduction gearbox means Tesla won't have a car with even half-serious towing capability in a car with >100 MPH top speed. Trouble is STARTING torque from stand-still and slow maneuvering - at 5 MPH Model S can only output about 25 kW / 35 HP.
This may sound "enough" but it may not be enough to pull a boat out of water. Forget about towing a trailer over some hilly terrain or expect power limiter to kick in and soon later to 'kill' the power altogether.
Dual motors with different reduction ratios sound as a good compromise. What is necessary though is a mechanical clutch to prevent the "low speed" motor to over-spin and self-destruct at high speed.
Such a mechanical clutch is also already at halfway to dual-speed transmission. Or maybe not because it is not under such tight timings - no problem if it needs a few seconds to engage while vehicle is slowing down.
I will correct myself: Such a clutch is only necesary if they where using different reduction ratio and motor with bigger radius (and hence higher torque).
But that is not the only way to go - the simplest way is just use exactly the same motor/inverter in front as they are using in the rear.
Maximum power of MSP is limited by battery power so it wouldn't increase but it would be available already from 21 mph all the way up to ~140 mph (where power drops below 1/2 max power).
Torque (and acceleration!) below 21mph would double - same effect as using dualspeed transmission.
It would improve track "longetivity" as it would double the motor cooling capabilites but only increase average power useage a bit, not double it.
It would seriously improve highspeed performance - put MSP AWD next to or infront of powerful ICE cars on autobahn.
MSP needs about 70kW to sustain 100 mph where maximum output is 220kW. So 'only' 150kW are available to accelerate the car to faster speeds.
Dual motor MSP at 100mph would need same 70kW to sustain the speed but have 240kW available for acceleration - more then half stronger acceleration as MSP.
I'd say this is the lowest hanging and biggest performance fruit for Saleen to pick
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I'm puzzled how you can watch videos where the traction control is having to pull back power through most of the range to avoid massive wheelspin and then think the car might not have enough power to tow with at low speeds. Once you hit the traction limit on the wheels, you can't put more power down, no matter what transmission you have.
The fact is that in most cars/trucks at 5 mph most of the power the engine outputs is being dissipated as heat in the clutch or torque converter, and no one can push more than about 1g through the wheels because of traction limits - and Tesla is already there.
There are some efficiency and top speed concerns, but there's no reason to question whether Tesla has enough low end grunt in the existing design to handle any rational need, including towing - at least until they start power limiting from rotor heating (which still shouldn't be a factor down here I'd think, but appears to be their biggest challenge from what I've read.)
Walter
Tesla Model S officialy does not have any towing capability - towing not allowed. It is not limited by max power/torque but with motor cooling i.e. average power/torque.
MS60's and MS85's 'propulsion force' in the 'constant torque' speed zone is around 2,680 pounds (MSP 3,660 pouds).
Normaly loaded MS85 weighs ~5000 pounds, so that 'propulsion force' suffices to move the car up 32 degree incline or accelerate at maximum 0,54g (MSP at max 0,72g).
But one cannot drive using all that power for more than a few seconds - car accelerates to some high speed where driver needs to step off.
Towing a trailer is whole another story. What if you needed to drive up a steep curvy road at speeds up to 20 mph towing a 1000 pound trailer? And stop a few times in the middle of the hill and start again?
ICE cars have built in 'fail safe' - if the (starting) load is to big they simply stall and no real harm done. Electric motor would also stall but it does not have automatic 'poweroff' - it just mimics short circut - where all power goes into heating. Computer detects this and shuts off the current.
Two motors would have twice as much 'breating room' as a single motor. Really enough for towing loads? Hard to say but better than a single motor nontheless.
There's lots of reasons Tesla might put "no towing" on the Model S, several of which I consider far more likely than the powertrain. (liability, structure, braking, handling, lack of demand.)
I think your torque delivered numbers are low and your weight is high - but all are in the ballpark +/-10%. So clearly there's no problem with Tesla managing the short term surge loading. Rotor heating is certainly a valid concern - I'm not sure any of us have a good feel for how limiting it will be. It seems like the folks who are hitting the limits hot-lapping are still able to manage over 100kW more or less continuously - but that's just my impression from the videos, with no math to support it.
A series DC motor might dump the whole load as heat, but I'm pretty sure any modern AC motor is better than that. It'll stall, yes, and dissipate what energy goes in as heat. But it won't be hundreds of kW being dumped. The full static torque can be put on the motor with just a couple dozen kW - well below what is getting dumped as heat in the other conditions described and not something to worry about IMO. My Volt stops at 3 kW when brake torqued at 0 RPM - with over 60% of max torque on the axle (torque softening to protect the driveline at 0 rpm prevents 100% axle torque.)
Walter
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