At launch the P85D and 85D Model S initially had a maximum speed of 130 miles per hour. That limit was set by the car’s electronics, not by any physical limitations. In an update to the car’s online spec sheet, Tesla now says a free upgrade available “in the coming months” will raise the P85D’s top speed to 155 mph.
Tesla has also updated driving range of the Model S family. The company has released some new charts that show off the Model S’s capabilities.
A comparison of all Model S variants based on EPA 5-cycle range is as follows:
|Variant||EPA 5-cycle Range2|
|P85+, P85, 85||265|
1 – Values for 85D and P85D are pending final confirmation from the EPA and use new dual motor torque sleep control software available by the end of January 2015.
2 – In the table above all vehicles, including the P85+, are using 19″ tires. See the paragraph below about performance tires below to understand their impact on range.
|Variant||65 mph Range1|
|75 mph Range1|
|P85+, P85, 85||285||242|
1 – All vehicles in the table above are using 19″ tires.
2 – Using new torque sleep control software available end of January 2015.
The physics of aerodynamics affects all moving vehicles (gasoline or electric) the same: reducing efficiency and range at higher speeds. This effect is more pronounced at higher speeds since the drag force of the wind on the vehicle increases with the square of the velocity, from 35 to 70 mph it doesn’t just double but goes up by four times!
Despite this aerodynamic challenge, highway cruising is where the unique benefit of the dual motor cars, to torque sleep one of the drive units when not in use, is most apparent. Much like a modern computer that can actually sleep in between keystrokes, the dual motor Model S will quickly torque sleep a drive unit when torque is not needed and instantly wake it up as the accelerator is pressed to command more torque. It continues spinning while asleep and the digital torque wake up is so fast that the driver can’t perceive it. It is far superior to the slow and awkward engine startup on stop-start hybrid vehicles.
The software update to implement torque sleep will be downloaded to the dual motor fleet by the end of January 2015 and will substantially improve the range of dual motor vehicles by roughly 10%.
Performance Tires and Wheels
With tires and wheels there are some physics tradeoffs between handling, traction and efficiency (rolling resistance and aerodynamic drag.) At the most intuitive level, as a tire becomes more sticky it will corner and accelerate better but also have modestly higher rolling resistance. Customers can make decisions on tires and wheels independently across all variants of the Model S. Of course these decisions are also often changed throughout the life of the car (summer vs. winter tires for example.)
The 19″ Cyclone wheel and tire that we offer on most of our vehicles is the best configuration for range, efficiency and cost effectiveness. The 21″ wheel/tire upgrade yields substantially improved handling performance and vehicle dynamics. The 21″ performance tires are a more commonly selected option on our performance variants (P85, P85D and formerly P85+) since many of these performance-oriented customers want the best possible handling. There is however roughly a 3% reduction in EPA 5-cycle range (compared to the values presented in the table above) for the selection of 21″ performance tires to any of the Model S variants. For customers who care about handling and performance driving this is a tradeoff that we think is well worth it. For customers who are focused on range, efficiency and best value the 19″ wheels can be configured onto any Model S variant to achieve the values in the EPA table above.
As an example calculation, if a standard Model S 85 with 19″ tires having 265 miles of range is changed to 21″ tires the range would be reduced by ~3% to about 257 miles. This is the range that most customers of the former P85+ configuration experience since nearly all of those variants are configured with 21″ tires.
It is also worth noting that all new tires have a break in period for the first ~1,000 miles where the total vehicle efficiency is reduced by up to 5%. This can surprise (negatively) new owners or customers who have just changed their tires but will quickly improve back to a normal baseline.
Range vs. Speed
The best way to see a more complete picture of this is actually in a graph of what range is possible versus driving speed.
And if we look in even more detail at the differences just between the 85kWh battery pack variants you can see the interesting complexity in how the dual motor operates. At some speeds the P85D is more efficient than the base 85 and equivalent to the 85D. At other, higher speeds the 85D and 85 are slightly more efficient, with higher range, than the P85D.
Which battery, drivetrain and tire configuration is best for you will depend on what kind of driving you enjoy most.