Official Tesla Model S thread

[abasile]

I cancelled my Tesla S order the other day, since they refuse to make my 60D.

Out of curiosity, in Florida, why do you care about AWD? No criticism intended - I'm just wondering!

 

[keydiver]

Several reasons:
1) Performance. Yeah, I know, only 0.2 seconds 0-60 improvement, but I have had a couple of very fast AWD cars before, and I really like how well they will launch, no matter what the road conditions are. With so much torque on tap, that is the one I miss on the Leaf. If I take off too fast in the rain the tires slip, the traction control kicks in, and the car stumbles on takeoff.
2) I expect a better resale value. The $4000 upcharge they quoted for a D was a good value, IMO.
3) Improvement in range. Yeah, again, its very minor, but with a 60 kWh pack it might help.

 

[apvbguy]

I cancelled my Tesla S order the other day, since they refuse to make my 60D.

Out of curiosity, in Florida, why do you care about AWD? No criticism intended - I'm just wondering!

there's a lot more to the D upgrade than AWD
IMHO passing on the car because he cannot have a 60 is a bit foolish, but it's not my call

 

[abasile]

Yes, the 'D' does seem quite compelling! Those of us who want to buy used, and also want the 'D', will have to wait. Of course, rather than "used", an inventory/loaner car might make more sense.

 

[donald]

3) Improvement in range. Yeah, again, its very minor, but with a 60 kWh pack it might help.

It dawned on me yesterday why the Tesla would be more efficient with more motors, that other EVs wouldn't.

Because it runs induction motors, the torque output is proportional to the 'slip' of the magnetic field to the rotor, but also the efficiency is a function of slip.

So if you have two induction motors you need less torque in each, thus less slip, thus more efficiency. It'd only be small, but perhaps that's where the gain comes from.

Wouldn't work for any other EVs, as Tesla is the only VM using 1880's motor technology (most others taking advantage of new stuff learned in the subsequent century! :twisted: )

 

[lorenfb]

3) Improvement in range. Yeah, again, its very minor, but with a 60 kWh pack it might help.

It dawned on me yesterday why the Tesla would be more efficient with more motors, that other EVs wouldn't.

Because it runs induction motors, the torque output is proportional to the 'slip' of the magnetic field to the rotor, but also the efficiency is a function of slip.

So if you have two induction motors you need less torque in each, thus less slip, thus more efficiency. It'd only be small, but perhaps that's where the gain comes from.

Wouldn't work for any other EVs, as Tesla is the only VM using 1880's motor technology (most others taking advantage of new stuff learned in the subsequent century! :twisted: )

Under normal driving conditions, i.e. very low load, the slip is low so the gain in efficiency by having two
motors is negligible. Most likely the gain (small) occurs at very high motor load conditions. Haven't seen
a published range increase from Tesla.

 

[donald]

Under normal driving conditions, i.e. very low load, the slip is low

Isn't that a bit like saying a 1 litre engine and a 5 litre engine both use little fuel at light loads, so their fuel economies won't be that different?

Slip's proportional to torque. Halve the torque, halve the slip.

 

[garsh]

It dawned on me yesterday why the Tesla would be more efficient with more motors, that other EVs wouldn't.

I think there are two simpler explanations.

The front motor reduction gear is probably sized for efficient highway cruising instead of low-end acceleration. Tesla probably switches to using mainly that motor during steady-speed highway driving.

If Tesla has started to incorporate regen into braking (my understanding was that they don't, unlike the Leaf), then with a motor in the front, they can allow stronger regen with the weight shifting to the front. Otherwise, hard braking unloads the rear wheels, and would cause skidding.

 

[muus]

If Tesla has started to incorporate regen into braking (my understanding was that they don't, unlike the Leaf), then with a motor in the front, they can allow stronger regen with the weight shifting to the front. Otherwise, hard braking unloads the rear wheels, and would cause skidding.

Are you kidding? Tesla always had very strong regen which enables one pedal driving (unless you choose to reduce it in the settings). The brake light will even go on automatically when quickly decelerating due to the strong regen. However having a motor up front will enable even more powerful regen and less wear on the rear tires.

 

[donald]

Just to point out, you have confused the two quoters their. I didn't say that.

I don't think it would make any different to homologation figures because the car is not pushed through such harsh regen braking events to get anywhere near that sort of scenario.

However, I would not necessarily discount that as making a, albeit very small, contribution to real efficiency because although the regen is strong it is still limited and is probably already pushing the tyre into slip. Any reduction on the friction demand on the tyre/road interaction will aid efficiency - both for drive and regen.

 

[lorenfb]

Under normal driving conditions, i.e. very low load, the slip is low

Isn't that a bit like saying a 1 litre engine and a 5 litre engine both use little fuel at light loads, so their fuel economies won't be that different?

Slip's proportional to torque. Halve the torque, halve the slip.

The point is that the majority of driving, i.e. energy consumption, occurs under a light load anyway
so adding another motor to reduce the load further on the single motor results in a very minimal
increase in efficiency. Again, where are the actual efficiency improvement numbers and under what
conditions were they observed.

 

[garsh]

Are you kidding? Tesla always had very strong regen

Not what I said. The brake pedal in a Model S does not add additional regen on top of what you get from just letting off the acceleration, IIRC. The brake pedal only operates the friction brakes. This is different from the Nissan Leaf, where the car will use additional regen when the brake pedal is pressed.

I'm guessing that part of the reason they designed it this way is because having really strong regen on the rear wheels would lighten the weight too much on the rear, causing the rear tires to start skidding.

 

[donald]

The point is that the majority of driving...

The figures provided are from fixed driving cycles are they not(?), which usually have plenty accels and decels.

 

[GRA]

Under normal driving conditions, i.e. very low load, the slip is low

Isn't that a bit like saying a 1 litre engine and a 5 litre engine both use little fuel at light loads, so their fuel economies won't be that different?

Slip's proportional to torque. Halve the torque, halve the slip.

The point is that the majority of driving, i.e. energy consumption, occurs under a light load anyway
so adding another motor to reduce the load further on the single motor results in a very minimal
increase in efficiency. Again, where are the actual efficiency improvement numbers and under what
conditions were they observed.

From a post on the teslamotors.com forum:

At 65mph range of each model according the Canadian order page:

S60 214 mi
S85 286 mi
P85 286 mi
S60D 225 mi
S85D 295 mi
P85D 275 mi

 

[lorenfb]

At 65mph range of each model according the Canadian order page:

S60 214 mi
S85 286 mi
P85 286 mi
S60D 225 mi
S85D 295 mi
P85D 275 mi

So just a 3% increase for the MS. As I said, if any gain very minimal.

 

[muus]

The brake pedal in a Model S does not add additional regen on top of what you get from just letting off the acceleration, IIRC. The brake pedal only operates the friction brakes. This is different from the Nissan Leaf, where the car will use additional regen when the brake pedal is pressed.

I'm guessing that part of the reason they designed it this way is because having really strong regen on the rear wheels would lighten the weight too much on the rear, causing the rear tires to start skidding.

Your correct about there being no connection between the brake pedal and regen, but the off pedal regen on a Tesa is much stronger than the maximum regen on the Leaf.

 

[pkulak]

Your correct about there being no connection between the brake pedal and regen, but the off pedal regen on a Tesa is much stronger than the maximum regen on the Leaf.

Like most things Tesla, you can set it to be a weak or strong as you like.

 

[DaveinOlyWA]

I cancelled my Tesla S order the other day, since they refuse to make my 60D.

Out of curiosity, in Florida, why do you care about AWD? No criticism intended - I'm just wondering!

rain

 

[TomT]

Of course, looked at the other way around, we would kill to get a 9 mile increase in range on the Leaf!

So just a 3% increase for the MS. As I said, if any gain very minimal.

 

[lorenfb]

Of course, looked at the other way around, we would kill to get a 9 mile increase in range on the Leaf!

So just a 3% increase for the MS. As I said, if any gain very minimal.

But remember where the problematic losses are:
Power Loss = k1 X W X V + k2 X Cd X A X V^2, where the rolling resistance losses (k1 X W X V)
are a function of W - vehicle weight.

Little of any significance can be done to reduce the drag losses (k2 X Cd X A X V^2), but the MS could
really lose some weight at its present approximate weight of 4600 lbs. Now there's where efficiency
could really be improved. If Elon had announced a significant weight reduction, that would have been
something to 'shout' about.