About time to unveil the D and something else

[dhanson865]

My DS told me that the motor spin backwards during regen. I didn't have the heart to correct him. In retrospect, I should have so he stops spread false info. I guess there's not much harm in him telling that theory.

motor spinning backwards is the simplest correctish explanation. It is applying torque in the reverse direction compared to travel. Explaining torque to the average joe is a waste of time so I'm OK with him saying it that way. On the Prius MG1 and MG2 can both spin forwards or backwards. I don't know the commonness of negative RPMs on the Tesla but it isn't impossible.

- - - Updated - - -

Not sure if this was directed at me but I was certainly not trying to pontificate. I simply misunderstood how the regen works on the model S and I assumed it was using the same electromechanical system I've seen on other cars (and perhaps even on the D). I apologize if I added to the confusion rather than clearing it up.

What we are trying to tell you is that regen on the Model S is no different than regen on any other car and you misunderstood how regen in general works.

Nothing about the D or the S changes how regen works in terms of the electric motor vs the friction brakes and no other car, not a Nissan Leaf, Toyota Prius, nor any other production car you can name does regen differently.

 

[brianman]

Not sure if this was directed at me but I was certainly not trying to pontificate. I simply misunderstood how the regen works on the model S and I thought it was using the same electromechanical system I've seen on other cars (and perhaps even on the D). I apologize if I added to the confusion rather than clearing it up.

No worries, hans. It didn't come across as pontificating to me, FWIW.

 

[hans]

motor spinning backwards is the simplest correctish explination. It is applying torque in the reverse direction compared to travel. Explaining torque to the average joe is a waste of time so I'm OK with him saying it that way.

- - - Updated - - -



What we are trying to tell you is that regen on the Model S is no different than regen on any other car and you misunderstood how regen in general works.

Nothing about the D or the S changes how regen works in terms of the electric motor vs the friction brakes and no other car, not a Nissan Leaf, Toyota Prius, nor any other production car you can name does regen differently.

My (miss)understanding of regen comes from watching a YouTube video where they added regenerative brakes onto an existing car (think it was an mini cooper but I'll try and track down the video). I didn't realize that these parts were not OEM parts from some other car. They must have come from somewhere? Are there not ANY production cars with electromechanical brakes? Will the D be the first with this setup?

 

[dhanson865]

My (miss)understanding of regen comes from watching a YouTube video where they added regenerative brakes onto an existing car (think it was an mini cooper but I'll try and track down the video). I didn't realize that these parts were not OEM parts from some other car. They must have come from somewhere? Are there not ANY production cars with electromechanical brakes? Will the D be the first with this setup?

The brakes on the D have nothing to do with regen.

Imagine a doorbell with a pull cord vs a doorbell with electrical wiring and a button. That is the difference between traditional brakes and what is coming on the D. It doesn't change what it does, it just changes the type of cable that is run between the controller and the pads. (yeah they'll have to change the actuators and stuff but in simplest terms we are just talking about moving from physical control to electrical "fly by wire" style control).

Now if you are talking about some video where someone added 4 motors to a traditional car to add regen braking then yeah, no such system exists on any production car.

Wheel hub motor - Wikipedia, the free encyclopedia lists some that have been toying with the idea but it's impracticle and if Tesla isn't doing it you can bet it isn't worth doing.

Unsprung weight concerns The major disadvantage of wheel hub motors are that the weight of the electric motors would increase the unsprung weight, which adversely affects handling and ride (the wheels are more sluggish in responding to road conditions, especially fast motions over bumps, and transmit the bumps to the chassis instead of absorbing them).

as to where they got the parts the motors from any source can be strapped to a car, the hard part is redoing the braking system and controls to play nice with the new hardware. Any engineering team can pick a off the shelf motor and strap it to a wheel. Electrical motors of that size aren't hard to find.

 

[tomas]

The brakes on the D have nothing to do with regen.

Imagine a doorbell with a pull cord vs a doorbell with electrical wiring. That is the difference between traditional brakes and what is coming on the D. It doesn't change what it does, it just changes the type of cable that is run between the controller and the pads. (yeah they'll have to change the actuators and stuff but in simplest terms we are just talking about moving from physical control to electrical "fly by wire" style control).

Exactly. And, let me add, a reason for the change to "fly by wire" is so that auto-pilot can intervene and brake (and steer) for you. If steering and braking remained mechanical, that would not be possible.
But.... ONCE AND FOR ALL... the brakes do not do the regen on the MS, the D, or any other car. Hans, if you can locate that youtube, send a link... doubt they retrofit regen via brakes, but if they did it is a goofy-assed, home brewed approach IMHO.

 

[ggr]

Does anyone know if the AWD in the D model S is active all the time? The only experience I have with AWD is from a Honda CRV and there was no driver manipulation at all. The car decided when you needed the AWD and turned it on and off accordingly.

By design, it's always active, but the load split shifts automatically between front and back. So you can imagine a situation where one pair of wheels is not actually providing any power, but that doesn't mean it is "not active". Since it INCREASES efficiency, there is never a reason to disable it.

 

[JRP3]

PML Flightlink fitted wheel motors to a Mini Cooper. Those motors are capable of regen, like most electric motors. That may be where Hans is getting confused.

 

[hans]

PML Flightlink fitted wheel motors to a Mini Cooper. Those motors are capable of regen, like most electric motors. That may be where Hans is getting confused.

Thanks guys for politely setting me straight. I try hard not to pass on bad information but I was clearly completely off on this topic and I failed.

 

[Shumdit]

I can't believe they're pushing the 21"s on us again. Just like the Sigs... And no, wider tires does not increase grip (discussed a thousand times) - it's 98% looks and 2% curve taking.

I think you mean larger wheels. Wider tires do increase grip.

 

[jerry33]

I think you mean larger wheels. Wider tires do increase grip.

Only laterally at the expense of forward/reverse traction. The total grip of the tire remains the same. (assumes all else is equal, which it almost never is)

 

[woof]

Exactly. And, let me add, a reason for the change to "fly by wire" is so that auto-pilot can intervene and brake (and steer) for you. If steering and braking remained mechanical, that would not be possible.

My BMW i3 can steer and brake by itself. The steering is electric assist but the brakes are standard hydraulics. So it is possible!

 

[tomas]

My BMW i3 can steer and brake by itself. The steering is electric assist but the brakes are standard hydraulics. So it is possible!

Brakes may be hydraulic but is pedal electronic or mechanical link to brakes??

 

[Johan]

I think you mean larger wheels. Wider tires do increase grip.

No. Same contact patch, different geometry.

 

[JST]

I know certain generations of the E class used electromechanical brakes, and they were widely hated in the reviews for lacking feel. Does anyone else use them?

 

[Doug_G]

No. Same contact patch, different geometry.

Wider tires help with cornering... but only if you're close to the limit of grip. In other words, for most cars it won't matter much unless you're driving on a race track.

 

[TEG]

I think you mean larger wheels. Wider tires do increase grip.

Debated. Probably depends on a lot of things like vehicle weight, tire compound, tread pattern, air pressure, road conditions, etc.

• You Thought You Knew - Tire Contact Patches - Road & Track
• Discussion: Wider tires=better traction, true or false?
• Eng-Tips: Automotive tire/wheel engineering - wider is better? or not? size of contact patch arguement
• Fact or Fiction? Tire contact patch and air pressure.

I would think that narrow tires act more knife-like and could cut through things like snow to get to the road surface better.


Dragsters are all about straight line acceleration, and don't care about cornering. They end up with relatively narrow tires (but ultra soft/squishy to maximize contact patch area).

Road race cars are more optimized for road holding in corners (lateral Gs), so tend to go with wide tires.

 

[Johan]

Thanks for adding a lot of "color" (as the analysts like to say) TEG. Empirical data from a lot of TMC members suggest better 0-60 mph times with 19" wheels than with 21" wheels. Go figure.

 

[Gear]

Thanks guys for politely setting me straight. I try hard not to pass on bad information but I was clearly completely off on this topic and I failed.

FWIW, before I got my MS I used to think regen was as you described. I seem to remember reading somebody saying the regen on the Prius worked the way you describe (when the Prius was new), but that was probably just somebody confused by part of the regen being mixed into the brake pedal. No harm, no foul.

 

[Yggdrasill]

There's always a learning curve.

Looking back to 2008, I had just finished college and was looking at buying my first car. My older brother told me about the Prius, and how it was a hybrid using both battery power and a gas engine to propel the car. Regenerative braking wasn't even a concept I was aware of, my rudimentry understanding of the "hybrid" concept was that you could charge it off the grid to assist the gas engine. When he told me it didn't plug in, I was like: "Well, then what's the point?", and I remember being very disppointed in that that was all there was to it. It's funny to think about how much I've learned since then.

 

[jweinstein]

Forgive me if the question has been asked/answered already, but is an LTE connection going to be on the newly announced models? Thanks!