How much extra would you pay for AWD

[ElSupreme]

- better cornering speed due to power being pushed through all wheels which increases cars stability

This isn't really true. With modern stability control each wheel is braked to allow it to gain traction. With AWD you are using a portion of your grip to drive, and the other portion to turn.

What you do gain with FWD is the ability to 'drag' your rear wheels around and drive directly where your wheels are pointed. Most cars have a front weight bias, so having FWD helps in that you are driving the wheels with more traction.

Really all AWD gets you (assuming good stability control) is more overall traction giving greater acceleration in poor grip situations. That and most AWD will function as FWD giving the 'dragging' dynamic which is beneficial at really slow speeds.

 

[60TTuC]

This isn't really true. With modern stability control each wheel is braked to allow it to gain traction. With AWD you are using a portion of your grip to drive, and the other portion to turn.

What you do gain with FWD is the ability to 'drag' your rear wheels around and drive directly where your wheels are pointed. Most cars have a front weight bias, so having FWD helps in that you are driving the wheels with more traction.

Really all AWD gets you (assuming good stability control) is more overall traction giving greater acceleration in poor grip situations. That and most AWD will function as FWD giving the 'dragging' dynamic which is beneficial at really slow speeds.

I have to disagree. Stability control is more of a safety feature.
Let me quote from Wiki:

Electronic stability control (ESC), also referred to as electronic stability program (ESP) or dynamic stability control (DSC), is a computerized technology [1][2] that improves the safety of a vehicle's stability by detecting and reducing loss of traction (skidding).[3] When ESC detects loss of steering control, it automatically applies the brakes to help "steer" the vehicle where the driver intends to go. Braking is automatically applied to wheels individually, such as the outer front wheel to counter oversteer or the inner rear wheel to counter understeer. Some ESC systems also reduce engine power until control is regained. ESC does not improve a vehicle's cornering performance; instead, it helps to minimize the loss of control.

Remember that many supercars use AWD, main reason being greater cornering speed. Their owners surely don't intend to drive them in snow.

 

[ElSupreme]

I have to disagree. Stability control is more of a safety feature.
Let me quote from Wiki:
...
ESC does not improve a vehicle's cornering performance; instead, it helps to minimize the loss of control.

Well I agree with this an disagree at the same time. ABS doesn't improve your braking either, it just keeps you from locking your brakes. Technically ABS makes braking worse, but functionally it makes it better. Same for stability control. It keeps you just within threshold on tire grip.

AWD (an really just FWD) doesn't help in snow slush above about 5 mph. If your fronts start sledding then powering them won't do anything more than pushing them forward with RWD.

Remember that many supercars use AWD, main reason being greater cornering speed. Their owners surely don't intend to drive them in snow.

This is due to two things; neutral handling in turns (less oversteer/understeer without stability control); but most importantly it is for more grip. A RWD Bugatti Veryon is Tire limited accelerating, heck a AWD Bugatti Veryon is tire limited accelerating. More tires gives more acceleration. This is really the only advantage AWD has versus a good modern stability control. You get 4 tires worth of grip (and in snow/ice/low grip you get 4 chances to get grip on something not slippery). This is why supercars have AWD.

In some race conditions sure AWD will give you advantages (not requiring braking/slowing for stability control). Greater threshold acceleration grip. But FWD and RWD cars also have situational advantages, even over AWD. But in real life driving AWD is just going to get you driving quicker in ice and snow. Stability control is going to give you grip turning, and ABS is going to give you grip stopping.

 

[vfx]

I can't help but think that people who are not interested in AWD have never experienced AWD. Just like we try to explain what it is to drive electric and that ICE drivers could never imagine what it's like, it may be just the same for AWD.

Personally I have never driven an AWD that was not a 4WD for off-roading. What has me pumped about it was a conversation with Peter Rawlings (from Lotus) when he described the amazing advantages of the AWD in the X he was working on, he could barely contain himself. That kind of excitement made me want it!! Now.

Considering how much easier it will be for electric cars to do it, having AWD on all Tesla's cars will be the final blow to ICE domination .

 

[Johan]

I have never understood the desire for 4wd. Reduced driving experience and increased mpg to get up an occational slippery hill?

Ok, but if that slippery hill leads up to your home, your workplace or maybe your kids kindergarden and you have to drive it up at least once a ay all winter with a car full of kids, groceries etc. then you'd think it was worth it! (this is my case).

Also, with an EV it will be an up-front higher cost but not necessarily reduced mpg (reduced range), at least not more than a few percent since the front motor can be quite small and light.

 

[60TTuC]

@ ElSupreme
Basically the way AWD works is that it distributes power between wheels. The way ESP works is by cutting power to the wheel.

Exemples of cars which use AWD and their prowess is cornering speed:
Nissan GT-R
Mitsubishi EVO
Subaru Impreza WRX STI

 

[Raffy.Roma]

I do believe Tesla promised to bring out Model S AWD after the Model X is released.

- - - Updated - - -



With proper winter tires AWD probably doesn't matter much, especially in modern cars with ABS and stability control.

AWD will help you accelerate on a slippery surface. It will NOT help you turn or stop quickly.

The reason people like FWD cars in the snow is the engine weight is over the drive wheels. This isn't an issue for the Tesla because there's plenty of weight over the rear wheels.

AWD is in the "nice to have" category as far as winter driving is concerned. Proper snow tires (not all seasons) are more important.

I don't agree with you. As I told in another thread the ESC with AWD could be "active" meaning that each wheel, in a completely independent way with respect to the other wheels, will be allowed not only to activate the brakes to keep the correct path but also to accelerate. In this way the correct path will be kept much better while turning with respect to normal ESC where the wheels were allowed only to activate the brakes. I like to call ESC with AWD active ESC.
Then the electric engines, having less inertia than ICE, will integrate much better with ESC giving faster answers to the ESC.
This way AWD will help very much ESC to turn the car and keep the correct path.

- - - Updated - - -

I created a poll above. Does this seem like reasonable choices?

AWD 10K
POWER FOLDING MIRRORS PROXIMITY SENSORS 2K
ACC 5K
VENTILATED FRONT SEATS 2K

 

[mikevbf]

As I told in another thread the ESC with AWD could be "active" meaning that each wheel, in a completely independent way with respect to the other wheels, will be allowed not only to activate the brakes to keep the correct path but also to accelerate. In this way the correct path will be kept much better while turning with respect to normal ESC where the wheels were allowed only to activate the brakes. I like to call ESC with AWD active ESC.
Then the electric engines, having less inertia than ICE, will integrate much better with ESC giving faster answers to the ESC.
This way AWD will help very much ESC to turn the car and keep the correct path.

That is a really cool explanation of "active" ESC I have never heard of before, but makes complete sense. Thanks.

Here is a little story to illustrate a couple of points about AWD, ESC, winter tires, and COG. It was the first slushy snow of the winter. I was driving an AWD Hybrid Highlander with all season tires following my wife who was driving a FWD jetta with Studded tires. She headed down a windy hill at about 40mph. As I followed at about the same pace, I lost traction steering a thin line between heading off the road or hitting a car going the other direction. I had just enough control to choose and not spin out. I chose the trees. Just as I pointed the car that way the ESC kicked on which did not slow the car, but gave me just enough control to stay on the road and not hit the on coming car. The kids were in the back and strangely I was very calm the whole time. Thank God for ESC. I am not sure the HH used active ESC, but it worked. My wife in her lower COG FWD car with studded winters drove home blissfully ignorant that anything happened!

 

[jerry33]

With proper winter tires, how critical is AWD? It's been many years since I've driven in snow.

With proper winter tires, vehicle stability control, and traction control you'll find that AWD isn't nearly as important as it used to be. The only thing AWD will help with is very steep grades where the traction will be spread out between four tires rather than just two. However, how often do you drive on 17% grades? If it's frequently, then AWD is a must. If it's once every two winters, then you're not likely to miss it.

Driving the Prius on ice days or in blizzards when I go up north in the winter, it's just hard to make it misbehave because of vehicle stability control. I'm usually the fastest person out there and I pass by all kinds of AWD vehicles that are in the ditch. AWD was a big deal when the only control feature was ABS. Now, not so much.

 

[doug]

Bottom line is that there are likely enough people that want AWD on the Model S that Tesla should (and will) offer it.

 

[Cottonwood]

With proper winter tires AWD probably doesn't matter much, especially in modern cars with ABS and stability control.

AWD will help you accelerate on a slippery surface. It will NOT help you turn or stop quickly.

The reason people like FWD cars in the snow is the engine weight is over the drive wheels. This isn't an issue for the Tesla because there's plenty of weight over the rear wheels.

AWD is in the "nice to have" category as far as winter driving is concerned. Proper snow tires (not all seasons) are more important.

Your comments on FWD and stopping are spot on.

I beg to differ about AWD not mattering much. It may be a corner case, but hill climbing has the same needs as acceleration. For the small numbers that we usually drive cars up, % grade is very close to G's of acceleration in terms of what the car has to generate. There are many places in Colorado where the grades go to 5 and 10%, being equivalent to 0.05 to 0.1 G needed. I have an extreme case with a driveway that tops out at 18%. Therefore, I need the equivalent of 0.18 G acceleration on snow and ice to make it up my driveway.

I am very interested in AWD and it will make a difference for me!

With proper winter tires, vehicle stability control, and traction control you'll find that AWD isn't nearly as important as it used to be. The only thing AWD will help with is very steep grades where the traction will be spread out between four tires rather than just two. However, how often do you drive on 17% grades? If it's frequently, then AWD is a must. If it's once every two winters, then you're not likely to miss it.

Exactly! My 18% driveway absolutely justifies AWD.

 

[jerry33]

I have an extreme case with a driveway that tops out at 18%.

No question that it will make a difference for you. Geometric design standards limit highways to a maximum of 6% grade, however, in mountainous regions this is often exceeded because of construction costs.

 

[mikevbf]

I was of the opinion that AWD was for getting grip faster when accelerating from a stop and more importantly up steep slippery slopes, but have changed my mind after reading Raffy's post #27. That post deserves a careful read. "Active" ESP will almost certainly be applied in the case of an AWD Model S. Read my post #28 and you might realize that that could save your life! Add to that all the performance gains for the 0 to 60 junkies and I think it will be less of a niche option than it is being painted out as.

 

[Boltz]

Let's face it, Tesla needs this option to compete with its competitors. Even the new Acura NSX will have AWD. The article below outlines the positives and negatives of AWD and the names the too ten sports cars with it (let's not forget that other sedans such as the Panamera and CTS have it)

Best AWD/All Wheel Drive Sports Cars For 2012 | Autobytel.com

 

[Johan]

I was of the opinion that AWD was for getting grip faster when accelerating from a stop and more importantly up steep slippery slopes, but have changed my mind after reading Raffy's post #27. That post deserves a careful read. "Active" ESP will almost certainly be applied in the case of an AWD Model S. Read my post #28 and you might realize that that could save your life! Add to that all the performance gains for the 0 to 60 junkies and I think it will be less of a niche option than it is being painted out as.

These are important considerations. AWD with electric motors will be something totally different than in a traditional ICE, I think it will bring a lot of extra performance not only when it comes to acceleration but also when it comes to handling and safety, not only in winter/on ice but all the time. The electric motors are so quick to adjust, something the ICE engine and the mechanical transfer to the wheels isn't. Many top super cars have AWD (Bugatti Veyron, Audi R8 GT, Gallardo etc.) for a reason.

With the electric car you can just get so much further out of the concept. The extreme example would be the Rimac Concept_One which is supposed to have one battery but 4 motors with each their own inverter and gearbox (I don't know if the gearbox is really necessary for anything else than achieving a high top speed?). They call this concept "All Wheel Torque Vectoring". Should be very interesting to see how that car performs when it reaches a production stage. IMO though, you will get plenty good results with Tesla's approach of 1 battery, 2 motors - each motor can draw as much current as it wants independently of the other at any given time (until maxed out of course) and once you have the motor connect to one left and one right wheel (front and back) it's easy to change the distribution of power between left/right wheel without much delay. I'd think this setup would perform almost as good as having 4 independent motors?

 

[Raffy.Roma]

These are important considerations. AWD with electric motors will be something totally different than in a traditional ICE, I think it will bring a lot of extra performance not only when it comes to acceleration but also when it comes to handling and safety, not only in winter/on ice but all the time. The electric motors are so quick to adjust, something the ICE engine and the mechanical transfer to the wheels isn't. Many top super cars have AWD (Bugatti Veyron, Audi R8 GT, Gallardo etc.) for a reason.

With the electric car you can just get so much further out of the concept. The extreme example would be the Rimac Concept_One which is supposed to have one battery but 4 motors with each their own inverter and gearbox (I don't know if the gearbox is really necessary for anything else than achieving a high top speed?). They call this concept "All Wheel Torque Vectoring". Should be very interesting to see how that car performs when it reaches a production stage. IMO though, you will get plenty good results with Tesla's approach of 1 battery, 2 motors - each motor can draw as much current as it wants independently of the other at any given time (until maxed out of course) and once you have the motor connect to one left and one right wheel (front and back) it's easy to change the distribution of power between left/right wheel without much delay. I'd think this setup would perform almost as good as having 4 independent motors?

All Wheel Torque Vectoring System performs exactly what I meant by "active" ESC. As it can be seen in the picture drawn in the above mentioned link the System is requesting three wheels to accelerate and one wheel to activate the brakes to keep the correct path. Of course this combination of wheels may change according to the needs.
Then as you said the electric engines are particularly good for such a System because they don't have the inertia of ICE and can answer to the commands coming from the ESC more quickly. So AWD on an electric car would help to implement a very good Electronic Stability Control because it would be like having an independent motors on each of the 4 wheels

 

[mikevbf]

All Wheel Torque Vectoring System performs exactly what I meant by "active" ESC. As it can be seen in the picture drawn in the above mentioned link the System is requesting three wheels to accelerate and one wheel to activate the brakes to keep the correct path. Of course this combination of wheels may change according to the needs.
Then as you said the electric engines are particularly good for such a System because they don't have the inertia of ICE and can answer to the commands coming from the ESC more quickly. So AWD on an electric car would help to implement a very good Electronic Stability Control because it would be like having an independent motors on each of the 4 wheels

To support what your're saying:

"Torque-Vectoring all wheel drive system monitors vehicle speed, wheel speed, gear position, steering angle, yaw rate, lateral G forces and other inputs, and automatically adds torque to the outside rear wheel in corners to make the car turn quicker."
Torque-Vectoring Awd | awd cars, 4x4 vehicles, 4wd trucks, 4motion, quattro, xDrive, SH-AWD, Haldex, Torsen, wiki - How it works

Notice the torque is applied to outside rear "wheel" not wheels.

 

[JRP3]

I don't see how they could add another motor and inverter for less than $10K, and would not be surprised it it's higher. Maybe they'll downsize the rear motor and inverter since duties will be shared, which would provide some savings, but not much.

The extreme example would be the Rimac Concept_One which is supposed to have one battery but 4 motors with each their own inverter and gearbox (I don't know if the gearbox is really necessary for anything else than achieving a high top speed?).

I believe when they say "gear box" they mean single speed gear reduction, not a multi-speed transmission.

 

[mikevbf]

I don't see how they could add another motor and inverter for less than $10K, and would not be surprised it it's higher.

Ahh, don't say that. I want to be able to afford it when it comes out. Well I guess I could always tell the kids to pay for their own college ...

 

[Johan]

I believe when they say "gear box" they mean single speed gear reduction, not a multi-speed transmission.

Yes, that seems correct when I checked, and makes sense.

However, in the Concept_One thread CroDriver (Mate Rimac) himself said the following:

Yes, but we don't consider the Roadster as competition. We consider Pagani, Bugatti and Koenigsegg as our competitors.

We're also working on the improvement of the acceleration and it might be improved significantly with a major development we're working on currently but I can't go too much into details at the moment. What I can say is that it is not just a simple change of gear ratio, we still want to hit the 300 km/h mark with a production EV.

This makes me think that they may be working on some form of variable transmission, either mechanical or more of an electronics/magnetics based one like the one discussed here (since this car is to have permanent magnet motors). Hard to reach 300 km/h with one fixed gear and still have good performance in the lower speed ranges?