Is the D version model S more efficient than the non D on highway?

[No ICE]

I have read conflicting information on this topic online and on this forum. I am going to purchase a model S for myself soon and I haven't really thought much about this topic until recently coming across a thread on here that briefly talked about the 85 and 85D for highway driving. I will be driving 85-90% all highway commuting miles, so would a D version model be more advantageous than a non D for this type of use? Would I hold better rage through out my day with a D? I have read no, yes, and as much as up to 20% more effeciant for highway driving with a D model?

Thoughts on this please.

 

[Saghost]

I don't think it's anywhere near 20%, but yes, the D is measurably more efficient on the highway (marginally less efficient in town due to the heavier weight.) That's why they have 5-10% higher EPA range ratings...

 

[davinci2017]

Well the D has more range than non-D, from the same battery, hence it has to be more efficient, ergo you will probably be more efficient on highway with a D compared to non-D.

I dont think its a reason enough to pony up several thousand dollars though. If you see benefits to having AWD (snow, frequent rain, spirited driving etc) then sure, but not for the sake of potentially few miles more per charge IMHO.

 

[Retired]

The graphic on (Model S | Tesla) shows about 4-6% more efficient as shown by the range calculations. I believe that Tesla noted that the front drive at cruise upped the efficiency at the time they incorporated it.

 

[cybergates]

Its a little more range which i needed for a 210 mile trip for extra margin. I think the D handles a bit better/cornering in my opinion

 

[scottm]

Buy any Tesla with sufficient range for your needs... doesn't matter if it's AWD or RWD. Really.. so what if you get 10 more miles from a D model if your daily need is satisfied by 50% battery charge of a model S60.

My thinking on this is ... fewer possible things to break with a RWD. And.. more frunk space in RWD (at least in my car... before they shrunk the frunk).. but maybe you're open to the idea of a used car and storage matters... ?

I think my wife is going to hold out for a AWD model 3, because up here in Canada, AWD makes a difference in winter.

When's the last time it snowed in Kansas?

 

[Saghost]

Buy any Tesla with sufficient range for your needs... doesn't matter if it's AWD or RWD. Really.. so what if you get 10 more miles from a D model if your daily need is satisfied by 50% battery charge of a model S60.

My thinking on this is ... fewer possible things to break with a RWD. And.. more frunk space in RWD (at least in my car... before they shrunk the frunk).. but maybe you're open to the idea of a used car and storage matters... ?

I think my wife is going to hold out for a AWD model 3, because up here in Canada, AWD makes a difference in winter.

When's the last time it snowed in Kansas?

I'm hoping the last part is a joke - Kansas is known for blizzards with wind driven snow on occasion, if not nearly as often as you guys get up there.

The theoretical benefit of fewer parts to break is more than compensated for by the worse reliability history of the large drive motors compared to the small ones - for whatever reason (design factors?) Tesla has had to replace most rear drive motors under warranty, sometimes a couple times - by contrast I think I've seen one AWD rear motor replaced on the forum.

The larger Frunk is certainly a valid point, at least on older cars (refresh cars get the same Frunk in either case.) I tend to think the AWD handles better, especially accelerating on a turn, but that may not be a big enough factor to matter to you.

 

[RichardL]

It was never clear to me if the torque sleep, which is supposed to improve D efficiency, works at all times, or only in Range Mode.

Can someone confirm when it is in effect?

 

[bob_p]

Based on two road trips we've taken with our new S 100D compared to our late 2012 S P85, we appear to be seeing about a 10% increase in range at typical highway speeds of our 100D vs. the P85.

 

[phaduman]

I bought the D to make it the year-around utility car - can head to slopes in winter and still be a great commuter all year long.

Additionally, I think the D is very efficient on stop and go traffic - I consistently get between 210-230wpm in my daily commute driving (18 miles each way) - I think the system intelligently drives two small motors more efficiently depending on slight acceleration and deceleration (recharge - I read is better with front motors too) etc.

Finally, D is the future (perhaps a Q someday will overtake D) and I think Tesla will continue to tweak the efficiency level on the D cars to make them safer/better handling and more efficient (even after the standard efficiency rating is done once for a model year car).

 

[DarkMatter]

It was never clear to me if the torque sleep, which is supposed to improve D efficiency, works at all times, or only in Range Mode.

Can someone confirm when it is in effect?

It used to only be in Range Mode. It's possible it is now in all modes, but I couldn't find anything saying that.

 

[xyeahtony]

Only buy the D for increased handling/traction/performance, not increased range. The extra 5-10 miles is negligible and not worth the $5k price difference if thats solely what you're going after.

 

[u00mem9]

In city, stop-and-go conditions, I think the potential for greater regen braking (front axle regen) makes the D more efficient and hence the better EPA range rating.

As you suggest, I think the highway efficiency is the same. The lack of detail surrounding 'torque sleep' usually means it was hype in Tesland.

Also, RWD frightens some people. For some reason that has a tendency to make them want to justify their AWD choices for a host of reasons other than stability. Not a big deal, but something you can observe playing out every day on the interweb.

 

[RayW]

I believe one motor is geared to be more efficient at lower speeds (rear?), the other is gear to be more efficient at higher speeds (front?), and power is shifted between the two for better overall efficiency... keep in mind electrons are cheap so you'll never recover the cost of dual motors.

 

[DarkMatter]

That's exactly it. Torque sleep stops inducing a field in the rear motor at low loads and high speeds. The front motor is geared higher so it suffers lower friction losses and is slightly more efficient at higher speeds. The range boost is real. It's also probably not much of an argument for getting the dual motors.

 

[Sir Guacamolaf]

I have a 70D, in summer At 60mph,
I routinely get 250wh/mi.
My friends with 85D in similar driving get 280/270 wh/mi.
My friends with S85 get 300ish.

In stop and go, I can go as low as 200, or even 190.

So yes, the D is more efficient.

However, let me put it like this, "It does not matter".
Why? You'll save a few cents of electricity every time you fill up.

What matters more re: D,
a) Much better handling
b) You can't make the tires slip in rain, in snow you can, but not easily.
c) Better acceleration.
d) More even wear and tear on tires.

For the above reasons, I feel the D is worth the extra 5K.
Efficiency, yes it's more efficient, but that's not a reason to buy D.

 

[whitex]

The old RWD had a less efficient motor, so probably somewhat less efficient. The new AWD has the gen2 motors, except for P which has the gen1 performance motor on the back. On the highway it doesn't seem to matter, whenever we drive our P85D and 60D together (one following the other) on trips, the energy uses (Wh/mile) are within 1% of each other. Maybe on the highway they both use mostly the front motor?

 

[Saghost]

The old RWD had a less efficient motor, so probably somewhat less efficient. The new AWD has the gen2 motors, except for P which has the gen1 performance motor on the back. On the highway it doesn't seem to matter, whenever we drive our P85D and 60D together (one following the other) on trips, the energy uses (Wh/mile) are within 1% of each other. Maybe on the highway they both use mostly the front motor?

Certainly on the highway the P85D is using front motor unless you accelerate hard, which means they both have the and gear ratio and motor technology at work.

I'm a little surprised you don't see a difference between the two, though. Small battery Teslas have consistently had EPA ratings (and rated Wh per mile in the car's systems) that indicate they are more efficient than large battery cars, and by more than the simple weight difference.

My X75D is rated at 308 Wh per mile, while the X90D is rated at 327 Wh per mile I believe.

 

[JohnnyG]

It was never clear to me if the torque sleep, which is supposed to improve D efficiency, works at all times, or only in Range Mode.

Can someone confirm when it is in effect?

It used to only be in Range Mode. It's possible it is now in all modes, but I couldn't find anything saying that.

...The lack of detail surrounding 'torque sleep' usually means it was hype in Tesland...

I believe one motor is geared to be more efficient at lower speeds (rear?), the other is gear to be more efficient at higher speeds (front?), and power is shifted between the two for better overall efficiency...

That's exactly it. Torque sleep stops inducing a field in the rear motor at low loads and high speeds. The front motor is geared higher so it suffers lower friction losses and is slightly more efficient at higher speeds...

...Maybe on the highway they both use mostly the front motor?

Certainly on the highway the P85D is using front motor unless you accelerate hard, which means they both have the and gear ratio and motor technology at work...

Please read this thread. It gives technical detail to answer the Torque Sleep questions on the "D" models.

In Summary:

Range Mode On
FWD - Always
AWD - When power requirements become higher

Range Mode Off
RWD - Below ~50MPH & low power Requirements
FWD - Above ~50MPH & low power Requirements
AWD - When power requirements become higher


Also, read here for info on gearing and top speed.

In Summary:

Front Motor:
Max Speed - 18000 RPM
Final Drive Ratio - 9.34:1

Rear Motor ("P" Model):
Max Speed - 16000 RPM
Final Drive Ratio - 9.73:1

 

[supratachophobia]

Well the D has more range than non-D, from the same battery, hence it has to be more efficient, ergo you will probably be more efficient on highway with a D compared to non-D.

I dont think its a reason enough to pony up several thousand dollars though. If you see benefits to having AWD (snow, frequent rain, spirited driving etc) then sure, but not for the sake of potentially few miles more per charge IMHO.

Not necessarily. One could argue based on epa numbers that the D models benefit from more braking Regen, hence the higher numbers. You'd need strict Watts per mile on the highway at certain speeds to just if the D was actually more efficient.