P85D Hypothetical

[Johan]

In the context of the original question, getting a P85D to drive exactly like - and have the same range as - an 85D: why emulate and not just be light on the go pedal? What is emulated?

And just to be clear: the front motors of both the cars mentioned in the original post are the same? And the rear motors are the same? But the inverters and software are different?

 

[Johan]

Thanks deon.

Is the cat out of the bag then?

 

[deonb]

In the context of the original question, getting a P85D to drive exactly like - and have the same range as - an 85D: why emulate and not just be light on the go pedal? What is emulated?

But the inverters and software are different?

There could be many difference why the P85 will get worse range - for example if the acceleration curve is tuned differently throughout. We know there has been software updates that affected range, so if a P85 runs different curves than an S85, it will have a different range.

 

[rowdy]

wk057 is talking about single motor cars (S60, S85, P85) which have a single large motor

The dual motor 70D, 85D, 90D have a small rear motor and small front motor

To answer the original question. The P85D can never be quite as efficient as the 85D because of the extra weight (large rear motor vs small rear motor).

 

[deonb]

wk057 is talking about single motor cars (S60, S85, P85) which have a single large motor

The dual motor 70D, 85D, 90D have a small rear motor and small front motor

Ok, fair enough. I can concede that he meant a different thing for S85 vs. 85D.

Sorry about that Brian - was a misunderstanding / miscommunication.


So while the 70 and P85D has the same (large) rear motor and inverter, the 85D has a different (smaller) one. Correct?


However, that still validates this statement from eclipxe:

You can put the P85D in 70 mode and get better range. Even disables front motor completely

which makes sense if the P85D and 70 uses the same rear motor.

 

[brianman]

I haven't been paying attention to what rear motor the 70 non-D has. That said...

P85D has ... (large) rear motor and inverter, the 85D has a different (smaller) one. Correct?

Agree.

However, that still validates this statement from eclipxe:

You can put the P85D in 70 mode and get better range. Even disables front motor completely

which makes sense if the P85D and 70 uses the same rear motor.

I see a few issues with that (combined) assertion:
1. The P85D will have extra weight (front motor) and thus different front/rear balance.
2. The P85D and 70 will have different frunks (space, contouring, etc.).
3. Some P85Ds have the Plus suspension. To my knowledge, no 70 does.
4. Wheel differences due to staggering or not, 21" or not, etc.
5. In the early days of Model S, the P85 was described as having different inverters and cabling. If the same applies to the P85D but not the 70, that's another pro/con (probably pro) for the P85D in the efficiency comparison.
6. Even with the front motor inactive/disabled, is there "bleed" of power "systemically" vs. the 70? I have no idea.

#1, #3, and #4 are likely significant. I suspect the rest are not.


Broad brush strokes...
My understanding and expectation is that the "performance mode" feature is designed to help people evaluated the visceral/performance difference not the economy difference of the configurations. As such, the (IMO) secondary opportunity to evaluate efficiency is interesting but not something to lean on too heavily.

 

[wk057]

40 - Large Rear Motor
60 - Large Rear Motor
70 - Large Rear Motor
85 - Large Rear Motor
P85 - Large Rear Motor
P85D - Large Rear Motor, Small Front Motor
P90D - Large Rear Motor, Small Front Motor
70D - Small Rear Motor, Small Front Motor
85D - Small Rear Motor, Small Front Motor
90D - Small Rear Motor, Small Front Motor

The large motors are the same. The small motors are the same. The large motors are NOT the same as the small motors. IE, 85D can not perform the same as a P85D.

 

[brianman]

@wk057 - Point of clarification...

When you say "X motors are the same (as other X motors)", are you speaking about the motor or the entire drive unit?

 

[rowdy]

85D can not perform the same as a P85D.

The small motors are rated at 259hp though. Wonder how close you can get to 518hp output from them combined. The later built 85D's did have ludicrous batteries installed...

 

[wk057]

@wk057 - Point of clarification...

When you say "X motors are the same (as other X motors)", are you speaking about the motor or the entire drive unit?

The entire physical drive unit, with the exception of some mounting differences for the front and rear small motors.

The small motors are rated at 259hp though. Wonder how close you can get to 518hp output from them combined. The later built 85D's did have ludicrous batteries installed...

They wouldn't have the combined torque capability of the P85D's two motors. My P85D now also can get somewhat close to the originally advertised 691 HP from the battery under ideal conditions. I think my best is 665 HP so far from the battery. No way even a theoretically modified 85D could touch that.

And..... that's enough TMC for me for a while. Still loathe this downgrade. Just been popping in when others link me to stuff.

 

[deonb]

And..... that's enough TMC for me for a while. Still loathe this downgrade. Just been popping in when others link me to stuff.

Thanks for stopping by to clear things up! Sorry to have misinterpreted you.

 

[lolachampcar]

For me, the proof was in the lifetime numbers. My P85+ was under 280 while my P85D is about 316 W-Hr/mile. Granted, this is not exactly on point but these are two back to back 20K mile runs with almost everything being equal apart from the + to D.

 

[commasign]

Imagine each motor has a unique power vs efficiency curve, and also imagine those curves are affected by the position of the motor (either front or rear). For the 85D there are certain conditions (throttle/power, speed, temperature, etc.,) such that overall efficiency is maximized when the front motor sleeps, and other conditions where efficiency is maximized when the rear motor sleeps, and various conditions in between. I.e. an additional front/rear small motor distribution efficiency curve. That is how Tesla squeezed out an extra 5 miles of rated range in the 85D over the original single motor 85 despite the increased weight of the 85D. Now, the P85D doesn't have the high efficiency small rear motor. Instead it has the carryover "low" efficiency large rear motor which is the same as in the original RWD Model S variants. So in every scenario where the 85D would have put the front small motor to sleep because the rear small motor was maximally efficient at that moment (from a front/rear distribution point of view), the P85D would have to either 1) also put the front small motor to sleep and rely on the much less efficient rear large motor, or 2) put the large rear motor to sleep and rely on the front motor which while more efficient than the large rear motor, isn't as efficient as a small rear motor (from a front/rear distribution point of view). Again, if it were simply a matter of having ANY small motor (in a front or rear position), then Tesla would be able to literally put the P85D rear motor to sleep in most situations (except when literally launching the car) and the car should have essentially the same range as the 85D (aside from weight differences). My guess is the front/rear motor distribution efficiency curve is most significant at higher highway speeds since that's where the range curves seem to diverge the most.

 

[sandpiper]

it does, i got my p90d do consume a meager 262 wh/mi in S70 mode. the best i got my P90D to do was 279, in sport mode.

90/0.262 = 340 mile range. that... would be crazy!

With all respect, that makes no sense.

a) There are mechanical reasons why the 70 is slightly more efficient. A button cannot make that change.
b) If it were that simple, don't you think Tesla would program the system to do that automatically while not demanding the power/traction that AWD provides?
c) This is effectively what "torque sleep" attempts to do. When under light load it drives / idles the motors as required to provide the best efficiency.

Now... I don't know much about these "modes" and if they do anything at all. But I could see some small gain available by simply limiting power output. You'd gain a little efficiency in stop and go by curtailing the possibility of mashing the throttle! Which I have been known to do on occasion!

 

[jerjozwik]

not stop and go, 20 miles highway / 5 miles street. medium traffic. these "modes" do alter the cars driving dynamics, regen is a lot less, front motor is off completely, rear motor output is FAR less than default. its the tesla equivalent of my honda fit ev eco mode.

 

[ArtInCT]

Totally agree with jerjozwik, my P90D in 70 mode "sips" watts and likewise feels like grandma's electric shopping cart. Very efficient. Very.

The "performance" settings are very interesting to use on the P90D and of all the Model S's probably the best platform to try them upon (the P85DL) is also probably right up there too, but I do not have one, so cannot say for sure.

 

[wk057]

That's ridiculous. The Performance Demo mode stuff 100% sure does NOT increase efficiency. If anything it will reduce efficiency since it wont be using the motors in the optimal mode for the actual car. Any efficiency gains while messing with it are entirely coincidental.

 

[ArtInCT]

WK:

If I go 6 miles in P90DL mode with a P90DL and use 366 w/m and then go to 70 mode, do the same trip and do 268 w/m am I not more efficient? If not, please explain...??

 

[Skotty]

If you want to test efficiency of regular vs 70 mode, make sure to eliminate as many variables as possible. Like make sure settings are the same, turn climate control off, maybe do an initial 15 minute drive to try to eliminate any efficiency differences that might happen during the first part of a trip (like battery conditioning). Do multiple runs. And try to do all testing under the same weather conditions. If your testing doesn't feel like a royal PITA to do, you probably aren't doing it right.

The first thing I would try to do, if I wanted to try to disprove the efficiency difference, would be to try running the tests in opposite order but otherwise under same conditions. If you ran the 70 test first, try running it second. If you ran the 70 test second, try running it first.

A good way to double check yourself is, once you think you have some significant data, take the opposing position and try to disprove yourself. If you fail at disproving yourself, your data is starting to look better. It is easy to be misled by factors you didn't initially consider, so it's good to be your own skeptic.

 

[wk057]

WK:

If I go 6 miles in P90DL mode with a P90DL and use 366 w/m and then go to 70 mode, do the same trip and do 268 w/m am I not more efficient? If not, please explain...??

6 miles? That's like, 2 kWh. Try 60 miles or better, 160 miles.