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About time to unveil the D and something else

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#1,001
Hey Andrew,

I think you'll be glad you went no matter what they show. We flew out for the Model X unveiling in 2012 and I must say that Tesla throws a great party. Enjoy it and I'll be looking for your tweets tonight. :)

Lanny

andrewket said:
Oh well. On a plane from DC for the event. I will admit I will be disappointed if the X doesn't make an appearance. I'm meeting up with some friends while I'm there so it's all good no matter what happens.
Click to expand...
 
#1,008
MartinAustin said:
"don't appreciate the magnitude" could mean that all Model S cars will be fitted with the dual motors from now on, just as the Model X will be. (initially there was going to be a 2-wheel drive version of the Model X)

Don't forget, Tesla are over 25% profit on cars at the moment... it wouldn't kill them to include the extra motor parts, and they'd get the cachet of all Tesla cars are all-wheel-drive. This would put to rest the discussions about dropping the base price of the Model S, etc..

And - if all the "Gen 2" cars (Model X and Model S) have standard all-wheel-drive, it would make things on the assembly lines easier, as you don't have to track dual or single motor manufacture.
Click to expand...

I have the exact same feeling and posted such last night. And if as someone posted last night that they don't want AWD, I would hope that Tesla includes an option to just disable the FWD motor (except for maybe when it could be used for active traction or skid control, then it pops on automatically)

MartinAustin said:
Finally, and perhaps crucially, we are fairly certain the front motor is smaller and uses less KWh/mile than the back motor. And, that the rear motor is only used for heavy acceleration, the front motor doing most of the work inc. cruising (at any speed).
Click to expand...

This is a great point that I missed. Just using the front motor while crusing on the highway could greatly reduce energy use and extend the range. Another reason it makes sense to make AWD standard on all Model Ss going forward. I'd guess the reduced energy usage outweighs the added weight of the FWD motor and suspension components.

MartinAustin said:
The only question would then be... what about the 60,000 rear-wheel-drive cars on the road, including mine... are they retrofittable?
Click to expand...

Sure, the only retrofit option will be selling your RWD Model S and buying a new AWD one. To actually retrofit a RWD MS to AWD would be a massive undertaking, much more expensive than just trading up.

As already mentioned, this will decimate the resale value of all existing Model Ss. That's disappointing, but good for those people who got they buyback guarantee (not me).
 
#1,009
MartinAustin said:
Don't forget, Tesla are over 25% profit on cars at the moment... it wouldn't kill them to include the extra motor parts, and they'd get the cachet of all Tesla cars are all-wheel-drive. This would put to rest the discussions about dropping the base price of the Model S, etc..
Click to expand...
25% gross margin, not profit. It's a huge difference and Tesla probably can't afford to give up profit (or margin).

MartinAustin said:
Finally, and perhaps crucially, we are fairly certain the front motor is smaller and uses less KWh/mile than the back motor.
Click to expand...
I'm not sure why this would be, but I don't know electric motors. My understanding is the motor is already extremely efficient. It's not like a big V8 ICE that sucks gas in mass quantity regardless. I thought a big advantage of the electric motor was high efficiency across usages. Which is why the P85 gets the same range/efficiency as the non-perf models.
 
#1,010
ckessel said:
I'm not sure why this would be, but I don't know electric motors. My understanding is the motor is already extremely efficient. It's not like a big V8 ICE that sucks gas in mass quantity regardless. I thought a big advantage of the electric motor was high efficiency across usages. Which is why the P85 gets the same range/efficiency as the non-perf models.
Click to expand...

Taller reduction gearing on the front axle. It was mentioned by ElonB Muskbel the context of how to keep enough range on the X.
 
#1,011
HankLloydRight said:
Just using the front motor while crusing on the highway could greatly reduce energy use and extend the range.
Click to expand...

I'm not sure I understand why this would be so. Surely a given vehicle requires a certain amount of power to maintain a steady speed - rolling resistance and air resistance. So whichever combination of big motor, little motor or dual motors - between them they have to produce that amount of power to maintain speed. Unless the smaller motor is much more efficient than the big one, I don't see how it would use less energy to achieve that? I didn't think there would be a big difference in motor efficiency?

I understand advantages with traction during hard acceleration, and obviously in bad weather etc. But surely in the steady state situation it wouldn't make a difference.

Can someone explain why this would be better?

Edit: Guess several of us had the same question around the same time!
 
#1,014
If the AWD can greatly increase freeway range, that would be a very big deal. Still, if I remember correctly from Tesla's graphs, wind resistance was the bulk of the energy cost at speed, not motor inefficiency.

Hmm, Tesla seems to have changed their blog structure. I can't see the old blogs to hunt down the graphs. I'm sure they're there though since the Tesla Secret Master Plan is there if you Google.
 
#1,015
callmesam said:
Don't be confused by the Quonset hut Tesla DesignStudio in the background. This picture is taken from the edge of the airfield at Hawthorne. Here's a picture of the setup for tonight.
Click to expand...

Interesting. Looks like the stage is outdoors. The battery swap event was indoors at the design studio and SpaceX.

callmesam, did you take this photo? Is it close to the airstrip?
 
#1,016
RichardL said:
I'm not sure I understand why this would be so. Surely a given vehicle requires a certain amount of power to maintain a steady speed - rolling resistance and air resistance. So whichever combination of big motor, little motor or dual motors - between them they have to produce that amount of power to maintain speed. Unless the smaller motor is much more efficient than the big one, I don't see how it would use less energy to achieve that? I didn't think there would be a big difference in motor efficiency?

I understand advantages with traction during hard acceleration, and obviously in bad weather etc. But surely in the steady state situation it wouldn't make a difference.

Can someone explain why this would be better?

Edit: Guess several of us had the same question around the same time!
Click to expand...

JB specifically mentioned in the Feb Euro talks the fact that they've kept the range on AWD (in context of the X) net neutral despite increase in weight. One of the best theories on TMC about how this is possible is different gear ratios, and perhaps more regen braking capture.
 
#1,017
ckessel said:
If the AWD can greatly increase freeway range, that would be a very big deal. Still, if I remember correctly from Tesla's graphs, wind resistance was the bulk of the energy cost at speed, not motor inefficiency.
Click to expand...
This is true. At best, you might get an increase from something like 80% efficiency to 90% efficiency. Assuming a 250 mile range at highway speed, that would mean 281 miles of range, i.e, an additional 31 miles of range. And you'd naturally lose some range to the increased weight, so 25 additional miles is close to the absolute maximum possible. (Most likely, you wouldn't be talking about more than 10 miles additional range.)
 
#1,018
eepic said:
JB specifically mentioned in the Feb Euro talks the fact that they've kept the range on AWD (in context of the X) net neutral despite increase in weight. One of the best theories on TMC about how this is possible is different gear ratios, and perhaps more regen braking capture.
Click to expand...

I hope it's not more regen capture. While it'd be nice, it doesn't address the case where range is most important, which is steady state freeway driving.
 
#1,019
kanylbullen said:
The rear motor is single speed, geared for optimal acceleration. The front motor would be geared differently, optimized for cruising.
Click to expand...

If I remember correctly, Tesla initially wanted to build the Roadster with an automated two gear gearbox.
Link: Breaking: Tesla has a solution for their transmission woes: get rid of it!
I never understood this topic as for my knowledge a huge advantage of electric motors over ICE is that energy consumption does not depend that much on the rev output.
There must have been some reason for for the initial two-gear gearbox, maybe someone with more knowledge of this topic?
 
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