Increasing range on AWD

[Wildbill]

We know that the RWD LR is more efficient and has slightly longer range than the AWD LR model 3. (I read that the RWD LR probably gets 330 miles per full charge vs 310 miles on AWD)

I was wondering if it is possible to get a software update so that we can get the option to turn off the front engine on an AWD LR so that it runs like a RWD to increase the range (similar to how we have the option to chose between standard regen and low regen braking).

The higher efficiency and extra miles might be useful on long trips.

 

[YisSerL]

Sounds like something you can ask Elon on Twitter and see what he says.

 

[tjkessler]

You can't rid of the weight of that extra motor and the friction of turning it even with no power. High pressure, high efficiency, non all season tires would help but you'll hate the ride, cornering, and braking performance. I've got the 19in wheels and will probably go with a summer/winter tire mix when the first set of all season tires wears out.

 

[Daniel in SD]

I have to imagine that they're already shutting off the front motor while cruising. It would be interesting if someone could verify this (inductive current meter?).
Tesla should make locking hubs (freewheeling hubs) for the AWD like old school 4x4s had. It seems like that would bring the highway range very close to RWD.

 

[Wildbill]

I believe the front engine weighs around 200+ lbs, the weight of a heavy adult. I agree you cannot get rid of this weight even if you turn off the engine.

I am not sure how much friction the front engine will generate when it is turned off, but I thought both engines are on all the time to provide stability.

 

[TEG]

I suspect that the drag of the front motor and gearbox is what hurts range on the AWD. The gearbox and motor is always engaged (no clutch).
The rear motor is different tech that is more efficient so the front motor just become useless drag when cruising at certain speeds.

 

[LoL Rick]

The feature that you are asking for is what Tesla calls torque sleep. When the dual motor Model S was introduced back in 2015, both motors were always active and the energy usage was horrible. A few months later they introduced torque sleep and it improved quite a bit. I have a suspicion that it isn't yet implemented or maybe isn't fully optimized on the Model 3 and hopefully we will get an update soon.

 

[Jedi2155]

I suspect that the drag of the front motor and gearbox is what hurts range on the AWD. The gearbox and motor is always engaged (no clutch).
The rear motor is different tech that is more efficient so the front motor just become useless drag when cruising at certain speeds.

I think you might've finally hit the nail on the head. The motor already turns off through torque sleep, but the direct drive drag losses really sounds like the cause.

 

[TurnFast]

I have an awd with 19” sport wheels, anyone know if the 18” areo winter set will get better efficiency?

 

[Adrien]

I have an awd with 19” sport wheels, anyone know if the 18” areo winter set will get better efficiency?

It will

Also, the front motor being small and geared higher is more efficient at highway speeds so actually the rear motor is put to sleep instead. At least that's the case for the Model S.

The problem is that the rear motor in the TM3 is a Permanent magnet motor meaning it actually has quite a bit more drag than the Model S even if put to sleep. You can actually feel it ticking over when you crawl at 2 inches/second. Almost like a cog. Due to that, I don't think we'll ever see better range through software.

 

[RyanT]

High pressure, high efficiency, non all season tires would help but you'll hate the ride, cornering, and braking performance. I've got the 19in wheels and will probably go with a summer/winter tire mix when the first set of all season tires wears out.

Is there a summer tire (or a non all season tire) that would get better range than the MXM4s?

 

[MountainRatMat]

I think we all know Tesla is smart so they are already doing everything suggested. As mentioned above the biggest issue between AWD and RWD is the rear motor is permanent magnet so torque sleep isn't as effective. You essentially have to "run" the less efficient rear motor at highway speeds. The motor itself is more efficient but because of higher gearing in the front motor you would want to run the front motor only. Any efficiency improvements made to the AWD could also be made to the RWD and therefore there will always be a difference between the two. S and X are all AC induction motors so torque sleep is more effective and the higher geared smaller front motor is run at highway speeds while torque sleeping the lower geared larger rear motor.

 

[SigNC]

It will

Also, the front motor being small and geared higher is more efficient at highway speeds so actually the rear motor is put to sleep instead. At least that's the case for the Model S.

This is not the case on the 3.

 

[RyanT]

It sounds like a good question to tweet at him. Is the front motor using torque sleep? If not, do they plan on adding it.

 

[kengchang]

Why do you think Tesla is not already doing that when Tesla has the experience on the Model S/X already?

Front induction motor can torque sleep, but not the permanent magnet motor in the rear.

 

[Daniel in SD]

Why do you think Tesla is not already doing that when Tesla has the experience on the Model S/X already?

Front induction motor can torque sleep, but not the permanent magnet motor in the rear.

The only reason to think that they're not doing it is that the highway efficiency of the AWD is so much worse than the RWD. Aerodynamics are the same and weight shouldn't matter much when cruising at highway speeds so the difference should be almost entirely drivetrain friction from the front motor.

 

[TurnFast]

It will

So just to clarify, you know of some kind of test that shows this? I’ve been trying to find the rolling resistance rating for the PIRELLI WINTER SOTTOZERO™ SERIE II but all I’ve found is it’s advertising listing it as “low rolling resistance “

 

[RyanT]

So just to clarify, you know of some kind of test that shows this? I’ve been trying to find the rolling resistance rating for the PIRELLI WINTER SOTTOZERO™ SERIE II but all I’ve found is it’s advertising listing it as “low rolling resistance “

I moved from OEM 19s to Xice on the 18s. They do seem better for efficiency (certainly not worse) and I don’t have the aero covers on. Different tire but just getting the information out there.

 

[StellarRat]

Drive slower.

 

[ulrichw]

Drive slower.

So much this!

The biggest factor in efficiency is speed (especially at higher speeds - the difference between 60 and 70 mph is *huge* - between 20 and 30 mph, not so much).

I also think the EPA results overstate the difference between the AWD and the RWD, but there almost certainly is some difference.