Increasing range on AWD

[Jedi2155]

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.

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.

The AWD Model 3 is as efficient as Tesla can muster as far as I know. In regards to the torque sleep, I believe the rear motor is providing most of the tractive force during drive as compared to the front motor due to it being much more efficient. After looking at some kinematic equations last night, I realized that that vehicle weight linearly increase rolling resistance (which is the primary energy consumption up until about 40-50 MPH). So the AWD adds 234 lbs (over the RWD model), which means rolling resistance increases about 6%. The AWD has about 6-10% less range than the RWD model most of which is accounted by the additional weight, but then there are other energy losses (drivetrain drag etc.).

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

I'm sure there are more eco-focused tires (i.e. BridgeStone Ecopia's, Firestone Champion Fuel Fighters etc.), but you'd lose a lot of grip and potentially performance/braking capability by doing so. Tesla selected the MXM4's as the best mix between range and performance.

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.

Air drag/resistance starts becoming a factor above 20 MPH (and is the main factor above 40-50 mph as stated above), so reducing your speed really helps with range/efficiency.

 

[RyanT]

I'm sure there are more eco-focused tires (i.e. BridgeStone Ecopia's, Firestone Champion Fuel Fighters etc.), but you'd lose a lot of grip and potentially performance/braking capability by doing so. Tesla selected the MXM4's as the best mix between range and performance.

Interesting. I had pirelli cinturato p7 on My Model S P85. They seemed to get better efficiency and they definitely lasted longer. The only downside I noticed was their wet performance was terrible.

 

[ninpb]

This article on increasing regen that might only be for AWD looks promising for increasing range.

Tesla improves regenerative braking on Model 3 through over-the-air software update

What's the physics here? 2 motors capturing energy mean double the regen or just same amount of energy but regen is done in parallel, half the work?

 

[Adrien]

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.

Tread wear ratings. Rolling resistance is directly correlated to that. A harder tire is less "sticky" to the road surface and therefore has less rolling resistance.

 

[Daniel in SD]

This article on increasing regen that might only be for AWD looks promising for increasing range.

Tesla improves regenerative braking on Model 3 through over-the-air software update

What's the physics here? 2 motors capturing energy mean double the regen or just same amount of energy but regen is done in parallel, half the work?

Definitely looking forward to this.
I would guess regen would be limited by the maximum charge rate of the battery. I wonder if they're increasing the max regen power or just the regen power at low speeds (for example 0.3g of regen at 60mph is twice as much power to the battery as 0.3g of regen at 30mph).

 

[TEG]

This article on increasing regen that might only be for AWD looks promising for increasing range.
Tesla improves regenerative braking on Model 3 through over-the-air software update
What's the physics here? 2 motors capturing energy mean double the regen or just same amount of energy but regen is done in parallel, half the work?

There has been much debate over this. I think the claim is that the rear wheels already have enough traction to provide close to max regen (how much energy the battery can accept safely) so there shouldn't be a huge difference between AWD & RWD.
On the other hand, driving dynamics and stability can come into play, particularly in slippery conditions.
I am not sure how much Tesla may neuter RWD only regen to help with safety & stability concerns.

I would assume that in conditions like ice & snow, AWD is likely to offer better regen capabilities.
(But then again the conditions may be cold enough that the battery starts to limit overall regen.)

 

[brkaus]

What's the physics here? 2 motors capturing energy mean double the regen or just same amount of energy but regen is done in parallel, half the work?

For the same stopping, it would be the same amount of energy. Assuming brakes are not used.

 

[CT200h]

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

Bridgestone ecopia tires have very low rolling resistance. They are oe on the leaf and hybrids.
Not bad for commuting quiet , good wear ok in the snow.

 

[M109Rider]

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.

Great topic Wildbill. However, if you do decide to tweet Elon about this, I would recommend you don't reference the motors as engines...

 

[StellarRat]

Bridgestone ecopia tires have very low rolling resistance. They are oe on the leaf and hybrids.
Not bad for commuting quiet , good wear ok in the snow.

I noticed quite a bit of range loss after I switched from the Ecotopia to another brand on my Leaf. I think if you're trying to maximize range the Ecotopias would be a good choice. I bet they are better than the Michelins that come with the RWD.

 

[RyanT]

Isn't the load index too small for the Model 3? I thought the OEM tires were 98 vs 94:
https://www.tirerack.com/tires/tire...ewall=Blackwall&partnum=345VR8EP422&tab=Specs

 

[ℬête Noire]

There has been much debate over this. I think the claim is that the rear wheels already have enough traction to provide close to max regen (how much energy the battery can accept safely) so there shouldn't be a huge difference between AWD & RWD.
On the other hand, driving dynamics and stability can come into play, particularly in slippery conditions.
I am not sure how much Tesla may neuter RWD only regen to help with safety & stability concerns.

I would assume that in conditions like ice & snow, AWD is likely to offer better regen capabilities.
(But then again the conditions may be cold enough that the battery starts to limit overall regen.)

No way they can regen RWD-only as strong as AWD without getting some small slippage, that's a fair amount of weight transfer off the rear Track mode bumping from 0.2g to 0.3g is even based around this to get noticeable oversteer on good road conditions with sticky tires. The slippage won't be as noticeable under good road conditions, like the more safety imperiling conditions you mention, but it'll still be there.

 

[Daniel in SD]

I guess you could switch to Ecopia tires if you don't care about being able to stop or turn. Those Tire Rack tests make them sound horrible! They're significantly worse than the MXM4s.

 

[AlanSubie4Life]

I have two Spark EVs - Ecopias on one, and RE71R tires on the other. RE71Rs are also a little wider (205 vs. 185). Circumference nearly identical so no impact to odometer.
On identical round trips, I can achieve at least 5mi/kWh with the Ecopias and about 4mi/kWh with the RE71Rs. So it's a huge difference. There's no other vehicle difference.

So, run the Ecopias if you find the load rating is safe! They're great for efficiency. I'll say that the grip isn't quite as good as the RE-71R! When I say not quite as good, I mean, they're like banana peels. Cornering is "fun" and the traction control light comes on a lot. I really have to be on my toes when I transition between vehicles. It should be just fine if you drive very cautiously though. Just don't expect to stop quickly, they will add quite a few feet to your emergency stop time. What is that worth to you?

Regarding regen increases: 0.3g * 4000lbs @ 60mph is about 140kW assuming full recovery (won't get that exactly out of the motors of course due to various losses). I suppose they'd want to limit it to around that to avoid excessive battery charging rate? Maybe they'd keep it to something like supercharger rate of ~120kW, but seems like they could go a bit higher, as it's not continuous? Don't know the battery limits for charging. Obviously you can take energy out of the battery a lot faster than that (340kW at least, probably closer to 360kW due to inefficiency) but it's not symmetric charge/discharge.

Marginally related Spark EV discussion:
FWIW, for the Spark EV, the regen in kW is indicated on my display. It has a ~17kWh (nominally 19kWh?) battery. It maxes out at 60kW regen (I've read somewhere that it's claimed for the Spark EV that any deceleration below 0.3g will be all regen (it has a brake pedal that is nearly entirely regen as far as I can tell, followed by brakes if needed) as long as battery has room - but that would presumably only apply below 36mph (36mph*2800lbs*0.3g = 60kW)). Scaling that, it seems like Tesla Model 3 SHOULD be able to get about 240kW of regen power if they really wanted to, with their ~80kWh battery. But possibly for various battery integrity and safety reasons, particularly in RWD, they want to limit it. Stability under regen braking is not an issue in the Spark since it is FWD.
Also, FWIW, the Spark EV max power output is 120kW indicated, while the motor is alleged to be a 105kW *output* motor. I guess the 15kW difference is conversion loss in inverter, and losses in the motor. But this implies that the 60kW regen display-indicated number above is actually what is being delivered to the battery; the motor is actually applying more deceleration than that, so calculation above is a bit off. (maybe 60*120/105 = 68kW stopping power).

 

[CT200h]

I noticed quite a bit of range loss after I switched from the Ecotopia to another brand on my Leaf. I think if you're trying to maximize range the Ecotopias would be a good choice. I bet they are better than the Michelins that come with the RWD.

Very surprised at Tesla’s choice for tire in the 18” setup which you figure is / should be looking for maximum efficiency within reason.
That particular Michelin is not the best for low rolling resistance .

 

[Msjulie]

Here's what I've seen - from a RWD with 19" OEM to a P3 with 19" OEM - I can get quite good WH ratings in local 45-55 mph roads, sometimes under 200. But it doesn't take much at all to punch that way up, on the highway I see a noticeable change in the cool energy app display edging over 65mph

The 'drive slower' comment makes a big different in my experience, it's just I often don't want to or can't (swallowed up by other traffic)

Car is taking a small road trip Sat (about 120miles of mostly highway) - I plan on keeping a close eye on that..

 

[ℬête Noire]

Very surprised at Tesla’s choice for tire in the 18” setup which you figure is / should be looking for maximum efficiency within reason.
That particular Michelin is not the best for low rolling resistance .

Tire choice is a set of compromises. The Primacys seem to have a very decent economy while still getting good marks for other aspects such has handling water, lower noise, and so on. Tesla likely figured that with the Aero caps and the capabilities of the car in general, they could live with a little shaving of tire rolling efficiency if it gave those other things. It's hard to argue with the range and MPGe results they got. ¯\_(ツ)_/¯

I'm most curious to see how they stand up to wear.

 

[SSedan]

I didn't read all of this but on the surface it seems rather stupid to presume Tesla didn't roll lessons learned on the Model S into Model 3 on launch.

 

[TEG]

Very surprised at Tesla’s choice for tire in the 18” setup which you figure is / should be looking for maximum efficiency within reason.
That particular Michelin is not the best for low rolling resistance .

All the more impressive that they have the 2nd best EPA efficiency numbers (for RWD w/18")

Looks like Ioniq also uses MXM4:
Michelin Tires Featured on New Hyundai IONIQ

 

[StellarRat]

Very surprised at Tesla’s choice for tire in the 18” setup which you figure is / should be looking for maximum efficiency within reason.
That particular Michelin is not the best for low rolling resistance .

I'm not surprised. The M3 is already "tire challenged" with the stock 18" tires. The Ecotopias would make that worse. Also, on my Leaf the Ecotopias only lasted 20 K miles, while the Michelins that I replaced them with barely had any visible wear at 20K. Since the M3 is a much more performance geared car than the Leaf I think Tesla would really be shortchanging the car's capabilities with Ecotopias. I consider the Michelins to be the minimum acceptable tire for the M3. But if range is all that matters you might try the Ecotopias assuming they have a correct size and rating for the car.