Dual vs Quad Motors, which would you get and why?

[Arky]

How will locking diffs be more capable than being able to independently control torque delivery to each wheel?

Because despite how neat whiz-bang electronic feedback control is, nothing is more precise in applying torque where it's needed than a locking axle.

A locking differential perfectly and instantly applies the correct amount of torque to each wheel to match their speeds. This means no spinning one wheel, less chance of ripping your tire, less tire/trail wear, and better crawling performance. Rivian's system isn't too bad but look at them crawling rocks and you'll see random wheels spinning as drivers try to 'bump' it over rocks, convincing the system to send the proper torque to the stuck wheel. Adding speed and power to get over something is a great way to break things - so slow crawling is much preferred.

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[mkg3]

Interesting to read how each person rationalizes one is better than the other.

When Rivian first announced the reservation opening, I purposely did not sign up (whereas I did for Model 3 introduction) because of quad motor. My thinking at the time was that more motors, higher probability of failure. Additionally, to maintain 4 motors running requires more power than 2; hence, shorter range.

Time has past since then, and I do hold a R1S pre March reservation, so somewhere along the line I've come to accept what I'd thought of shortcomings with Rivian architecture.

The data for the quad motor reliability appears to be no worse than other twin or single motor EVs. I'm not talking about the CV joints or other gremlins. Simply looking at the motor failure reporting, anecdotally.

I realize that motors, drivetrain and batteries are covered completely for a long time and most likely beyond my ownership of the vehicle. Other than the inconvenience, if broken down, I like the rest of the vehicle enough that made the decision to reserve one, knowingly that I would end up with more than wanted number of motors. No I don't need an eSUV that goes to 60 in 3 seconds. I'm waiting for a pure sports EV 2 seater to do that (e.g., e718).

It's my understanding that the EDVs are riding on the Rivian motor as FWD vehicle logging lots of miles. This is probably the best real world testing for the new motor.

If Rivian was smart and want to increase their margin for the pre-March orders, they should offer a no cost 2 motor without delivery time impact and 350+ mile range option. Between the lighter weight (2 motors vs 4) and Conserve mode with only 1 motor can result in much improved range with the same battery pack.

I know some of you say I want the $8K discount for going to 2 motors from 4, but look at the range improvements and power consumption over time for 2 vs 4. Just need to think in terms of life cycle rather than just acquisition cost.

 

[brancky3]

If Rivian was smart and want to increase their margin for the pre-March orders, they should offer a no cost 2 motor without delivery time impact and 350+ mile range option. Between the lighter weight (2 motors vs 4) and Conserve mode with only 1 motor can result in much improved range with the same battery pack.

I know some of you say I want the $8K discount for going to 2 motors from 4, but look at the range improvements and power consumption over time for 2 vs 4. Just need to think in terms of life cycle rather than just acquisition cost.

I would have liked to see the option for 2 motor without impact to delivery time. I wouldn't have done it, but I still would have liked to see it.

Lifetime cost is going to be pretty much a non-issue between the two models. $8k goes a LONG way in terms of EV costs; I'm looking at 100k miles or more for $8k worth of electricity charging at home (assuming 1.5 kwh/mi and $0.11/kwh charging cost). This is about 12 years for me.

 

[crashmtb]

Because despite how neat whiz-bang electronic feedback control is, nothing is more precise in applying torque where it's needed than a locking axle.

A locking differential perfectly and instantly applies the correct amount of torque to each wheel to match their speeds. This means no spinning one wheel, less chance of ripping your tire, less tire/trail wear, and better crawling performance. Rivian's system isn't too bad but look at them crawling rocks and you'll see random wheels spinning as drivers try to 'bump' it over rocks, convincing the system to send the proper torque to the stuck wheel. Adding speed and power to get over something is a great way to break things - so slow crawling is much preferred.

I have a vehicle with three! helical LSDs, with the centre being also lockable.

It is not as precise or quick as an independently controlled motor driving each wheel would be. Conventional differentials cannot function the same way.

Rivian's system keeps a wheel that's not on the ground rotating in order to sense how much grip it has or doesn't have.

 

[Dark-Fx]

Updates we plan to make early next year:

• R1T with Max pack will only be available in a Dual-Motor AWD configuration.

Love that they wrote that but then said they'd reintroduce it later. Looks like they're forcing people out of their price advantaged orders in order to get quad+max.

 

[Biturbowned]

It's much easier to control axle speed with a locker. Torque control is relatively instantaneous with an electric motor, but speed control is much more difficult because you have to sense and adjust to a varying load. With a locker this is all done for you. After seeing R1s try to offroad it's no question I would take a locker every time if I cared about offroad performance.

That said the 4 motors provides much more flexibility in street performance, torque vectoring, and practically eliminates the problem with tire size imbalance since there's no drive connection between the wheels.

No argument that it’s easier to force equal wheel speed with a locker vs a virtual locker. You want my completely unsolicited and unqualified opinion? Of course you do - I think there’s probably ~20% overhead in the rear motors based on the Munroe motor tear down, which Rivian may unlock via a free or paid OTA update. That much power increase would essentially make the torque at the rear tires equal to a 300-ish lb-ft of torque dual motor config w/ a mechanical locker. There’s got to be a reason MB went with a quad motor config for their EQG.

 

[Rivian_Hugh_III]

How big of a deal is it to lose torque vectoring? Will the 2 motor truck be awkward in corners on asphalt?

 

[Virgil T2]

For me, my hope for the dual motor R1S I have ordered is that the drive will be more refined, and a lot quieter than the 4 motor version. I really dislike the whiny motors is in my R1T. Coming from a Tesla model X, the noise of the motors in the Rivian is a disappointment for me. I know others say they like it, but I don’t

 

[Speedrye]

How big of a deal is it to lose torque vectoring? Will the 2 motor truck be awkward in corners on asphalt?

I wouldn't say awkward, but when you lose to ability to separately increase wheel speed on the outside wheels in a turn, you'll certainly lose some ability to power through a turn as effectively. Ultimately, it won't feel as planted when you're really pushing it in the corners.

 

[Rivian_Hugh_III]

I wouldn't say awkward, but when you lose to ability to separately increase wheel speed on the outside wheels in a turn, you'll certainly lose some ability to power through a turn as effectively. Ultimately, it won't feel as planted when you're really pushing it in the corners.

I appreciate the reply. May I ask, how likely do you think it may be that the enduro motors will torque vector by increasing the speed of the outside wheel? That would seem to be valuable enough that I’m sure it would be a goal. The question is whether it would be possible, to what extent, and if possible would it be likely.

 

[R1Sky Business]

Still hoping for a quad-motor Enduro option. 835hp simply isn't enough for me in a vehicle this heavy. Yes, I have problems...

Hang in there...coming SooN

 

[Speedrye]

I appreciate the reply. May I ask, how likely do you it it may be that the enduro motors will torque vector by increasing the speed of the outside wheel? That would seem to be valuable enough that I’m sure it would be a goal. The question is whether it would be possible, to what extent, and if possible would it be likely.

As Rivian is now getting into cost-cutting, I'd say it's unlikely to use a mechanical solution on their non-flagship model. If they do anything at all, I think they'd do a software-based approach and will use the brakes to slow the inside wheels down to give a similar, albeit slower, feel when driving in the twisties. I doubt 95% of drivers would ever know the difference honestly.

 

[crashmtb]

As Rivian is now getting into cost-cutting, I'd say it's unlikely to use a mechanical solution on their non-flagship model. If they do anything at all, I think they'd do a software-based approach and will use the brakes to slow the inside wheels down to give a similar, albeit slower, feel when driving in the twisties. I doubt 95% of drivers would ever know the difference honestly.

ABS based traction control with a helical LSD(torsen, Quaife, etc) is the golden ticket. Also expensive.

 

[Dave711]

For me, my hope for the dual motor R1S I have ordered is that the drive will be more refined, and a lot quieter than the 4 motor version. I really dislike the whiny motors is in my R1T. Coming from a Tesla model X, the noise of the motors in the Rivian is a disappointment for me. I know others say they like it, but I don’t

I agree. There is a microphone above the rear view mirror. I am wondering if that can be used for active noise cancellation. I have asked if they can add active noise cancellation. That can be done if the rivian had an aux port.

 

[Speedrye]

ABS based traction control with a helical LSD(torsen, Quaife, etc) is the golden ticket. Also expensive.

HLSDs don't work when one tire is in the air at last check. Great for street driving or drifting, but not so much for off-road/rocks. Haven't really looked into what happens when you apply the brake on the hanging wheel/tire, but the resistance should be enough to engage the other side.

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