Dual vs Quad motor pros and cons?

[Olsonsolar]

So can anyone shed some light on the pros and cons of the dual vs quad motors. I know the quad has more torque. Not a huge deal for me 600+ pounds on dual is good with me. 0-60 in 3 vs 4 seconds I could care less.

I assume the dual would be more efficient.

But what would it mean off road? I am not at all interested in rock crawling but would want to be able to get off the beaten track mild 4x4 terrain. What wouldn't the dual motors be able to do that the quad could or what could the dual do that the quad can't?

Sponsored

 

[jebinc]

Be delivered by Rivian?

 

[COdogman]

Rivian has not yet made any dual motor versions so we don’t actually know how it will perform or affect efficiency. I would bet the dual motor can do any off-roading the quad can, as that is just fun overkill. My guess is there will only be marginally better efficiency from the dual motors but who knows….

 

[connoisseurr]

I’m assuming power output to be similar. The primary advantage to quad motor, alluded by others, is torque vectoring.

 

[Bee]

In theory the quad-motor is supposed to perform better across the board. It's supposed to be the whole reason to go through the effort. Rivian in the design phase was probably less interested in 0-60 speed than they were in ensuring they could actually do the quad motors to begin with. The reason this necessarily makes the truck damn fast is that each motor needs to have the hps and torques to move the truck in exceptionally difficult situations. If you don't have traction on 3 wheels in mud but have it in 4th but that 4th wheel only has 50 horses to push you because you decided 400 hp is enough total for a midsize truck while going up a 20 degree grade, good luck.

So this is where we get into what I scare italicized, supposed to perform better. I personally have faith we all just need more time in the machines and there will be a back and forth between users and software engineers on preferences but it does operate differently than a mechanically locking differential which would occur on a dual motor setup to achieve 4 wheel drive. People seem to leave wheels unspinning in odd situations and in general you're not as aware of what is going on with your wheels where as if you flick a switch in your Rubicon, you know, both (or all) wheels are moving.

If they screw up how locking differential stuff actually performs in 4x4 situations the quad motor is going to be short lived I'd hope since I don't think torque vectoring or other potential benefits are worth the tradeoff. If they can make it feel like the old locking diffs or convince us it's actually doing it better and we're just not noticing it, that's different but it be early days and there are question marks as to whether or not it's any kind of benefit in extreme offroading over a dual motor with locking diffs.

 

[SoCal Rob]

I don’t think we’ll know for sure until final specs are released. For off road use, is there a locking diff front and rear, open diffs front and rear with traction control, or something else?

 

[sub]

I think the 2 vs 4 motor question will primarily depend on how Rivain decides to prioritize their R&D time.

If Rivian's product mix ends up being 10K flagship quad motor R1 vehicles and 200,000 dual motor R1 and R2 vehicles each year, then I would expect the dual motor vehicles to nearly match or even exceed the quad motor performance because they will end up putting more effort into the optimizing the drivetrain that makes up the vast majority of their sales.

If they end up closer to a 50:50 mix of dual and quad motor vehicles and they therefore put more effort into ensuring the flagship is a worthy upgrade, then the quad motor will be significantly superior.

 

[mikehmb]

Note: this is coming from my engineering brain, and I don’t work for Rivian, so YMMV (literally).

There are 3 primary benefits of a dual motor setup.
1) Cost reduction
2) Simplification & reliability (single motor, single inverter, simpler software, etc)
3) Theoretical doubling of power to an individual axle/wheel vs. an identically-powered 4-motor setup

I imagine there may be a 4th, which is a modest reduction in power consumption. But only barely.

For Rivian, it gives them control of their ecosystem with potential the benefits of customization to their platform.

 

[R1Tom]

So can anyone shed some light on the pros and cons of the dual vs quad motors. I know the quad has more torque. Not a huge deal for me 600+ pounds on dual is good with me. 0-60 in 3 vs 4 seconds I could care less.
I assume the dual would be more efficient.
But what would it mean off road? I am not at all interested in rock crawling but would want to be able to get off the beaten track mild 4x4 terrain. What wouldn't the dual motors be able to do that the quad could or what could the dual do that the quad can't?

You sound like perfect market for dual, if you can wait. All the things you don't care about are some of the benefits of the quad.

 

[Dark-Fx]

I don’t think we’ll know for sure until final specs are released. For off road use, is there a locking diff front and rear, open diffs front and rear with traction control, or something else?

You can simulate a locking diff with brake pressure on the spinning wheel. I have to imagine Rivian is doing a lot of testing right now with control either way. Locking diffs would make the dual motor even better off road on slippery stuff than the current quad motor.

 

[Count Orlok]

dual might have less stuff to break or to be incorrectly installed to start with.

 

[Mathme]

I'm a H2 2023 delivery and by the time I get to ordering the dual motor will be available. The question I keep pondering is: Will I really notice the difference between two and four motors for $8,000 difference?

 

[thrill]

...Locking diffs would make the dual motor even better off road on slippery stuff than the current quad motor.

I don't understand this thinking. Any *single* wheel on the Rivian can deliver 200+ HP and so has enough power to lift the entire vehicle 15 feet per-second (10mph straight up). A quad motor design with a control system can put *exactly* the required power to each wheel to the point of slippage. If all four wheels are slipping then it's not a question of power but one of technique in delivering continuously rotating force to capture what traction each grain of sand can deliver, rather than modulating it such as is normal on a firm(er) surface. That's a question of the quality of the "sand mode" software. Software can be improved to the limits of the hardware, and the only limits are the tire design and size and the frequency of the sensors of the weight on and rotational speed of each wheel. I think they're still a ways from maximizing the best application of force to each wheel, but you need individually controlled wheels to do that in the first place. With a locking system you are limited to a transfer of power from one wheel to another, and as stated, the amount of power is not a limitation. The only "thing" a locking system gives you is the ability to manually spin the wheels by applying too much power, which is basically what the sand mode gives you (not that I've driven it).

 

[moosehead]

I’m assuming power output to be similar. The primary advantage to quad motor, alluded by others, is torque vectoring.

IIRC dual motor is expected to be 600 hp and 600 ft lbs torque total. Quad is 835hp/900 ft lbs torque.

 

[Dark-Fx]

I don't understand this thinking. Any *single* wheel on the Rivian can deliver 200+ HP and so has enough power to lift the entire vehicle 15 feet per-second (10mph straight up). A quad motor design with a control system can put *exactly* the required power to each wheel to the point of slippage. If all four wheels are slipping then it's not a question of power but one of technique in delivering continuously rotating force to capture what traction each grain of sand can deliver, rather than modulating it such as is normal on a firm(er) surface. That's a question of the quality of the "sand mode" software. Software can be improved to the limits of the hardware, and the only limits are the tire design and size and the frequency of the sensors of the weight on and rotational speed of each wheel. I think they're still a ways from maximizing the best application of force to each wheel, but you need individually controlled wheels to do that in the first place. With a locking system you are limited to a transfer of power from one wheel to another, and as stated, the amount of power is not a limitation. The only "thing" a locking system gives you is the ability to manually spin the wheels by applying too much power, which is basically what the sand mode gives you (not that I've driven it).

I don't know what the actual power curve is, but usually at very low speeds you are restricted on the total power you can put into a motor since the eddy currents build up pretty quickly.

Sponsored