PDM/DM/QM Need input to confirm order

[R1Tom]

Actually, it is better than that. DM uses the rear motor and the front motor when you start moving. It de-couples the rear motor when the torque decreases, you reach about 20 mph. You keep accelerating and the rear motor stays engaged. The rear motor is geared differently for more torque for this reason. So you use both motors to get started, and then it settles in on the front motor. It is very smooth and you don't notice the decoupling. If you punch it to pass someone or accelerate, the rear motors kick in. The QM in conserve mode doesn't do any of that, it is just the front two motors. The PDM is the same as the DM, except that there is more horsepower when all four motors are engaged. I've owned QM and DM and I prefer the DM. The efficiency is very good, I'm getting 2.5 to 2.6 for 30 mile trips when I precondition.

How about regenerative braking? Does the DM kick back in the rear motor for that or does it simply stay in front wheel drive and only use the front motor for regen? Does that reduce the amount of regenerative braking available vs. a QM?

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[R.I.P.]

How about regenerative braking? Does the DM kick back in the rear motor for that or does it simply stay in front wheel drive and only use the front motor for regen? Does that reduce the amount of regenerative braking available vs. a QM?

Yes, the DM will engaged the rear for regenerative braking when the computer deems it necessary.

The amount of regenerative braking available on the DM is the same or very similar to the QM, but the amount of energy reclaimed is theoretically higher for a given inertia set. This is because most of the energy regained is through the very high efficiency front inverter, instead of multiplying losses through four separate slightly lower efficiency inverters. Each additional inverter used in this process adds to the loss.

How much does this matter? Not much, really, but it is there.

 

[R1Tom]

Yes, the DM will engaged the rear for regenerative braking when the computer deems it necessary.

The amount of regenerative braking available on the DM is the same or very similar to the QM, but the amount of energy reclaimed is theoretically higher for a given inertia set. This is because most of the energy regained is through the very high efficiency front inverter, instead of multiplying losses through four separate slightly lower efficiency inverters. Each additional inverter used in this process adds to the loss.

How much does this matter? Not much, really, but it is there.

Makes sense. I like how it works then with it clutching in the rears for regen and not just staying in FWD.

 

[runwithscissors]

QM is a no brainer especially for a lease since it's hundreds less per month vs DM. With financing/owning I would still get QM personally but would wait until the refresh comes. I'll switch the 20 AT's out for AS and get roughly the range of the 21's once they get loud.

 

[CrazyOne]

Conserve in QM is for occasional use only, because of tire wear issue. If you need this extra range often, go for DM/PDM. If you push in corners a lot, the torque vectoring in QM is great - but not as good as it can be. I have driven ICE cars that do this better. Else, get DM and save money. Lesser warranty on DM is a tricky thing though.

If you are pushing things off-road, it's again tricky. It will depend on what kind of off-road you do.

 

[Mathme]

QM - 20ATs here. Since you've decided on QM, I'll share my thoughts on this topic...

I rarely - as in I only use it if I REALLY need those few extra miles/KMs - use Conserve and drive it in AP most of the time. For my QM, these thoughts drive this:

First: Best practice is to engage and disengage Conserve once on the freeway as if under a load, as I've heard an audible 'clunk' from the rear end when changing before. Some people have horror stories about bad rear-end things happening when changing under a load.

Second: In the one Conserve trip I did over the course of three hours, the truck was noticeably more sluggish and drove like a marshmallow.

Third: Asking your tires to push, pull, and steer a 7k+ pound vehicle on a constant bases will wear them out faster. That's a lot to ask of those two tires. Tires for these vehicles are $$$$.

Fourth: And this is key. Rivian says that on a 100-0% charge you have a net gain of 30 miles (48km) range. My truck says 284 miles in AP, and 313 on a full charge - so 29 miles. Using 30 miles as a basis, on these trucks we rarely ever go that far and the typical road trip charge is likely something like an 85-25% (or so) charge. This effectively removes 40% of the battery capacity on a typical trip - that means you're really only adding 18 miles (29km) on a typical road trip charge. How often do you REALLY need that much mileage.

Caveats: In cold/icy/snowy/rainy conditions, you'll want to use all four drive wheels. When Towing, Conserve isn't available.

In 13k miles and numerous road trips up, down, and over mountain passes I've found that the in-dash GPS estimation of miles at your destination/charge stop is extremely accurate - usually within +/- 3-5 miles.

As you can see, I use AP, Snow, Sport, depending on my particular need. If I'm getting twitchy about range, then I'll go into conserve. Generally speaking the costs of Conserve outweigh the benefits.

I hope that helps what I've found in my specific truck.

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