Electric AWD implemented by Toyota for the 2021 Sienna minivan

Back in 2019 I wondered Why aren’t AWD cars half electric?

The latest 2021 Toyota Sienna, redesigned with a grille large enough for a 400 HP diesel Freightliner truck, works this way (as does the Toyota RAV4, as a reader comment pointed out on that 2019 posting). From the press release:

Sienna uses a new kind of AWD called Electronic on-demand AWD. Instead of a heavy AWD transfer case and space-robbing driveshaft to the rear wheels, this AWD system uses a separate independent electric motor to power the rear wheels the instant additional traction is needed and at all vehicle speeds.

One bizarre feature of this brand-new-for-2021 minivan is that it has a older generation of the driver assistance technology: Toyota Safety Sense 2.0. The 2021 Toyota Camry, for example, offers “Safety Sense 2.5+” (why not just “2.5”? Is this like “LGBTQIA” where it isn’t complete without the plus sign?) and can perhaps drive itself in a stop-and-go highway situation.

Some excerpts from Consumer Reports:

From our brief time with this preproduction Sienna, it feels as if the van is no longer playing second fiddle to the polished Honda Odyssey. The van is responsive to steering inputs and happy to hustle along winding roads.

Yes, the Sienna is quiet and composed at low speeds when running on electric-only power. But when the Sienna transitions from electric power to the gas engine as a result of added throttle inputs, the engine comes on with a roar. The four-cylinder engine is loud when the driver tries to hurry the Sienna along, particularly on the highway. Sienna owners who are used to the V6 engine’s refinement may find this experience a bit of a letdown.

From Car and Driver:

The all-new Sienna is much improved and heavily refined over the old model, but stops short of leading the minivan class.

From CNET:

One of the best arguments in favor of this Toyota is fuel economy. After a good ol’ thrashing on a wide variety of roads, I averaged just shy of 35 miles per gallon in my Platinum-trim, all-wheel-drive tester. That’s practically economy-car efficiency, plus it’s right in line with this Toyota’s window sticker. According to the EPA, it should return 35 mpg city, 36 mpg highway and 35 mpg combined. Front-drive models are rated at 36 mpg across the board, and all-wheel drive is available across the lineup.


5 thoughts on “Electric AWD implemented by Toyota for the 2021 Sienna minivan

  1. Getting rid of the transfer case and driveshaft is a great idea as long as the electric motors are at least as reliable as Toyota’s existing setup (which are pretty rugged, from what I’ve been able to tell.) I know that on a lot of Ford AWD models, both cars and trucks, the transfer cases are a weak spot and basically built to fail. Getting rid of that componentry saves weight and the associated geartrain power loss, so all to the good.

    That’s excellent mileage for a minivan if you can handle the engine noise. I guess a test drive is in order. Why did Toyota take two steps forward and one step back? Can’t anyone build a smooth, quiet inline four (like Honda?) The 2.5l Atkinson-cycle 4-cyl. engine in my ’10 Ford Escape Hybrid is pretty good – at least for something 11 years old. It’s a little bit loud, but the vibration is very well-controlled. I think it has at least one balance shaft.

    A lot of that NVH can be solved with careful tuning / engine mounts, noise dampening, etc., but I’m still boggled that in 2021, manufacturers have trouble building a smooth inline-4. (And yes I know about primary and secondary balancing issues).

    • I’d also like someone in the SAE Department to explain why more manufacturers of I4 automotive engines don’t use cross plane crankshaft timing? ( https://en.wikipedia.org/wiki/Crossplane ) In I4 motorcycles (higher revving) they provide a smoother and more linear power delivery by smoothing out the inertial torque fluctuations of the crankshaft. They require a balance shaft to counter the rocking torque couple, and that must be more expensive, hence why few manufacturers do it. Yamaha uses cross plane cranks on its high-end I4 street/race bikes.

      Go out to 2:00 here to avoid the heavy metal intro.

  2. Reading that press release, we know why your neutered friend loves Sean Connery! It’s the most hilarious thing I’ve ever read.

    • I’m sure it’s a great minivan, and really, you should just tolerate the Marketing Department and test drive one. But they should all come with a “Grab ‘Em By the Pussy” sunshade for the windshield.

      “With dark 20” split 5 spoke wheels and aggressive front and rear bumpers that are unique to XSE, this model looks like it was born on a race track.”

      “Beneath the bridge is a large open area for convenient storage of larger personal items such as a purse or bag.”

      “based on door sequencing logic in which the Combi Meter MID provides a warning “Attention: Check Rear Seat for Passengers and Cargo.”

      “A Quiet Place to Make Some Noise”

      “Seeing the Invisible”

  3. If they’re making an AWD minivan with a version of the Toyota synergy drive and I was in the market for a minivan, I’d strongly consider buying one. Those drives are a marvel and regularly drive UBER priuses a half-million miles. They are also almost completely silent when you’re stuck in traffic, which makes it much more tolerable! (Quiet all the time!)

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