The point is that symmetrical all-wheel drive, along with (Yes, Toyota took a minority stake in Subaru 20 years ago, an eight percent stake that has slowly grown to 20 percent over time.)
As Toyota and Subaru work together in greater harmony on various models, Subaru’s AWD will play a bigger role in what Toyota does. Here are the hows and whys of Subaru’s technology, and why it makes so much sense for Toyota to adopt it too.
Subaru’s AWD is different
What’s better: all-wheel drive that really drives all four wheels all the time, or part-time AWD? Well, if you’re a Subaru, the argument is always AWD. That is symmetrical four-wheel drive, and it was invented (in an earlier form) in the 1970s. Their system, which distills the concept a bit for a Subaru you’d buy today, uses a multi-plate transfer clutch that splits torque, with power delivered at 60 percent front and 40 percent rear as standard. Subaru uses multiple sensors to transmit the output between the wheels. Sensors measure, among other things, your foot on the accelerator, the torque at the transmission, the engine speed and the wheel speed, to determine which wheel needs more muscle power and which wheel less.
It’s faster (according to Subaru)
Conventional AWD systems, for the most part, come with full-time front or rear-wheel drive as standard and only engage the opposite axle when the wheels spin under the accelerator pedal. Subaru claims its electronic system is faster than mechanical approaches to AWD, which engage the opposite axle to drive the other wheelset.
Brake-based Torque Vectoring
On most Subarus (that aren’t the BRZ), the automaker adds an extra layer of control called Active Torque Vectoring (yes, more acronyms!). ATV throws the cars’ brakes into the mix to reduce understeer in corners. Understeer is the tendency of a car to overshoot the intended apex. ATV brakes the inside front tire as you turn, essentially forcing more power outward and reducing the radius in response to steering input. Subaru is not unique in its use of brake-based torque vectoring, but this, combined with the constantly engaged all-wheel drive, is important, as driving all four wheels tends to cause more understeer.
The miracle of CVT
Things changed in 2014. It was the year Subaru launched an all-new Forester, and this car marked the debut of X-MODE. Until then, Subarus, which did not have manual transmissions, used conventional torque converter automatics. But the Forester marked a new era of Subarus with continuously variable transmissions. CVTs in their earliest iterations were, quite frankly, bad. Accelerate and the engines spin fast and hard, then idle at high idle for seemingly forever. That led media critics (like us) to heap scorn on them. And thankfully, they eventually improved.
Meanwhile, they have one very strong advantage off-road: infinite tunability. And that, from Subaru’s perspective, has led to a crucial upgrade to their off-road AWD system, X-MODE.
X-MODE equals control
A Subaru spokesperson explained that by adding the CVT to the growing list of electronically controlled systems, such as Subaru’s symmetrical all-wheel drive, accelerator pedal, dynamic control, ABS and stability control, X-MODE can now be integrated as a predominant program. This allows extensive control over how Subaru vehicles perform on unpaved and snow-covered roads.
We know that our SUV customers are more likely to actually go off-road than many other brands, so it was important for us to offer more advanced capabilities and really maximize what Symmetrical AWD can do in off-road situations.
– Spokesperson for Subaru USA
X-MODE explained
Subaru shared the following scenario to explain what happens with X-MODE and why switching to a CVT was beneficial. Remember: Subaru already distributes torque between the front wheels (60 percent) and the rear (40 percent) by default. You are driving up a snowy or muddy hill and you want to maintain control as you climb. That means not only sustained momentum, but also the distribution of power between each wheel.
These are the conditions you would want in this situation, compared to normal road driving:
A less responsive throttle map than normal to soften throttle input and prevent wheelspin.
More central differential lock to distribute torque front/rear more evenly.
Vehicle Dynamics Control (traction and stability control) programming tailored to the slippery surface.
Once again different CVT ratio logic to smooth out torque delivery to the road and reduce wheelspin.
What’s going on?
Please note that none of the above technologies are actually proprietary. However, it is rare for Subaru (and Audi) to have all four wheels engaged at all times. And in X-MODE they can also drive both axes effectively, especially in this scenario. But this is also a benefit for downhill control, where you use the brakes and also engine braking (by adjusting the CVT logic) to give control back to the driver, allowing your Subaru to slowly creep downhill with maximum traction. Furthermore, the revised CVT map and delayed throttle on very slippery surfaces give the driver something of what you would have in a manual off-roader, downshifting at low speeds to achieve a crawler gear. Subaru said the CVT has an off-road advantage over fixed gears:
Instead of just changing the shift logic between fixed gears, we can continuously adjust the ratios to find the most suitable gear for every situation, both on and off-road. It means we can achieve more complex and advanced control over the vehicle’s dynamics.
– Subaru USA spokesperson
Subaru recently added what they call Dual X-MODE, which is a further refinement based on different conditions, such as deep mud or deep snow.
Breakdown of the X-MODE model
Forester: X-MODE standard Premium versions; Dual function on Wilderness models.
Outback: Standard on all versions; Dual-Function available on upper trims and Wilderness.
Crosstrek: Included on all models with CVT; higher finishes offer dual function.
Rise: X-MODE standard; Dual function available on selected versions.
Solterra: Subaru’s fully electric SUV is equipped with Dual-Function X-MODE as standard.
Subaru explains that the dual-function X-MODE releases traction control to allow for more wheelspin. This is especially important if you need to “loosen up” and engage the transmission to rock the car back and forth, quickly shifting between D and R to create a harmonious whole and free your Subaru.
What Toyota is offering
This is where Toyota comes into the picture. With the bZ4X and now just the bZ, Toyota and Subaru worked together and built one machine that is mainly cosmetically different. Subaru got the Solterra. Now Toyota has introduced the bZ Woodland and Subaru, its twin, the Trailseeker, and all of these EVs have X-MODE.
Off-road cruise control for EVs
Subaru explained that it also offers dual functionality on its vehicles, again for deeper mud or snow. And both Toyota and Subaru are adding what they call Grip Control, which works like a “…low-speed off-road cruise control. You can use the toggle switch near the shifter to adjust your crawl speed when X-MODE is engaged.” The use of battery regeneration allows the two automakers to add simulated low range, which is very useful when driving at very low speeds on slippery surfaces. Subaru says they calibrate X-MODE differently for EVs because the sensors don’t assign torque distribution between the front and rear electric motors, but measure the same input and available grip.
TopSpeed’s opinion
Toyota’s slow approach to EVs has meant they have to hybridize everything they do instead of going full BEV. However, X-MODE can also work with hybrids, and I see a further proliferation of Subaru taking advantage of Toyota’s small four-cylinder technology and dropping the boxer for all but smaller volume vehicles. X-MODE is super cost-effective. Boxer engines only matter to WRX fan kids who actually lift the hoods of their Subarus. Sorry, Forester, Ascent, Outback and Crosstrek customers are the opposite of tuners. Meanwhile, there’s a clear win for Toyota by adding X-MODE to, oh, a more rugged version of the RAV4, for example, and a rumored future small pickup.
This route will lead to branding and technological benefits for both automakers, and a rare win-win situation for both.
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