2. Active Torque Split + Multi-Plate Transfer Clutch

 

2.

Only the WRX uses VTD in it's CVT.

 

Thank you for such a fast response. I forgot to specify 2.5 normally-aspirated engine vs. 2.4 turbo engine. Is the AWD system the same for both?

Also since the "Active Torque Split + Multi-Plate Transfer Clutch" system is the most commonly-used AWD system, why does the Subaru outperform some others with the same system on some slip tests I've watched. I'm thinking Honda and Toyota.

Is it because the front-to-rear torque split on the Subaru sends more power to the rear wheels than those others? Is it because Subaru just has better programming?

Also, what is this current front-to-rear split on the normally-aspirated 2023 Outback? Is it 55% front and 45% rear? I've seen different numbers so I don't know for sure.

Also, I've read that the newest Hyundais let you manually lock the center differential. Does that make it a better system than the Subaru?

 

Also, I've read that the newest Hyundais let you manually lock the center differential. Does that make it a better system than the Subaru?

Meh,...It's a 1-to-1 lock. I've owned both. Hyundai, It disengages at 18mph, but you can leave it in the on position unlike Subaru X-mode. On dry roads, the front tires will bind with it engauged. If you are trying to do a dougnut in the snow, and hit the button mid-drift, the lock engauges with a BANG! You don't have the brake pressure vectoring. In a normal world senario, the Subaru handles better in on-road sloppy stuff.

 

It's because most companies use what effectively is an open differential in the middle, and at each wheel.

Subaru does the same thing but you notice how there's that slight delay then it starts working? I assume you're watching those roller ramp videos...

That's because the Subaru system sees the wheel spin, and applies brakes to the spinning tires so that torque has to go to the other tires that have traction.

This is because the ABS unit in the Subarus run their own proprietary software while most other manufacturers run the software provided by Bosch or whoever makes their ABS unit, and they just configure it.... I say just configure it but the tuning for it is actually quite in-depth. The Subaru system is pretty advanced software for what it does. The reason the other manufacturers don't do this is not a hardware advantage but rather that they haven't put the development into that type of system yet.

 

It's because most companies use what effectively is an open differential in the middle, and at each wheel.

Most companies do not use an open center diff, nor does Subaru in the Outback. The industry standard for AWD crossovers that the Outback uses and most others is an active torque coupling in the center. This is not at all the same as a center diff. Refer back to the original article posted, "2. Active Torque Split + Multi-Plate Transfer Clutch".
What may set Subaru apart in the area of the center coupling is two things:

• The maximum amount of torque they can send through the coupling. I have seen information indicating Suburu can send more torque through the coupling than is typical. This results in better ability to drive the vehicle off the rear wheels when the fronts do not have traction. This effect is very easily seen in roller tests where the front wheels are placed on rollers.
• Suburu likely keeps the coupling engaged during normal driving, resulting in faster reaction to wheel slip. Most manufacturers keep the coupling open during normal driving for fuel economy.

That's because the Subaru system sees the wheel spin, and applies brakes to the spinning tires so that torque has to go to the other tires that have traction.

This is the fundamental function of brake traction control (BTC). Every single vehicle on the market does this. Even non-AWD vehicles.

This is because the ABS unit in the Subarus run their own proprietary software while most other manufacturers run the software provided by Bosch or whoever makes their ABS unit, and they just configure it.... I say just configure it but the tuning for it is actually quite in-depth. The Subaru system is pretty advanced software for what it does. The reason the other manufacturers don't do this is not a hardware advantage but rather that they haven't put the development into that type of system yet.

To imply that other manufacturers are behind or haven't put time into BTC development (or that using Bosch calibration is somehow inferior) is nonsense. BTC has been around for a long time and is a very mature technology among all manufacturers. Yes, Subaru's BTC may have a slight edge over competitors here, but its a stretch to say thats a result of them somehow just being better than everyone at calibration. It very well could be a hardware advantage. Transmission temperature, brake temperature, brake system response time, and driveshaft sizing all effect the ability of the BTC system to compensate for slip.

 

The other factor is that Subaru's AWD is symmetrical, with nearly equal length axle shafts left and right, making the AWD system just that much easier to control, not needing to compensate for strange one axle short and one long as is typical of transverse engine transmissions:

Subaru has many different AWD systems and they've been doing it on more cars for longer than almost anyone - refining the algorithms etc.

 

This was a bigger deal 20 years ago... But pretty much every front wheel drive vehicle out there today has nearly equal length drive shafts and run a stub shaft to get the far side the same length as the short side.

 

This is all very educational and interesting. So I also just read that the 3.6 liter 6-cylinder from the past has the more advanced Variable Torque Distribution AWD system. Is this true? Just confirming this. A friend has that engine and would be happy to hear that. I think most owners don't really know all the technical details of their AWD system. I want to know.

 

Yes and no. The 6 cylinder OBs, as early as GEN2 sported the VDC system which relied on the brake pressure vectoring. Some 6's of the area had limited slip rears. The 4 cyclinders of the era relied on mechanical limited slips. Later GENS, the limited slips went away from the OBs and VDC with the brake pressure vectoring took over the AWD packaging. So, if we are talking about early GENs, yes, the 6 cyclinders had a better AWD system.

 

On a related note, the diagrams also show one of the reasons why Subaru switched to a CVT after discontinuing the 5-speed automatic transmissions: there's not room in the package for a larger transmission with more gears. As it stands now, the center console is the size it is in order to fit the transmission and center clutch pack. More gears would mean a bigger transmission hump.

 

I test drove a 2023 Sante Fe and decided I liked the Outback better. It was close. The Outback fit skis inside better and has a flatter cargo area with the back seats folded down. I liked the Outback interior better. I just couldn't warm up to the dash and console layout of the new Sante Fe. The Outback Limited seemed more conventional and higher quality inside.

 

So is Subaru’s 60/40 torque split simply “ready to go” when needed only, essentially a fwd car?

 

Yeah it's essentially a front wheel drive car most of the time.