Subaru Impreza AWD System

[thescreensavers]

Subaru uses the VDC system to control wheel spin and work as an E-diff as the front and rear diffs are open.

Since the front wheel is spinning he turned VDC off.

Also the CVT models are 60/40 power distribution iirc

 

[Noobie]

I'd guess it all depends on how the TC module is programmed.
Look at the Porsche one, same test and no diff locks or LSD AFAIK, all electronic and it got through everything. Seems more like the Japanese/Korean manufacturers got the TC programming wrong or are lazy to do it properly. (Or maybe they want it spin a lot?)



I'm waiting for him to test a BMW with X-Drive since it can send up to 100% of the power to both front and rear axles and at the same time TC helps shifting torque and power left and right.

 

[geeman789]

Originally Posted By: oilpsi2high
AWD is for suckers who know nothing about the physics of an automobile.


Right...

Having driven FWD, RWD and AWD vehicles in some of the nastiest canadian winters imaginable, I will say this...

RWD with premium winter tires is manageable until snow gets deep, then it becomes a challenge. FWD with all season is manageable, and with winter tires is pretty good, until the snow gets deep, or roads are really icey.

Awd with all season tires is pretty good. With good winter tires, AWD is utterly FANTASTIC. Pure ice, no problem. Deep snow never an issue... in 4 years I have never been even close to getting stuck.

And the video of an Impreza on a severe incline lifting the wheel off the ground... yeah, thats what the car was designed for...!? The car is not an OFF-ROAD vehicle... it's an excellent all-round, winter capable road car.

 

[badtlc]

I think subaru's AWD with an MTX would perform like you are expecting when you disable the traction control system.

 

[JTK]

Originally Posted By: thescreensavers
Subaru uses the VDC system to control wheel spin and work as an E-diff as the front and rear diffs are open.

Since the front wheel is spinning he turned VDC off.

Also the CVT models are 60/40 power distribution iirc


I'd like to see a comparison test between exact models, except one CVT and the other a 5spd. The 5spd is purely mechanical as far as I know, with a 50/50 split being normal operation. I'd try this test with my 2014 5spd XV Crosstrek, but I hate the smell of burning clutch, which is what you'd get trying this.

 

[Nate1979]

Originally Posted By: geeman789
Originally Posted By: oilpsi2high
AWD is for suckers who know nothing about the physics of an automobile.


Right...

Having driven FWD, RWD and AWD vehicles in some of the nastiest canadian winters imaginable, I will say this...

RWD with premium winter tires is manageable until snow gets deep, then it becomes a challenge. FWD with all season is manageable, and with winter tires is pretty good, until the snow gets deep, or roads are really icey.

Awd with all season tires is pretty good. With good winter tires, AWD is utterly FANTASTIC. Pure ice, no problem. Deep snow never an issue... in 4 years I have never been even close to getting stuck.

And the video of an Impreza on a severe incline lifting the wheel off the ground... yeah, thats what the car was designed for...!? The car is not an OFF-ROAD vehicle... it's an excellent all-round, winter capable road car.


Well there's your problem. Don't you know that it is only correct to compare FWD with snow tires and AWD with all season tires? By putting snow tires on an AWD you have disrupted the universe and people on this site won't know what to do.

LOL.

 

[horse123]

Originally Posted By: thescreensavers

Also the CVT models are 60/40 power distribution iirc


I contacted SOA and they claim the CVT has no set distribution of torque, and it's always changing. That's for the 2.0i, the car in the video.


Originally Posted By: Noobie
I'd guess it all depends on how the TC module is programmed.
Look at the Porsche one, same test and no diff locks or LSD AFAIK, all electronic and it got through everything. Seems more like the Japanese/Korean manufacturers got the TC programming wrong or are lazy to do it properly. (Or maybe they want it spin a lot?)



I'm waiting for him to test a BMW with X-Drive since it can send up to 100% of the power to both front and rear axles and at the same time TC helps shifting torque and power left and right.


And again, luxury SUVs have FAR more suspension travel than a small sedan (or hatchback on a sedan chassis), the front left tire never even comes close to leaving the ground. It only has one wheel off.

 

[Ramblejam]

Originally Posted By: horse123
And again, luxury SUVs have FAR more suspension travel than a small sedan (or hatchback on a sedan chassis), the front left tire never even comes close to leaving the ground. It only has one wheel off.


I think you're searching for excuses where none exist. This isn't about heavy off-roading, but artificially simulating what occurs when only one or two tires can provide forward momentum.

You can easily find videos on YouTube of Subaru sanctioned events that are set-up to demonstrate their AWD system capability. Notably as it relates to our discussion, they have a "side ramp" obstacle:

(From: https://www.youtube.com/watch?v=hVWJyGYEI9g)

However, what you'll quickly observe is that it's cleverly designed as to not include a break-over (as I'm calling it...) point, which is what we see in the original video where one front/one rear tire leaves the ground, and the electronic traction control system must determine the course of action. If anything, I'd say Subaru well understands the capabilities of their AWD setup, and there's a very good reason they don't include such a test, whereas other manufacturers do (knowing it's a strength):

 

[CKN]

Originally Posted By: oilpsi2high
AWD is for suckers who know nothing about the physics of an automobile.


Another useless comment.....

 

[emg]

Originally Posted By: thescreensavers
Subaru uses the VDC system to control wheel spin and work as an E-diff as the front and rear diffs are open.


Certainly does with 'X-Mode' enabled on the Forester, but I don't believe it does on the Impreza?

Quote:
Also the CVT models are 60/40 power distribution iirc


I believe it's electronically controlled from 50/50 (X-Mode) to 90/10 (highway driving). 60/40 is the default from a standing start.

 

[emg]

Originally Posted By: Ramblejam
With all I hear about Subaru and their supposedly superior AWD system, I just expected better spin management and ability to direct power.


If you've got an Impreza's wheels off the ground, and it's not a WRX or STI on a rally course... you're doing something wrong. They don't have the ground clearance for even soft offroading.

The Forester has basically the same AWD system, but with different programming for off-road use, and should handle that with few problems.

 

[SwampSurvivor]

Originally Posted By: geeman789
Originally Posted By: oilpsi2high
AWD is for suckers who know nothing about the physics of an automobile.


Right...

Having driven FWD, RWD and AWD vehicles in some of the nastiest canadian winters imaginable, I will say this...

RWD with premium winter tires is manageable until snow gets deep, then it becomes a challenge. FWD with all season is manageable, and with winter tires is pretty good, until the snow gets deep, or roads are really icey.

Awd with all season tires is pretty good. With good winter tires, AWD is utterly FANTASTIC. Pure ice, no problem. Deep snow never an issue... in 4 years I have never been even close to getting stuck.

And the video of an Impreza on a severe incline lifting the wheel off the ground... yeah, thats what the car was designed for...!? The car is not an OFF-ROAD vehicle... it's an excellent all-round, winter capable road car.


It's not going I care about, it's stopping. In an emergency situation, my Focus will out stop ANYTHING AWD that does not have proper tires for road conditions.

 

[IndyIan]

I was messing around with the Tracker this weekend and did the same test on the edge of our driveway. Dragging the brakes with the open diffs worked pretty decent for a bit of torque transfer. Plenty to do the test in those youtube clips easily enough.
Pointed up a decent hill on 2 diagonal wheels I couldn't dance around on the 3 pedals well enough to stop and then get going again, but if I dragged the brakes into the diagonal situation without stopping, it usually would maintain momentum. Anytime I go through a mud hole, I always drag the brakes to keep 2 tires from spinning prematurely.

I do wonder what my new 06 CRV would do with the TC on? In theory it should work for some torque transfer with its open diffs, but I won't off road for fun until we have a replacement lined up.