[adgjqetuo]

I apologize if this has already been discussed, I tried to search but couldn't find exactly what I was looking for.

Since I’m completely new to Subaru I’ve been doing tons of reading up on various sites (IE - Here, Cars101 and Subaru.com).

I've found what appears to be an inconsistency of information on the Symmetrical AWD system.

Cars 101 (screenshot attached) says "Electronically controlled, primarily front wheel wheel but constantly monitoring and varying the front/back power split."

Source: (Subaru 2013 Outback research webpage- specs, options, colors, photos, and more)


Subaru.com states the vehicle is in AWD all the time and diverts some additional power to other tires when needed.

Source: (Subaru Symmetrical All-Wheel Drive | Subaru AWD)

So which is it??

 

[rockhopjohn]

Both are correct. There are tons of threads on this subject. But the short of it is that with the CVT and 4EAT the power is constantly being shift between the front and rear axle. No more than 90% ever goes to the front, and no more than 50% ever goes to the rear. The 5 speed autos have a slight rear wheel bias, and the manuals are constant 50/50 split

 

[plain OM]

I think it's semantics and marketing words that satisfy some, but can be more confusing.

The AWD is always functioning, and the rear wheels are always (i.e., when the engine is running and the transmission is in D or R) being powered. What varies, in your 2.5 with the CVT, is the pressure being applied to the multi-plate clutch that connects the rear wheels to the transmission output. When there's more risk of wheel slippage (e.g. under high acceleration), or a wheel does slip (e.g. on an icy surface) the pressure is increased; when cruising steadily (e.g. down a clear dry interstate), the pressure is backed off somewhat (but not completely) because it simply isn't necessary under these conditions in order for all four wheels to be "pushing".

The AWD control system on these cars is very sophisticated and effective. However, the marketing material does not go into detail on how it works as it's also somewhat complicated. Instead it uses various simple-to-understand terminology which is what you noticed. But this can also lead to confusion, especially as others try to interpret what is being said.

In http://www.subaruoutback.org/forums...426-freessm-complete-access-your-ecm-tcu.html, a number of members have monitored the control signals for the AWD in their vehicles. It's a long thread, and begins with discussion of various scanning tools, but later on there's a lot of discussion on how the AWD control functions, including data measurements and graphs. Might be worth reading if you're so inclined.

(Woops, doubled with rockhopjohn . . .)

 

[Euchre]

Keep it simple.

Some cars are equipped with symmetrical AWD. Others are equipped with asymmetrical AWD. Which you have is based on your transmission type for your year.

If you have symmetrical, the power is delivered evenly to all wheels, all the time. If you have asymmetrical, power is delivered variably based on available traction and vehicle state.

For the most part, the type of AWD power delivery you have won't matter to you unless you are drifting or doing some fairly serious offroad driving, or drive a LOT in severely bad conditions. The most important part is that Subaru AWD is truly full time, by design.

 

[subiesailor]

The word Symmetrical used by Subaru is their easy marketing term to point out that right side of the car is identical to the Left side of the car. There are NO AWD vehicles built today other that subaru that have this design aspect.

Meaning that all the other AWD vehicles out there have axles that are not the same length left to right - they have transverse ie sideways mounted engines etc.

This mechanical difference where the left is not identical to the right regarding mechanical function - creates mechanical differences in where power is sent left vs right. As a result the AWD system is not balanced regarding power sent to wheels. The very well designed old full time AWD vehicles like the old Land Cruisers and Mercedes G wagons had lots of engineering done to make the mechanical make up as balanced as possible so left vs right side power was as equal as possible. Now days even Toyota and Mercedes depend on advanced vehicle stability control systems and traction computer systems tied to the brakes to even up power sent to one side over the other in effect using one technology to correct the lack of balanced design in the transmission / engine placement and mechanical power delivery.

Subaru simply due to having the same length and mechanical bits on the left that it has on the right side - creates a mechanically balanced power delivery to both sides of the car with no band aid correction from computer systems and brakes.

 

[adgjqetuo]

Thanks for taking the time to reply - great information.

So you're saying I have "asymmetrical"? I see how this can be confusing because even the badge on the back of my Outback says "Symmetrical AWD".

Is one system preferred over the other? It sounds like "asymmetrical" is a more adaptive system?

 

[Novablue]

Thanks for taking the time to reply - great information.

So you're saying I have "asymmetrical"? I see how this can be confusing because even the badge on the back of my Outback says "Symmetrical AWD".

Is one system preferred over the other? It sounds like "asymmetrical" is a more adaptive system?

*sigh

No you have Symmetrical AWD.

Symmetrical vs. Asymmetrical refers to how the engine and transmission are configured in the car to get power to the wheels. Symmetrical is another word for balance.

The Subaru system is balanced equally between all the wheels and doesn't require extra computers and parts to keep you from sliding off the road, it's engineered to be balanced with minimal parts. An Asymmetrical design adds extra mechanical parts and computers to try and mimic what a symmetrical design does. Asymmetrical designs are cheaper because they use design components for a current car and "bolt-on" AWD. Engineers then have to add parts to try and balance a designed unbalanced system. Asymmetrical would then be perceived to be "bad" but it's the system all cars have used since 4x4 and AWD first started so I'm not sure it's flawed per-say just the first way we figured out how to get power to more than one axel.

 

[subiesailor]

Getting away from the marketing words - the more mechanically balanced AWD systems are superior to the less balanced AWD systems.

A good friend runs his own GWagon adventure company. Sells Gwagon parts - rebuilds old G's etc. He has a 1964 Gwagon and a 2006 Gwagon. The 1964 G is actually nicer to drive on slick snow covered roads vs the new 2006 G. Why? The 2006 is less balanced left to right power delivery ie depends on advanced computer and brake systems to correct this. The 2006 G likes to break traction when turning right and will almost always want to spin in the same direction when traction goes south. The 1964 G with its more mechanically balanced drive system - more or less tracks strait and when traction goes south will spin either way with little preference due to both sides of the truck getting more or less equal power to the wheels.

So yes a higher quality more mechanically balanced AWD system is always preferred over a less balanced system even if high tech computers and brake systems are being leveraged to correct the imbalance issues.

 

[adgjqetuo]

Keep it simple.

Some cars are equipped with symmetrical AWD. Others are equipped with asymmetrical AWD. Which you have is based on your transmission type for your year.

If you have symmetrical, the power is delivered evenly to all wheels, all the time. If you have asymmetrical, power is delivered variably based on available traction and vehicle state.

For the most part, the type of AWD power delivery you have won't matter to you unless you are drifting or doing some fairly serious offroad driving, or drive a LOT in severely bad conditions. The most important part is that Subaru AWD is truly full time, by design.

I was replying based on the above reponse - I appoligize if i'm coming accross as not understanding. I thought I had Symmetrical but line bolded made me question otherwise.



Edit: That second video was very helpful - thank you for posting it!

 

[Novablue]

I was replying based on the above reponse - I appoligize if i'm coming accross as not understanding. I thought I had Symmetrical but line bolded made me question otherwise.



Edit: That second video was very helpful - thank you for posting it!

We got your back!

All this stuff is can be confusing. Especially when competitors start trying to say their system is good as or better than Subaru (some can be right, others not so much). At the end of the day what maters is did you get home?

 

[plain OM]

Symetrical drive train, with AWD. The "symetrical" does not refer to the AWD.

My 76 Suburban is symmetrical even though it doesn't have AWD. The drive shaft goes down the center of the car, and the rear differential is in the middle between the two rear wheels. That's symmetrical.

In many FWD cars with transverse (side-to-side) engines, the output comes out at one side. As a result, the drive axles to the two front wheels are different lengths. That's not symmetrical.

Some 4WD trucks have in-line engines and transmissions, but use a transfer case to connect to the front differential. Because of the shape and location of the case, the drive shaft coming out of it isn't along the center line of the truck. The shaft goes straight forward to the front axle, so the front differential is also off center. The axles going to the two front wheels are, again, not the same length. That's not symmetrical.

As has been noted, the Subaru drive train is balanced -- the front and rear differentials are in the center of the car, and the axles going out from each to the wheels are the same length.

The "Symmetrical AWD" isn't describing the AWD. In fact, the basic AWD system does not control the power to each of the wheels; only the relative power distribution capability front-to-rear. Read it as "Symetrical drive train, with AWD."

But as Novablue said: "At the end of the day what maters is did you get home?"

Enjoy!

 

[subiesailor]

With any AWD system you have front to rear power allocation ability how fast it can change and how much power can be moved from front to rear or rear to front when needed. This is determined by the system ie transmission and how it operates nothing to do with Symmetrical design.

Symmetrical involves side to side left side vs right side power which has a dramatic impact on handling in slick conditions for obvious reasons.

Also hard core off road vehicles have differentials moved farther to one side in some cases - the theory is that by moving the diff closer to a wheel you gain road clearance ability vs having it hanging center line but that is more of a very specialized off road specific use type factor. However due to left axle vs right side being different lengths its not symmetrical in a mechanical sense.