CHaynes112

Greetings,

I am considering getting an '09 X Premium 4EAT. I have been reading and researching for a few days now. There are a few things I keep hearing conflicting information about pertaining to the AWD system. I was wondering if anyone actually knew the correct answers... (keep in mind, I am only asking about 2009s, as I know other years have some differences)...

1. What is the 'normal' torque split? I have seen the following listed: 95/5, 90/10, 20/80, 60/40, 55/45, 50/50, 45/55, 40/60, 20/80, 10/90, 5/95...

2. What can the torque split 'go to' (like maximum boundaries)? Again, I have seen anything from 95/5 to 5/95...

3. When the 4EAT is in 1 or 2, does it 'force' the torque at 50/50? Remember, I am asking about '09 4EAT...

4. Referring to question above... Is it 1 AND 2, or JUST 2? I have seen posts indicating that 1 does not force 50/50?

5. I have seen posts stating that when the tranny is in 2, it will 'lock' the front and the rear... was this just meaning 50/50 or does it actually "lock" something?

Do any of these ratios (50/50, 90/10, etc.) even 'really' exist on the new '09 with Active AWD, as it's supposed to be constantly changing?

-Thanks

Real Lyte

http://www.subaruforester.org/vbulle...12/#post509916

1.) in drive it is 90/10 (unless slippage is detected, then it changes accordingly)
2.) I believe 90/10 to 50/50
3.) 50/50 in 1 and 2
4.) ^^^
5.) It's in 50/50, it isn't a true a locking differential AFAIK.

__________________
'99 SF (Mine) &
'02 Civic LX (hers)
Leggy Lives

funkymonkey1002

Basically you have a center clutch pack that sends the power front to rear. In drive it wants to get you the best efficiency so it tries to send power mostly to the front, if slip is detected or if you go WOT it sends more power to the rear. In 1 and 2 it sends more power to the rear automatically. In drive it's never really in a constant split, the clutches are always varying how much pressure they're applying. When people mention the center diff switch mod, what it does is force the center clutch pack to apply full pressure.
On certain models subaru uses a VTD awd system, which uses a planetary gear setup to vary power front to back, this is much less FWD biased, but in normal usage most people won't notice the difference.

1 and 2 force it to send more to the rear, in 2 it won't downshift into first though.

__________________
04FXT/4EAT Snorkus Free, WRX suspension, sti up, prodrive ypipe, rota/falken/racingbrake/hawk

CHaynes112

Real Lyte,

I believe you and funkymonkey have confirmed that it is 50/50 in 1 and 2... and that it is not 'locked', which I was sure it couldn't be. However there is still some confusion for me as to the 90/10 split stuff. I can't find any info for 90/10 on Subaru's website now on the 09's. It was there previously with 08s. I read this post from the Edmunds forums:

"...the torque split for the AWD system constantly varies according to acceleration, deceleration and wheel slip, and as much as 100 percent of power can be directed to the wheels with the most grip."

This is not correct. I sent an email to Subaru asking the questions about the torque split, and got reply from them as below:

------------------------------------------------
Thank you for contacting Subaru Canada, Inc.

The Forester does not have a Variable Torque Distribution (VTD) centre differential. For the 2009 model year, the Forester 2.5XT includes a Multi-plate Transfer (MPT) System that adjusts torque from 60/40 (F/R) to 50/50 (or anywhere in-between) depending on throttle input, road conditions and input from the Vehicle Dynamics Control (VDC) System. VDC operates like most electronic stability control (ESC) systems in that it can adjust engine output, adjust individual brake pressure and even front rear torque distribution to retain/regain vehicle stability.

It is not possible for the system defeat the role of the centre differential and thus torque output will always be split between the front and rear differential. Meaning, the system cannot direct 100% of power to a single wheel - whether it be with VTD or MPT.

We trust this information is helpful.

Sincerely,

Rosanne Kernerman
Bilingual Consumer Support Representative
After Sales
1-800-894-4212
www.subaru.ca"

That post (if legit) makes it sound as if the new Forester is less FWD bias and more 'like' the split of the VTD (which is no longer an option).

funkymonkey,

Does the Center Differential switch mod you mentioned even apply to this vehicle? I didn't think the new 4EAT had a center diff...? Am I misunderstanding? Also, you stated that when the tranny was in 2, in wouldn't downshift. Isn't this true for all the gears... I mean when it's in manual mode, it should never downshift right? Like if you had it in 3, it wouldn't downshift to 2 would it?

-Thanks

CHaynes112

sorry about the double post... but if you take a look at this link (post #28)

Detroit 2008: '09 Subaru Forester shows its US face in Detroit

you will see it mentioning the split is no longer 90/10, but 60/40 max. not trying to beat a dead horse here, just trying to figure out how FWD biased an '09 would be. i mean, 90/10 (and i understand it is variable) sounds a LOT more like a FWD than 60/40... i'm just trying to get all the knowledge i can before i pull the trigger on this thing.

-Thanks

funkymonkey1002

The center "diff" mod is for models with the MPT setup (not vtd) it makes it basically the same as in 1 and 2.

Talking about torque splits is completely irrelevent. When you take off it sends more power to the rear, when you slow down it sends more power to the front, on the highway it tries to be FWD when cruising at constant throttle etc.

I'm not sure how 1 and 2 work with the sportshift however. It's still the same transmission but with a different controller. On the older models with just the stick, if you put it in 2 it would hold it in 2 only, while in 3 it uses 3 gears and in D it uses all 4.
The FWD bias doesn't really matter, it will still send the power evenly all around when you're sliding. I can easily kick the back end out with a little gas. The only time it really has the FWD feel is in 3 or D when letting off, as it tends to lift off oversteer like a fwd.

With the mpt center you can basically think of it as having a clutch on the rear driveshaft that has varying levels of pressure on it based on different ECU and TCU parameters.

I wish subaru would state on their website which models have mpt, vtd, and vdc.

__________________
04FXT/4EAT Snorkus Free, WRX suspension, sti up, prodrive ypipe, rota/falken/racingbrake/hawk

CHaynes112

So the Center Diff Mod is for an Auto MPT. It makes the split 50/50 in 3 and D too, just like the viscous Center Diff in a manual... hence the name center diff mod. It will be at 50/50 all of the time, however, this 'mod' would seem like a downgrade instead of an upgrade on the new Active MPT w/ VDC... as it would eliminate any 'adjustments' the new system could make. Does all that sound correct?

Subaru states that no 2009 Forester has VTD or even a LSD. They also state that all 2009s have VDC. And all '09 4EATs have MPT (aka VTC), whereas all 5Ms have a viscous Center Differential.

Ahmad_Z

Hi Haynes,

I guess we share the same concerns. I've own my '09 Forester XT since December last year and can't stop wondering about its AWD system. I've read tons of articles online and have yet to see AUTHORISED information on its torque distribution ratio.

However, I'd rather believe the official reply from Subaru Canada which states 60/40 than the 90/10 info I've seen online.

On the forced 50/50 ratio at lever '2', I still wonder if it behaves the same while in 'D' but low speed mode (i.e. in 1 and 2 but driven by the 'D' lever). Does it still split torque at 50/50 until it reaches gear 3 speed onwards then split torque towards 60/40?

I wonder...

Phrattr

Hello,

I wonder also - but for the 5 speed MT tranny.

Has this subject been answered on any othe thread (i do not seem to find it)?

funkymonkey1002

At low speeds in D it will vary the ratio as much as it would at higher speeds. I probably wouldn't do the center lock mod on a model with VDC. I'm surprised the XT doesn't have the VTD center diff and is still using the mpt setup, the VTD is mechanically superior to MPT but with all the computer control with the VDC setup I'm not sure how much of a difference would be felt unless you were modified running much more torque than stock.
Theres never been a time in my 04 XT that I've felt the awd system was lacking except in lift off oversteer situations. I would be really curious to see how a model with VDC and no LSD's does compared to a model without VDC but with a rear LSD.

__________________
04FXT/4EAT Snorkus Free, WRX suspension, sti up, prodrive ypipe, rota/falken/racingbrake/hawk

CHaynes112

I still have a few questions...

1. Has a Subaru ever had LSD + VDC? I ask this because they are stating that LSD is gone (not available on 09+), and it was replaced by VDC (standard on 09+). But this wouldn't make sense if at one point in time, they were both (LSD + VDC) used on the same vehicle... right?

2. What exactly is the difference between VTD and VDC? I mean, what does the addition of VTD (I believe VTD is an 'upgrade' to a normal LSD) give? Again, they are saying VTD is now gone, and it was replaced by VDC. Has VTD + VDC ever been used on the same vehicle (If question 1. = NO, then this must also be NO)?

3. Everyone is saying the MPT w/ VTD is the best option out (2008 being the last year). I am curious as to why? With a VTD setup, you have a true open front diff, whereas with an 09 VDC, you have a 'virtual' LSD front diff. And what does VTD do that VDC can't?

-Thanks

funkymonkey1002

VTD is a center diff that replaces the MPT in some models. I believe some outbacks now have VTD and VDC. VDC is a computer stability program that uses the brakes and controls the power split etc, all 09's it appears have it standard. VTD is a planetary diff, while the MPT is just a clutch pack without any "true" differential action. The vdc basically can act as a virtual lsd, but in low traction situations a real lsd would probably be most beneficial.

Some members have swapped in the VTD center diff to replace the MPT found in the forester. I had hoped that they would have put the VTD in at least the 09 XT, but I guess they stuck with mpt.

__________________
04FXT/4EAT Snorkus Free, WRX suspension, sti up, prodrive ypipe, rota/falken/racingbrake/hawk

Torsen

MPT is rediculous to me... if i wanted MPT i'd get a CRV ;)... the only auto drivetrain sub should have is VTD... but they don't do it because they don't want grandma's spinning out... they will only use VTD if it comes along with VDC to keep people from spinning out... :-(

__________________
2003 Subaru Forester XS Premium (5MT)

Phrattr

I do not wish to break up this conversation - but...

Since I am a newbie to the Subaru world (and most probably not the only newbie that will read this thread), would someone mind giving me the definition of:

LSD
VDC
VTD
MPT


Many thanks...



For those who wonder - I am determined to get a Forester (MT). I just don't know what options... yet!

Ahmad_Z

09 Subarus comes with VTD in the top line Outback and Tribeca models. Let's focus on the '09 Forester and its AWD system.

Phrattr, I believe the definitions of the abovementioned can be found in Subaru global website.