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Discussion Starter #1
ok,
so i'm new to offroading with suv but have some experience with "real" offroad vehicles-landrover defender, lada niva, mazda 4x4 pickup...
with all of the listed above when i was in trouble, meaning got stuck into some steep hill with deep snow, i would engage reductor and some sort of differential blocking. this would always solve the problem.
with forester (2010, 2.0 manual with reductor) first of all reductor does not help a lot. ok , it cuts down gears for cca.25% which is probably good for towing but makes only small difference in offroading. more inportant thing is that, as far as i experienced, there isn't any help with central/rear/front differential blocking. on terrain this means that when one wheel looses traction it spins and your stuck in place, eventhough other three wheels have some grip.
is this normal for this vehicle or am i (or vehicle) doing something wrong?:crazy:

thanks
 

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The manual Forester uses a viscous-coupled limited slip differential in the centre which is reasonably effective in forcing torque front or rear as conditions require (not quite as effective as a fully locking differential though). On the MY09 and newer Foresters, the front and rear differentials have no internal limited slip functionality however these newer cars do have the ability to apply braking to a spinning wheel by way of the traction control component of the VDC. This can be a bit slow to react but will still help in cases of cross-axle wheelspin - you just need to keep your foot down on the accelerator and wait for it to start working.
 

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Subaru is not a true dedicated off road vehicle.

[/thread]
 

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Alokin,

Greetings from the USA! Many years ago, my family lived in Beograd (Belgrade), Serbia, in what was then Yugoslavia. We used to vacation in Opatia, Croatia. Beautiful location!

with forester (2010, 2.0 manual with reductor) first of all reductor does not help a lot. ok , it cuts down gears for cca.25% which is probably good for towing but makes only small difference in offroading.
The dual-range five-speed manual transmission is no longer available in the North American market. This Subaru.hr website indicates the low-range reduction ratio is 1.447:1.

more inportant thing is that, as far as i experienced, there isn't any help with central/rear/front differential blocking. on terrain this means that when one wheel looses traction it spins and your stuck in place, eventhough other three wheels have some grip. is this normal for this vehicle or am i (or vehicle) doing something wrong?
There appears to be some discussion of the viscous center differential feature in this Subaru.hk website. The same website appears to discuss Vehicle Dynamics Control (VDC) with an automatic transmission equipped car, but I can’t figure out if it’s included in your area’s manual transmission equipped Foresters.

Can you find the VDC features and controls in your car?

Here is the U.S., the VDC and Traction Control (TC) feature is standard equipment, and it can be turned off. However, there’s no function that allows the driver to manually lock any of the differentials.

Instead, the all wheel drive (AWD) and VDC/TC systems are supposed to automatically engage based on operating conditions. For example, the viscous fluid inside the center differential is supposed to heat up and lock the differential when there’s enough of a difference in speed between the front- and rear torque tubes (prop shafts).

As I understand it, the VDC/TC system is supposed to provide a “virtual”, or functionally equivalent, limited-slip differential function. Specifically, if one wheel spins, the VDC/TC system is designed to activate the anti-lock braking (ABS) system to “pinch” the brake rotor on the spinning wheel, thereby transferring torque to the opposite wheel at that end of the car.

I played with the VDC/TC system in my manual transmission equipped 2009 Forester this past winter. With VDC/TC manually turned off, I was able to briefly spin one wheel for a little while on a snow-covered uphill road until the center differential locked. With VDC/TC engaged (the normal operating condition), all four wheels seemed to grab rather quickly, and I drove up the hill with no problems.

I hope this information is useful to you!

Regards,
Jim / crewzer
 

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Discussion Starter #5
simxs,crewzer-thanks,very helpfull info:icon_razz:

maybe this solves the issue, since ,when in deep/steep snow trouble, i would turn the esp(or vdc, however it is called) OFF. my main reasoning was that i expected this system to be designed for on road situations ( where i really appreciate it's help-i.e. cornering on slippery asphalt road). following this i was also planning to put the abs off button inside the cabin, since it hinders off road/snow braking for me.

one other thing why i turned vdc off was that it was drastically cutting down the engine power. as far as i inderstand it, it works by selecticve braking of all 4 wheels but also with decreasing engine power to regain the grip of wheels?
this loosing of power was really felt because at this slow speed engine was at the limit of choking because if tried not to fry the clutch and got it to engage as soon as possible and other thing that it is gasoline version (so not as much torque at slower speeds.


so, tu summarize your info:
a) 2009 and newer foresters have central lsd but no front or rear. this means, with vdc off, if i get front left wheel spinning , central lsd will engage and help with rear axle. but if my rear left wheel also spins, i wila have my left wheels spin and vehicle stand still , even if right hand wheels have traction?
b)if i have vdc on, central lsd will equaly work, but vdc will "imitate"rear and front diff.blocking by individuall braking on spinning wheels and thus get me out of situation mentioned under a)?
 

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Alokin,

Based on my limited experimenting with VDC/TC and my understanding of the system, I would think that turning off your car’s VDC function probably contributed to the traction problems you experienced.

I understand that the VDC system may reduce engine power under some circumstances. However, I did not experience this when experimenting with my car’s VDC/TC system. My assumption is that only the TC functionality of the VDC system was working during my uphill traction tests. If you’re experiencing reduced engine output, you may want to consider using the transmission’s low range.

so, tu summarize your info:
a) 2009 and newer foresters have central lsd but no front or rear. this means, with vdc off, if i get front left wheel spinning , central lsd will engage and help with rear axle. but if my rear left wheel also spins, i wila have my left wheels spin and vehicle stand still , even if right hand wheels have traction?
b)if i have vdc on, central lsd will equaly work, but vdc will "imitate"rear and front diff.blocking by individuall braking on spinning wheels and thus get me out of situation mentioned under a)?
This pretty well summarizes my understanding of the VDC/TC system’s operation. To that end, you might enjoy this YouTube video of an older Subaru Forester, presumably without VDC/TC, stuck in the snow:

YouTube - Subaru Forester in snow, two wheels in the air
Regards,
Jim / crewzer
 

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Discussion Starter #7
yep, with vdc off i was experiencing exactly the same as in video:icon_confused:
 

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Interesting, and I think we're getting somewhere! I hope you'll post the results of trying that while leaving VDC engaged.

Best of Luck!
Jim / crewzer
 

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The whole thread has info.
http://www.subaruforester.org/vbulletin/f89/awd-snow-58695/

Here is a decent post I made about VDC and its function in offroad conditions(post #20).
The vdc does out perform the old stock LSD for that very reason. Plus in the rear it has a more positive power distribution then the LSD could ever have. In essence the VDC can simulate a vehicle having locked differentials in the front and rear.

Take a vehicle with locked diffs and put two opposite corner wheels in the air. Due to the locked diffs the wheels on the ground still have 100% power.

Same situation with the older rear LSD like in my '08 Fozz. The front wheel in the air will spin wildly as it is the path of least resistance. The rear wheel on the ground will only get a small amount of power as the center viscous coupler only helps to equalize the power distribution, it still favors the path of least resistance(the front). Now the rear LSD works on the same principal as the center viscous coupler. So it in turn sends the majority of the power to the rear wheel in the air. Which in the end equals you going no where.

Again same situation but with the VDC. The VDC sees the wheels in the air spinning wildly and the wheels on the ground not turning(does so via the ABS wheel sensors). It then starts to apply the brakes at those two wheels, until their speed matches that of the wheels on the ground,never fully locking them up. Simulating the function of the locked diffs with out a locker.

As funkeymonkey mentioned you can also simulate this same action in a vehicle with open diffs or LSD by applying the brakes until all the wheels have the same resistance then powering through the brakes with the gas. Known as driving through the brakes. However you can't do this at 70 MPH on an icy road, VDC can.
 

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Discussion Starter #10
interesting discussion and video

too bad i can't try it out now since the snow has melted ;) i still have one cocern and that is that vdc kills a lot of power from the engine , which already is grasping for air being gasoline version and at slow speed (meaning low revs)
 

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Discussion Starter #11
well ,could not wait for next winter so yesterday i found steep grass hill, right after rain- as close as i could get to snowy conditions now:icon_biggrin:

it worked without a problem,occasionally i would se vdc icon showup at dashboard. biggest problem, as i epected , was when i came to e steeper "step" where i had to go really slowly so i didn'h have enough power in reduced 1st gear- here i had to play with clutch pedal.

tomorrow is first service interval at my dealer , at 5.000km - have this issue resolved:icon_wink: so the left questions are why is my gear shifting so difficult, what is it buzzing all the time in cargo space and why the car won't start sometimes in the morning:icon_question:
 

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Discussion Starter #12
The whole thread has info.
http://www.subaruforester.org/vbulletin/f89/awd-snow-58695/

Here is a decent post I made about VDC and its function in offroad conditions(post #20).
hello again,
tried the above described situation (two opposite corners wheels in the air, vdc is turned on) and i could not get moving. front left and rer right wheel kept spinning in the air, i was standing still, vdc wasn't doing anything (both that i could feel and that i could see on dashboard-vdc icon blinking).
up to now, from my experience, vdc helps when slip starts but vehicle is still moving (dynamic conditions) - you see vdc icon blinking and feel that something is going on. whan i come to a halt, in static conditions, it seems as i don't get help from vdc any more (wheels keep spinning,nothing is happening).

anybody else have similar experience (manual forester)?
would it help if, when i came to a halt, not to keep pressing gas pedal but to press the clutch and try to start again in first gear (if vdc would then start to help me and imitate locking of front and rer differentials)?or maybe to press gas pedal and brake and to imitate "locking"myself?

thanks
 

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hello again, tried the above described situation (two opposite corners wheels in the air, vdc is turned on) and i could not get moving. front left and rer right wheel kept spinning in the air, i was standing still, vdc wasn't doing anything
Bear in mind that the traction control function of VDC takes a second or so to actually do anything useful. That is, you will need to keep your foot down and allow the wheels to spin a while (counter intuitive I know) before it will help by braking the spinning wheels.

The traction control on some other vehicles (eg Mitsubishi Pajero, VW Toureg) works much more quickly and aggressively (and, therefore, effectively) in braking spinning wheels than Subaru VDC. I suspect our driveshafts are not up to handling the torque that such sudden braking would result in.
 

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Discussion Starter #14
hm, i was pressing gas pedal and allowing wheels to spin for at least 5 seconds (probably more) .. this is not long enough?:icon_question:
 

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Discussion Starter #16
Alokin,

Check out these videos: YouTube - headape0headape's Channel

HTH,
Jim / crewzer
i did watch all six, in one and four you can see wheel spinning issue, especially in first. unfortunatelly i could not see in japaneese all details, but i would presume this is turbo forester (has air intake on hood) and by the sound of it it is gasoline version and all those are equiped with automatic transmission. could not remember exact details, but i think somewhere in this forum it was explained that automatics have slightly different 4wd driveline and they are more effective with the issue i was telling about
 

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I suspect you're correct about the car being a turbo. I thought video #4 was a good presentation of the VDC/TC system's operation.

Regards,
Jim / crewzer
 

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could not remember exact details, but i think somewhere in this forum it was explained that automatics have slightly different 4wd driveline and they are more effective with the issue i was telling about
The four wheel drive system in the automatics is indeed different from that in the manuals. However the differences concern how torque is split front-to-rear and how the vehicle handles your situation of "two opposite corners wheels in the air" is actually more affected by cross-axle torque split which is where the traction control of the VDC is effective. Auto and manual should both cope pretty much the same in this situation.

I'm surprised it didn't help after 5 seconds of wheelspin as you mention in your earlier post. Was this in a "two opposite corners wheels in the air" situation, where at least 2 wheels still have traction, and not just a slippery slope where none have traction?

You can see the traction control working here in a diagonal wheelspin situation, 0:30 to 1:40:

 

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Discussion Starter #19
Yes ,the car was tilted on one side an it was very gripy surface so wheels on it could easily moved the car. I would suspect thhat VDC is omehow mulfunctioning, but it works perfectly when going trough slippery corners?
 
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