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Old 01-21-2012, 11:12 AM   #1 (permalink)
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Default VDC off - what really happens

I read this in a document from the web but I wanted to see it this might be true. " A Vehicle Dynamics Control 'off' switch is useful for driving out of slushy roads, deep snow or gravel. The 'off' position deactivates the system's torque-reduction control, while the ABS and traction control remain active. " I'm mostly interested in retaining brake traction control to stop wheel spin while not limiting engine power. I read a 2009 owners manual but it are not clear. I actually wrote an email to the Subaru customer service people but they did not explain what would remain functioning after the VDC was turned off. So when VDC is turned off does brake traction control remain functioning?
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Old 01-21-2012, 01:34 PM   #2 (permalink)
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no, the traction control is turned off when you turn vdc, what still seems to be on is the stability control.
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Old 01-21-2012, 03:23 PM   #3 (permalink)
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But why do I need stability control when I'm sitting in a snow covered parking lots with my tires spinning?
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Old 01-21-2012, 03:25 PM   #4 (permalink)
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Lightbulb

The '09 OM contains this statement on page 7-29:
Quote:
With the Vehicle Dynamics Control system deactivated, traction and stability enhancement offered by Vehicle Dynamics Control system is unavailable.
Contrary to previous interpretation, this sounds to me like TC is disabled if the VDC system is turned off.

HTH,
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Old 01-21-2012, 03:27 PM   #5 (permalink)
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Here's a quote for the 2011 owners manual:

"Even when the Vehicle Dynamics
Control system is deactivated, components of the brake control system may
still activate. When the brake control
system is activated, the Vehicle Dynamics Control operation indicator
light illuminates."

But this paragraph in not in the 2009 or 2010 owners manual.
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Old 01-21-2012, 11:56 PM   #6 (permalink)
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the ABS still works. That's for sure. TC is off, that's for sure.

Stability control? Some folk feel it's on like normal, it's my experience that it's either off or greatly reduced in sensitivity.
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Old 01-22-2012, 07:40 AM   #7 (permalink)
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Arrow Subaru Official Info

Quote:

Vehicle Dynamics Control
Vehicle Dynamics Control is standard on all Forester models. Vehicle Dynamics Control is a highly sophisticated electronic stability control system that monitors input from the ABS brake system as well as taking input from steering wheel angle, and yaw and lateral g-force sensors. The system adjusts individual wheel braking as needed, helping to maintain vehicle control under a variety of driving conditions. A Vehicle Dynamics Control 'off' switch is useful for driving out of slushy roads, deep snow or very loose gravel. The 'off' position deactivates the system's torque-reduction control, while the ABS and traction control remain active.

In all 2009 Foresters, Vehicle Dynamics Control system also provides traction control and a 'virtual' limited slip rear differential (LSD) function. Using the virtual rear LSD in place of a viscous-type unit provides the traction benefits of an LSD but without the weight or the potentially negative impact on steering response, turning ability or stability.
source: News Detail - News - Subaru Canada
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Old 01-22-2012, 08:01 AM   #8 (permalink)
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If TC is still on, wheels will still be braked; just the engine power won't be reduced.

Is that your experience? It sure isn't mine...
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Old 01-22-2012, 08:49 PM   #9 (permalink)
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I'm trying to understand before I buy a forester. My 2001 outback does not have VDC. I read the same Canadian document regarding the 2009.
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Old 01-23-2012, 06:32 AM   #10 (permalink)
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Exclamation

Quote:
Originally Posted by Lone Ranger View Post
I've posted that same info before. Based on the statements in my OM's and my on-the-road experiments, I don't believe it's true.

Regards,
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Old 01-23-2012, 07:08 AM   #11 (permalink)
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As indicated above, "VDC off" actually means "TC off" (engine will not cut power, brakes will not catch spinning wheels - so NO "virtual LSD"). ABS still works, and "dynamic control" is still active (at least when you get above certain - rather low - speed). Tested numerous times.

The only way found so far to disable everything without consequences is to pull the ABS fuse.
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Old 01-23-2012, 09:20 AM   #12 (permalink)
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Hmmm...The first time I was "delayed" in deepish snow, I didn't turn the VDC off but another forum member recommended I try it.

So, the very next time, I was "delayed" on a steep road in about a 3/4 foot of fresh snow on compact snow. Instead of backing down, I tried starting with VDC off. I actually found it didn't really work. I rocking and revved but to no avail. I then turned VDC back on and using the smae technique, I managed to get going upwards again.....so,

I'm guessing it really depends a lot on conditions. Turning the VDC off in my case did not "help" at all.
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Old 01-23-2012, 10:24 AM   #13 (permalink)
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I had to run off VDC on the sand dunes, it was a game ender while on. Once off, and with 12 psi in the tires, the Foz ran around the dunes okay.
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Old 01-23-2012, 10:52 AM   #14 (permalink)
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See the video below... It is a subaru demonstration by a professional subaru driver. They indicated on the 09+ models that when traction control is taken off, the VDC still works to control the wheels spinning (gets the other wheels to kick in). However, the engine will not cut out allowing for wheel spin for dirt, sand, mud, snow, etc...

TC OFF
"Instead of only two wheels spinning when stuck or going through something the VDC will make all four wheels work (symmetrical all-wheel drive) while at the same time not allowing the engine to cut out."

TC ON
"Still the same all-wheel drive as above but cuts the engine rpms down so you don't spin out of control on the road."

Here is the video:
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Old 01-23-2012, 03:03 PM   #15 (permalink)
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Great video. Explains and demonstrates exactly what we've been debating.
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