VID: "Manual VDC" Test

Blue Fox

Blue Fox

Forum Member
Joined
Dec 29, 2009
Messages
198
Location
Durango, Colorado
Car Year
2005
Car Model
Forester XT - 2" Lift
Transmission
5MT Dual-Range
"Manual VDC" Test

Today, I performed a "proof-of-concept" test on my Forester for a "Manual VDC" idea so to speak. As we know, Subaru's VDC uses the brakes to stop spinning tires, and does so intelligently by using each of the four brakes to independently brake spinning wheels to allow the car to climb when wheels start to slip and diagonal spin starts.

So my concept was, as long as I can stop one of the spinning tires, the diagonal spin would stop (being that it's no longer diagonal at that point). I was sure that if I individually braked one of the rear spinning tires using the parking brake with separate handles (one for each of the rear brakes), it would move power to the other wheel on the same axle (at least enough to get the car moving and overcome the diagonal spin).

Boy, was I wrong. In theory, it sounds like it should work perfectly. But in the testing, it didn't do squat, sadly..

So in my video (posted below), I carried out a few tests. I disconnected the parking brake line to the rear left tire, so the parking brake was ONLY connected to the rear right tire (before I went about modifying my car with two handles). The test carried out in my garage "seemed" promising as the car would actually climb, but it struggled doing so, and the front tire still had a little traction against the concrete. Once I moved the test to a dirt/gravel area (more applicable conditions), it all fell on its face and it didn't climb at all, just spun up the front tire, and didn't even think about moving power to the other rear wheel.

My sway-bars were still connected during the tests, and my RSB is from an STi, so that's why it seems so pathetic that the car can't climb up two ramps. lol. But still, if the older Forester's had VDC, or at least could be retrofitted with VDC from a newer model year, it would help SO much.

Here's the video of the epic fail......

[ame="https://www.youtube.com/watch?v=G5FX3K3h1d0&feature=channel_video_title"]YouTube - Diagonal Spin Test[/ame]
 
Well, no matter the outcome, it's awesome that you did this and posted about it!!!:ebiggrin: Your efforts are greatly appreciated. Thank you.

My question is this; is your car auto or manual? and would the test results differ with the other tranny?
 
My car is an auto. Outcome might have been slightly different with a manual, but, as some other members have brought to my attention, the center diff doesn't allow enough power to the rear, which is why the front was spinning up, and both rears weren't.....essentially making it one wheel drive at that point.
 
Good point carljwnc, I was thinking the same thing :)
From what I understand, (& correct me if i'm wrong) isn't the manual is an even 50/50 split, front to rear all the time, where as the auto's are not ?
That being the case, it may work better (or only) on a manual :shrug:

Regards
Mr Turbo
 
mr turbo said:
Good point carljwnc, I was thinking the same thing :)
From what I understand, (& correct me if i'm wrong) isn't the manual is an even 50/50 split, front to rear all the time, where as the auto's are not ?
That being the case, it may work better (or only) on a manual :shrug:
Click to expand...

We need a volunteer from the audience with a manual to get out the ramps and try the same test please.:iconwink:

Yup, 50/50 in the MT.
 
garrettG said:
ive got the ramps, and a manual... if someone can tell me how to disconect the left E-brake ill give it a shot.
Click to expand...

garrettG said:
... but i dont have sway bars. so i might just crawl right over the little ramps
Click to expand...

To disconnect one of the e-brakes, you need to remove the center console where the e-brake is (should take no more than 10 minutes). There, you should have one metal cable going into a junction looking thing, then you disconnect one of the two metal cables that go to either rear brake. (disconnect the one you are going to have up in the air)

As for you not having sway-bars, you can perform the same test if you stack some wood planks or something underneath the ramps just to get them further in the air (probably only need 2 or 3 inches worth. I would test this on a dirt road BTW (unless your tires are COMPLETELY off the ground while in your garage, which mine weren't)

An easier way would be to place the ramps in the configuration you want, and dig out where the tires would be opposite of the ramps so they hang and don't touch the ground as you try to crawl up the ramps.

I'd love to see how different (or not different) the test is with a manual. But as others have already said, it's most likely a center-diff thing at this point. I'm going to try to perform the "4EAT Lock Mod" and see if that makes any difference.
 
Blue Fox said:
... (disconnect the one you are going to have up in the air...
Click to expand...

This statement is wrong, did you mis-type it?
Cause pulling the E-Brake on the wheel on the ground aint gunna help...
Daza.
:ebiggrin:
 
daza said:
This statement is wrong, did you mis-type it?
Cause pulling the E-Brake on the wheel on the ground aint gunna help...
Daza.
:ebiggrin:
Click to expand...

Yeah, I meant it the other way around. KEEP the e-brake connected for the one up in the air. Thanks for catching that!
 
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