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1998 Forester S
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50 Posts
Discussion Starter · #1 ·
I bought an 98 forester so I was disappointed to find out that it does not have a LSD especially since I do some overlanding/offroading with it. I was debating getting a lsd but I also have read they are not the most effective. And a LSD would only help split torque in the rear. If only I could get VDC in a 98. VDC can apply brake to help transfer torque to the wheels with grip. The first year with VDC is 2001 for H6 outback. I was originally thinking I would need to swap a lot to get this to work or it probably not even be possible since it might be limited by the transmission and ecu. So then I thought about it and VDC is just using the abs system to do the VDC work. My 1998 Forester has ABS so if I can hijack the ABS system, then I could maybe apply my own VDC.

What would be needed for VDC:
Wheel spin sensor
ABS pump
Module to control braking

So if we can read the Wheel speed sensors, then we can determine which wheel is spinning and which is not. Then based on the information, the module sends signals to the ABS pump to apply baking to the appropriate wheel.

Wheel Diagram:

W1 --- W2
LI--p--LI
----|
----|
LI--b--LI
W3 --- W4

Basic microcontroller logic:
If W1 speed >500rpm and W2 is <200rpm
Then brake W1
If W2 speed >500rpm and W1 is <200rpm
Then brake W2
If W3 speed >500rpm and W4 is <200rpm
Then brake W3
If W4 speed >500rpm and W3 is <200rpm
Then brake W4

To control this I would use a Arduino microcontroller since I have a couple in my parents basement and I think it would work. One issue I see is I think the 98 ABS pump only modulates braking and does not actually apply it. I think I would need to get a 2001 VDC ABS pump or later to be able to apply braking. I'm not sure on this so I will have to do more reading. Because this does not incorporate the more complex computation and input of the real VDC system, this would have to be part time (on/off switch) for off-roading and snow use.

Feel free to give me any input. This is a concept at the moment but there is a 2007 VDC forester I could steal a ABS pump from at a salvage yard if figure it out.
 

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Super Duper Admin Guy
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3,202 Posts

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Registered
1998 Forester S
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50 Posts
Discussion Starter · #4 · (Edited)
Does anyone know the differences between the not VDC abs pump and vacuum pump verses a VDC abs pump and vacuum pump? Basically I am trying to figure out how the VDC (or any ESC systems) applies braking without brake input from the driver.
There are two abs pumps and vacuum pumps based on whether the 2001 outback had VDC
ABS pump module (w/o VDC) 27539AE02A
ABS pump module (w/ VDC) 27539AE001
Vacuum pump (w/o VDC) 26402AE05A
Vacuum pump (w/ VDC) 26402AE200

So What is the difference in these part?

This video is a great overview in how the ABS pump works
 
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