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Road racing, DCCD and VDC/TC
Road racing, DCCD and VDC/TC
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Old 06-02-11, 11:11 AM   #1
Xaqtly
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Default Road racing, DCCD and VDC/TC

I've looked, and haven't really found any good info regarding DCCD, VCD/TC and road racing in STis. I might have missed it, and if so sorry about that. But what I'd like to know is what settings people have found to work for them in road racing, like at Willow Springs or Buttonwillow, etc.

Like VDC and TC all the way off (orange)? Or in sport mode (green)? DCCD on auto, or all the way rear biased (65r/35f I think)? Or somewhere in between? I know some of it is going to come down to personal preference, just wondering what people like. I've done a decent amount of road racing, but never in an STi, or any car that I've been able to control the center diff and traction control.

I used to road race Sentra SE-Rs, and my built one had a Quaife mechanical LSD which was absolutely awesome. It dug into corners similarly to the way the STi does. Now that I have the STi I've sort of been hankering to get back into it.
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Old 06-02-11, 02:05 PM   #2
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Default Re: Road racing, DCCD and VDC/TC

Quote:
Originally Posted by Xaqtly View Post
I've looked, and haven't really found any good info regarding DCCD, VCD/TC and road racing in STis. I might have missed it, and if so sorry about that. But what I'd like to know is what settings people have found to work for them in road racing, like at Willow Springs or Buttonwillow, etc.

Like VDC and TC all the way off (orange)? Or in sport mode (green)? DCCD on auto, or all the way rear biased (65r/35f I think)? Or somewhere in between? I know some of it is going to come down to personal preference, just wondering what people like. I've done a decent amount of road racing, but never in an STi, or any car that I've been able to control the center diff and traction control.

I used to road race Sentra SE-Rs, and my built one had a Quaife mechanical LSD which was absolutely awesome. It dug into corners similarly to the way the STi does. Now that I have the STi I've sort of been hankering to get back into it.
Subaru uses Torsen diffs which act more like open diffs, so don't be fouled because these can't be compared with the Quaife diff. If you really want your Subaru to turn in then have your front diff changed. You can make it turn by trail braking but this is not a very good idea for street driving and also with the e-brake but the stock STI has a lot of understeer. You have to get used to it before you will be able to drive it to its potential.

Regarding traction control and VDC, these are off when the light is orange. When is green you only have the TC off and the VDC will be more permisive. I would suggest to got with the all off (orange) option after you start learning how to drive this car.

Regarding DCCD use it on Auto- when you have good grip and Auto+ when you have less grip. If you want to be in control then change it in manual and go to the bottom on dry surfaces with good grip and upper when is slippery. Don't lock the diff only on snow or ice or you could damage the center diff...
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Old 07-17-11, 02:40 PM   #3
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Default Re: Road racing, DCCD and VDC/TC

What is the point of locking the diff if not to use on snow or ice?

Snow or ice should give way for the wheels to slip if they need to.

Full lock when you do have grip causes things to bind?
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Old 07-17-11, 02:59 PM   #4
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Default Re: Road racing, DCCD and VDC/TC

If you are on a road track there should be no difference between vdc green and vdc amber cause you should never activate the vdc. The TC on these cars is imo pretty scary if you are driving hard, but green or amber should make no difference.

diff should be run in auto imo as it is really a best of both worlds type scenario where you get less front drive preapex when you are working to turn the car and more post apex to suck it though.

+/neutral/- settings imo should be used as another front to rear biasing tool like f/r camber ratio, f/r tire pressure ratio, or f/r sway bar ratio. It makes a big difference in that way to help dial in the car and its super easy to adjust while you are driving to find what is best relative to that day, track surface and temp, and all the rest of your settings that cannot be adjusted while you are moving.
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Old 07-17-11, 07:11 PM   #5
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Default Re: Road racing, DCCD and VDC/TC

Don't use VDC green. It will overheat your rear brakes.
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Old 07-17-11, 07:22 PM   #6
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Default Re: Road racing, DCCD and VDC/TC

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Don't use VDC green. It will overheat your rear brakes.
Have any proof?
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Old 07-17-11, 07:48 PM   #7
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Default Re: Road racing, DCCD and VDC/TC

I can see it happening in a track situation. VDC will use the brakes to make up for the front and rear diffs acting like open diffs when without any traction or to prevent them from being over run. I haven't seen it happen, but it's certainly possible.
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Old 07-17-11, 09:00 PM   #8
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Default Re: Road racing, DCCD and VDC/TC

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Originally Posted by Koncept View Post
Subaru uses Torsen diffs which act more like open diffs, so don't be fouled because these can't be compared with the Quaife diff.
Torsen and Quaife make the same kind of LSD, typically called a helical or automatic torque-biasing LSD. They should behave almost identically in any given application. (Except for the Torsen T-3, which the STI does not come with.)

Last edited by no1v2; 07-17-11 at 09:05 PM.
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Old 07-18-11, 11:16 AM   #9
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Default Re: Road racing, DCCD and VDC/TC

Yeah, I don't have any knowledge of the diffs Subaru uses, all I can say for sure is that when the STi digs into a corner I can feel the diffs working in the same way my SE-R's Quaife did. It's an odd, almost physics-defying sensation. I could go full throttle in first gear around a corner and not break the front tires loose, it was great.

In the STi when I have the vdc on green, I can get into a corner and when the front diff starts working I can get light oversteer, and just glide through onramps with the tail hanging slightly out. It's pretty awesome.

Thanks for the collected info. I'm looking forward to getting my car onto a road course at some point, this will all help.
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Old 08-03-11, 05:02 AM   #10
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Default Re: Road racing, DCCD and VDC/TC

Quote:
Originally Posted by Xaqtly View Post
In the STi when I have the vdc on green, I can get into a corner and when the front diff starts working I can get light oversteer, and just glide through onramps with the tail hanging slightly out. It's pretty awesome.
Do you have any issues with your rear brakes overheating from the VDC?
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