Welcome to IGOTASTI! You've come to the right place. There is a ton of good information here and helpful people to point you in the right direction.
Good to hear you're back in an STi. I'm not the most knowledgeable in terms of the GR chassis, I'm more of a GD guy myself. 2007 is one of my favorite model years.
Anyways...in regards to DCCD settings, I'll have a look around and find you some links on the DCCD and it's settings. How familiar are you with it right now? I *think* the GR has slightly different settings than the GD (2004-2007 STi) so what I may tell you might not be as accurate for your model year. When it comes to Gymkhanas, Autocross and so forth, there are two general schools of thought on DCCD settings.
1. Put the DCCD in manual mode and move the selector all the way to the bottom (dark green) setting; often referred to as Full Open.
- This prevents the DCCD from taking inputs from multiple onboard sensors and adjusting the center diff settings in real-time. The thought process is, "the behavior of the car shouldn't change during my lap and is therefore easier for me to control the car only how I want to."
- Ultimately, what it is doing is allowing the most variance in wheel rotations between the front and rear wheels. Conversely, the further "up" (yellow) towards LOCK that you set the DCCD, the more the front and rear wheels HAVE TO rotate together at the same speed.
- Thus, Full Open can tend to promote more oversteer while closer to LOCK promotes more understeer (or traction and stability in low grip environments). That said, do NOT drive the car in LOCK unless you are an ice road trucker. :lol: LOCK on drive pavement ruins the DCCD and associated drivetrain. It's also not a great idea to set the DCCD close to LOCK for long periods of driving. You will notice drivetrain binding during cornering, if you do.
- If the course is REALLY wet and slippery, bring the DCCD (in manual mode) up a couple marks from Full Open and that will help reduce the tendency to spin out a bit.
2. Leave the DCCD in AUTO and forget about it.
- I have searched high and low for this thread (on a couple other sites) from years and years ago, where a track day junkie made numerous laps at different DCCD settings and recorded his results. Since I can't find the thread, I'll summarize from memory: "There are many different tracks, driving conditions and other situations where various DCCD manual settings will FEEL faster than others. That said, in almost every instance AUTO produces the fastest lap times, even if it doesn't feel like it."
With that considered, if you are frequently making incredibly tight turns at lower speeds and such, the Full Open manual setting might be for you. But for everything else, AUTO is the preferred setting.
I know that's a lot to digest, but hopefully that helps.
Anyways... :welcome: