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Discussion Starter · #1 ·
You can see what I currently have in my sig. Now thinking hard about going to a Turbo setup. I've enjoyed the 3.91 gears with the current car but I'd think that such short gears would be nuts with the kind of horsepower I'd have with a turbo. The engine has held up great (105,000 miles total; 55,000 miles SC'ed, driven VERY hard on a number of track days), but I want new internals when I go turbo.

What should I do about the transmission and the diff?
 

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You can see what I currently have in my sig. Now thinking hard about going to a Turbo setup. I've enjoyed the 3.91 gears with the current car but I'd think that such short gears would be nuts with the kind of horsepower I'd have with a turbo. The engine has held up great (105,000 miles total; 55,000 miles SC'ed, driven VERY hard on a number of track days), but I want new internals when I go turbo.

What should I do about the transmission and the diff?
I prefer the factory gear ratio for the street. But you'll still be good to go with the 3.91 and a turbo
 

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Discussion Starter · #3 ·
Thanks for the reply. How do the differentials listed on your site (the OS Giken and the Carbonetic carbon) compare to the original OEM differential?
 

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Thanks for the reply. How do the differentials listed on your site (the OS Giken and the Carbonetic carbon) compare to the original OEM differential?
The OS Giken kicks butt. It makes a massive difference in traction and especially being able to lay down the power exiting turns. I'm not sure if we've put the Carbonetic in peoples M3's yet. You'll have to ask our sales guys on that.

Chris.
 

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The OS Giken kicks butt. It makes a massive difference in traction and especially being able to lay down the power exiting turns. I'm not sure if we've put the Carbonetic in peoples M3's yet. You'll have to ask our sales guys on that.

Chris.
I understand most of the science behind the OS Gikken. Sort of. Can someone do a quick LSD 101?(not the Dr Leary type). I understand that the percentage of "lock up" can be set/changed on the OSG when it is installed...up to 100%. What is default/recommended for the M3? (50%?) and would there be any reason to deviate from default?
I never did get a really good explanation on how it FEELS. Can anybody help?
I think many might be interested in that answer.

I know this has been discussed in previous threads, but I would really like some additional discussion if any one wouldn't mind.
 

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Due to our short 1st gear and the fact that the stage 2.5 cars are hitting the limiter in 4th gear before the end of the 1/4 mile, i'm considering going one or two gears higher.
I'd drop a 2.x from a 330/325 into the car, should help a LITTLE with first gear. I definitely wouldn't go any lower than the stock 3.63 (iirc).
 

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Discussion Starter · #10 ·
4.10's are gonna feel tiny with f/i. My SC is just 5.5psi; I dyno'ed 393 rwHP, and my 3.91 gears are as short as I'd want with this.

BTW, Marcus, I love your car. LSB brake calipers are the bomb, are they not?
 
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