Originally Posted by HDDP
I did the math on the ratio change and based on the length of the straightaways at the tracks I usually run, max. 1800' at California Motor Speedway and much shorter at Laguna Seca, then only 1100' at Willow Springs.
I had to balance the RPM change with the fact that I still drive the car on the highway. the 3.69:1 ratio will put me at a good range for highway driving in 6th gear and still give me much more torque going through the turns at the track. A +13% change from the OEM 3.27:1 ratio.
Trust me, I debated a much steeper change and would have gone up to a 4.02:1 if I was only driving the car on the track. But then I would be running in the high 3,000 RPM range at 65 MPH on the freeway for extended periods of time, which as you know, wouldn't be too good for engine life, not to mention my gas mileage.
Also, from what I understand, the 3.69:1 differential comes from a Mercedes W123-240D and bolts right on to the car with the gears matched from the factory. The other differentials are custom built by an outside vendor. I figured I would go with the factory equipment.
3.69 should be perfect -- anything more, like you said, would be a PITA to drive on the street. I would think the ratio change would be good for .3 or .4 seconds in the 1/4mile.
What is the difference between the stock brake setup and the AMG setup? I was under the impression that the stock setup (with track pads) would be plenty of stopping power.
HDDP -- do you use your car for real wheel to wheel competition, or for open lapping days at the track? If for W2W, do you have a roll cage inside?