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      07-14-2011, 02:40 PM   #50
dcstep
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Drives: '09 Cpe Silverstone FR 6MT
Join Date: Nov 2008
Location: Colorado

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2009 M3  [8.40]
I've got the 4.10 FD in my 6MT. That's a 6% change. To me 14% sounds like too much. In the DCT you DO have another gear, but I can't imagine 1st gear being of much use after that much change in the FD ratio.

The 4.10 is perfect for my 6MT because my main "sport" with the car is autocross, where I spend all but the first 100-ft in 2d gear. I've also got the Dinan chip that gives me another 200-rpm before the revlimiter kicks in, which it does for a second or two when I hit 70-mph on a course. It also feels better around town for third and fourth-gear acceleration on the interstate.

Remember, the gears were selected by BMW with the FD in consideration. When you make a 14% change in the FD you're going to start limiting the usefulness of one or two of your gears. The stock FD was selected with fleet mileage goals in mind, so I'm all for getting a little more agreesive with FD, but within limits.

Remember also that our E9x M3 have relatively low torque and any rolling acceleration "competition" (street race) will demand more than 5,000 rpm for any chance at getting "a jump". Whether you've got the stock FD or Dinan 3.62, you'll need to be in the right gear for any success. You can get the jump on some high-torque cars, BUT you must be high up in the rev band or you'll be toast, no matter what FD you have.

I vote for a FD change, but only a moderate change.

Dave
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