[db235]

Hey guys, considering I do lots of drag racing with some friends I would like to get the maximum acceleration from my m235 (fbo), if any of you guys know how to get those shifting points from my dyno chart it would really help! Because sometimes I just feel the car pulls more shortshifting it but down the drag at higher gears the power starts to fall and it shouldnt happen considering that i have an intercooler. Anyways, the car is making 358whp at 5350rpms and 377wtq at 4300rpms.

[Shayan55]

I usually shift around 5900-6000 and that works well when i do some 1320 action (almost everyday)

[Bee Pee]

As per advice given to you already in your thread below

http://www.2addicts.com/forums/showthread.php?t=1333452

As your car is AT, push the shifter to the left and set a bench mark with the gbox self shifting in sport mode.

Then, as already suggested, experiment shifting manually.

[overcoil]

For road racing (I know you said drag racing ) the shift points would be 1/2 between max power & max torque so 4,825 rpm and you try to never let the rpm to drop below max torque, in your case 4300 rpm.

That's kind of the base line shift point to set a time for the road. And with additional info and testing you can go from there.

I read that in Ayrton Senna's book from 1991.

I always thought lots of drag racing was the hardest test on the drivetrain?

[XutvJet]

Using your dyno data or a few dyno plots (same type of machine) for two to three other cars with the same mods, this calculator will determine your optimal shift points.

http://glennmessersmith.com/shiftpt.html

I've run the calcs for a stock M235 and the shift points are redline (7,000rpms) on the 1-2, 2-3, and 3-4 shifts. Contrary to popular belief, just because power drops after ~6300pm in the M235's stock N55 doesn't mean that's where you shift. Shift points are based on way more factors.

With it's turbo motors (especially the N55, B58, S55), BMW went to great lengths to make the power delivery more NA like, meaning a more linear power delivery and keeping torque flat. When you tune these cars, typically the power increases dramatically in the low and midrange and the power linearity dissipates a bit. The overall power, though higher, has its peak power shifted to lower in the rpm range. Instead of the power peaking at ~6300rpms in the M235 stock N55, the tuned power peak typically occurs somewhere between 5300-5700rpms. Thus, it's possible the shift points can change in some or all gears.

[mike@x-ph.com]

Originally Posted by db235

Hey guys, considering I do lots of drag racing with some friends I would like to get the maximum acceleration from my m235 (fbo), if any of you guys know how to get those shifting points from my dyno chart it would really help! Because sometimes I just feel the car pulls more shortshifting it but down the drag at higher gears the power starts to fall and it shouldnt happen considering that i have an intercooler. Anyways, the car is making 358whp at 5350rpms and 377wtq at 4300rpms.

According to the dyno you posted, i would shift at 6000 rpm

[pikcachu]

In most cases it should be at redline... here is why

[overcoil]

Does anyone feel the acceleration tapper off as the rpm's go beyond 5700 or 6700 rpm? In 2nd 3rd 4th or 5th gear ?

In 1st gear it so easy to hit redline but acceleration seems to tapper off 2000 rpm earlier - that first gear ratio is very high (2015 235) - what do you think ?

[XutvJet]

Stock motor? If so, shift at redline (just before you hit the limiter). Just because you can "feel" acceleration taper off does not mean it's time to shift. Turbos pack a bit torque surge and when you feel that big surge end, it feels like it's time to shift. Don't. Your brain is being fooled. Please use the optimal shift point calculator I posted. So many people would be surprised that they're shifting at the incorrect time.