znod

Oops.

znod

Hi needforspeed and all:

I checked out the calculator using BMW's 545i torque curve and other known 545i values. As needforspeed indicates, the calculator ignores rear-end ratio since it is a constant--which I also ignored in my earlier optimal shift point analyses for the same reason.

I think that the caculator has merit, but the problem with it, and all such calculators, is that it ignores aerodynamic drag and other factors that would affect engine load differently in the various gears. Thus, to really get a good feel for optimal shift points one needs to use a g-meter to get all-loss RW torque values across the RPM range in each pertinent gear. The calculator is good, as I read it, in the sense that it is based on optimal shift theory--which utilizes the idea that the optimal shift point in a gear is the RPM that minimizes the drop in RW torque that will occur given the shift. The calculator produces values that correspond very closed to those that I developed in my earlier analyses.

For the 545i, the caculator yields (see below) exactly the same picture as my first optimal shift point analysis in which I used the BMW 545i torque curve and assumed implicitly that the curve is the same in each gear. As some of my other analyses show, the torque curve is far from the same in each gear. For clarification, see post #108 here. As indicated earlier, I'll get around to a new optimal shift point analysis for my car using these curves one day. The only problem is that the analysis would be interesting, but irrelevant, since, under full throttle, the Step allows the user no significant shifting flexibility anyway.

The key to understanding the calculator's results for the 545i, assuming that I understand them, is to note that the almost parallel lines for each pair of gears come closer and closer together as 6.5k RPM is approached--implying that the decrease in torque is minimimized at the optimal shift point of 6.5k in each gear--which is where the Step makes the 545i shift under full throttle in a 545i. Note that the key values produced by the caculator exactly match the key values in my attached analysis (the second attachment). Ignore the last three sections of my analysis. They duplicte the first three sections, and I forgot to omit them. Note that my analysis shows the actual decrease in RW torque occurring after each shift--although I don't present enough of the analysis to show that 6.5k appears to be the optimal shift point in each gear. The key torque values are 1088.37 vs 1088; 610.74 vs 611, and 386.72 vs 387. And, note the corresponding RPM levels.

Regardless, shifting sooner than 6.5k really may be optimal for the 545i--as some of my prior analyses suggest. This possibility may end up being even more "real" given a per-gear torque curve analysis. Then, all I'll need to improve my performance is a decent shift program.

0700700

red is after chip-tuning... I follow your logic, and maybe the D mode is quicker... i always use DS though ... much more willing to downshift and thus quicker to get going