[CSBM5]

Update #2:

We had a CCA Sandlapper chapter autocross at the Performance Center yesterday, and once again Mike and company laid out a wonderful, fast and flowing course using essentially all of the PC's real estate. To recap - stock M2C with OZ stock width and offset wheels and 255/35-19, 275/35-19 RE-71Rs. I've got many runs on roughly the same track layout over the past 13 years but either in my E39 M5 (sold now) or my E90 M3, so I was a bit weary of really laying into the M2C right off the bat given the nature of the S55 (worry for naught in hindsight) torque.

I set some very good times but still leaving some on the table in various spots. I ended up switching to Sport+ and adapting to its response since in the faster corner exits (generally much faster than a typical autocross), Sport just felt too dull and delayed getting it done. Since forever when driving an event (autox or track) and always when instructing others, I've been a firm believer in non-sport throttle settings, but that is on older gen normally aspirated cars where all it does is (in many cases) interfere with fine weight transfer control via a jumpy throttle.

Hence I needed the response of Sport+ to get as much power as fast as possible on some of these higher speed corners coming off the apex. The car could really suck up the power into the 275 RE71Rs with only minor drift angle and/or appropriate throttle management out to the track out area. Sport+ really helps build boost faster (obviously) when coming off zero to minor maintenance throttle at the apex. Clearly I need a LOT more experience driving this car on a venue like this to get used to the engine response. That said, the overall power curve once you're into boost fully (WOT) is very linear feeling all the way up over 7k rpms.

I tried all day to keep pressures at 34-35, but I also needed to fool around with those (ran equal front/rear all day). I think I bled out about 15 psi total from the fronts. Fronts get very hot from the brakes too on this course (85.6 second runs), and you get right back in line for your group of ~15 cars, so not too much cooling off time between runs.

One other post-event thought that only late in the day occurred to me. The starting line is on a straight with a sideways sloping camber; hence in my past experience, when you launch hard (typical LSD) and get just the right amount of wheel spin, you get some sideways movement of the car as expected. I didn't really get any of that with the M2C. I had trouble getting a really good hook since if I just barely missed that window of slip, the rear would wheelhop, but a few times I got it just right and it hooked hard and laid down smooth rubber through most of 1st with proper throttle management. No sideways road-camber-induced drift that I can think of in retrospect.

I'm curious now if the programming of the Active-M LSD clutch engagement is responsible for this awesome outcome. After all it has inputs from everything, so if knows the car is on an angle, it knows your steering input angle, throttle intentions, etc, and it also knows the derivatives of all of those (rate of change of each), all in continual real time. Hence its very well possible it is managing rear lock-up amount in order to keep the car headed in the intended path under full throttle slight wheelspin launch conditions. Maybe?

Nonetheless to this old analog guy, I'm not used to this stuff, but I'm learning albeit a bit slowly. I sure love the open nature of the LSD on corner entry as this thing just turns in with abandon as opposed to pushing like a plow with some static LSDs (i.e. equal ramp angle like OE LSDs) do in something like the E39 M5. Corner entry is actually one (maybe only) good aspect of the Visco-LOK LSD in the M3 too as it has very little to zero locking on slow corner entries and allows the car to turn-in nicely.

I hope to get more seat time in a couple of months with a proving grounds autocross huge course on the schedule. Lots to learn...