[Max Well]

Originally Posted by trey100

Appreciate all the data by the way. All good stuff. I think my main point was that even with just brake boost or stomping on the gas, a 2.4ish 60' time isn't great for a high powered AWD vehicle. For reference, in the very poor launches of my F80 M3 6MT, I was hitting 2.2-2.3 60' times, and that is mostly rolling out at part throttle. I assume that the X3M 60' times without launch control are just highlighting the turbo lag down low in the rpm band with the S58 … In any case, the real difference that stuck out for me was the post above from RoyB. He ran a 12 flat and a 1.85 second 60' time by just brake boosting which is a big difference from your non-LC runs. I did notice that RoyB had traction control off. I assume you too? Or could that be the difference?

Thanks, trey100. I think you’re spot on with the roughly 0.6s difference being due to the well-described 'lag', turbo delay, or whatever term best describes that issue. It's possible that traction control may have been playing some subtle role I guess, since I was using just regular Stoplight starts in Comfort/Sport/Sport+ with normal default traction, but my gut feeling is more in the ‘lag’, especially since I had lowered the tire pressures for my Feb runs which shouldn’t have been as much of an issue for traction control (and the times were similar on both days).

Originally Posted by RoyB

OK I figured out LC. ... I then tried standard 4wd and it seems to go much better since it's not spinning as much. ... Looking Max Well sheet above, this could had easily been an 11.7x run. Which has me wondering, are the non comp models really that much slower than the competition model? Off the cuff they appear to run very similar. I am really looking forward to when the track opens so I can get some clean runs. Living in the suburbs it's hard to find 1/2 mile straight road which is safe for running a full pass.

Not sure what your tire psi settings were, RoyB, but back in Nov my tires were spinning like a belt sander at 33 Front/38 Rear as BMW suggests. This time out I lowered to 32/35 and it made a huge difference – didn’t feel like they spun at all. Next time I’m planning on 32/32 just to see if that grabs even better for a lower 0-60 foot interval.

Looking at the Tech documents, it isn’t that surprising that they are pretty close as the only difference is 30HP (torque is the same). This translates to a Wt/HP for the X3M of 9.05 and 8.52 lbs./HP for the X3MC. And if you consider most non-Comps come with 20” wheels/tires, I suspect the unsprung weight is less (haven’t seen those weighed but would be helpful to know), so that might actually offset the slight HP advantage the X3MC has? Here are the numbers again -

X3M – 1970 (4343 lbs.)/2045 (4508) DIN/EU; CdxA = 0.36x2.69; 353kW or 480HP, torque 600Nm; Wt/Power ratio kg/kW 5.58, or 9.05 lbs./HP
X3MC – same as above except: 375kW or 510HP, Wt/Power ratio kg/kW 5.25, or 8.52 lbs./HP

And BMW claims a difference of only 0.1s (4.2s vs 4.1s) in the 0-62 km/h.

Originally Posted by new2the3

Is launch control available in 4wd or only 4wd sport?

Per the 'Complete Vehicle document' found in the 'Sticky' thread, p.24, the conditions for LC are: must be stationary and engine warm, M Dynamic Stability Control deactivated (4WD), and Manual mode with S3 selected. On p.25, indicates LC “automatically shifts up using the shortest possible gearshift times and performance-optimized shift points as long as the driver keeps the accelerator pedal full depressed.”