JohnM

You are being a touch obsessive about the fc and accel limits, Tim. Schumi can't take the car beyond the physical limits of adhesion, but he would be so much faster around the circuit it would hardly be funny, because he knows how to find the best line and how to ensure the car is always in a condition where it can deliver the behaviour needed for fastest progress around the circuit. A skilled driver can lap a lot faster than a less skilled driver even if he stays comfortably inside the limits of the grip envelope.

Simple example of the limited relevance of being on the edge of available grip: the classic "fastest line", i.e. largest inscribed radius, around a corner involves full braking, the fastest possible transition to on-the-limit constant speed cornering and another fastest possible transition to full accel after track out. That line is on the edge of the fc almost all the time, bar the very rapid transitions at the beginning and end of the corner. It is also one of the longer paths around the corner, so the driver using that line will spend nearly all his time on the fc and will have a big area under the gsum curve because he travels a long way to get around the corner. However, even timing over just the few hundred feet before and after a corner an optimal line with later and slower entry and earlier accel will be faster by a good 0.2s or more - even without trail braking. It is easy to work out figures for those simple lines and prove that.

Line and smoothness are much, much more important than using the last few percent of available grip when it comes to getting the fastest laptimes.

ColorChange

Eric: Damn I’m mad I missed his lecture. I am going to beg for the data from him. If I get it, I will post it here.

JCP911S:
With the data, it isn’t that hard to know where the limit is (real close anyway). You can look max g’s or different laps, or when the driver passed the fc momentarily.

Sunday: I get my Countach’s numbers form skid pad testing and actual track data where I have been on, and sometimes passed the fc. In all cases, I have never been able to get (actually, no one can get) higher than about 1.0 g’s in my car no matter what I do (super high speed aero effects taken out of the equation). The max g’s are largely a design/set-up/tire problem. The driver cannot exceed the max, only handle the car poorly and reduce the max g’s. You are correct about the variability (zig zagging) around the fc though.

JohnM: OK, I probably am a bit obsessive about the fc but that is because so many people don’t see its importance. For that one turn you are correct, the g sum would be higher for the largest inscribed radius if you stopped integrating at the track out. If you keep going into the corner entry of the next turn, the driver who drove the racing line will have maxed the g sum total because he will have much more –long g braking g’s to bleed off then he lost by choosing a racing line because he is gong so much faster at the end of the straight.

JohnM

Tim, the speed at the end of the straight is not as much different as often thought. I think you are on the wrong track with this maximising area under gsum idea, not least because most cars (regardless of power) can only generate longitudinal accel at 70% or less of their max lateral accel, and even that only in the first two gears, in higher gears the long. accel is much lower - trying to maximise gsum integral favours lateral accel over longitudinal accel, but the more longitudinal accel you get in, the faster you will get around the track! The lecture quote posted earlier referred to maximising accel in the appropriate direction which is the key.