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      11-07-2012, 07:23 PM   #373
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Drives: 2015 M4 DCT
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2015 BMW M4  [4.75]
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Originally Posted by bigjae1976 View Post
Interesting...I would like to hear the results. I don't have what I consider a really accurate data logger to figure out which one is I'll look to you for some info

I usually take the shorter line in tight 180s but its REALLY hard to tell if the wider/faster line is better. What happens is I catch the car under braking and then I have to really slow the car well under its max cornering capabilites to keep from running them off track. Then that kills my exit speed, I'm bogged down in 2nd and then the car that I caught takes off. But the real question is am I faster on exit? I can't really tell.
Funny coincidence that you ask, because I spent some time last weekend analyzing track footage to figure which line is quickest. I wasn't patient enough to wait until next season to get a data logger

So I calculated the sector times from the turn-in point of turn 14 to the start-finish line using the time stamp in the videos. I only considered "clean" sectors where I did not have to pass any cars.

I only had one video with the new tight/short/slow line with six "clean" passes in the sector with the following times: 2x 13.20", 2x 13.23" and 2x 13.27" for an average of 13.23". I was happily surprised with my consistency, with a max difference of only 7 hundredths of a second between passes .

I then checked two recent videos where I am taking the wide/long/fast line. Out of 10 "clean" sectors, I averaged 13.58" with a fastest of 13.37" and slowest of 13.98".

So I think I can safely conclude that the tight/short/slow line is the overall faster approach with my car in this specific sector at LCMT. There is an average difference of 0.35 seconds on a 13.5 second sector. To put it in perspective, 0.35 seconds at 100mph (the speed at the end of the sector) is 51 feet, plenty to pull a clean pass. From a different perspective, it would be the equivalent of more than 3 seconds on a 2 minute lap, not negligible. Further my fastest time of the wide line (13.33") is slower than my slowest time of the tight line (13.27").

On the specific session where I tried this new line, I did my best ever lap at 1:55.30 compared to my previous best of 1:55.53. So I am assuming that this new line was a important contributor .

I will post the video shorty as proof .

To your point of your car bogging down when you catch other cars in a corner, I believe it is important to adapt your line based on the traffic you are faced with. In an HPDE, where you cannot pass in a corner, there may not be a benefit in catching up under braking if it kills your exit speed. It is sometimes better to keep a distance going into the turn to allow you to maximize your exit speed; and then slingshot by on the straight (as long as the other driver is quick enough with the point by ). Folks with momentum cars need to be quite familiar with this technique, as it is the only way they can get by higher hp cars .

Last edited by CanAutM3; 11-07-2012 at 09:03 PM.