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      11-08-2012, 11:13 PM   #375
bigjae1976
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Drives: 11 E90 M3 Individual
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Location: Milwaukee, WI

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2004 BMW M3  [4.50]
2011 BMW E90 M3  [5.00]
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Quote:
Originally Posted by CanAutM3 View Post
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 .
Good analysis. Yes, when I catch a car under braking, I probably need to take the wider line.

I think this also depends on the capabilities of the car. Most of the tighter 2nd gear corners (40-55mph) in TX are off camber on the outisde since the pavement is crowned. So it pays off to stay tighter towards the inside. As you widen the line you are fighting the off camber outer edge. Heavier, poorer handling cars can't even consider taking a tight line.

I'm kind of at a crossroads here. When I have an occasional instructor in the car, they are pushing me towards the "normal" line. But I'm catching people in certain places by turning on from the middle, early apex with heavy trail braking. Its hard to be consistent but I think its cutting my lap times. I need to start running data so I can confirm or deny this type of stuff.
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