Maverick PCA on MSR 3.1 mile track 4/25 - 4/26
04-30-2009, 05:36 PM
#106
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04-30-2009, 05:48 PM
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04-30-2009, 05:50 PM
#108
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05-01-2009, 02:04 AM
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05-01-2009, 04:07 AM
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I noticed that you had a pretty consistent line at Boot Hill that could be improved. That turn has a displaced apex, but it looks like you're trying to apex it at the curbing. That leads to corrections during the more important turn (Tombstone). At higher speeds, it could lead to an off at Tombstone track-out.
Russell, saw your video and I see what you're talking about. Cool double cam setup and driving BTW! I looked back over my video from September and some before that and I actually used to displace that first apex. I guess the change this weekend is from me looking for more speed through there. My data and video from September show that I'd shift to 3rd at track-out, accelerate up to about 69-70mph and maintain that until the car was turned enough to go WOT out of Tombstone. This weekend, I was accelerating through the apex of Boot Hill. I think I just had to get closer to the apex because my speed was greater and the momentum would push me to track-out. Basically, this weekend I'd stay on the gas more, where last time, I'd kinda coast through there. Speed was about 8mph more at track-out from Boot Hill this weekend than it was in September, but this was causing trouble for Tombstone. I may have just been over driving that section, probably would have had it better sorted with a few more sessions! Damn rain.
These are solid points. However, you will often find some of the fastest guys/gals actually more or less double apexing Boot Hill (at the curbing) in order to place the car straighter towards the top & get to WOT sooner. In other words, giving up the entry in order to get to WOT at mid corner & be more stable up top entering Tombstone.
I was going to say the same thing. From what I've observed riding with some fast drivers through there, the faster you are going through that boot hill/tombstone complex, the more the car is sliding, and therefore, the closer to the first apex the car needs to be to line up for the second half of the turn.
Funny thing is, I thought I had this set of turns nailed down pretty well back in September, but clearly there's a lot more to learn! Looking forward to the next DE.
05-01-2009, 09:31 AM
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05-02-2009, 12:47 PM
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05-02-2009, 01:21 PM
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The lap time value of ABS
The first graph below illustrates the part of the track that is analyzed in the 2nd graph. The 2nd graph shows speed and longitudinal acceleration vs. distance. The Sept lap is in red, last weekend in blue. Without ABS, I was braking about 15 ft. sooner, and could not reach the same amount of maximum deceleration. Brake release occurs at the exact same point on the track, and from there, speed vs. distance continues to match the Sept. lap until the next hard braking zone. This particular turn contributed about 1/8 of the total gap for the lap, which was 6 seconds. 6 seconds - all traceable to earlier and lighter braking.
Threshold braking (w/o ABS) in a lighter car that was never designed to have ABS might be a different case, but in my 3300 lb. 996, I think it's safe to say that I could never make up those 6 seconds no matter how good I got at it. So my conclusion is that in this car at least, there is no lap time value to running w ABS off, and therefore, there is no value to learning how to drive it w ABS off. I had previously thought i was getting a good lesson by being forced to run with it off, but now I'm not so sure about that.
05-02-2009, 04:32 PM
#115
Threshold braking (w/o ABS) in a lighter car that was never designed to have ABS might be a different case, but in my 3300 lb. 996, I think it's safe to say that I could never make up those 6 seconds no matter how good I got at run with it off
I'm not sure what the data files I sent you indicate in this area (if anthing at all) but I rarely engage ABS after the out lap - even under -1.1+ long Gs in this corner [MSR turn 10, max I've hit here is -1.266 longGs!]. Same thing even after I switched from pagid yellows to PFC 06/97 combo. I did have issues when running tires of different compounds and when I ran rears that were too big relative to the front.
The Sept lap is in red, last weekend in blue.
-td [edited]
Last edited by himself; 05-02-2009 at 05:52 PM.
05-03-2009, 12:36 AM
#116
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Interesting commentary regarding ABS. Do you know why it went out? Also were you on your R6s both times? What sizes did are you running? Pads?
I'm not sure what the data files I sent you indicate in this area (if anthing at all) but I rarely engage ABS after the out lap - even under -1.1+ long Gs in this corner [MSR turn 10, max I've hit here is -1.266 longGs!]. Same thing even after I switched from pagid yellows to PFC 06/97 combo. I did have issues when running tires of different compounds and when I ran rears that were too big relative to the front.
One other interesting thing is that the blue trace appears to be faster all the way around by 2+ MPH. Braking zone difference is 10+ MPH! [are the colors labeled right [red=sept/ blue=april?]
-td [edited]
I'm not sure what the data files I sent you indicate in this area (if anthing at all) but I rarely engage ABS after the out lap - even under -1.1+ long Gs in this corner [MSR turn 10, max I've hit here is -1.266 longGs!]. Same thing even after I switched from pagid yellows to PFC 06/97 combo. I did have issues when running tires of different compounds and when I ran rears that were too big relative to the front.
One other interesting thing is that the blue trace appears to be faster all the way around by 2+ MPH. Braking zone difference is 10+ MPH! [are the colors labeled right [red=sept/ blue=april?]
-td [edited]
In Sept, I was running sport cups. I was on street tires (PS II's) when the ABS failed this past Friday, and on the R6's the next day, so the pbox comparison is Sport Cups vs. R6's. (yes, I mis-stated the colors... Red = April and Blue = Sept). I don't know if you could attribute the initial 2 mph difference to the sport cups vs. street tires, but I just discounted it as noise compared to the much bigger difference in the braking zone (several other turns showed the same thing).
Pads: I had only 1 track day (TWS in the rain) on Pagid orange, and the same 1 track day on a set of new front rotors, and the same 1 track day on new brake fluid. Bottom line: the brake system was excellent shape before Friday.
I didn't mean to imply that I typically engage ABS under hard braking, so I should clarify what was happening on Saturday.... I was having a very hard time preventing wheel lock-up due to ABS having been out since Friday. But that was more due to the way brake bias is changed when ABS is off (it moves to the front). So the Sept/April comparison is actually "normal brake bias" vs. "front brake bias", and the Sept braking didn't necessarily engage ABS.
So I still think that I could never drive this car w/o ABS faster than I could with it, and I still don't see value in learning how to drive this car w ABS off given how difficult it is to brake w/o locking up, or losing lots of time. I do believe there is value in learning how to drive w/o ABS... but only in a car that doesn't have ABS to begin with!
BTW, when ABS failed on Friday, it was sudden. Felt like there was no initial response to the brake pedal, which led me to get on it harder, and then harder, and then the next thing I know, I'm locked up, and off and running for a sleigh ride. Happened coming into T6(?)... the left turn down the hill to the new section. You can see my skid marks in the the picture below. I went into the grass, then across the pit-out lane, and then back into the grass beyond. As you can see, the left tire seems to lock up first, and right tire second, but I don't know if anything can be concluded from that.
Thanks for the data files! Looking forward to seeing where I need to improve to catch up!
05-03-2009, 11:12 PM
#117
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