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12-19-2011, 12:19 PM | #111 |
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Frank,
I left foot brake, and trail brake.... |
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12-19-2011, 07:32 PM | #112 |
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No problemo with trail braking, as that's still just one pedal at a time.
When you left-foot brake, are you actually applying the brakes and throttle at the same time, or doing it to minimize transition time between brakes and throttle but not applying both simultaneously. If the latter, then it'll still work fine. If the former, the math channel will return the net value of throttle and brakes at that moment, which'll be pretty meaningless.
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12-19-2011, 08:04 PM | #113 |
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At the beginning, it is just one peddle at a time. At the apex, start to release the brake and apply throttle. Many times I have to do this to transfer weight to the rear (the front is already set) to keep the rear planted...
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12-19-2011, 10:08 PM | #115 | ||
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The only problem here is that it wouldn't work well when presenting the 'pedal inputs" in map format using Track Report view. You'd want the combined channel to have, I think, the throttle input instead of brakes there. Of course, you could make yet another combined math channel just for the Track Report view... Any of this make any sense?
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12-19-2011, 10:24 PM | #116 | |
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I guess you have to step back and say what are we really trying to see? If we want to see the major thing the driver is doing, then we just need whichever input is greater. That is an easier problem to solve. If we want to see all inputs, then we have to figure something different out. I'm not sure the best way to do that. |
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12-19-2011, 11:26 PM | #117 |
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Sunday turned out to be a great day. Had tons of track time with no traffic, weather couldn't have been better for December. There were times that I had the whole course to myself. Had issues with my in-car camera mount so had to go with the front bumper mount. Here is some video from my 5th run of the day.
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12-20-2011, 07:32 AM | #118 | ||
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I’ll work on constructing the formula, which will get a little bit complex, but testing is going to be the issue. Right now, my left foot is programmed in on-off fashion for the clutch, and so I’m a lousy left-foot braker… Quote:
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Last edited by MFGJR; 12-20-2011 at 01:26 PM.. Reason: typo |
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12-20-2011, 07:35 AM | #119 |
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The standard I've seen for choosing whether someone is on the brakes or not using Long G is .25 G. I would guess something around that would be good here too.
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12-20-2011, 08:29 AM | #120 | |
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1. It's the faster way around the track 2. Smoother transition, more controlled transfer 3. Carrying more speed into the turn, slowing to the same speed for turn-in, but getting on the power sooner 4. Practice.. practice...practice You will brake a little later than using the 'one foot' method, but your turning speed is not really any faster. Yea, some but not significant. As you know this ‘braking a little later’ is relative. Maybe 5-10 feet. If that. This allows you to be smoother, which results in being faster. I am still a believer in slow in, fast out, but my corner entrance speeds are only about 3mph faster but my exit speeds are now 5-6mph faster Still learning left foot braking. I find left foot braking in the MC much harder than other cars due to peddle placement. |
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12-20-2011, 07:31 PM | #121 | |||
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If the clutch is in, use brake pressure. If it’s a heel-toe downshift, we want the brake input and this ignores the throttle blip. If it’s a non-heel-toe downshift or an upshift, there’s 0 brake and 0 throttle input—effectively coasting—so the 0 brake input reflects both brake and throttle input. If the clutch is out, and if the throttle is down, and if the brakes are also down, and if long accel exceeds the braking threshold, use brake pressure. This is the left foot braker giving both throttle and brake inputs, and braking is the dominant input. If the clutch is out, and if the throttle is down, and if the brakes are also down, and if longitudinal acceleration does not exceed the braking threshold, use throttle position. This is the left foot braker giving both throttle and brake inputs, but the inputs are equal or throttle is dominant. We us the threshold to allow for some manipulation of the throttle as acceleration begins. Note that the threshold is a negative value, so “exceeding” means more negative, i.e., less than the threshold. Looking at Randy’s data, coasting generally resulted in up to -0.16 longitudinal accel, so I’ll use that as the threshold. If the clutch is out, and if the throttle is down, and if the brakes are not down, use throttle position. Straightforward acceleration. If the clutch is out, and if the throttle is not down, and if the brakes are down, use brake pressure. Straightforward braking. If the clutch is out, and if the throttle is not down, and if the brakes are not down, use throttle position. This is coasting, with 0 brake and 0 throttle inputs. The 0 throttle position value will represent both. When If-THEN-ELSEd, some items above become “THENs” and others ‘ELSEs”. With the statements nested together, it looks like this: ( IF clutch is in , THEN use negative brake pressure , ELSE ( IF throttle is down , THEN ( IF brakes are down , THEN ( IF longitudinal acceleration exceeds the threshold , THEN use brake pressure , ELSE use throttle position ) , ELSE use throttle position ) , ELSE ( IF brakes are down , THEN use brake pressure , ELSE use throttle position ) ) ) Note that wherever we use brake pressure, we’re using the negative of the logged value as we want braking to appear “below the line” on the Measures Graph. In RS2 syntax, and using the channel names from the Z4M ECU protocol, it looks like this: IF(EQ(Z4M_CLUTCH_SW,1),-Z4M_BRAKE_PR,IF(GT(Z4M_PPS,0),IF(GT(Z4M_BRAKE_PR,0 ),IF(LE(GPS_LonAcc,-0.16),-Z4M_BRAKE_PR,Z4M_PPS),Z4M_PPS),IF(GT(Z4M_BRAKE_PR, 0),-Z4M_BRAKE_PR,Z4M_PPS))) This exactly replicates my simple “throttle – brakes” approach using Randy’s data, which doesn’t include heel-toeing or left foot braking/simultaneous throttle input. I’ll work out a test protocol involving those techniques, and will see how the formula works with those. Might be after the holidays before I can do that and report back. My head hurts now. Time for a beer.
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12-20-2011, 07:46 PM | #122 |
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Frank,
Just a reminder, the car does a plausibility check when both the throttle and brakes are applied. The more brake pressure is applied, the more the throttle is retarded. I don't know when or what the intervention points are when reached and the ECU intervenes, but I know it will happen. I don't think it should matter in these cases, but we/you have to be aware of it when reading the data and something is screwy..... |
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12-20-2011, 07:58 PM | #123 | |
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IIRC duration is a factor in the car's programming, mayybe allowing a couple seconds of simultaneous input. Note that we can still blip the throttle even with mega-pressure on the brakes. Also, I have an extra-wide throttle pedal on my car, and when other guys have auto-Xd it, they frequently hit the gas when braking, and the car allows a good bit of it, even with the clutch out. I'll keep it in mind when I look at some test data, see if I can figure out how it handles the situation.
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Last edited by MFGJR; 12-20-2011 at 08:18 PM.. |
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12-20-2011, 08:15 PM | #124 |
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You'll know when the ECU cuts things becuase of LFB. I have a couple of friends who ran a 3 series in the Continental Series and had to shut the car off and on about 4 times per lap at Watkins Glen becuase the ECU went into limp mode. Had the same problem at Trois Rivers too.
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01-02-2012, 08:06 PM | #125 |
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Let’s see…when we left off before the holidays, we were trying to figure out a math channel that would indicate what was going on with the pedal inputs, allowing the production of a track graphic with information more granular than longitudinal accel would show. The single channel would combine the inputs from the accelerator and brake pedals, but complexities were introduced when both pedals are applied, either in a heel-toe downshift or when left foot braking and feeding in gas while still not completely off the brakes.
I went out and logged some data, including a heel-toe downshift, and a series of six instances of left foot braking, each time beginning to add throttle before the brakes were completely released. I had previously identified that my original, match channel that was simply the difference between throttle and brake pressure inputs would show wacky results on a heel-toe downshift. In the graphs below, the upper pair of lines are the individual throttle (dark green) and brake pressure (red) channels. Note that, to present them this way, I reversed the brake pressure channel so that it’s negative—below the line—and set the scale on both throttle and brake channels to range from -100 to +100. The lower graph’s orange line is longitudinal acceleration, so we can see where the car is actually being accelerated or decelerated. The bright blue line is the original simple formula, and you can see where it gives misleading info when the throttle is blipped for the downshift. The dark blue line—which covers most of the bright blue line as they have the same values much of the time—does a much better job of depicting when the car is actually being decelerated or accelerated. It uses an if-then-else statement conditioned on the clutch switch to ignore the throttle blip. On to left foot braking… We last discussed using additional if-then-elses to select the dominant input, conditioned on which pedals are engaged and on longitudinal accel as the tie breaker. As I feared, the single channel makes big, instantaneous jumps from the brake value to the throttle value as soon as the long accel value is crossed. It seems that the best solution, when both pedals are being applied, is to blend the values. Weighting the brakes 80% and the throttle 20% seems to do a pretty good job of crossing the line from braking to accelerating around the point where longitudinal accel goes from negative to positive. In the below graph, once again the upper set are the throttle and brake traces—note how throttle is being added before complete brake release in each braking/accel event. The lower set’s orange line is longitudinal accel, the bright green line is the flawed formula that makes the instantaneous leaps, and the purple line is the good, blended, 80/20 version. The 80/20 ratio might need to be adjusted to something else at track speeds, however. So, the final formula using RS2 syntax and Z4M ECU protocol channel names is as follows: IF(EQ(Z4M_CLUTCH_SW,1),Z4M_BRAKE_PR,IF(GT(Z4M_PPS, 0),IF(LT(Z4M_BRAKE_PR,0),(Z4M_BRAKE_PR*.80+Z4M_PPS *.20),Z4M_PPS),IF(LT(Z4M_BRAKE_PR,0),Z4M_BRAKE_PR, Z4M_PPS))) Note that earlier, when I was using the default settings on the brake test channel, it was a positive value and so I was using the negative of its value in the new math channel. Now that I’ve reversed the brake channel as discussed above, it’s already a negative value and so it can come straight into the formula and it’s added to the throttle value when blended. Now, I’m going to have to learn to left foot brake so all this isn’t for naught.
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01-02-2012, 08:21 PM | #126 |
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Speaking of braking, pretty interesting article on Matt's site: http://www.trailbrake.net/2/post/201...oa-horsey.html
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02-27-2012, 10:28 PM | #127 |
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Finally got out on VIR with the Solo. Best laps were 2:30s, just OK for C Group... Was able to compare to Randy's data from December, where he has a nice 2:24 best lap.
In the below graphs comparing our respective best laps, I'm red and Randy is blue. Corner numbers are at the top, straights are shown in green. (Note that AiM doesn't let you label corners "a" or "b", so VIR's 5 and 5a are all labeled as 5, 11a and 11b are shown as 11 and 12, 14a and 14b are 13 and 14, and 17a and 17b are combined as 17.) The top graph shows throttle (above 0) and brake (below 0) application. The middle graph is speed, and the bottom graph is the time differential--my time in excess of Randy's as the baseline. All three are plotted against distance around the circuit on the horizontal axis. It's easy to see that I give up the bulk of the time approaching and through the Climbing Esses and South Bend (from turn 6 through 10). Randy's much more confident attacking this section, entering the beginning of the esses at turn 7 at 111 mph vs. my 88. If you look at the top graph, you see me coast off a bunch of speed on the straight before turn 7, where Randy's only gradually rolling off the gas. That coast alone cost me 1.5 seconds. I did have a 98 mph entry on another lap, but then blew the braking for 10 and ruined the lap... no good corner goes unpunished. Looking at the braking zones, Randy is quite noticeably more efficient in compressing the braking. See how steep his transitions from throttle to brakes are approaching turns 1, 3, 4, 10 and 13. Plus, I'm a wuss and just can't keep the hammer down all the way through and past the front straight's kink, hence the trailing off the gas and another big coast between turns 17 and 1. I feel I can make up significant time just focusing on these couple areas... gotta get some new (stickier) tires first, though. That, and more seat time. Ain't data acquisition great?
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02-29-2012, 10:23 PM | #128 |
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Randy you the man!
Seriously nice breakdown and interpretation of this data. Nice to know HOW to improve lap times... applying what you see in this data will net you a serious reduction in time. I am still working on getting myself situated with using RS2...biggest issue is getting a track map incorporated with the data like you have above. |
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03-01-2012, 06:38 AM | #129 |
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Nick--my maps are here: http://www.trailbrake.net/aim-track-maps.html
One map is individaul corners (see above on numbering), other is segments. Download them and, assuming you did the standard install of RS2, put them in C:\AIM_SPORT\RaceStudio2\TRACKS and you should find them available in Map Manager.
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03-01-2012, 09:33 PM | #130 |
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Thinking about Randy's 2:24 (actually, he was down to 2:23 this past weekend) compared to my 2:30...
Looked at my split report with the last two Sunday sessions loaded up. Lo and behold I have a theortical best time of 2:24.709 using my best individual segment times from among the 15 laps in those two sessions. Actually, only 5 laps contributed to the theoretical best time, and three of the seven segments came from a single lap. So, maybe I'm closer to a decent lap than I thought--just have to string all the good segments together into the same lap. Gotta love data acquisition: improved lap times and self-image at the same time!
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03-02-2012, 06:25 AM | #131 |
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That's awesome Frank, just need so more seat time to bring them together.
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