SundayDriver

Well said. Here is one huge problem with trying to use raw data. How do you determine what the g limit is for the corners? Tim has said that he uses skid pad numbers that he got for his car. IMO, that only tells you the max g;s for a corner of that radius and with the car in the same balance.

TIRE GRIP CHANGES WITH LOAD. A tire may be able to give 1.1 g's with it's static share of the car weight, but if you add another 50% to that load, it can only pull .8 g's (that is an example). That is the nature of tires. That is what makes driving at the limit so challenging. One tire (or more than one) is always losing grip. That does not mean you are going as fast as you can. You, as the driver, can manage the weight and still get more out of the car.

Lap time is what ultimately matters in terms of going faster. How does one driver's times stack up to others? In the DE environment, that is tough as there is probably not another car that is the same. BUT, you can go look at lap records for certain classes to establish a target. Spec Miata is a low HP car on DOT tires and the drivers tend to be very good. T1 is another calss to compare to - better as the cars are more powerful but the fields are smaller so it is not clear that the lap record for T1 is real. That is an excercise that Tim (or anyone else) can go through.

RJay

Personally, I think its usefulness probably depends on a number of factors. I'm installing an AIM this winter because, while I'm a firm believer in butt feel, you're butt lives in the moment (at least mine does), it can fool you. AXing has proved this to me. Oft times the runs you think are the fastest are the slowest and vice versa. There are times where you try something radically different and wind up with almost exactly the same time. What the hell happened? Why didn't the overall lap time change? Thats what I hope to find out.

I think at my experience level, precise analysis of the numbers on a particular corner is pretty useless. My plan of use is is two-fold. First, add video. Use the maps and data to identify fast and slow laps, identify where I was faster, where I was slower and then use the video to help identify what I was doing right/wrong. Second, convince everybody I know to buy a system so we can overlay our data and compare notes. My intent is to use the tools at a very high level, not trying to examine each scrap of data,which I suspect is too myopic. My attention span is sufficiently short that I have littel hope of analysing G-Sum data for each corner. I admire CCs determination, but I for one, can't emulate it. OTOH, If I can reasonably relate the numbers back at a high level to what I was doing when I generated them, then, for me, it will have been money well spent.

carreracup21

My tire grip seems to change constantly. I mean my tires tend to peak at lap 3 when the temps and pressures are perfect then start to fade. Grip will also change from one heat cycle to another. Last time I was driving, I couldn't seem to hit my best lap times and was not sure why. Was I going to slow ? I changed tires and was 2.5 seconds faster.

I was thinking it would be cool if you had a DAS that could talk to you through a headset during the run, like a coach. It might say something like "go faster you idiot" , or maybe for the more analytical, "brake now, 2.5 mph slow mid corner, accelerate" , or even "g-sum is dangerously low, go faster now please". Hey someone will probably patent that idea...oh, well. Another thing the DAS can do is give you a "best possible" time where it looks at different segments of the track and figures your best speed for each section during a run of several laps, then gives you a cumulative best time. Then you can shoot for that great time because you know it's possible, if you can put it all together for the perfect lap.

ColorChange

Larry, I agree and that is why I rode with Fishman and am hoping to ride with and get Norm's data.

Actually Carrera, on this turn, I handled the entry pretty well. This is normally the hardest part of the turn but on this particular lap, I did it fairly well.




A. For the first second and a half of the turn, I transition from threshold braking to full lateral g’s while maintaining a g-sum of around 1.2 You can see the cursor is at a point where I am pulling -0.8 long g’s and -1.0 lat g’s. That's real nice trail braking.
B. At point B, I overbraked/under accelerated just a little bit or didn’t tighten my line enough and this is what dropped my g-sum to 1.0 for about a second.
C. By C (about 2 seconds) I am back to pretty good and maintaining a high g-sum using the throttle while lat g’s stay about -1.1g.

After that, I got into the previously discussed oversteer trouble.


Mark:

I use corner radius to partially look at the line I chose. A detailed response would take a while. I am not real concerned about steering smoothness unless it affects g-sum (and I don’t have steering input yet on this car). As far as I am concerned, you can saw the wheel like a banshee as long as your g-sum is high.

I agree with comparing hot lap data. I just need to find someone who is comfortable in a similar car. Norm, are you listening?

I disagree about your conclusion on the data saying I need to be thinking throttle. The data shows the exact opposite. On this turn I blew the exit, precisely because I was trying to squeeze too much throttle too early and snapped ‘em loose.

Guys, street tires have less variation the r-rubber. My data shows how consistent a lat g max of 1.1-1.2 and a g-sum of max 1.3-1.4. Yes elevation and camber change this but the data is wholly usable.

Robert Henriksen

BWAHAHAHAHAHAHAHAHAHAHAHA!!!!!





Thank you, that was great.


.

Premier Motorsp

What a pathetic little life you must lead.

GhettoRacer

how about you go away. you just another hater. all you attacks people like ghettoracer an colorchange. colorcgange has good idaes ane will being a very good driver very soon. you think you so specail because you having motorsports in your name? well that is nothing so why dont you show courtesty to everyone here, even colorchange.

Premier Motorsp

My post was in reply to Henriksons

carreracup21

CC, It's interesting how well the Lat. g (yellow line) and the speed (green line) inversely correlate. They almost look like the same curve. One thing that I noticed when I was getting faster was how you can use lat G's to slow you down rather than brakes in some corners. You will feel to fast on entry, but by balancing the car and turning in a little earlier, you can scrub the speed with g's and stay at peak g longer at entry. It's hard for me to see, just where you released the brakes here, but it looks like you may have taken braking too far into the corner and it resulted in lower g sum at point B after you had it nicely maxed at point A. The graph also shows just how spinning the wheels can ruin your exit speed. It looks like the green line lost 3 mph on exit and dropped the whole green exit speed curve to a lower level. That is where the time is lost down the whole next straight and is a bigger mistake than the drop at point B as far as lap time goes.

forklift

I agree with this and what I have done is find a few PCA racers who either race or have raced 964s and asked them what my car is capable of with the current setup. For Summit Point most have said they could probably run in the 1:27s in my car, which I just started doing at the end of the season. I did speak to another racer last week though and said he ran in the low 1:26s with a similar set up in his RSA w/ RA-1s. So obviously there is more time to find. For VIR I have been told my car should be able to do 2:17's and right now I am doing 2:19's so a few seconds left there as well. The good thing is, is that I know where some of that time is, I just need to work up to faster corner entry on a few (or all!) corners.

I have looked at the PCA race results and will compare them again after I put my Hoosier's on (after I wear out my RA-1s, which could take a while).

Jim

carreracup21

Jim, I think C. Price did a 2:12 at VIR in a D class 964 C2 ( re-classified to RSA) at 2760 lbs. in the last PCA race. Full race set-up with JRZ's, Hoosiers. A E class 964 driven by someone like Savenor ( or maybe Ghetto ) could probably do 2:12 -2:13's also. The VIR times are actually nearly exactly the same as WG with maybe a tenth or 2 difference believe it or not.

carreracup21

Someone I respect a lot who drives a 964 Euro Cup and used to race D class, now GTC1 told me " the only thing I ever did to my car that made a difference was tires". I tend to believe it that, but a good set-up and alignment is also critical to getting good handling. I use the non-adjustable bilstein cup shocks/springs and they are fine. I've got sway bars that I can adjust for balance. I think 2:17's might be a good number to shoot for with the RA-1's. Hoosiers will be 3 seconds or so quicker.

924RACR

LOL, thanks for jumping back in, Haiku target.

Though I may not quite agree with how he states it, I'm all with Henriksen. To put it in terms that are of interest to Tim, I think there's a well-established relationship between steering wheel input and long. accel. Hey, the less you steer, the faster you go. The mu-slip characteristics of tires are easily understood, if not so easily quantified. Gaining the intuitive understanding of how to best employ them while behind the wheel is what Tim and indeed all of us continually strive to improve.

I'd be most interested to see comparison between lat g, yaw rate, steering wheel input, vehicle speed, and corner radius calculated from the above (from lat accel, steering input, and the other sources). Once you can compare those, you really get an idea of what the driver's doing with the car vs. what the car's capable of... but applying that in the real world is still tough due to elevation and loading changes. I do have data with all of the above excluding steering wheel angle, unfortunately. Watching the yaw rate stability gives a half-decent idea of how well the driver's driving, in the absence of steering angle, but the primary focus is still smoothness, there still completely lacks any ability to compare with the "idea" or "best" line.

Which brings us full circle back to step 1, how do you even use the data to determine a "Best" line? and we're still back to the #1 criteria, minimum sector time. Back to the old (proverbial) stopwatch. Though I will agree the DAS system gives me a far better opportunity to compare the minutia of my driving, it's still up to me to turn the good lap times...

carreracup21

Here is an interesting link that may help explain the theories behind taking a corner.

Robert Henriksen

Chris, if you'd like to explain to me why it's rational to maximize gsum at the expense of laptimes, I'm all ears. From where I'm sitting, the emperor has no clothes. LOL is an overused acronym - that 'saw the wheel like a banshee' had me busting out laughing at my keyboard. I actually wasn't being snarky, I appreciated the belly laugh!

Edit: Oh, and thanks, Ghetto