Here is some data to amuse everyone
04-15-2004, 05:06 PM
#31
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Originally posted by ColorChange
OK, let’s try one correction first.
Your comment about slight veering on all the straights (very rare) could be correct but is not in this case. If that were true, you would have an off center concentration, and equal left and right maxes. That is why I pointed out that both your lat g maxes appear to be off by the same amount, roughly +0.1 g's. So your left is off, your center is off, and your right are all off by the same +0.1 g's. It is a simple calibration error that you can easily correct by a math channel correction and is not track or condition dependent at all.
If this goes well and you want me to continue I will.
OK, let’s try one correction first.
Your comment about slight veering on all the straights (very rare) could be correct but is not in this case. If that were true, you would have an off center concentration, and equal left and right maxes. That is why I pointed out that both your lat g maxes appear to be off by the same amount, roughly +0.1 g's. So your left is off, your center is off, and your right are all off by the same +0.1 g's. It is a simple calibration error that you can easily correct by a math channel correction and is not track or condition dependent at all.
If this goes well and you want me to continue I will.
First, it appears to me that the left and right g concentrations differ by .2-.3 g's, not .1g.
Why would you expect these to be balanced - I see no reason to expect that balance so what am I missing here?
04-15-2004, 05:35 PM
#32
Three Wheelin'
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DJ, yes some drivers are more aggressive to one side or the other.
Professor, possible.
924 Most track cars are corner balanced and set up to be equally balanced unless maybe you have a really advanced crew and are an advanced driver and can set-up the car for each individual track where it is faster to be imbalanced (a non balanced course where what you gain in the critical turns(s) in one direction offsets what you lose in the less important other direction turns). I don’t think most of us do that and we strive for a balanced vehicle (but I’m sure you’ll tell me if I’m wrong). It is more difficult (and unnerving at least initially) to drive an unbalanced vehicle because it behaves quite a bit differently turning one way than the other.
Sunday:
Yes, slight veering an all straights is common where you go from a right to a left turn (or visa versa, veering the other way) but that will rarely add up to a serious 0.1 offset in g-g data, but yes, it is possible.
Now, you clearly have more data points on the right side of your graph and that would indicate a predominance of turns to that side. I agree that there is a large average difference on the right side but I assumed that was down force (DF) related. There still looks to me like there is at least a 0.1g offset across the board.
A tire has roughly equal traction capabilities in all directions. Your car, having significant DF, makes the analysis more difficult on a g-g plot and that is why it is nice to color code the g-g plot (different color traces at different color speeds). Yes I know, Homer would now be multicolor.
Tell me the track the data was taken from and I can improve my analysis, again, assuming you’re interested.
Professor, possible.
924 Most track cars are corner balanced and set up to be equally balanced unless maybe you have a really advanced crew and are an advanced driver and can set-up the car for each individual track where it is faster to be imbalanced (a non balanced course where what you gain in the critical turns(s) in one direction offsets what you lose in the less important other direction turns). I don’t think most of us do that and we strive for a balanced vehicle (but I’m sure you’ll tell me if I’m wrong). It is more difficult (and unnerving at least initially) to drive an unbalanced vehicle because it behaves quite a bit differently turning one way than the other.
Sunday:
Yes, slight veering an all straights is common where you go from a right to a left turn (or visa versa, veering the other way) but that will rarely add up to a serious 0.1 offset in g-g data, but yes, it is possible.
Now, you clearly have more data points on the right side of your graph and that would indicate a predominance of turns to that side. I agree that there is a large average difference on the right side but I assumed that was down force (DF) related. There still looks to me like there is at least a 0.1g offset across the board.
A tire has roughly equal traction capabilities in all directions. Your car, having significant DF, makes the analysis more difficult on a g-g plot and that is why it is nice to color code the g-g plot (different color traces at different color speeds). Yes I know, Homer would now be multicolor.
Tell me the track the data was taken from and I can improve my analysis, again, assuming you’re interested.
Last edited by ColorChange; 04-15-2004 at 05:53 PM.
04-15-2004, 05:43 PM
#33
I would agree with CC that the calibration is off. As he has noted, the telltale sign of this is NOT the maximum amounts of lateral G as those should be different because of banking in the track. The telltale sign is that the big mass that should be centered around point (0,0) looks to be centered around (0.1, 0)
Granted, maybe driver weight is throwing it off, but you should then recalibrate with the driver. I know with the DL1 software, the software is assuming that if the car isn't moving, you'll be at (0,0).
I suppose it's also possible that you are driving on a slightly banked track. I think what he's trying to say is that you may want to double check your calibration for future usage.
Granted, maybe driver weight is throwing it off, but you should then recalibrate with the driver. I know with the DL1 software, the software is assuming that if the car isn't moving, you'll be at (0,0).
I suppose it's also possible that you are driving on a slightly banked track. I think what he's trying to say is that you may want to double check your calibration for future usage.
04-15-2004, 06:24 PM
#34
Lifetime Rennlist Member
Thread Starter
Originally posted by Brian P
I would agree with CC that the calibration is off. As he has noted, the telltale sign of this is NOT the maximum amounts of lateral G as those should be different because of banking in the track. The telltale sign is that the big mass that should be centered around point (0,0) looks to be centered around (0.1, 0)
Granted, maybe driver weight is throwing it off, but you should then recalibrate with the driver. I know with the DL1 software, the software is assuming that if the car isn't moving, you'll be at (0,0).
I suppose it's also possible that you are driving on a slightly banked track. I think what he's trying to say is that you may want to double check your calibration for future usage.
I would agree with CC that the calibration is off. As he has noted, the telltale sign of this is NOT the maximum amounts of lateral G as those should be different because of banking in the track. The telltale sign is that the big mass that should be centered around point (0,0) looks to be centered around (0.1, 0)
Granted, maybe driver weight is throwing it off, but you should then recalibrate with the driver. I know with the DL1 software, the software is assuming that if the car isn't moving, you'll be at (0,0).
I suppose it's also possible that you are driving on a slightly banked track. I think what he's trying to say is that you may want to double check your calibration for future usage.
On most tracks, especially in faster cars, you spend very little time going straight. You are going to have a bias left on CCW tracks, which this is and opposite on CW tracks.
It would have made a really good question, but of course it wasn't presented as a question - it was presented as an absolute.
So here is a challenge -name some tracks where you actually spend more than 50% of the time on the 'straights' actually going straight. I can only think of one, from those I have run - Road America.
Not true at; Mid-Ohio, Grattan, The Glen, Nelson, Gateway, HPT, PIR, Fontana, LVMS Daly, Buttonwillow, Willow Springs, Sears Point, Laguna Seca and Thunderhill.
I don't think it is true at Gingerman, but I have only one time there and would never claim to be an expert on a track after only one weekend.
Might be true at IRP - it's close.
04-15-2004, 06:30 PM
#35
I've just been playing with my DL1 for the past weekend, so I'm still a relative newbie at interpreting it. My best guess was that there should be very few points right around (0,0) because that would mean that you aren't accelerating, braking, or cornering. I.e., you are maintaining neutral throttle on a straight (not very likely) or you are sitting still (very likely if you turn your system on/off in the paddock)
That was the basis on which I guesstimated the error. As you said, I wasn't at the track with you, I'm not familiar with the track, and there are many other reasons why the points might not be centered around (0,0). I thought CC was just providing a heads-up that you may want to double check the calibration. If you think everything's correct, that's good enough for me.
That was the basis on which I guesstimated the error. As you said, I wasn't at the track with you, I'm not familiar with the track, and there are many other reasons why the points might not be centered around (0,0). I thought CC was just providing a heads-up that you may want to double check the calibration. If you think everything's correct, that's good enough for me.
04-15-2004, 07:02 PM
#36
Burning Brakes
Originally posted by SundayDriver
So here is a challenge -name some tracks where you actually spend more than 50% of the time on the 'straights' actually going straight. I can only think of one, from those I have run - Road America.
So here is a challenge -name some tracks where you actually spend more than 50% of the time on the 'straights' actually going straight. I can only think of one, from those I have run - Road America.
Should I continue ?
04-15-2004, 07:06 PM
#37
Lifetime Rennlist Member
Thread Starter
Originally posted by Brian P
I've just been playing with my DL1 for the past weekend, so I'm still a relative newbie at interpreting it. My best guess was that there should be very few points right around (0,0) because that would mean that you aren't accelerating, braking, or cornering. I.e., you are maintaining neutral throttle on a straight (not very likely) or you are sitting still (very likely if you turn your system on/off in the paddock)
That was the basis on which I guesstimated the error. As you said, I wasn't at the track with you, I'm not familiar with the track, and there are many other reasons why the points might not be centered around (0,0). I thought CC was just providing a heads-up that you may want to double check the calibration. If you think everything's correct, that's good enough for me.
I've just been playing with my DL1 for the past weekend, so I'm still a relative newbie at interpreting it. My best guess was that there should be very few points right around (0,0) because that would mean that you aren't accelerating, braking, or cornering. I.e., you are maintaining neutral throttle on a straight (not very likely) or you are sitting still (very likely if you turn your system on/off in the paddock)
That was the basis on which I guesstimated the error. As you said, I wasn't at the track with you, I'm not familiar with the track, and there are many other reasons why the points might not be centered around (0,0). I thought CC was just providing a heads-up that you may want to double check the calibration. If you think everything's correct, that's good enough for me.
I really didn't mean 0,0 - I misspoke but you understood what I meant. BTW - I have other data, both from my car and others. Almost all show about a .1 g offset consistent with the direction of the track.
The intersting thing about CC is that he makes good observations, but does not seem interested in learning from them because he states them as absolute fact, rather than a question. I had the same issue with the offest in g's, but instead of knowing that calibration was off, I first checked it and it was close. Then I looked at the data and thought about actaully driving to understand how little time you spend going straight at most tracks.
CC, you seem bright and you ask all the right quesions, except you close you mind before you find the right answer. While your absolute statements are irritating, the initial posts do cause me to dig and learn something, though most of your assertions fall short of being accurate. But that is part of the process, make an assumption, then test it and learn something. I do that a lot, but with people I consider far more knowledgable than I am about data aq. It is amazing how many of my initial impressions were just flat wrong, but I listened and learned.
04-15-2004, 07:10 PM
#38
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Thread Starter
Originally posted by Professor Helmüt Tester
Pomona. US Dragway 13. Raceway Park in Englishtown, NJ. Rt. 66 Dragway in Joliet. IRP. Irwindale.
Should I continue ?
Pomona. US Dragway 13. Raceway Park in Englishtown, NJ. Rt. 66 Dragway in Joliet. IRP. Irwindale.
Should I continue ?
04-15-2004, 07:10 PM
#39
While we are still talking calibration issues. Let's say that I mount my DL1 in my car and try to make it perfectly flat. How do I ensure that my car is level? I have the car in my garage, but I noticed that when I took a wheel off and left it standing up, it started to roll. That seems like a good indication that my garage floor isn't level.
04-15-2004, 07:42 PM
#40
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Thread Starter
Originally posted by Brian P
While we are still talking calibration issues. Let's say that I mount my DL1 in my car and try to make it perfectly flat. How do I ensure that my car is level? I have the car in my garage, but I noticed that when I took a wheel off and left it standing up, it started to roll. That seems like a good indication that my garage floor isn't level.
While we are still talking calibration issues. Let's say that I mount my DL1 in my car and try to make it perfectly flat. How do I ensure that my car is level? I have the car in my garage, but I noticed that when I took a wheel off and left it standing up, it started to roll. That seems like a good indication that my garage floor isn't level.
Go get a laser level from Home Depot or anywhere else and check it. Front to back can be an inch off and it won't make any real difference but you need the sides to level, both at the front and rear.
You can do the expensive way - buy scales and a setup platform or you can go cheap - use newspapaer or a stack of floor tiles to get a level pad. Make sure you bounce the suspension to get the mid point. You should also disconnect sway bars and soften the shocks, but that is usually more bother than it is worth for a street car.
Also, almost all tracks have a level concrete pad for set up. Find that and you can zero your accelerometers. Another quick check - take a 45 degree triangle with you and check at that tilt. You should get 1.0 g.
04-15-2004, 08:22 PM
#41
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I've been following this thread with interest because I've been considering picking up something like a DL1 to play with at the track. I figured I could use it to better understand what the car is doing, but after reading this thread and others, I'm begining to think I'm going to spend more time confused than enlightened. Are there any good resouces (besides this list) out there to help translate the output of a DAS? Do you guys find that a DAS is actually useful, or should I just stick to my tried and true Butt-O-Meter?
SJ
SJ
04-15-2004, 10:59 PM
#43
Still plays with cars.
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One more data point - tracks are not level. Straights have a crown fro drainage and corners are usually slightly banked for the same reason. This messes up lateral G readings in my experience. I also agree about not going straight on the straight for very long.
04-15-2004, 11:37 PM
#45
Three Wheelin'
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Sunday, I can't tell if your jerking me around again or not. You could be right about the offset. I don't think you are. If you show me the track map, I believe I can prove it's a calibration error. Without it, I can't. I also can't offer more detailed analysis with higher confidence without it (as you correctly pointed out)
And if you don't want my input, OK.
And if you don't want my input, OK.