32 replies to this topic

[Tom Hampton]

Hi-

So, I've been going through data from my most recent trip to MSRC. One of the things that I see is a lot of "noise" in my lateral G data. I don't know if this is normal for all tracks, specific to MSRC, or some error in my driving that I should be working to correct. So, that is my question.

Here is what I see. Both graphs show lateral G vs. distance (in feet) from the start/finish. The one thing I note is how "in phase" the oscillations are. I assumed that it was just me being "un-smooth", but the in-phase-vs-distance makes me wonder.


First a whole lap comparing two different laps, from two different sessions, are overlayed:

http://www.tomhampto...7-29_202516.png

Second, just one section of the same laps:

http://www.tomhampto...7-29_202554.png

[G-Man]

Maybe related to data display? My G-forces smooth out a lot when I adjust the display from the 0.1 second up to 0.5-1 second. Do you have that option?
Possibly your accelerometer/GPS is moving inside its mount?
Hard to say more without knowing what the X axis intervals are.

[KentCarter]

Hi-

So, I've been going through data from my most recent trip to MSRC. One of the things that I see is a lot of "noise" in my lateral G data. I don't know if this is normal for all tracks, specific to MSRC, or some error in my driving that I should be working to correct. So, that is my question.

Here is what I see. Both graphs show lateral G vs. distance (in feet) from the start/finish. The one thing I note is how "in phase" the oscillations are. I assumed that it was just me being "un-smooth", but the in-phase-vs-distance makes me wonder.


First a whole lap comparing two different laps, from two different sessions, are overlayed:

http://www.tomhampto...7-29_202516.png

Second, just one section of the same laps:

http://www.tomhampto...7-29_202554.png

You can apply a smoothing filter to the data in the G2X software. If I remember correctly, you right click on the channel.

[Keith Novak]

You're probably picking up the vibration of the car which is causing the noise in your data. Mine looks like that on a Michron 3 even on nice smooth sweepers.

Curious though...your data seems to show that you hit higher G's in one direction than another. Mine consistently shows peaks around 1.45 on RH turns but more like 1.25 on LH turns on different corners and different tracks. I've been wondering if that's a car thing or a datalogger thing.

[Tom Hampton]

<Sigh> I had a long reply composed...and it got erased. Grrr....second time this week.

You're probably picking up the vibration of the car which is causing the noise in your data. Mine looks like that on a Michron 3 even on nice smooth sweepers.

Perhaps, but I wouldn't think vibration would be "in phase" between laps in different sessions vs. distance. That feature makes me think its a track thing....but, I wondered it was some obvious diver fault I should be working to fix.

Curious though...your data seems to show that you hit higher G's in one direction than another. Mine consistently shows peaks around 1.45 on RH turns but more like 1.25 on LH turns on different corners and different tracks. I've been wondering if that's a car thing or a datalogger thing.

Maybe a little. But, when I used the software to average the flatG sections of each turn I see 0.98 for RH, and 1.03 for LH turns. But, there is a bigger stddev on the RH data (it is a RH dominant direction so I have more chances to screw them up!!). Both LH and RH turns managed at least one turn at 1.05g. The car does have 50.5% cross/wedge....I'm not sure how that would affect RH/LH sustained G. The car was a tick looser in the RH turns. At this point, I'd probably attribute any LH/RH G differences to driver inconsistency.

I'm still learning what that REALLY means, and how my inputs affect it. I have a habit of sawing the wheel just slightly even when its not necessary, and I tend to brake late and hard, but for too long. I get "caught up" in the high-G sensation, and over-slow. If I brake earlier and lighter, I have a better sensation of the CAR and the right point to release the brakes so that I carry more speed through the turn. The biggest example of this was turn 1 (Big Bend). Early in the day I was braking way late and near threshold, but I'd end up at 55mph by turnin. When I backed up the braking zone and didn't brake as hard I was able to release the brake at a more consistent entry speed and by the end of the day I was carrying 73mph or so through turnin. I know I need to work up to braking later/harder and still releasing at the right entry speed.

So, my guess is those lower G turns are more a result of my over-slowing rather than some effect of the car.

[Tom Hampton]

You can apply a smoothing filter to the data in the G2X software. If I remember correctly, you right click on the channel.

Yeah, I wish they had more advanced smoothing functions, though. Rolling averages aren't great low-pass filters. I have to apply such a heavy filter to get rid of the bumps that it affects the transition zone Gs skewing any interpretation of car-driver dynamics (G-G plots, etc). So, I've avoided using that option, but I have played with it.

[Jim Boemler]

You don't want to remove the bumps -- those are your inputs at work. You just want to remove the high-frequency noise. Your wheel sawing is showing up beautifully, which is just the feedback you need.

The side-to-side variation may be your driving and the track, but don't overlook the zeroing of your accelerometers. If you do that on a slopped surface, your G readings will have an offset.

[Tom Hampton]

You don't want to remove the bumps -- those are your inputs at work. You just want to remove the high-frequency noise.

Ok, cool---something to work on. So, you're saying that is showing me that I need to hold a steadier wheel. I already knew that, but now I have something to look for (or look for it to lessen/go away).

Your wheel sawing is showing up beautifully, which is just the feedback you need.

That and someone to tell me that I'm being a dumbass. I can see the obvious things in the data, but some stuff is hard to see without the experience to interpret what I'm looking at, and know what its showing me.

The side-to-side variation may be your driving and the track, but don't overlook the zeroing of your accelerometers. If you do that on a slopped surface, your G readings will have an offset.

That's an interesting point. I don't think I've seen a zeroing procedure in the G2x manual. Hmmm.....Maybe it self-zeros at power on? I always start the data on the grid which is level-ish.


Thanks, Jim. Glad to see you back here.

[Jim Boemler]

I wouldn't call it dumbass, but over time you do learn to filter out the unnecessary data and focus on what counts. As for sawing, what I found for me was that as I learned to drive more smoothly, I got faster and faster. But then, as I got faster, more corrections are necessary, so there's more wheel movement. It's always a battle to put what you see into perspective.

BTW, I'm using an AiM EVO3. It has an explicit zeroing technique, although I confess I don't bother with it -- it just hasn't seemed needed. While Keith's data may have more offset, I wouldn't be too worried about yours. It seems pretty well balanced, so I don't think it's skewing your view of the world. While the noise shows max Gs at 1.3, once filtered it looks to be actually under 1G, suggesting you've got some room to corner faster.

Once you kill the habit of sawing unnecessarily, you'll probably speed up to where you're correcting out of necessity. In fact, you may find that you're sawing precisely because you're not going fast enough to feel much tension in the wheel -- that is, forcing yourself to speed up may help you smooth out as well.

Where you typically come out in local standings, in terms of lap times?

[Tom Hampton]

I wouldn't call it dumbass, but over time you do learn to filter out the unnecessary data and focus on what counts. As for sawing, what I found for me was that as I learned to drive more smoothly, I got faster and faster. But then, as I got faster, more corrections are necessary, so there's more wheel movement. It's always a battle to put what you see into perspective.

BTW, I'm using an AiM EVO3. It has an explicit zeroing technique, although I confess I don't bother with it -- it just hasn't seemed needed. While Keith's data may have more offset, I wouldn't be too worried about yours. It seems pretty well balanced, so I don't think it's skewing your view of the world. While the noise shows max Gs at 1.3, once filtered it looks to be actually under 1G, suggesting you've got some room to corner faster.

Once you kill the habit of sawing unnecessarily, you'll probably speed up to where you're correcting out of necessity. In fact, you may find that you're sawing precisely because you're not going fast enough to feel much tension in the wheel -- that is, forcing yourself to speed up may help you smooth out as well.

Where you typically come out in local standings, in terms of lap times?

I should clarify, I'm running street tires (Fuzion ZRi). So, lap times don't really compare. I'm planning on getting some RA1's "real soon now". Nevertheless, I pass every other car in my group (intermediate HPDE), except for one full race Porsche. Its the usual compliment of HPDE cars. The SM track record is 1:23.5-ish. I'm running 1:36 on street tires with a bone stock 1.6L engine including stock air-box, catalytic converter and muffler---best guess is 99 rwhp, based on acceleration and weight.

Max sustained "average G" that I've recorded is 1.06g, on the big sweeper at this track. I can feel the rear end starting to let go at this G level a tick before the front. Its a RH sweeper, and I'm setup at 50.5% cross, medium front-bar, soft rear-bar....so that probably makes sense for the rear to go first. I'm sure someone else could eek a little more out of these tires, but I think 1.06g is pretty close to their limit.

[Jim Boemler]

Ah, got it -- tires do make a huge difference. So get your ass in gear and get into SM trim!

[Tom Hampton]

Ah, got it -- tires do make a huge difference. So get your ass in gear and get into SM trim!

Spending money as fast as I can. Faster probably.

[Jim Boemler]

Spending money as fast as I can. Faster probably.

Now you're really a member of the community!

[Keith Novak]

I pass every other car in my group (intermediate HPDE), except for one full race Porsche. Its the usual compliment of HPDE cars. The SM track record is 1:23.5-ish. I'm running 1:36 on street tires with a bone stock 1.6L engine including stock air-box, catalytic converter and muffler---best guess is 99 rwhp, based on acceleration and weight.

You must be driving flatout and moved to the fastest rungroup.

[Tom Hampton]

Lol. No, I'm well aware of my place in the universe. I'm perfectly fine in the intermediate group for now. I can't hang with the guys in the advanced group yet.

But, all those minis, rx8, and porches on street tires and suspension with stock interior still don't stand much chance against a stripped miata on the SM suspension and almost 3 degrees of camber. Even if I do still have street tires.

[dstevens]

But, all those minis, rx8, and porches on street tires and suspension with stock interior still don't stand much chance against a stripped miata on the SM suspension and almost 3 degrees of camber. Even if I do still have street tires.

"You must have stripped all the weight out of that little Miata and put in a turbo or V8 or something..."

[Tom Hampton]

Can you say "bodyroll"?

http://hart-photogra...ewImage=1310373

I thought you could!

[Jim Boemler]

Wow.

[Todd Green]

but I'd end up at 55mph by turnin. When I backed up the braking zone and didn't brake as hard I was able to release the brake at a more consistent entry speed and by the end of the day I was carrying 73mph or so through turnin. I know I need to work up to braking later/harder and still releasing at the right entry speed.

55 to 73 is a huge delta. I can't see that just being a change in technique. Sounds more like you were not warmed up to the car/track in the morning more than any particular technique. I'd get warmed up in a session later in the day and then do a few flyers with hard braking, then a cool down, then a flyer or two with easier braking, then a cool down, and one last flyer with hard braking and then compare the speeds/times. If you start comparing your technique times from your first session to your last I think you'll draw some improper conclusions,. (IMHO of course.)

[Tom Hampton]

<br />55 to 73 is a huge delta.  I can't see that just being a change in technique.  Sounds more like you were not warmed up to the car/track in the morning more than any particular technique.  I'd get warmed up in a session later in the day and then do a few flyers with hard braking, then a cool down, then a flyer or two with easier braking, then a cool down, and one last flyer with hard braking and then compare the speeds/times.  If you start comparing your technique times from your first session to your last I think you'll draw some improper conclusions,. (IMHO of course.)<br />

I wouldn't have called it a "technique" change, but rather more of an epifany that the turn could handle more speed than I'd felt. That realization was precipitated by the earlier/lighter braking. I use the word FELT above, on purpose, as opposed to THOUGHT. Another change I made was to switch the secondary display on my G2X to MPH from some other random data channel. So, now I have "predictive lap time" and "MPH".

So, the evolution of the change was driven by:

1. A similar change I was already making in another corner for different reasons that gave me a better sense of what the car could handle.
2. Experimenting with applying that change to this corner
3. Having MPH available to see the immediate effect on speed, and predictive to see the ultimate benefit.

So, in essence I think you are right, it was more about warming up to the car/track. But, the warmup was more fundamental than limited to "that day"...but, was really me learning some new limits to the car that I previously didn't know.

I'm new. I've driven on a track at speed 5 times. Once in a 220HP turbo 1990 Miata; once in a rented SM; three times in my own car. This was my second time in my own car to drive this configuration. I still have lots of "fundamentals" to learn. Some come in great revalations like this one.