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bastarddsm

20+ Year Contributor
5,620
1,457
Aug 26, 2003
Mendota, Illinois
I made a data logger out of an Arduino, and an SD card sheild. I went to the track sunday and pulled off a new PB 10.85@132, and pulled some data with the logger. It definatly shows a text book example of why AGX's are garbage. Didn't have time to get a wheel speed sensor hooked up, but I will for the next time I go. It defiantly need some sort of limiter straps or something to keep the nose down, as it's using almost all the travel.

Anyway anyone have any input? Anyone have any interest in this sort of stuff? Anyone trying to go fast should have some sort of chassis logging. It got seriously tiring of watching gopro footage trying to see what was happening.
 

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Are you doing any sort of low pass filtering for your accel data, either with physical damping of your accelerometer, in hardware, or in post-analysis? Just curious as I just picked up a Race Capture Pro system and there's need for filtering due to noise transmitted from the chassis. Targetting a 50hz filter I picked up some small isolation mounts (which according to a website's calculations might work) and will be testing them soon. The developers of the RC Pro are working on implementing post-analysis low pass filtering in their software but it's not there yet. Curious what you're doing if anything. With your scale it's hard for me to see if your data is noisy or not (also I'm pretty inexperienced so even if it's obvious I might not be able to tell LOL.

Have you tried the GEMS Data Analysis software for playing with your data? It's pretty amazing at a glance and free. It's well beyond what comes with the Race Capture Pro and I'm just about finished with a perl script to convert the RC Pro data to be compatible with the GEMS DA app. If you haven't seen the software download it and as soon as you run it and try the demo data you'll see what I mean by "amazing" :)

edit - Also, what sensors did you use for the suspension? Are they strain gauges, ride height, or something else? I have plans to start playing with some optical ride height sensors though I don't know if their frequency range is sufficient for monitoring suspension in general, though I do expect they'll still be useful in aero tuning
 
I don't know that it is fair to blame the shocks as some people have managed to go extremely fast on them.

It absolutely is. The nature of an orfice damper is that the damping force goes up with the shaft speed. So at low shock speeds there is little to no damping. This leads to a suspension that is soft yet harsh, and wallows around.

With real valving, the damping can have an almost flat response to shaft speed. That allows a suspension that is plush yet firm. Which is what you want, or at least what I want.

Sure people have gone fast on a set of AGX's, doesn't mean they don't suck. There ends up being little front traction, so people crutch this with a welded cd, and when your car weighs 3400 like mine you break tons of stuff running 1.7short times struggling to get into the 10's. With better suspension both ends pullthe car and it 60's better easier.

Tsiawd6666666666666

There is no filtering yet, this was my first try, and I wanted to see where it got me. I honestly haven't had much time to do anything with this yet. I'm just happy it sort of works, and I wanted to see what others were doing/what other ideas were out there. edit the accelerometer has a 50hz low pass built in I believe.

I think it is pretty noisy, i was sampling at about 25hz. I can send you the excel file if you want to see it. My plan is to figure out a way to fit a curve to the accelerometer data independently in each gear so I can see whats going on for shift points. As of right now it looks like I might be better off riding out 3rd gear.

For the position sensors it's pretty ghetto, but it's just a 10k pot with a bell crank. I know it's not linear, but it's close enough for me. My plan is to redo the cranks and make them a little longer to flatten out the response curve, then get some ~50k pots and short out most of the trace, to sensitize it a bit and get better resolution, then I can speed up the ADC in the arduino and still have better resolution with more samples.
 
It absolutely is. The nature of an orfice damper is that the damping force goes up with the shaft speed. So at low shock speeds there is little to no damping. This leads to a suspension that is soft yet harsh, and wallows around.

With real valving, the damping can have an almost flat response to shaft speed. That allows a suspension that is plush yet firm. Which is what you want, or at least what I want.

Sure people have gone fast on a set of AGX's, doesn't mean they don't suck. There ends up being little front traction, so people crutch this with a welded cd, and when your car weighs 3400 like mine you break tons of stuff running 1.7short times struggling to get into the 10's. With better suspension both ends pullthe car and it 60's better easier.

Tsiawd6666666666666

There is no filtering yet, this was my first try, and I wanted to see where it got me. I honestly haven't had much time to do anything with this yet. I'm just happy it sort of works, and I wanted to see what others were doing/what other ideas were out there. edit the accelerometer has a 50hz low pass built in I believe.

I think it is pretty noisy, i was sampling at about 25hz. I can send you the excel file if you want to see it. My plan is to figure out a way to fit a curve to the accelerometer data independently in each gear so I can see whats going on for shift points. As of right now it looks like I might be better off riding out 3rd gear.

For the position sensors it's pretty ghetto, but it's just a 10k pot with a bell crank. I know it's not linear, but it's close enough for me. My plan is to redo the cranks and make them a little longer to flatten out the response curve, then get some ~50k pots and short out most of the trace, to sensitize it a bit and get better resolution, then I can speed up the ADC in the arduino and still have better resolution with more samples.

What I'm trying to say is that they may not be perfect, but they are good enough. You have other things to change in the combination that will have better bang for the buck results than going to set of penske's or the like.
 
Ok so i have a question are ksport coilovers junk as well or what would you recommend for a street driven and occassionaly tracked car...and i am not meaning to thread jack...i am just asking cause of the nature of this post
 
Normally for us the shock doesn't do much. We just run a shit ton of spring and limit the front weather i be with preload on the spring to limit travel or with straps.
 
If you want to play with some really nice analysis software AEM's Data Analysis software is free. It's based off GEMS Data Analysis standard but for whatever the AEM DA has features normally locked in GEMS DA standard and reserved for the pro version (which isn't free). So you get Math channels for one thing, along with some other neat stuff. I have a workflow for getting my logs into AEM DA and can help you with that (basically run my perl script, then import into GEMS Dlog99, save file in .srt format, then open in AEM DA). PM me if interested. I may start a thread about this and since it's slightly off-topic here I won't clutter your thread any further.

Meant to include a screenshot of AEM DA:
 

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What I'm trying to say is that they may not be perfect, but they are good enough. You have other things to change in the combination that will have better bang for the buck results than going to set of penske's or the like.

Well I wasn't exactly saying go out and get a set of penske's, What I'm meaning is that agx's or any other orifice shock is no better than the oem imho. I'm sure just a set of limit straps would do wonders. I'm going to a set of bilstein HD's, and not because I feel that it will make my car 60' better, but because I hate the way AGX's feel. I hate the harsh mushy feel these have. I shouldn't have to run stupid high spring rates to make the car not feel like its a rowboat in the ocean. Honestly, considering my goals, getting the car to 60' better and more consistently is about all I have left to do. Seems like suspension, and rear toe eliminators is up.

Ok so i have a question are ksport coilovers junk as well or what would you recommend for a street driven and occassionaly tracked car...and i am not meaning to thread jack...i am just asking cause of the nature of this post

I've never had one in my possession. If they are piston shocks, serviceable, and don't blow seals, they can be as good as any imho.


If you want to play with some really nice analysis software AEM's Data Analysis software is free. It's based off GEMS Data Analysis standard but for whatever the AEM DA has features normally locked in GEMS DA standard and reserved for the pro version (which isn't free). So you get Math channels for one thing, along with some other neat stuff. I have a workflow for getting my logs into AEM DA and can help you with that (basically run my perl script, then import into GEMS Dlog99, save file in .srt format, then open in AEM DA). PM me if interested. I may start a thread about this and since it's slightly off-topic here I won't clutter your thread any further.

Meant to include a screenshot of AEM DA:

Don't worry about clutter. My next plan of action is a decent gui for my contraption, but if this other stuff is freeware and I can get my hardware to work with it, it will save me from making one!
 
Good stuff man and congrats on the new best time, that car is moving with that HY on there!

Thanks man. It's been a challenge for sure. Keeping it a full street car make it hard, but I've learned a lot along the way and had a lot of fun with it. I'm actually working with liberty to get some trans parts that will hold up better. If that goes thru I' either going to a HX40 in a t3 garret housing, or a HE351 with a HX40 turbine, or a GT3788VA off a duramax and play wth VGT stuff. I'd like to see it go 140mph consistantly.

Hopefully this logger buisiness will help me get the chassis working better, as the cars got the power to go faster. I'm also hoping this will inspire others to take advantage of the technology around us. I bought all the stuff for the logger at radioshack for $125. And it beats the hell out of watching the tach in on the gopro, trying to see how long the shift was by counting frames, if I need to wind it higher based on the time slip, or how agressive I was with the clutch on the launch. With this I KNOW.
 
AEM has their clone on their forum and it's also free. Killer software. Does so much cool stuff you can spend more time playing with it than driving your car.
 
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