antisquat %, IC height & length discussion - S197 mustang

lindertw

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bottom line up front: I'd like to build up a setup reference/database - maybe it'll help us as we try to dial in our suspension setups for the strip.

If you've plotted your suspension (http://www.baselinesuspensions.com/instant-center_general.php), can you post your info? If you haven't, consider doing it and adding your info here. I did mine with the car on ramps and subtracted the height of the ramps from my measurements...

18apr13_suspensionplot_UCA_upper_LCA_upper_zpsbccf11ac.jpg


Antisquat %: 105.24%
IC length: 45.89"
IC height: 9.53"
springs front: cobra jet (M-5300-Q)
springs rear: cobra jet (M-5300-Q)
airbag: NO
ride height front: 28.5" (measured from floor to top of fenderwell arch)
ride height rear: 28.5"
tire dia front: 27.1" (OEM pirelli)
tire dia rear: 26.5" (M/T ET street)
strut type front: strange single adjustable
strut type rear: strange single adjustable
wheelbase: 107.1"
center gravity: 21.125" (crankshaft bolt + 6" I need to find the source that mentioned this for OHC engines)
LCA relocation brackets: YES, BMR
LCA position: upper hole
UCA bracket: YES, METCO
UCA position: upper hole
pinion angle: -2.5deg

best 60' to date: 1.95 (last fall, driver mod needed and additional suspension mods completed since
http://www.s197forum.com/forum/showthread.php?t=82789 )

I know there are a lot of variables (weather, tires, track condition, driver skill, etc.) but it could be interesting to see if there's any correlation to 60' times and how the AS/IC plots. I've read lots of threads where folks list their setups generically (springs/shocks/tires/LCA position/etc.), but having the numbers to go along with it might paint a better picture.

some reference links here, I'll add more later:
http://www.s197forum.com/forum/showthread.php?t=93895&highlight=instant+center

http://www.s197forum.com/forum/showthread.php?t=97209&highlight=instant+center

thanks!

*edit to add a pic of how the rear sits

mt_et_streets_apr13_zps4bf262ed.jpg
 
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BMR Tech

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YES! Awesome, was going to start one of these myself when time permitted.

The IC/AS does, absolutely play a role in 60' times. We have tested it, many times.

There are two reasons I try to avoid this stuff, when speaking with my average customer. A, to avoid confusion and B, you really only have a few "easy" ways to adjust, and the options are minimal unless you really start modifying things.

These cars react drastically from IC change.

I typically like to see, on calculators like yours, anywhere from 95-115% depending on the persons goal. The problem with that is, though, other items play a large role in how well the AS setting will work, like, a DA rear shock. You can run less AS, with a nice set of DA shocks, and make your set-up work as well as more AS and a set of cheaper SA shocks.
 

BMR Tech

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Here are a few drawings I have made over the years, to help explain this stuff:





 

fdjizm

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Linder I believe I found one of your posts when I was studying this stuff on the internet heavily last month.
http://www.wmdracing.net/forum/show...instant-center-length-height-for-S197-mustang
Were you on cobra jet springs in this post? if they are stock ride height then just comparing I would be at around 119% AS being that I have a BMR UCA Mount using the bottom hole and the BMR LCA relo brackets using the top hole.

ideal instant center length/height for S197 mustang?
I've been playing around with the baseline suspension calculator and I'm curious what is a good starting point IC length/height for S197 mustangs

- Metco UCA mount has two adjustment holes: upper hole (similar to factory setting), and a lower hole
- Metco UCA is adjustable, but currently set to factory length
- Metco LCA (non-adjustable)
- BMR relocation brackets with three adjustment holes (upper/middle/bottom)

running the calculator, here are results with approximate measurements:

UCA upper hole + LCA reloc upper hole: anti-squat 95%, IC length 58.41", IC height 11.28"
UCA upper hole + LCA reloc middle hole: anti-squat 119%, IC length 51.01", IC height 12.37"
UCA upper hole + LCA reloc bottom hole: anti-squat 140%, IC length 45.92", IC height 13.12"

UCA lower hole + LCA reloc upper hole: anti-squat 119%, IC length 39.48", IC height 9.55"
UCA lower hole + LCA reloc middle hole: anti-squat 138%, IC length 36.67", IC height 10.28"
UCA lower hole + LCA reloc bottom hole: anti-squat 154%, IC length 34.53", IC height 10.84"

my car:

2005 mustang w/302rwhp, 5spd manual, stock clutch
M/T ET streets 26X11.50-17LT
cobra jet springs (M-5300-Q)
strange adjustable struts/shocks
4.10s, truetrac diff, LPW diff cover
swaybar removed, UPR/GMS radiator support installed

I understand I'll need to try different strut/shock settings and tire pressure, but where is a good starting point with respect to the UCA/LCA configuration?

Thanks in advance for any insight you all can provide!
Love reading this stuff! :)
 

lindertw

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Linder I believe I found one of your posts when I was studying this stuff on the internet heavily last month.
http://www.wmdracing.net/forum/show...instant-center-length-height-for-S197-mustang
Were you on cobra jet springs in this post? if they are stock ride height then just comparing I would be at around 119% AS being that I have a BMR UCA Mount using the bottom hole and the BMR LCA relo brackets using the top hole.
Love reading this stuff! :)

fdjizm, I think my numbers from that other thread are off, the numbers here are good... best to measure yours - and post the results here :thumb:
 

Radar Doc

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Here are some numbers on my 2011:

Antisquat %: 99.12%
IC length: 35.86"
IC height: 6.97"
springs front: BMR SP-011 (SP-009 Set)
springs rear: BMR SP-012 (SP-009 Set)
airbag: NO
ride height front: 27.5" (measured from floor to top of fenderwell arch)
ride height rear: 27.875"
tire dia front: 27.2" (OEM Pirelli)
tire dia rear: 27.2" (OEM Pirelli) (also use MT ET Street Radial II @26.4")
strut type front: Strange single adjustable
strut type rear: Strange single adjustable
wheelbase: 107.1"
center of gravity height: 21.0
LCA relocation brackets: CHE
LCA position: Roush billet LCA rear bolt in only hole (2.5" down from stock)
UCA bracket: Roush UCA/Bracket
UCA position: upper hole
pinion angle: -2.4 deg (pinion to rear driveshaft)

No 60 ft times with this suspension yet, but thought I'd post anyway to show the numbers with this combination of parts.
 

lindertw

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so I've been playing around with measuring my suspension points and I'm trying to come up with a drawing/model that I can use to visualize changes (i.e. diff springs give a resultant front UCA/front LCA mount height, etc.). I took the model and overlayed it against a blueprint view of the S197 chassis that I found online.

s197_plot_zpse945a537.jpg


if I get the model cleaned up, in theory I can have a base suspension plot, and then move around the mount points based on tire size, ride height, relocation bracket mount points, etc. and have approximate measurements that I can then throw into the baseline suspension IC/AS calculator without changing any physical parts and remeasuring...

we need more folks to post their numbers in here; we've got some cars with great 60' numbers and I'd like to see your suspension data :beer:
 

wbt

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Great thread. I did some measuring and realized I had been running too much AS. I have backed off that some and plan to do some testing at the track in the near future to see how that works. ;)
 

fdjizm

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oh yea that sounds serious lol, if my research is correct that will cause the car to unload after the initial hit and lose traction?
 

lindertw

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Great thread. I did some measuring and realized I had been running too much AS. I have backed off that some and plan to do some testing at the track in the near future to see how that works. ;)

that was the switch back to stock springs, right?
 

wbt

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oh yea that sounds serious lol, if my research is correct that will cause the car to unload after the initial hit and lose traction?

If I ran on a decently prepped track I never had that issue and consistently produced mid 1.5 60' times.

that was the switch back to stock springs, right?

This was before and after the springs. I made some additional geometry changes. Hopefully it is a do more with less approach. :)
 

wbt

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so, uh, when you're done with the shootout will you share some details ya big tease? :boobies:

It's not so much I am keeping info to myself as much as just needing to try out some ideas. If it works I will post what those changes were. I am not one to hide anything. :thumb2:
 

N20JUNKY

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I assume by running too much AS that it bites more then needed meaning using power that could be used to get down the track?
 

lindertw

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I assume by running too much AS that it bites more then needed meaning using power that could be used to get down the track?

http://www.baselinesuspensions.com/info/Launching_A_Drag_Car.htm

=====

Anti Squat (AS):
This is a term used to describe how much the rear of the car will Rise or Squat during launch. If a chassis has 160% of AS then the rear will rise drastically, planting the tires violently. By comparison if a chassis has 100% AS then the rear of the car will not rise or squat and if a chassis has less than 100% the rear of the car will squat.

~A common problem with high horsepower cars running Too Much AS is that the tires will plant the tires very hard for the first several feet but then start to unload the tires and spin when the chassis starts to settle. If your car does this, then look into the value of the AS. Much too often racers will detune the engine to "calm down" the launch instead of look into the suspension geometry.

~A common problem with high horsepower cars running Too Little AS is that the suspension will cause the rear of the car to squat which tries to unload the tires. Again racers detune the engine to maintain traction instead of looking into the suspension geometry.

<snip>

~4-link settings of 100% Anti Squat should accelerate the car w/o any raising or squatting of the rear of the car.
~4-link settings with MORE than 100% Anti Squat will Raise the rear end and hit the tires HARDER.
~4-link settings with LESS than 100% Anti Squat will cause the rear end to Squat and hit the tires SOFTER.


=====
not sure if our 3-link acts/reacts differently than the above 4-link information...
 

luv2cheat

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bottom line up front: I'd like to build up a setup reference/database - maybe it'll help us as we try to dial in our suspension setups for the strip.

If you've plotted your suspension (http://www.baselinesuspensions.com/instant-center_general.php), can you post your info? If you haven't, consider doing it and adding your info here. I did mine with the car on ramps and subtracted the height of the ramps from my measurements...

So I went to the above website and was going to plot my suspension and am unsure about "Control arm LENGTH is not the actual length. It is the parallel/projected length along the horizontal axis."

Is it bolt hole to bolt hole or?
 

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