experiences 4link setup slippery tracks?

[ccrp]

Hello all,

I am from Europe and we are racing Outlaw class which means anything goes as long as you are faster then your opponent - but we run on unprepped airfields mostly. Unprepped means totally unprepped so traction and search for every tiny bit of traction is the name of the game.

I run a new car (1968 Camaro tube frame) now which was built as a Pro-Stocker and the last ran in SuperComp. I have converted it two a 14-71 blown 632 with a modified competition TH400 as 3 gears give me a slight advantage if I miss out on the start, with a Powerglide if the launch ain't good there is no chance to catch up anymore.

Car is about 2200lbs heavy, has 50/50 weight distribution and I use Hoosier D6 33/17-15 drag slicks. Front has double adjustable Koni struts, rear has double adjustable Konis plus a ARB. Springs in the rear are soft 90lbs, front are about 225lbs.

here is my problem, if I use the original SC setup with about 50% anti-squat, I can leave on the tbrake at 5000rpm and no wheelspin but car leaves like a turd with low 1.60 60' times. It doesn't give you the feel of a launch at all!

I tried to go the other way with 160% anti squat and it leaves violently with a lot of wheel spin, in the end ET about the same, 60' about the same.

somewhere there must be the sweet spot!!!! but where?

[ccrp]

one thing I need to get is better weight transfer to the rear, however the Koni front struts are seriously limited in travel. What can I do to improve that besides having someone built me a special strut?

I played a bit with IC length and height, but either I am dong the wrong things I have not yet fiond something where I could be confident to improve upon....

[John_Heard]

Something don't add up - or sound right with your car...

632 with a 14-71 blower, 3 speed, 2200 lb car, huge slicks leaving at 5000rpm on the chip (flashing to?)... with 1.60 60' foot times? If it's hooking well, which it sounds like it is at least with that one setup, power must be hurting badly. What kind of ET/MPH are you getting?

What kind of rear gear and trans gears do you have in it? Are you guys racing 1/4 mile or 1/8th?

[ccrp]

the 1.60 were with the old 472 BBC with a 8-71 blower, the 14-71 blown 632 is new but the problem with traction will be same if not worse now. Racing 1/4 mile of course. Power of old combination was around 1180hp + 200hp shot of nitrous. New engine dynoed @ 18 psi at 1700hp on E85 if tuned very conservatively, an aggressive tune might not help me to find traction. It is a 16 injector EFI driven by an Haltech E11v2 ECU so I can dial in sort of traction control with slow slew rates for advance off the line. However, first I want to get the suspension mechanically right to leave as hard as possible!

Tranny is a TH400, rear gears are 3.55's with those 33" slicks, Coan Racing 4400 stall converter - all an attempt to get traction.

As I wrote, if I use the original SuperComp 4 link setup which has just about 50% anti-squat dialed in I could leave with high rpm with little wheelspin but still lousy 60' times. If I went to 160% anti-squat and bottom car angled down on front it just lit up the tires, even at low rpms. But still bad 60' times......

best ET on those concrete unprepped airfields was 8.90/ 155mph, the best the car ever did on a professional race track like Mantorp in Sweden (where it was build) was 7.08/192mph (although with a Lenco and nitroused 555 Shafiroff motor)


And YES, you are right, something is not RIGHT with the suspension setup at the moment - and I believe any help to get me started would be appreciated a lot. The goal are 8.50'S to low 8's no matter what on our "tracks"
this is the car:

[John_Heard]

Increasing anti-squat should be putting more bite in, it ought to plant the tire harder and quicker - but you're saying it worked backwards. More anti-squat - spun, less anti-squat = no/little spin.

I'm not a 4 link wizard, but we have a few on here that will likely chime in. Rough guess on why more anti-squat didn't work is you didn't have good enough shocks to control the hit. However to diagnose the tune up on the chassis, good video and some data logger info (engine rpm, driveshaft rpm, g-force, etc.) would help immensely to detail where when and what is going on. If you don't have a logger, it would be worthwhile to get one... and a good video camera.

[Moparious Maximus]

here is my problem, if I use the original SC setup with about 50% anti-squat, I can leave on the tbrake at 5000rpm and no wheelspin but car leaves like a turd with low 1.60 60' times. It doesn't give you the feel of a launch at all!

Blower suspensions are tricky on good tracks sometimes, I cant even think how hard it would be on a non-prepped surface.

What your saying about leaving like a turd with no wheelspin might confuse people, but you are right, you need some amount of slip to get the tires to work right. You cant leave dead hooked.

I was always told to shoot for as much wheelspeed as you can get away with, without going up in smoke. I dont know if that applies to you, running on crappy tracks and all.

We fight it with our car, we can run a 8.0 in the 1/4 but we cant get it to 60' better than 1.3, and thats on a great track.

[ccrp]

I have a video but disregard what happens after about 1/8 mile when a nitrous backfire blew my blower off..........

http://www.youtube.com/watch?v=OsSVzih6tfE

my scenario is as follows:

-little anti-squat short IC length:
it leaves of the line very mild but little wheelspin and is not launching hard at all

-a lot of anti-squat short IC length:
it leaves hard and quickly thereafter unloads tires and goes up in smoke.

for comparison, the same engine in above video in my old dragster, a Jeep CJ7 bit like crazy
http://www.youtube.com/watch?v=3rlMwxyszoQ

I tried to apply what I learned from the Jeep but it doesn't apply all.

I believe I am on an errant somewhere and probably one of those 4 link experts like Bill and Mr. Morgan could get me a good head start from where I can improve.

I have all 4 link measurements and 4link Software if that helps

BTW.: Mr. Morgans book is under my pillow every night....

[John_Heard]

For what it's worth, but the sound of the engine it doesn't sound like it's trying to hook, just sounds like it's hazing the tire to me, but not crazy as the pattern doesn't get skinnier like it would if you had a ton of wheel speed. Video from the side of the car showing what the tire is doing would help next time.

If I had to guess it sounds to me like you're blowing through the converter? But that's a lot of guessing..

[ccrp]

those runs were made with the old Vigilante race converter with 3500 stall. I have now a new Coan Racing 4400 stall (a 1700 $ race unit) but haven't tried it yet due to winter.

Do you think one of the 4 link experts might chime in and explain differences with long IC and short IC and what effects it might have on slippery tracks? I was always under the impression that a high Anti-squat value rams the tires into ground whilst a long IC give enough leverage to keep tires planted.

maybe I am wrong here, at least I never saw the effect - unless you are right and the converter was fooling me all the time.

what basic setup would be a good starting point, like what IC lengths, anti-squats values and more importantly IC height?

I am just re-mapping my suspension and I am open for all suggestions and like to hear different points of view of course

[John_Heard]

I think your take on what the IC's do and how they react is correct - the problem I see is you really don't know what is going on right now in regards to how the current settings are affecting the car - shooting in the dark so to speak. If it was blowing through the converter like it sounds like, we can't tell, we also don't know what kind of wheel speeds you have, etc.

Don't take that as a slam, I just don't think you have much data to work with to help you make decisions. Very good investment would be a data logger as mentioned before. Do you have a MSD digital box? Got an run traces to look at?

[ccrp]

I have a Racepack logger in car now, but did not have at time when videos have been made - unfortunately.

I can also run traces on Haltech (again new, before EFI I was running carbs).

the idea behind picking some brains in what basic setup to use was simply to have a ballpark setup to start with. And go from there based on collected data. I believe you are right that the converter was fooling me, the more I think about it the more it makes sense now, and that'S why all those changes to suspension did not show any effects which caused a lot of confusion and frustration.

[John_Heard]

Cool - Sounds like all you're needing now is some good weather to get out and test.

[BillyShope]

When you're that far away from 100% antisquat (50% and 160%), you're going to get some violent launch reactions. You're pushing the rear of the car either down or up. When the rear of the car is accelerated downward, the rear tires are unloaded; when accelerated upward, the loading is increased.

But, that's a very misleading simplification. Note that the loading is a function of ACCELERATION, not position. At 50% antisquat, the rear of the car is accelerated down from its ride height position. But, about half way between the ride height position and the lowermost position, the acceleration reverses. With the acceleration reversal, the rear tire loading is INCREASED. The shocks are doing all they can to stop the bouncing, but there will always be some oscillation about the final position.

So, to say that antisquat less than 100% decreases rear tire loading and that over 100% increases rear tire loading is misleading. Such a simplification describes only the first few milliseconds of launch. Beyond that, it must be recognized that tire loading is oscillatory. And, oscillatory loadings are generally to be avoided in friction applications. The negative effects can be seen in the increased stopping distances when wheel hop occurs during braking.

I would strongly recommend that you seek an adjustment which gets you as close to 100% antisquat as possible.

(As an aside, large deviations from 100% antisquat can be acceptable with low power levels, but, as power is increased, launch problems become apparent.)
http://www.racetec.cc/shope

[ccrp]

thanks for the reply Bill.

from reading through all topics in here this was what I was shooting for, around 100% AS. I need all help to load rear tires (and keep them loaded) and to do that I need to get front into the air. Since our tracks are not glewed it is highly unlikely that front tires will actually lift off, but I believe a trade off between force needed to lift front end and force remaining to accellerate car is needed or need to be carefully balanced - what IC length and position might give the most front rise?

what I can see from suspension mappings, most AS values around 100% give me rather short IC lengths with lower bar angled upwards. Both doesn't seem to be too good for my application

[want-a-be]

What kind of IC have you been running/trying? How high are you running the IC off the ground? Where are you running the front shocks and the rear shocks at on the settings?

Have you used a jack and made sure that the rear suspension is freely moving through out it's range of travel? Sounds like you may have some sort of binding going on.

Are you running a wishbone track locator? If so,... are you sure it isn't bottoming out some how?

Don