4 Link Dragster tuning

Suspension Tuning, Troubleshooting, Design and Discussion

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Bucky
Posts: 1
Joined: Mon Jul 01, 2013 12:59 pm

4 Link Dragster tuning

#1 Post by Bucky » Mon Jul 01, 2013 2:33 pm

I have a 4 link dragster that has a problem that it seems like a lot of rear suspended rails have: At the hit, the tire wads, the suspension extended, all is good and we are getting traction...Then the rim starts to rebound back toward the chassis. There is little if any weight transfer on dragsters, so that isn't much of a tuning aid, nor is the front suspension for that matter....since there isn't one.
Here is a snap shot of the shock and driveshaft data:


No amount of extension dampening seems to remedy it. Compression dampening helps make the shock data look better, but the entire back of the car simply goes up with the rebound of the tire, and the driveshaft data looks exactly the same.
Image

I have tried a lot of different suspension settings and it seems like having a setting that is very neutral at the hit helps, but doesn't make the driveshaft data exactly perfect either.
I have tried settings that had a tad bit of compression just after the hit, and my reaction times suffered greatly. I have tried lowering the two step and raising the two step. Softer hitting converters seem to help, but it is difficult to have them hit somewhat soft and still perform decently.
Oh, it is a small block car that runs the best of so far 7.85 167-168

Image

So, how does one limit the amount of hit, but still have the leverage to keep the tire planted after the initial hit? If you flatten the top bar, it hits less hard, but also has less upward pull on the top bar to keep the tire planted.
Here is a look at the 4 link:

358t
Posts: 7
Joined: Sun Oct 18, 2009 8:41 pm

Re: 4 Link Dragster tuning

#2 Post by 358t » Mon Sep 23, 2013 12:17 pm

Bucky, looks like your IC is pretty long (ahead of the instant center) just by looking at the bars. And going by your description of shock movement the IC is also about the anti squat. One would think this would hit the tires less aggressively while also planting them later in the run (in comparison to a short and hi IC). Have you determined where your CG is?

Maybe revalving your shock for even stiffer extension dampening would give you the ability to control it? How close to toping out the shock in extension is it?

Wish more people would chime in with experience in this... I find this subject interesting and have a 4-link SBC powered dragster myself.

Scott

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Hookdaddy
Posts: 47
Joined: Tue May 04, 2010 8:49 am
Location: Eagleville PA & Ocala FL
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Re: 4 Link Dragster tuning

#3 Post by Hookdaddy » Sat Nov 02, 2013 12:19 pm

On my 4-link on our dragster.

416" Iron Eagle small block , 4.57 gear 14.5 x 33 Hoosier 8-1/4 pounds 7.70's @ 170 off the stop but we mostly Super Comp race 8.90 @ 168 on the stop

1720 # with my 190 # driver on board

we're 44" out and 10" up
Don Scholl
S&W Race Cars - retired
145H Super Comp
145Y Stock Eliminator & ET Brackets

358t
Posts: 7
Joined: Sun Oct 18, 2009 8:41 pm

Re: 4 Link Dragster tuning

#4 Post by 358t » Sun Nov 03, 2013 8:38 pm

Hi Don,

Thanks for sharing. What angle is your bottom bar when driver is in the seat?

Scott

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Hookdaddy
Posts: 47
Joined: Tue May 04, 2010 8:49 am
Location: Eagleville PA & Ocala FL
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Re: 4 Link Dragster tuning

#5 Post by Hookdaddy » Fri Nov 08, 2013 2:47 pm

Scott - I never had a level finder on it. Give me your Email and I'll send you a graph

Don
Don Scholl
S&W Race Cars - retired
145H Super Comp
145Y Stock Eliminator & ET Brackets

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