Down track traction issues.

Hi guys.
I'm looking for a little advise on what appears to be a down track traction issue.
We have recently broken the 7 second barrier on drag radials- https://www.429-460.com/boost-and-juice-f10/into-the-7s-in-full-street-trim-t1309.htm - but having studied the videos & timing tickets fron the last meeting, I think we may be spinning the tyres a little after the front wheels touch down.
The car dead hooks on the line , picks up the front wheels about 8-10" and will carry them, at that height for 60-70 feet. i believe that the spin starts as soon as the front wheels touch down. We were playing with the launch and nitrous delivery at the last meeting and the 60ft varied between 1.24 & 1.31. the top end is deadly consistent with a variance of only 0.05 from the 1/8th to the finish line over 6 runs. the big differences between runs is from 60ft to the eighth mile with a variance of 0.210 over the same passes.Our best 1/8et (on the 7 second pass) is 5.16 @ 140mph.
Car info:
wheelbase 112"
race weight 2700lb 48% front 52% rear
M/T ET Street radials @ 12psi
I/C length 39" @ 7" high
rr shocks(strange dbl ajustables) extension 4 clicks from full tight/rebound 7 clicks(half way)
fr shocks(single adjustable) approx 1/3 from full tight
No wheelie bars

My gut feeling is the I/C wants to be longer & higher.........any suggestions welcome!

Brain.

An I/C change might help but it depends........

Your I/C isn't drastically short or long. Its within that large 38" to 55" general adjustment window that a lot of people work with. And since it's currently hooking with what sounds like very usable "normal range" valving settings, the I/C might be real close to where the car likes it for the given power you have to work with at this time.

Moving the I/C will really effect the traction (good/bad) more for the launch than it will down track. And since your saying it's not spinning the slicks until the front tires set back down it just sounds to me that the front tires touching back down are unloading the rest of the car as they collapse the front suspension & it rebounds "X" number of times.

So looking at it from both sides........

While a longer I/C might be thought of more for the actual launch hook, it could also calm the launch leverage (and wheel stand height) enough so it's not as much of a jolt to the front suspension when the fronts set back down from a lower wheelstand at 60-70 ft out. This could help as long as the front suspension wasn't really the cause of the problem all along (from front spring weight wrong, or compression valving wrong).

If you do decide to play with the I/C placement, be sure to take good notes where everything is at now so you can find your way back.

Could softer front shock compression dampning ease the shock to the car when it sets the front wheels down? I suppose you wouldn't want to mess with the extension dampning as that may make it wheel stand more.

It sounds like the four link is set really good if you can balance the wheel stand at 8-10" with out wheelie bars.

Bill

I've been doing a bit more number crunching with the data from last weekend.
The lost time can all be accounted for between 60-330ft.
Interestingly, it appears that the more aggresive we are with the nitrous ramp, the more time we lose after the 60ft!
The nitrous controller is a very sophisticated piece,which allows us to change the nitrous ramp by as little as 1% increments and 1/10th second time intervals. We set the controller by watching the videos of the N/A launch and using the frame count to tell us where to start adding nitrous. We were able to very quickly tune the launch to carry the front wheels until the nitrous ramp reaches 100%.

Right, that's the factual stuff, now the theory.........

My understanding is: We have a short/high I/C which makes for a violent launch. The shock extension damping is stiff to control the hit. As the front wheels touch down, the rear axle is "lifted" due to the stiff damping and unloads the tyres for a split second.
When the front comes down there is a very small bounce but the front shocks remain pretty much fully extended.

Would lengthening and raising the I/C slightly allow us to run less extension damping, still get the plant on the tyres and be compliant enough up the track to stop the unloading?

The video is our 1st 8.1 second run (with 300hp of nitrous) all the later runs were with 400hp but the car carries the wheels so far, you can no longer clearly see whats going on!
ps. I get the feeling we may be very close to a BIG wheelstand- don't really want to go there.............

https://www.youtube.com/watch?v=6_b_A2BCzTU

Cheers,
Brain.

brain@fbracing wrote:Would lengthening and raising the I/C slightly allow us to run less extension damping

Yes (well, theoretically longer and/or lower) to stay in the same general area of the launch "balancing act" between I/C placement & shock extension valving. If you make one part more "lazy" (say for example longer I/C) you compensate (to a point) by making the other part more "violent" (say for example looser rear extension valving).

Actually looking at the video it does look like a damn good squirt. Much better looking launch than the older clips you posted a while back on the old site. If it's spinning on the set-down it can't be much judging from the sound cuz I cant really hear any big change. It sounds like a good pull the whole way. So as I said before just make sure you can find your way back to this setting if you change anything. Also is it possible that track prep might be causing the problem?


I do love a dragster wing on a door car...........

Wow, thats one BAD drag radial car ! That car not only looks great, it launches really nice. Sounds like you've the drag radials pretty much figured out, with only a little fine tuning in order to run faster! How big are the drag radials?
Gary

DILLIGASDAVE wrote:

brain@fbracing wrote:Would lengthening and raising the I/C slightly allow us to run less extension damping

Yes (well, theoretically longer and/or lower) to stay in the same general area of the launch "balancing act" between I/C placement & shock extension valving. If you make one part more "lazy" (say for example longer I/C) you compensate (to a point) by making the other part more "violent" (say for example looser rear extension valving).

Actually looking at the video it does look like a damn good squirt. Much better looking launch than the older clips you posted a while back on the old site. If it's spinning on the set-down it can't be much judging from the sound cuz I cant really hear any big change. It sounds like a good pull the whole way. So as I said before just make sure you can find your way back to this setting if you change anything. Also is it possible that track prep might be causing the problem?


I do love a dragster wing on a door car...........

Well it certainly worked. I moved the I/C foward 4" , up 1.5" and took two clicks of ext. damping out. The car launches pretty much the same but with the wheels not as high in the air- it looks a lot more controlled!

The result was 7.80 @ 174 mph the 60ft was exactly the same @ 1.24 but we picked up 0.15 by the 1/8th and ran 5.01 @ 142mph (that's WITH a brief pedal at about 300ft as the car drifts to the right- might be time for a little preload).

I'll post the video in a couple of days, in the excitement I left my camera behind.............

Brain.

GTmustang wrote:Wow, thats one BAD drag radial car ! That car not only looks great, it launches really nice. Sounds like you've the drag radials pretty much figured out, with only a little fine tuning in order to run faster! How big are the drag radials?
Gary

315/60/15 M/T ET Street radials- works out at about 29" tall.

Brain.

brain@fbracing wrote:Well it certainly worked...........The result was 7.80 @ 174 mph

Nice job.

I like the fact that you made a small conservative increase in I/C length instead of a knee-jerk reaction by moving it forward a bunch & possibly getting lost.

Roll on next season.................
https://www.youtube.com/watch?v=iKd67sI4_G0

Brain.

The result was 7.80 @ 174 mph the 60ft was exactly the same @ 1.24

Even more impressive with the 1.24 60'. That thing really backhalves well and on drag radials to boot. Two thumbs up!!!

DILLIGASDAVE wrote:

brain@fbracing wrote:Well it certainly worked...........The result was 7.80 @ 174 mph

Nice job.

I like the fact that you made a small conservative increase in I/C length instead of a knee-jerk reaction by moving it forward a bunch & possibly getting lost.

What do you think done the trick here Dave ,just trying to take this in and learn.

When the ic was lengthened and raised in theory would it have increased the amount of force and time it was placed on the rear springs or do you think the shock valve setting let it settle without unloading the tires ?

KY JELLY wrote:What do you think done the trick here Dave

It probably wasn't one adjustment or the other that was most important, but the combination of both creating a nice working balance.

I think it would be damn interesting to see what effect a set of electric Koni's would have on a lot of guy's big torque cars. The ability to have stiff valving for the launch, then looser valving as the pass unfolds to "work" both sides of a balanced I/C vs shock valving setup could be an eye opener on a number of cars.

DILLIGASDAVE wrote:I think it would be damn interesting to see what effect a set of electric Koni's would have on a lot of guy's big torque cars. The ability to have stiff valving for the launch, then looser valving as the pass unfolds to "work" both sides of a balanced I/C vs shock valving setup could be an eye opener on a number of cars.

Hi, I'm Ian, owner/driver of the '34 above. Brain & I have often discussed the possibility of loosening the shocks down track. The Koni set-up is mega bucks and waaay out of my price league. However, we currently have Strange double-adjustables on the rear and I notice that they offer a retro-fit remote control 'kit'. I know of nobody over here using one so real world info is hard to come by. Could you or any other members shed any light on this? Kit is here:http://www.strangeengineering.net/catalog/pdf/116.pdf

Never messed with the electric shocks before, but I was hoping to get the chance this year. I tried to talk a guy into putting them on his car, but his money was just too tight this year.

One thing I have learned is that if you run the top bar in the top hole on the housing, it will make a car feel loose on top end. I always wind up with the top bar in the bottom hole on the housing. My .02

BigDave65 wrote:One thing I have learned is that if you run the top bar in the top hole on the housing, it will make a car feel loose on top end. I always wind up with the top bar in the bottom hole on the housing. My .02

When looking at 4-link changes I always try to keep both axle ends as low as I can in their respective brackets.
The softer extension settings seem to have done the trick. If funds allow we will be adding the remote adjuster kit over the winter.
The only other issue to fix is the right pull..........looking at the video the car puts the wheels down at about 80ft, but what you can't see is it picking them back up and carrying them until Ian has to pedal at about 300ft!
The extra torque we are now making, coupled with the new longer 4 link setting has caused a lot of axle rotation and body roll on launch, giving the L/H tyre more bite. Time to connect the anti roll bar I think...!!

Once we get the launch straight we will experiment with adding weight to the front to see if we can apply more power,faster. I think we can go high 1.1 60fts and 4.80 1/8ths next season. We may have to be careful as our chassis is 7.50 tagged mild steel!

Brain.

My thought on what changed the most, is the IC height change of 1.5"......drag radials seem to like a higher AS than slicks...

A different view of our 7.80 pass, taken from the Street Eliminator series DVD.....

http://www.streeteliminator.com/html/videos.html#r7video09

Brain.