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Launch dilema
Posted By: 7sec.cuda
Launch dilema - 10/19/11 09:08 PM
Posted By: 7sec.cuda
Re: Launch dilema - 10/19/11 09:13 PM
Posted By: 440lebaron
Re: Launch dilema - 10/19/11 09:22 PM
cold damp track? tire pressure? try this saturday
Posted By: 7sec.cuda
Re: Launch dilema - 10/19/11 09:29 PM
track was good tire pressure was 7.5 3 runs 3 spins
Posted By: MR_P_BODY
Re: Launch dilema - 10/19/11 09:32 PM
Have you tried raising your wheelie bars some so it
will transfer more
EDIT
I assume this is a 4 link... whats the length and height
Posted By: 2QUICK4U
Re: Launch dilema - 10/19/11 09:45 PM
whats rpm are you trying to leave at?
Posted By: 7sec.cuda
Re: Launch dilema - 10/19/11 09:48 PM
we have tried anywhere between 6000 to 7300 does the same thing
Posted By: 7sec.cuda
Re: Launch dilema - 10/19/11 09:54 PM
we have gone through the chassis from bumper to bumper twice. what is strange is that when it is 70 degrees or more this car has consistant 1.12 /1.13 60 ft times and the car will hook on ice. under 65 degrees this is what the car does no matter what i try
Posted By: SSDAcuda
Re: Launch dilema - 10/19/11 10:01 PM
Raising wheelie bar won't help, its not even trying to transfer, let alone hitting the bar.
Have you checked your tire gauge against another. Slicks look like radials to me…
Did you try loosening front shock extension?
Posted By: 7sec.cuda
Re: Launch dilema - 10/19/11 10:03 PM
shocks are as loose as they can go 2 different sets rears also new never compared guages
Posted By: SSDAcuda
Re: Launch dilema - 10/19/11 10:05 PM
Maybe try softening rear compression also. What # spring on the rear? Where is the IC of the four link?
Posted By: smokinwoody
Re: Launch dilema - 10/19/11 11:03 PM
Quote:
Maybe try softening rear compression also. What # spring on the rear? Where is the IC of the four link?
watching the vids, and seeing the bouncing, looks like the springs are too stiff, tires looked hard or over inflated...
maybe a change in the 4 link setup...
Posted By: B1CUDA
Re: Launch dilema - 10/19/11 11:46 PM
Have you changed anything in the suspension since it was last out? If not, here is my .02
I had the same PS Hemi in the car I just sold, and I know how finnicky they can be. I would start by taking timing out of it, at the hit, so that you can get the car to leave (although it may be a pooch to start off), and than start ramping the timing back in, as you get the chassis figured out. I would share my old launch RPM settings, etc., but, with your big tire, I am sure that your settings are far more agressive.
Do you have a Racepak? If so, what has the driveshaft rpm been in the past, at the 1 second mark? I would back it down with timing, than sneak back up to where the graph is showing it's happiest point.
Posted By: MR_P_BODY
Re: Launch dilema - 10/19/11 11:48 PM
I didnt see a vid the first time I looks... but looking
now and seeing it, it looks like the springs are real
stiff and it looks like the tire pressure is high...
do you know what the IC is... whats the weight
(front and rear)
Posted By: CHAPPER
Re: Launch dilema - 10/19/11 11:49 PM
If I had a car that was leaving with some 1.teens,,and then started acting like that,,,I'm not sure what I would do..!! You are spinning the tires on the line easier than I can in the water box..!!
Hard to tell from videos, but appears the tires might have WAY to much air for some reason, if that is possible...I suppose the tires are still 'decent' for this time of the season..? That is surely amazing that this would happen over 5* temperature. I can't give you any info on 4 link suspension,,I can't even get my ladder bar sled to work like I want it to..
But, that is one of the most frustrating launches I have ever seen.
Posted By: 7sec.cuda
Re: Launch dilema - 10/19/11 11:59 PM
we thought we had tire issues so we just bought new ones beginning of year these only have bout 15 runs like i said its amazing when its hot the car 60fts awesome but get colder the car is a different animal
Posted By: smokinwoody
Re: Launch dilema - 10/20/11 12:03 AM
Quote:
we thought we had tire issues so we just bought new ones beginning of year these only have bout 15 runs like i said its amazing when its hot the car 60fts awesome but get colder the car is a different animal
what are the tires and compound rating..
are they Goodyear's D compound?
Posted By: Bigcube
Re: Launch dilema - 10/20/11 12:06 AM
Could it have been the track prep at LVD? I know Shakedown was off the hook, I've only been to LVD a few times and the prep was never stellar. I agree with the rest, something in the back seems way too stiff, could the shocks be frozen up?
Posted By: 7sec.cuda
Re: Launch dilema - 10/20/11 12:07 AM
M/T 34.5 17 16 m5 compound
Posted By: 7sec.cuda
Re: Launch dilema - 10/20/11 12:10 AM
Jim brand new shocks,springs front and rear chasis gone over front to back twice this year car works excellent when hot does not work in cold weather .track prep wasnt the best but i had same issues at shakedown
Where are the shocks set compression and extension?
Donald
Posted By: BBLM23
Re: Launch dilema - 10/20/11 12:35 AM
I think the prep was good on Sunday. New best ET, 8.88 and 60 ft, 1.22, on first time shot. Video is from 2nd time shot.
http://photosbyjim.smugmug.com/Competiti...51_msPRgw3-A-LB
Posted By: SSDAcuda
Re: Launch dilema - 10/20/11 12:39 AM
It could work good in the heat but may be borderline and when track temps go down…
Time to change the setup. You have alot of horsepower and I'm sure once it hooks it works the suspension, but the suspension just doesn't seem to be working in the cold.
If the front is full loose, nothing to do there. You can try hitting the tire softer by moving the IC out and down a hair.
I agree with B1 also and would take a couple,4,8 degrees out in first gear to get it down through there.
Also take a .5lb out of the rear tire and see if it helps.
Your video is excellent and definitely helps. I have to get a camera man next year. Its nice to see what its doing besides relying on the racepak or the seat of the pants...
Posted By: Guitar Jones
Re: Launch dilema - 10/20/11 12:45 AM
Have you checked the wear on the rear tires to see if it's even across the tread width? I would have to say that it does look stiff for some reason. What gets me thinking is that it works when it's hot but not when it's cold. That could be a tire issue. Have you only used the M/T's or have you tried a softer compound in a different brand? Your car is pretty fast and most tracks I've run on would have a hard time holding that consistently.
Have you played with the pressure at all? Your videos don't show the burnout, maybe when it's cooler you need to do longer or shorter burnout. Lot's of stuff to try.
I know this may sound crazy but I have heard guys getting between 8 and 20 passes on a set of tires. From what I have been told your high HP cars break down the sidewalls very quick, you my want to call the tire manufacture and see if they have any ideas.
Posted By: gregsdart
Re: Launch dilema - 10/20/11 01:40 AM
I am not familiar with cars that run better than 1.2+ 60 fts, but will offer what I see. Looks to me like you nailed the setup for a fast surface/best scenario but this day was much different. By that I mean the rear suspension is not hitting the tires, you use torque and available traction to get needed weight transfer. The surface won't handle the hit without a softer rear shock and shorter IC , or maybe one or the other. Same with the front. It didn't even try and rise.
You might have to start with a setup that will handle this type of track and see just how much that setup will cost you on a good traction day. You may be able to leave it close to the same settings, maybe not. But it should have at least let the wheeliebars touch the track on the hit, IMHO.
What was the track temp?
Posted By: fishy340
Re: Launch dilema - 10/20/11 01:56 AM
i would try at ATCO if the car dont hook there,then theres something wrong
etown track prep is poo poo.. good luck Bobby
Posted By: Guitar Jones
Re: Launch dilema - 10/20/11 01:59 AM
Quote:
I am not familiar with cars that run better than 1.2+ 60 fts, but will offer what I see. Looks to me like you nailed the setup for a fast surface/best scenario but this day was much different. By that I mean the rear suspension is not hitting the tires, you use torque and available traction to get needed weight transfer. The surface won't handle the hit without a softer rear shock and shorter IC , or maybe one or the other. Same with the front. It didn't even try and rise.
You might have to start with a setup that will handle this type of track and see just how much that setup will cost you on a good traction day. You may be able to leave it close to the same settings, maybe not. But it should have at least let the wheeliebars touch the track on the hit, IMHO.
What was the track temp?
I think that is a very good observation Greg.
Posted By: Al_Alguire
Re: Launch dilema - 10/20/11 05:49 AM
Well from what I see in the video the rear suspension is doing nothing at all. I agree with some of what has been posted already. You are going to need to loosen the rear shocks on both extension and compression and IMO a four link adjustment woulg be on my to do list. Any idea what the IC and hieght is now?
My junker was doing similar things on cold tracks-vs-hot tracks although not to that extent. I was having a problem "holding" on to the track on cold days. We found a 4 link setting that works well in both, with a much shorter IC than before. now we just make adjustments to the shocks for varying track conditions/temps. I am not as quick as you but 60' but in the 1.teens on a good day at sea level and can go 8'ohs.
Would love to pick your brain a little on the 99 hemi thing.
Oh yeah BTW I think your problem is to much wheelspeed
Posted By: Al_Alguire
Re: Launch dilema - 10/20/11 05:58 AM
Well actually after watching it a few more times in the second video it appears like it is trying to hit the tire but loosing it quickly. Did you make any changes between that first video and the second one? If so what were they? In the first video it really appears as if nothing is happeneing n the rear.
It also appears to be hitting the tire at the 6 o'clock position, not farther forward. But as i said it definitely did not stay there. Perhaps loosening the compression a few clicks may have helped keep it planted better.
Have you loosened up the compression to help keep it planted? There is a slight downward movement to the wheelie bar and a little wrinkle of the tire before it goes up. I still would look at moving the IC closer but woudl be curious to hear exactly whats up with the rear shock settings. What shocks are they and what springs? Could be WAY to heavy a spring but I doubt that is the issue.
Posted By: SSDAcuda
Re: Launch dilema - 10/20/11 11:46 AM
Al, from my experiences, shortening the ic seemed to hit the tire harder. Maybe, I'm wrong, but out and down was definitely softer on the tire.
I do think your assesments are dead on...
temps like that can have a huge effect on shocks..its making the settings on the rears act much stiffer.
plus the motor is making more steam with cooler denser air.
im with greg move the bars to hit the tires harder .
sans making physical adjustments..
short term/or in a pinch..you could try to run the car up and down the retrun road or over some bumps and put/get some temperature in the shocks before you stage..see if that does anything.
Posted By: MR_P_BODY
Re: Launch dilema - 10/20/11 01:58 PM
For some reason he hasnt said the 4 link IC... but from
what I have seen a longer IC will tend to lift the front
more and the lower IC will sustain the hit longer,
also pushes harder forward.... and shorter IC lifts
the rear of the car... higher IC hits the tire harder
and for a shorter period of time...about the optimum
point is right around the CG or slightly behind it
then its a matter of how high...I only get a 1.19 60'
so his car is out of my comfort area..... JMO
Posted By: 7sec.cuda
Re: Launch dilema - 10/20/11 02:10 PM
really not sure of 4 link IC i have to find out and let u know
Posted By: Al_Alguire
Re: Launch dilema - 10/20/11 02:50 PM
Well it is kinda all speculation at this point since we dont know where it is now. Or the weight bias of the car. At any rate something needs to change or is broken, binding or just not working. I think we could all use a bit more info for sure.
Posted By: hvyweight
Re: Launch dilema - 10/20/11 07:00 PM
Is that a wishbone on that four link? check for binding! My friend had that same issue and his wishbone was literally seize!
