Who wants to help a novice, launch? <long>
04-06-2007, 11:56 PM
#1
11 Second Club
Thread Starter
Who wants to help a novice, launch? <long> OK I just got back from a sucky Friday night at Cecil, I don't know if it was a cold track, horrible prep, all the imports rolling through the water box, or all of the above but I couldn't get traction to save my life... The car was pretty consistant in MPH but I went to try and figure out this new suspension setup and it is causing me a few headaches...
My car is a stock internal LT1 F-body, I was always good at getting a decent 60' with the stock suspension and gears. This was my first time out with a new setup and can't quite get a feel for it yet.
Over the winter I added 3.73 gears over the stock 2.73, draglites with skinny metric tires up front and 275 60 15's MT drag radials out back over stock rims with stock size nitto drag radials, subframe connectors, solid drag style rear sway bar, and comp eng drag shocks. The rear was much stiffer after adding the sway bar, but adding the shocks with the rear set to 50/50 seems to have evened it out a little. It definitely doesn't seem to squat or transfer weight like it used to, or at least that is how it feels. I have been getting conflicting stories on what is better as far as squat is concerned. Most hard core racers avoid squat, yet most of the stock suspension guys thrive on it. Is this just the difference in suspension? How do you launch a car that doesn't squat?
Right after a burn out it seems to dry hop nicely, but off the line with the same technique I am used to using with stock suspension it just seems to shock the tires. I've tried multiple different air pressure settings and where my launch was progressively worse as I lowered air pressure, I also got my best overall time using the lower air pressure, approx. 16 psi per side. I have also tried to vary the launch RPM, but nothing appears to make a difference. Examples: The first run out without checking the tire pressure I got a 2.152 60' launching off idle. I then checked the pressure and found I had ~18psi on the driver side and 11psi on the passenger side. I took the pressure up to 21 psi on each side and on the next run got a 2.19 60' again off idle. Dropped it to just under 20 psi per side, raised the RPM some and got a 2.053 60', and still felt like I was shocking the tires. I even tried stalling higher with the same tire pressure and got a 2.133 60'. Dropped the tire pressure to ~16 psi per side and launched off idle again and spun to a 2.22 60'. On one of my last test runs of the night I did a short burn out, avoiding the water box, dry hopped and it grabbed rock solid so I tired to mimic the dry hop on launch and got the best of the night but it was still only a 1.795 60', felt like there was a lot of spinning, and almost no weight transfer. I can't quite get a handle on what works best yet because the car seems more stiff and unwilling to transfer weight like it used to.
Any suggestions on how to test next or thoughts on what might help me get a better launch would be appreciated. Then again, would track prep change all this anyway?
My car is a stock internal LT1 F-body, I was always good at getting a decent 60' with the stock suspension and gears. This was my first time out with a new setup and can't quite get a feel for it yet.
Over the winter I added 3.73 gears over the stock 2.73, draglites with skinny metric tires up front and 275 60 15's MT drag radials out back over stock rims with stock size nitto drag radials, subframe connectors, solid drag style rear sway bar, and comp eng drag shocks. The rear was much stiffer after adding the sway bar, but adding the shocks with the rear set to 50/50 seems to have evened it out a little. It definitely doesn't seem to squat or transfer weight like it used to, or at least that is how it feels. I have been getting conflicting stories on what is better as far as squat is concerned. Most hard core racers avoid squat, yet most of the stock suspension guys thrive on it. Is this just the difference in suspension? How do you launch a car that doesn't squat?
Right after a burn out it seems to dry hop nicely, but off the line with the same technique I am used to using with stock suspension it just seems to shock the tires. I've tried multiple different air pressure settings and where my launch was progressively worse as I lowered air pressure, I also got my best overall time using the lower air pressure, approx. 16 psi per side. I have also tried to vary the launch RPM, but nothing appears to make a difference. Examples: The first run out without checking the tire pressure I got a 2.152 60' launching off idle. I then checked the pressure and found I had ~18psi on the driver side and 11psi on the passenger side. I took the pressure up to 21 psi on each side and on the next run got a 2.19 60' again off idle. Dropped it to just under 20 psi per side, raised the RPM some and got a 2.053 60', and still felt like I was shocking the tires. I even tried stalling higher with the same tire pressure and got a 2.133 60'. Dropped the tire pressure to ~16 psi per side and launched off idle again and spun to a 2.22 60'. On one of my last test runs of the night I did a short burn out, avoiding the water box, dry hopped and it grabbed rock solid so I tired to mimic the dry hop on launch and got the best of the night but it was still only a 1.795 60', felt like there was a lot of spinning, and almost no weight transfer. I can't quite get a handle on what works best yet because the car seems more stiff and unwilling to transfer weight like it used to.
Any suggestions on how to test next or thoughts on what might help me get a better launch would be appreciated. Then again, would track prep change all this anyway?
04-07-2007, 08:37 AM
#2
M/T does not recommend dry hops. When the tires are subjected to the burnout, the oils in the rubber come to the surface, and make the tire sticky. A dry hop removes patches of that sticky rubber.
A burnout should last only long enough to raise the tire temp approx 10-15* hotter than the strip surface. Long burnouts only kill the tire, and shorten it's useful life.
Does the car still have the ft sway bar? If so, try unhooking it, to allow for better pitch rotation.
Maybe loosen the shocks a bit, and hit the tires harder?
As Madman says: "Girls squat, racecars don't". A good statement to tune with!
A burnout should last only long enough to raise the tire temp approx 10-15* hotter than the strip surface. Long burnouts only kill the tire, and shorten it's useful life.
Does the car still have the ft sway bar? If so, try unhooking it, to allow for better pitch rotation.
Maybe loosen the shocks a bit, and hit the tires harder?
As Madman says: "Girls squat, racecars don't". A good statement to tune with!
04-07-2007, 10:22 AM
#3
11 Second Club
Thread Starter
Originally Posted by Old Geezer
M/T does not recommend dry hops. When the tires are subjected to the burnout, the oils in the rubber come to the surface, and make the tire sticky. A dry hop removes patches of that sticky rubber.
A burnout should last only long enough to raise the tire temp approx 10-15* hotter than the strip surface. Long burnouts only kill the tire, and shorten it's useful life.
Does the car still have the ft sway bar? If so, try unhooking it, to allow for better pitch rotation.
Maybe loosen the shocks a bit, and hit the tires harder?
As Madman says: "Girls squat, racecars don't". A good statement to tune with!
A burnout should last only long enough to raise the tire temp approx 10-15* hotter than the strip surface. Long burnouts only kill the tire, and shorten it's useful life.
Does the car still have the ft sway bar? If so, try unhooking it, to allow for better pitch rotation.
Maybe loosen the shocks a bit, and hit the tires harder?
As Madman says: "Girls squat, racecars don't". A good statement to tune with!
Thanks for the heads up on the burnout and dry hopping, I will try to keep that in mind, too bad I am used to running this car the same way for many years and now I have to relearn it all...
BTW, the front sway bar hasn't been on the car in years...
Oh, and does anyone thing a spinning rollout would also loose this sticky patch mentioned above?
04-07-2007, 11:19 PM
#4
11 Second Club
Thread Starter
I took the car to a guy that sets up suspensions for a lot of the local 4th gen f-body club. He instantly found that the rear suspension was way too tight. Since a 200+# man was shoving/jumping on the rear of the car and it barely moved... 
Once under the car we found that I had bind in a few spots, my swaybar was binding and didn't allow much rotation at the axle because the bushing was mounted too close to one of the bends in the bar and since the tube bended there it could not rotate in the bushing, and my adjustable shocks were binding as well as set too tight. We tweeked it all and resolved the bind in the rear and also set the shock to their loosest setting. He said this was because the stock front suspension needs the help, and it would work the best this way unless the track is absolutly perfect and that rarely happens, but I'm sure you guys understand that...
So I tested it on the street (nothing crazy, just stabbing at it a little) and it seems to transfer weight a lot better now, so next step is to get it to the track and work on the launch...
*** EDIT ***
BTW if your reading this, Thanks again for the all the help today Steve...
Once under the car we found that I had bind in a few spots, my swaybar was binding and didn't allow much rotation at the axle because the bushing was mounted too close to one of the bends in the bar and since the tube bended there it could not rotate in the bushing, and my adjustable shocks were binding as well as set too tight. We tweeked it all and resolved the bind in the rear and also set the shock to their loosest setting. He said this was because the stock front suspension needs the help, and it would work the best this way unless the track is absolutly perfect and that rarely happens, but I'm sure you guys understand that...
So I tested it on the street (nothing crazy, just stabbing at it a little) and it seems to transfer weight a lot better now, so next step is to get it to the track and work on the launch...
*** EDIT ***
BTW if your reading this, Thanks again for the all the help today Steve...
Last edited by 1SlowFormula; 04-07-2007 at 11:29 PM.
04-08-2007, 05:34 AM
#5
So what were you getting 60' wise with the old setup? Also, if your car has a 3500 stall, I definetly wouldnt be launching off idle. I would stall it up to near or at that 3500 so everything is prelaoded, and the engine is warmed up, and let her rip. With your engine flashing up to 3500 rpm, and the the stall just grabbing, I would think this could easily shock your tires like you are saying. Good luck. 
04-08-2007, 09:50 PM
#6
i think i spanked yah pretty bad that night... i was the dude in the pewter ls1. my car was hooking great that night on 255/60/16s. 30 psi and i weak 3 sec burn out. the track seemed sticky. but than again i have 273s and stock converter.
Last edited by monsterbreather; 04-08-2007 at 10:01 PM.
