Who wants to help a novice? <long post>

[1SlowFormula]

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?

[Richard Maitre]

I realy have no experience with the D/R but was thinking a little less pressure and get rid of that "dry hop". A small amount of spin isnt a bad thing with a small/not so torque-y motor. Maybe dont leave off idle, preload the chassis ever so slightly with some rpm?

Remember I am a cylinder head guy, what do I know about chassis 

Rich

[REDGAR]

The conditions have not been optimal so that is the first thing working against you.

I would also agree with rich you want leave with some load, your reaction times will reward you   I usually leave at 1800-2200 when footbraking on my 5000 stall converter

I have used 275 17" mt radials and if I remember right it seemed like 15 psi was about the best pressure for me.  I don't do dry hops, I was always told not to so I never have.

[1SlowFormula]

Thanks, good to know I should avoid dry hopping it...

[1SlowFormula]

Oh I did attempt to raise the launch RPM, but it didn't seem to help. The car has a 3500 stall if that helps, but not too sure on all my attempts where I launched at but a few were in the 1800 range...


After doing some reading I think Rich is on to something with forgetting the dry hops, it appears this is also what MT recommends...

Well I am going to head to Atco next week to give it another few practice runs and to get familiar with the track since I have never been there, I guess we'll see how it goes...

Anyone else have any recommendations?

[REDGAR]

Now there is a great plan!!!


I will be at E-town for a double header Corvette Challenge and Pro 10.0 race... It is going to be a crazy day for me!!!

[1SlowFormula]

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...

[Bob Cosby]

I bet you will probably have a good handle on it now, but I do have a couple of comments...

First, those 275/60/15 DRs are tall - about 28".  That's killing your gear.  I'd suggest a set of 275/50/15s, as they are about 26" tall, and will improve your overall gearing.  It will also lower the rear a bit, perhaps slightly helping transfer weight better. 

Definately bring the air pressure down.   I used to run 12 psi in my 275/50/15 BFG DRs, and they hooked great.  Go down in small increments and keep good notes.  Tire pressure should be within a lb or two on each side.

Concur completely with getting rid of the dry hop.  "Your first launch is your best launch".  And if the dry hop is your first 'launch', you just used it.

Try launching right off idle - this will allow the converter to 'flash' to near its stall speed, and put more torque to the tires.  Note:  This assumes you're not spinning the tires hard.  If you are, then bringing the motor up a few hundred rpm would help.  But also if you are, those things above should help you cure that. 

Good luck!

[1SlowFormula]

Thanks for the advise Bob...

The tires were on the rims when I bought them off of another board member so I was OK with taking the hit in gearing since I calculated it out and the fianla drive with 3.73's and 28" tires would be the same as 3.42's with a 26" tire and that was already a decent increase over the 2.73's and 26" tire I was running last season...

When I break this rear, or get the money whatever comes first, I will be looking to install 4.30's or 4.56's depending on where I see the car running and will want to keep the 28" tire at that point...