I wanna get some idea's of what I need to do.So far I've been getting decent short times but I feel there is more there if I can get it to leave straight.The car torques over alot on launch and seems to be unevenly loading the tires.

Here's my setup:
1989 GTA
3575-3610 race weight(w/driver)
3.8L turbo V6 w/TH400 trans and 12 Bolt(3.08 gears)
Front suspension:
tubular k-member and control arms
Koni adjustable struts and coil overs
no sway bar
Rear suspension
Hotchkis arms and tubular panhard rod and Jegster torque arm
stock springs and KYB shocks
air bags
no sway bar

My two best runs are as follows:
60ft - 1.578
330 - 4.668
1/8 - 7.290@93.02
1000 - 9.575
1/4 - 11.517@115.52

60ft - 1.586
330 - 4.671
1/8 - 7.285@93.27
1000 - 9.564
1/4 - 11.498@116.19

Those were the only two times I was able to get 1.5's out of it and was my first time out with the airbags(15# left/20# right) - other times it's been fairly consistant mid 1.6's.I went out the next weekend to play with the air bag settings and it hooked so hard I snapped my alum driveshaft in two - I now have a chrome moly shaft to keep that from happening again

Any suggestions?The only thing I was thinking about was maybe getting a sway bar for the rear.

Steve

 

those times seem pretty impressive to me :hail: How wide are your rear tires? I was thinking maybe wider tires and better gears maybe.

 

whoa! you have 4 turbos?????

 

Aluminum driveshafts are for the street. They flex too much on the dragstrip. Mine is a 3" x .083" steel shaft with 1350 series u-joints.

My front suspension is stock except for V6 springs, no sway bar and Koni SPA1 struts.

Rear suspension is ladder bars, Herb Adams panhard bar, air bags (LH is usually empty, RH has around 30 psi. Stock IROC springs with one coil cut out and Koni SPA1 shocks.

9" diff with 4.56 gears, 31 spline axles and a spool. TH400 with a transbrake. 8" 5700 stall converter. I usually launch at 3000 rpm.

29 x 9" slicks and the car runs straight but I still get a lot of wheel spin. Custom made sub frame connectors, 6 point roll bar and solid engine and tranny mounts keep the car from twisting from all the torque.

That's pretty impressive 60' times for such a heavy car, highway gears and a V6 turbo. The rear sway bar would really help. I ran one until I installed the ladder bars on the 9".

My best run at altitude was:

60ft - 1.582
330 - 4.601
1/8 - 7.153@96.46
1000 - 9.353
1/4 - 11.241@117.81

If you don't already have it, get a roll bar. Running mid 11's I have to assume you have one. Install a rear sway bar. You might even be able to make one adjustable so that you can preload the RH side. Play with the air bag pressures some more. If you don't want to put solid engine mounts in, at least use a torque chain on the LF of the engine.

 

You need LCA relocation brackets. They'll help plant the tires and make it go straight instead of dancing every which way.

 

89Irocz23 - I run either 26x11.5x16 ET Streets(10" actual contact patch) or 28x10x16 Hoosiers slicks on stock GTA wheels.

As for why I have 3.08 gears - well I'm dealing with a low rpm motor,I shift at 5000-5200rpm.And so far I've only been running on 94 octane with rather low boost,when I switch to 116 and up the timing/boost the car should/could pick up 10-12mph in the quarter putting me in the 126-128mph range which will only be possible with 3.08 gears on a 5000 rpm motor.

Also,while my motor may only be making 450 or so horse power it is probrobly making 550-600 lbs.ft. of torque or more which is helping me get out of the hole.Plus it's a street car,and driving to the track with 3.08's makes real nice highway cruising

Stephen 87 IROC - You have a good running car there,those times are real impressive at those altitudes.I'm lucky to be so close to sea level,I belive Englishtown and Atco are 48-52ft above sea level(not sure though)

Anyway,yes I have an 8 point bar along with SSM subframe connectors.I have poly motor mounts/trans mount along with a torque strap for insurance.

Did you cut one coil out of the rear springs to level the car out?I was thinking the same thing and that maybe it would help get the weight on the rear tires better/quicker.The air bags really put the rear of my car in the air.

I think I'm going to try getting a sway bar for the rear along with playing more with the airbags to see if I can get it to leave evenly.

RB83L69 - Can you explain what the relocation brackets do and how they work.Also anybody using them on a car that 60fts in the 1.6-1.4 range or better?Pics?

Thanks again,
Steve

 

On the stock suspension of these cars, the rear mounting point of the LCA (on the rear end) is higher than the front mounting point (on the frame). Do the thought experiment, imagine a thing built like that, and push forward on the rear end like it does under acceleration. With the rear higher than the front, if the motor produces lots of power and the tires hook really hard, it's going to try to rotate upward; this raises the tires off the ground, causing them to lose traction; they spin; the pushing forward force goes away; the springs begin to push the rear end back downwards; eventually the rear end travels down enough that there's enough downward force on the tires that they hook up again; the forward pushing force resumes; the rear end tries to rotate upward. etc. etc. etc. Classic wheel hop.

A lowered car, or one with soft rear springs, makes it even worse. Either of those conditions makes the frame go even lower with respect to the other end of the LCA during launch. That's one of the reasons that air bags help these cars so much.

What the LCA brackets do is to lower the rear of the LCA below the front end of it. That way, when the big forward pushing force applies itself to the rear end, the rear end tries to rotate itself [i[downward[/i], into the pavement, increasing traction rather than reducing it. That way you can run soft springs for weight transfer and other aspects of traction, yet maintain the correct geometry at all times.

http://www.spohn.net

http://www.spohn.net/index.cfm?fusea...t&productid=11

There are several other makers of these. These are as good a product at as good a price as I've seen.

 

When I still used a torque arm suspension I made my own set of LCA relocation brackets. I produced so much torque that the diff was trying to push the lower control arms forward so hard that the floor and driveshaft tunnel on the passenger side is wrinkled.

Cutting the rear coils was to just lower the car since it's so much lighter than factory now. It just happens to sit level now and the air bags change the height only a little bit. I could just as easily play with my shock settings but adjusting air pressure is easier.

You only need enough octane to resist detonation. I use 92 pump gas. I've tryed straight VP C12 and a mixture of 50/50 and have seen little to no improvement except my wallet is lighter.

If the engine starts to ping under more boost then you'll need to increase the octane level.

 

how come your not running sway bars on the front or rear? does that help when launching?

 

Front sway bars don't do anything except add weight. The rear sway bar can help a stock type suspension by helping keep the right rear wheel on the ground. Since I use ladder bars the diff can't rise up like a stock one. Because of how ladder bars work if one side lifts the other side also lifts. I use rear air bags to fine tune the rear suspension but the rear sway bar will do nothing for my setup.

I do recommend a rear sway bar for anyone running a torque arm suspension.