Throwin' parts at the car - now I need someone to teach me to launch it.

I have a 94 Camaro with M6 and an LT4 conversion with all the bolt ons. Dual friction clutch and 4.10 gears with the following suspension parts:

Frame connectors, LCAs, LCA relocation brackets, BMR Extreme torque arm, QA1 double adjustable rears, QA1 fronts with drag springs, 26 x 10.5 x 15 ET Streets on 8" Telstars.

Can very rarely get below a 2.0 sec 60' time. I have the front shocks set to 0 (out of 12) to get the full rise out of them (which happens). I have the rear compression set to 2 (out of 24)to get the weight down quick, and the rebound set to 12 (out of 24) to hold it there.

I dump the clutch ( at just about any rpm 2000 - 2800, I have a launch rev limiter so I can set it at any rpm) and spin the tires.

I can somewhat limit the amount of tire spin by going half throttle against the launch limiter, but it will spin violently if I go full throttle against the limiter.

I've had the air pressure from 15 to 30 lbs. I get a full contact patch at 24-26 lbs. At fifteen pounds I get two thin stripes on the outside only.

It seems that people have less traction parts on their cars and can get 1.60's with ease.

I've read the message on pre-loading the suspension, but a transbrake doesn't pre-load the suspension and I've read where guys are launching manual transissions at 5-6 grand.

Can someone tell me how to launch the car?

 

need to know what bolt holes you are using on your relocation brackets, if your car is lowered, what is your pinion angle set at, any weight reduction, what rear sway bar, do you still have front sway bar? all this info is important. then i think i can help you alot.

 

You don't want the rear to squat. You need the rear to be as stiff as possible and still hook.
Which hole are your LCA's in-what angle?
Pinion angle set at-2?

I run my et streets at 11-12 psi even though I have a perfect patch at 16psi
I have been compesating for my front road race springs/shocks using the rear but when I get front adjustables I will stiffen the rear back up.

 

The car is not lowered. I'm not sure if I need the the lowering brackets, it was a suggestion from BMR before I decided to put on the Extreme torque arm.

I'm using the top hole in the brackets (there's 2). Pinion angle is set to -2 degrees.

For weight reduction I've removed both bumper inserts, replaced the driver seat, removed the spare tire and jack and relocated the battery to the spare tire compartment.

I have stock sway bars on the front and rear. There is a tubular panhard bar that appears to be adjustable. I also have a shock tower brace.

Car weighs 3618 # w/ driver.

 

try removing the front sway bar. it will help the front get UP quicker. Which method did you use to get -2 on the pinion.

 

Try about 6-7 for comperssion and rebound on the rear shocks.
About 15psi warm with those tires.
Make sure that you have -2 to -3 degrees pinion angle
Get that front swaybar off and lose it.
And try the bottom hole in the relocator brackets.

 

Chassis shop that installed the torque arm said it was set to -2 degrees.

Here's my measurements by placing magnetic angle finder on the drive shaft and then on the torque arm bracket that is attached to the bottom of the rear end:

Drive shaft = 2 degrees
Rear end = 5 degrees

I think that is 2-5 = -3 degrees?

How do you guys launch your cars (rpm, slip/dump clutch, etc)?

I've seen cars with my exact set-up and much more power hook unbelievably hard. I don't get it.

 

MADMAN and I both say that is driveshaft angle. I just starting doing to the madman way and the result is the pic I posted.
You have SFC?
With someone in the car get the angle of the car with the gauge on the SFC. Then check the pinion angle and +/_ the sfc angle. Driveline angle does nothing for traction just vibration. This method sets the angle in which the rear axle pushes on the LCA and chassis

 

SFC = -1/2 deg
Pinion = +2 deg
LCA = -1/2 deg in top hole of LCA reloc. bracket (2 holes)

All of these angles with me in the car.

 

You definitely need to drop the LCAs for better traction at the track.
With parallel LCAs and soft shock settings you are unloading the rear tires at launch.

 

I think madman said around 4 degree's for the lca.
keep the front loose (1-2). lose the front bar and maybe the strut tower brace too.
set the rear at 5/5 or 6/6. tires around 13-15.
I don't slip my clutch but alot of people do. I may try once but I want to get mine to hook without slipping it.
When you dump it stay at about 1/2- 3/4 throttle for a few feet

 

OK - Let's see if I understand this.

1) remove front sway bar
2) remove shock tower brace

3)I should put the LCAs in the lower hole in the relocation bracket. This will probably give an agle measure of around -4 or -5. (looking at the driver side with the front of the car to the left- the lca will angle downward from left (frame connection) to right (relocation bracket) {front to back}

Let me see if I understand the theory behind all this.

1)Apply a load to the rear end and the tires create a counter-clockwise rotation (moment or torque) which loads up the front of the tire. I believe loading up the tire does two things, a) it distorts the tire creating a "longer" contact patch and b) stores kinetic energy in the sidewalls to help launch the car forward. Correct?

2)The ring gear then tries to climb up the pinion creating a clockwise torque which tries to unload the tires. (And this is why you want a negative pinion angle at rest so that when the rear end rotates, it will move into a position of 0 pinion angle).

3)The car moves forward and the reaction force travels rearward through the frame to the rear end. The lower the lca attaches to the rear end, the further it is from the axle and the bigger the moment (torque) applied to the tires. This is also counter-clockwise rotation which again serves to load up the front of the tire.

Is this on track so far?

Now I'm trying to learn understand the shocks:

4) If the compression setting is too low, this allows the rear end to squat. When the car squats, it creates a clockwise moment (rotation) around the rear end which again unloads the tires.

5) The rebound setting does what? I think it applies the pressure to the tires longer after the launch by pushing up on the car after the shock compresses therefore applying down force on the tire.

Is this why the soft shock settings unload the tires?

Does any of this make sense?
Are there any books out there that truly explain this?

 

when the rear suspension is too soft the weight being transfered from the front isn't used to push the rear end into the ground. It just compresses the suspension.
With the lca in the lower holes the axle will try to push the car UP and in turn push the axle harder into the pavement

 

About the 4 degrees for the LCAs.

Is this the difference in angles between the SFC and the LCA or the LCA and the pinion?

I'll make the changes today and record all the angles.


Thank you guys for all your help with this!

 

dropping the lca's could hurt your 60' also. mosy people i have talked to including myself with 9 second cars have found that using the bottom hole on a non-lowered car will actually hurt your 60'. give it a shot though. it only takes a few minutes to change. it may have a different effect on a lower horsepower car.