Cadillac CTS-V - Tuning the IRS for drag racing




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NEED MO POWA!
05-21-2012, 09:53 PM
Im trying to set up my car for drag racing at the track. I want to know what can i do to get the IRS to hook better. Here's what i have so far.

Built 9" IRS
solid cradle bushings
subframe connectors
stock springs (cut to lower the car)
stock shocks (with lowering spacers)
stock sway bar/ end links
BMR trailing arm
BMR Toe rods
26x10.5-16 MT ET streets

The best i was able to do was a 1.9 60' with a 4500 clutch dump so i'm looking to reduce that. One of the things i know i need to do for sure is raise the rear of the car either using stock springs or some other form. What else can i do, it just feels like the car doesn't plant the tires down they sort of just float. It doesn't wheel hop at all so thats not a problem.


itsslow98
05-21-2012, 10:21 PM
Its old school but Air Lift Drag Bags do help and they are cheap.

NEED MO POWA!
05-21-2012, 10:25 PM
yeah i've looked into them, however i don't know if i'm suppose to increase or decrease the spring rate.


itsslow98
05-21-2012, 10:40 PM
How much air are you running in the slicks?

NEED MO POWA!
05-21-2012, 10:51 PM
I started at 17 psi and worked my way down about 13.5 was the sweet spot.
What do you think about raising the rear of the car using stock cts springs. I imagine they are a little taller than v springs but are also softer.

DrSpeed
05-21-2012, 11:54 PM
Can you fit 16" rear tires? Will it clear the brakes?

NEED MO POWA!
05-22-2012, 12:16 AM
16's fit with smaller brakes.

itsslow98
05-22-2012, 12:28 AM
I started at 17 psi and worked my way down about 13.5 was the sweet spot.
What do you think about raising the rear of the car using stock cts springs. I imagine they are a little taller than v springs but are also softer.

Id try and put a taller tire on the car to start. The extra sidewall should help with the launch. Might be worth seeing if someone has a set you can try out and if they help grab some ET Drags next go round.

CTSV_510
05-22-2012, 08:06 AM
Do you have the FE4 or FG2 shocks? Wouldn't shocks with a stiffer rebound help keep the tires planted? I don't really know anything about setting up a suspension for drag racing but it just seems like that would help.

DrSpeed
05-22-2012, 09:28 AM
16's fit with smaller brakes.

So, you put the standard CTS brakes on?

NEED MO POWA!
05-22-2012, 10:46 AM
Yeah im going with a taller tire, I have a set of 28x11.5-16 et drags that i want to try. However i have to raise the car back up to fit them and i have to modify the trailing arm since they are wider and they rub.

About the shocks, i actually don't know what kind i have. Also not sure if a stiffer shock works better.

Yes i am running cts calipers and rotors in the rear.

i have a launch control and WOT box im about to install to see how that helps.

Thanks for the input so far guys lets keep the discussion going i'm headed to the track friday again and i want to mess with it during the week.

NIKDSC5
05-22-2012, 11:23 AM
what are you et's with a 1.9 60' and 402 procharged :confused:

serik21
05-22-2012, 12:10 PM
http://www.highperformancepontiac.com/tech/hppp_0710_pontiac_gto_traction/photo_07.html
I would give that a try should help, stiffer shocks ( faster rebounding) should also help. Cts springs are a lot thinner, I have a set laying around if you are interested but IMHO it's a waste of money

ichpen
05-22-2012, 12:26 PM
Yeah im going with a taller tire, I have a set of 28x11.5-16 et drags that i want to try. However i have to raise the car back up to fit them and i have to modify the trailing arm since they are wider and they rub.

About the shocks, i actually don't know what kind i have. Also not sure if a stiffer shock works better.

Yes i am running cts calipers and rotors in the rear.

i have a launch control and WOT box im about to install to see how that helps.

Thanks for the input so far guys lets keep the discussion going i'm headed to the track friday again and i want to mess with it during the week.

Disclaimer, I don't do drag BUT I do dabble with shocks.

From what I've gleaned you want softer rebound and stiffer compression for launches. I know a lot of drag guys use qa1 shocks as they offer adjustment for comp/rebound. Plus they're relatively cheap. Going ultra stiff on shocks may not help you much and may make things worse.

Check also that you've not blown your shocks.

DMM
05-22-2012, 12:32 PM
Being lowered is really hurting you. I don't know if anyone makes adjustable shocks for the front of our cars, but the front has to lift and the rear has to squat to transfer the weight properly. OE STS springs may be the way to go since they are softer on a heavier car...don't know about the shocks though.

I would also try to add some positive camber at the rear wheels so that when you launch the tires stay flat on the ground rather then going negative camber when it squats.

cts-vls6
05-23-2012, 09:42 AM
I would try to launch the car at 3000 to 3500rmp and rides out the clutch,too much power at line cause wheel spins,thats all was help me on a manual car,a launch controler will help u out at lots

odthetruth
05-23-2012, 01:49 PM
You have a KARs subframe connector or something else? Pics?

BudRacing
05-23-2012, 02:23 PM
Being lowered is really hurting you. I don't know if anyone makes adjustable shocks for the front of our cars, but the front has to lift and the rear has to squat to transfer the weight properly. OE STS springs may be the way to go since they are softer on a heavier car...don't know about the shocks though.

I would also try to add some positive camber at the rear wheels so that when you launch the tires stay flat on the ground rather then going negative camber when it squats.

:stupid:

Both things I was thinking while reading.

Weight transfer and tire contact are keys to a good launch.

NEED MO POWA!
05-23-2012, 03:18 PM
Yeah i realize being lowered is hurting me , that's why i'm looking to raise the car back to stock height. With it being lowered the car has more negative camber, raising it should help a ton to get proper contact patch. would it be beneficial to raise the front also?

Anybody have some stock cts v springs laying around?

The subframe connectors were part of the madman rear end package, they are welded to the rear cradle and bolted to the front subframe.

here are some pics:
http://i110.photobucket.com/albums/n96/rub3n_05/IMG_3544.jpg
http://i110.photobucket.com/albums/n96/rub3n_05/IMG_3548.jpg
http://i110.photobucket.com/albums/n96/rub3n_05/IMG_3550.jpg
http://i110.photobucket.com/albums/n96/rub3n_05/IMG_3551.jpg
http://i110.photobucket.com/albums/n96/rub3n_05/IMG_3556.jpg
http://i110.photobucket.com/albums/n96/rub3n_05/IMG_3560.jpg
http://i110.photobucket.com/albums/n96/rub3n_05/IMG_3568.jpg

Skidmarcx
05-23-2012, 04:32 PM
I like the subframe connectors I plan on doing something like that on mine

serik21
05-25-2012, 10:16 PM
AnY updates?

NEED MO POWA!
06-03-2012, 11:48 PM
AnY updates?

1.80 60' :drive:
still has alot more in it, it's spinning pretty bad.

got only one pass tonight, was testing the launch control.
I will continue to update as i dial it in.
I still need to raise the car up and put on the taller slicks.

I am having some timing issues up top that im working on, but ill post an ET and video as soon as i make a full pass.

NEED MO POWA!
07-20-2012, 09:43 PM
Here's a quick vid of the car at the track this was the 1.8 60'. I was not able to make a full pass due to some issues up top. The car is currently down undergoing some changes:secret2: I'll be back out on the fall once the temps drop.
http://www.youtube.com/watch?v=LqMzr1rUTyA

adanieljohnson1
07-20-2012, 09:59 PM
Man that is so sexy! Love the 5 lug conversion too....

BudRacing
07-21-2012, 07:13 PM
So what is your current setup? Did you ever change up the springs?

NEED MO POWA!
07-21-2012, 07:43 PM
Currently the car still sits the same however i'll be going over the suspension pretty soon. I have a set of stock(uncut) springs already waiting to go on. I'll also be going to a taller tire plus some other engine changes.

skydiver
07-22-2012, 01:09 PM
Currently the car still sits the same however i'll be going over the suspension pretty soon. I have a set of stock(uncut) springs already waiting to go on. I'll also be going to a taller tire plus some other engine changes.


Went with air bags on mine, cut the springs down a little to be able to get a full range of height adjustment . Did this after 1st trip to drag strip & realized I really needed some control that I could experiment with changes at the track .
Using a cordless remote system that lets you adjust air pressure individually from anywhere & shows pressure on remote .
Just keep it on the sun visor
Also comes in handy when you get some heavyweights in the back seat & need to compensate for the load

RADEoN
07-22-2012, 01:11 PM
skydiver what was your best quarter mile?

skydiver
07-22-2012, 01:41 PM
skydiver what was your best quarter mile?



10.28 , But I wasn't the driver, guess I'm just getting to old for all the things
You gotta be to get this thing down the track that quick

NEED MO POWA!
07-22-2012, 04:26 PM
you have any video and/or time slip of the 10.28 run? what tires were you using at the track?

skydiver
07-22-2012, 04:47 PM
you have any video and/or time slip of the 10.28 run? what tires were you using at the track?



Nah....... You know it was one those times your just screwing around & a friend wanted to take it down the track & I said Ok, wasn't even thinking about the fact this guy has been racing with a manual trans for years.... "and it showed"
I wasn't even watching it till the end.
It was his run & his time slip
This was last year & I haven't even mentioned it since it's kinda a situation where if I didnt do it & with no slip it didn't happen .
Just blurted it out when radeon asked ........( shoulda kept my mouth shut)

Runnig M/T. Et.s 305/35/18. With about 16 psi & the air bags definately helped