03/04 IRS drag setups?

Anybody have any experience with getting good short times from 03/04 IRS's? I can cut 1.70's-1.72's on my ET streets but that's it, and I'm on a stiff autox/aggressive street setup right now. What I'm really looking for is what shocks/struts spring rates (coilovers) should I go with?? Right now I'm running 350lb front and 575lb rear springs on bilstein HD struts and 03/04 cobra bil shocks with max motors coilover kit.

My goal is 1.65 consistently, think that's possible with changing my spring rate/damper setup???

H0SS302 said:

i hate to put it to ya like this, but in MOST cases its cheaper just to swap your IRS for a SA setup. a straight axel is much cheaper to build and have hold up than IRS.

A lot of times you can trade your IRS with someone straight up, saving you money, or you can sell it.

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Been there done that; this is a street/strip car - and I like the ride of the IRS for daily driving (plus it handles like tits the way it is now, haha). For my moderate power levels I don't need to do any "building" really...just more bushings, and change shocks/spring rates, I'm just not sure what to run!

Uncle Meat said:

Well you can look into the following upgrades for your IRS...

Billetflow girdle.
'03/'04 cross brace. (Beefier than previous models)
Level 3 or 5 half shafts from DSS.
Upgraded bushings all around.

As for springs & shocks I'm not really in the know... I replaced my stock Bilsteins with a set of 10-way adjustable units from HBH. They had additional rebound dampening in them to help combat wheel hop.

U.M.

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Billetflow girdle - check
'03/'04 cross brace - check
Level 3 or 5 half shafts from DSS - only making 430rwhp, max i'll be making is 500rwhp, so until I break the 31 spline 03/04's I have i'll wait on that.
Upgraded bushings all around - I currently have max motors urethane diff and subframe bushings...think this kit would be worth it http://www.svtperformance.com/forums/showthread.php?t=260665&highlight=delrin ???

I'm already on a coilover setup, and max motors didn't have much to say about running a softer spring rate, except that it SHOULD help weight transfer...and that different shocks/struts MAY help but didn't have any real recommendations (kinda odd, coming from them). I'm not getting any hop with the slicks, and I'm launching at 6150RPM off the rev limiter, it just hooks and goes. I just want that extra five 100ths off my short time, and I figured with how stiff my suspension is currently softer/different springs/shocks/struts might help - seems like nobody likes to drag race an IRS though haha

Uncle Meat said:

No you're right... there's not a lot of people trying to seriously drag race with the IRS. Your 1.7 60-ft times are not bad though.

I don't think you'll see any benefit from swapping the urethane for delrin though. I guess you're down to dialing in your current setup if you want to improve on those 1.7's.

U.M.

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Yeah, and thanks, heh... I think control arm bushings would help with suspension articulation, and maybe aluminum diff bushings just as extra insurance for breakage.