STX WRX Setup / Discussion thread

[Emanuel]

Originally Posted by BeBop86

That's with the new 15" wheel setup? Nice!

Yes, thanks.

Here is the current setup:

Camber: -3.5front/-1.5 rear (measured with a level and ruler, so slightly rounded)
Caster: ~4.5 (again measured with home improvement tools)
Toe: zero all around
Koni: 1/2 turn from full soft all 4 corners
Tire pressure: 38f/33r
Springs: 500f/400r
Sway bars: OEM front/ disconnected rear
Wheels/tires: 15x8 et 40 Ronal slipstream with 225/45 15 BFG Rivals
Ride height: 14" wheel center to fender arch all around. (lowest I could go in the front with the 8" Eibach coils on the Ground Control sleeves) If I want to go lower I need to shorten the strut sleeves and weld on a support ring for the GC sleeves to sit on. But then I also would get really close to riding on the FatCat bump stops.

I drilled holes in the strut towers to allow me to turn the Cusco plates in favor of max inner angle, while still giving extra caster over stock.



Next step: Replace the rear bushings of the front lower control arms with STi ones that I have already in my garage. That should help camber control under full lateral force and help rotation a little.

Also working on setting up a street tuning session with a recommended guy, to get a little more meat in the lower to middle RPM range.

Next event: Hopefully May 11th Route 66. Let's see how it does against some more serious guys.

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[MNbiker]

Looks like a decent start. I would assume the car doesn't rotate real well with the current setup? Mine has a combinaition of more rear spring, stiffer rear shock settings, stiffer rear bar, and a bit of rear toe out, versus your current setup.

[BeBop86]

If you want more rear rotation, why not try reconnecting the rear sway bar or leave it disconnected and swap springs F -> R?

Also, why did you drill and not just swap plates L -> R? I'm 99% sure you can obtain those same angles with how they come? (maybe a liiiittle more caster). Or better yet, set it back to max caster and slot your upper camber bolt holes in the struts to obtain more camber (it's a better location to add camber anyways).

[MNbiker]

Originally Posted by BeBop86

...Or better yet, set it back to max caster and slot your upper camber bolt holes in the struts to obtain more camber (it's a better location to add camber anyways).

Not always better. The issue with slotted struts is tire to spring clearance. This might not be as much of an issue with 225mm tires, but with 245's, I have to run thin spacers to keep my tires off the springs WITHOUT slotted struts.

[Emanuel]

Originally Posted by MNbiker

Looks like a decent start. I would assume the car doesn't rotate real well with the current setup? Mine has a combinaition of more rear spring, stiffer rear shock settings, stiffer rear bar, and a bit of rear toe out, versus your current setup.

Originally Posted by BeBop86

If you want more rear rotation, why not try reconnecting the rear sway bar or leave it disconnected and swap springs F -> R?

Probably going to re-connect the rear bar and play with the shocks. Toe out would be a last resort kind of thing. The reason I disconnected it, was that the car showed snap oversteer in the previous events and I wanted to find out if there is something fundamentally up back there, so I over corrected.
I'm not in favor of equal or higher spring rates in the rear. That might work for some people, but suspension frequencies are way off that way.

Originally Posted by BeBop86

Also, why did you drill and not just swap plates L -> R? I'm 99% sure you can obtain those same angles with how they come? (maybe a liiiittle more caster). Or better yet, set it back to max caster and slot your upper camber bolt holes in the struts to obtain more camber (it's a better location to add camber anyways).

No and no.

The Cusco camber plates give you three max options and that already includes swapping them left and right. Either you get max camber(inner angle) or max caster or what the picture showed an unsatisfactory mix out of both.
You don't want max caster as it jacks up the car and causes wheelspin with the open diffs, but you want some extra caster.
Getting the upper strut turning point as close as possible to the center line (limited by the center hole in STX) of the car is very desirable, because it allows for more dynamic camber gain. Also slotting the struts causes very quickly tire<->strut clearance issues with the 40mm offset of the 8" wheels.

PS: looks like MNbiker already beat me too it.

[MNbiker]

Originally Posted by Emanuel

...I'm not in favor of equal or higher spring rates in the rear. That might work for some people, but suspension frequencies are way off that way.

It depends on whether you're trying to optimize the car for autocross or not. For autocross, WRX's are typically fastest when set up scary-loose. This type of setup means stiffer rear springs and/or bigger rear bar, and requires a bit different driving style. The WRX Fenter won Nationals in a few years ago was set up extremely loose. Yes, the setup defies all semblance of "proper" suspension setup, but many optimal autocross setups require similar compromises - especially when dealing with nose-heavy cars with less than ideal suspension designs.

-Steve

p.s. STi's are a bit of a different beast., in terms of setup. It's amazing what a huge difference some real limited slip differentials makes.

[Emanuel]

Originally Posted by MNbiker

It depends on whether you're trying to optimize the car for autocross or not. For autocross, WRX's are typically fastest when set up scary-loose. This type of setup means stiffer rear springs and/or bigger rear bar, and requires a bit different driving style. The WRX Fenter won Nationals in a few years ago was set up extremely loose. Yes, the setup defies all semblance of "proper" suspension setup, but many optimal autocross setups require similar compromises - especially when dealing with nose-heavy cars with less than ideal suspension designs.

-Steve

p.s. STi's are a bit of a different beast., in terms of setup. It's amazing what a huge difference some real limited slip differentials makes.

Hmm, interesting. In my quest of trying to keep this car also a semi comfortable daily driver I might have to leave some performance potential on the table. I do have a few options to bring controllable life in to the tail end of the car though.

I met Chris Fenter at a tour in Peru 2010 driving my friends MX5 and I believe I am not quite at his level of driving.

Yes STi's are quite different in behavior, so lets hope the SCCA keep them apart from regular WRX's.

[penderperson]

For snap oversteer or understeer check your bump stops and your available shock travel. The first thing I do with new setups is cut the bumpstops. Use zip ties on the shaft to determine how much travel you use. High spring rates or damper settings can partially mask a bump stop issue.

[Emanuel]

Originally Posted by penderperson

For snap oversteer or understeer check your bump stops and your available shock travel. The first thing I do with new setups is cut the bumpstops. Use zip ties on the shaft to determine how much travel you use. High spring rates or damper settings can partially mask a bump stop issue.

Thanks, I might give that a try.

[UWMechEngr]

Originally Posted by MNbiker

It depends on whether you're trying to optimize the car for autocross or not. For autocross, WRX's are typically fastest when set up scary-loose. This type of setup means stiffer rear springs and/or bigger rear bar, and requires a bit different driving style. The WRX Fenter won Nationals in a few years ago was set up extremely loose. Yes, the setup defies all semblance of "proper" suspension setup, but many optimal autocross setups require similar compromises - especially when dealing with nose-heavy cars with less than ideal suspension designs.

-Steve

p.s. STi's are a bit of a different beast., in terms of setup. It's amazing what a huge difference some real limited slip differentials makes.

Huh, guess I should put the rear bar back on stiff and learn to like it...

[mccanixx]

Originally Posted by MNbiker

It depends on whether you're trying to optimize the car for autocross or not. For autocross, WRX's are typically fastest when set up scary-loose. This type of setup means stiffer rear springs and/or bigger rear bar, and requires a bit different driving style. The WRX Fenter won Nationals in a few years ago was set up extremely loose. Yes, the setup defies all semblance of "proper" suspension setup, but many optimal autocross setups require similar compromises - especially when dealing with nose-heavy cars with less than ideal suspension designs.

-Steve

p.s. STi's are a bit of a different beast., in terms of setup. It's amazing what a huge difference some real limited slip differentials makes.

Nailed it. Set it up so it spins on the way to the start line and then figure out how to drive it fast. That's always my advice when dealing with Subaru's in ST*. They just push too much with stock diffs to deal with it any other way.



STi's a bit less but they're still front heavy under tired pigs in STU.

[BeBop86]

Does anyone here in STX run the Whiteline Com C camber plates?

[newtothescene]

I do Nick.

[BeBop86]

The rubber ones right, not the Max C all metal ones?

What's the most about of negative camber you can obtain with them and at the knuckle?

[newtothescene]

Yes rubber. Last year on STI struts and no slotting I got -2.1 on max caster/camber setting. This year with Koni inserts in stock struts + slotting I have -3.4 max caster/camber.

[BeBop86]

Awesome, glad to hear that!

I'm trying to find a camber plate that will give me back some lost travel (compared to my Cusco ones) as well as add a rotating bearing to stop my springs from rotating on their perches.

I was looking at the RCE and HSD lowering plates, but they're $400+ dollars for adjustability that I don't need.

[newtothescene]

They will probably solve your issue. More deflection though. $180 a set is much less than $400. My caster is around +4.5. That's with the offset bushing. Have you cut your bumpstops?

[BeBop86]

The bumpstops that came with my H&R coilovers are inside (they're inverted Bilstein struts). Plus, I don't think I need to.

(It's mainly the noise during turning I'm trying to fix)

[newtothescene]

Ok I see.

[jord55]

I've been looking through the SCCA rules and this thread, but I'm having a hard time finding a solid answer.

I see in the rulebook where headers can be replaced with an alternate unit. Does that include ported/polished/coated stock units?

[MNbiker]

Originally Posted by jord55

I've been looking through the SCCA rules and this thread, but I'm having a hard time finding a solid answer.

I see in the rulebook where headers can be replaced with an alternate unit. Does that include ported/polished/coated stock units?

Yes. Something like the GrimmSpeed ported manifolds and crossover pipe would be ST-legal.

-Steve

p.s. The question you need to ask is whether the change will be worth the $ spent. In my case, I elected not to install headers or ported manifolds, as virtually every dyno graph for such mods shows the powerband moving up at least a few hundred RPM. With a 2.5L engine & tiny turbo, such a powerband change IMHO would be counterproductive for autocross. However, with a 2.0L engine, it's probably a trade-off worth making.

[jord55]

Good point about the powerband. I had read that there were power and spool gains to be had, but I haven't studied the dyno plots to see exactly where that power is. Thanks for the reply!

[Butt Dyno]

Originally Posted by MNbiker

p.s. The question you need to ask is whether the change will be worth the $ spent. In my case, I elected not to install headers or ported manifolds, as virtually every dyno graph for such mods shows the powerband moving up at least a few hundred RPM.

http://web.archive.org/web/200505021...d.com/headers/
http://web.archive.org/web/200510261...m/Overall2.jpg


The Borla, one of the cheaper ones, has the OEM manifold whipped at pretty much any point after 2500 RPM. Unless you spend a lot of time below 2500 RPM, it's definitely worth doing.

(This is on a 2.0L but I would still heavily bet it's worth doing on a 2.5)

[MNbiker]

Originally Posted by ButtDyno

The Borla, one of the cheaper ones, has the OEM manifold whipped at pretty much any point after 2500 RPM. Unless you spend a lot of time below 2500 RPM, it's definitely worth doing.

(This is on a 2.0L but I would still heavily bet it's worth doing on a 2.5)

I'd take that bet.
I used a header on my old 2.0L WRX and it definitely was worth the investment. Pretty much as you indicate, the dyno graphs showed increased power everywhere over 2,500 RPM.

HOWEVER, tuning for the 2006-2008 WRX's with the 2.5L and smaller turbo is a different story. The turbo is the same one used on the 2.0L engines, and it quickly runs out of juice as RPM's climb. As a result, a header essentially narrows your powerband, with far less benefit at the top end than on the 2.0L engines.

I'm getting 230whp and 281wtq (on a conservative Mustang Dyno) with an STX-legal tune and stock manifolds. The torque peak is around 2,850 RPM, which is just about perfect for digging out of corners in 2nd gear.

-Steve

[Butt Dyno]

Originally Posted by MNbiker

HOWEVER, tuning for the 2006-2008 WRX's with the 2.5L and smaller turbo is a different story. The turbo is the same one used on the 2.0L engines, and it quickly runs out of juice as RPM's climb. As a result, a header essentially narrows your powerband, with far less benefit at the top end than on the 2.0L engines.

So are you saying it's actually worse than running the OEM manifold, or that it makes more power than the OEM manifold but levels off sooner? What does it look like midrange?