An STi for STU

I've been auto Xing my 2011 STi since I got it in 2014. Until now I've stayed in Street class, largely to work on driver skill. I've worked in 7 track days the last few years to include Button Willow, Willow Springs, and Laguna Seca. I finally hit the point that things were getting old and needing to be replaced and now find myself with extra time on my hands. Though I'd say my driving skills have progressed significantly, I'm not going to pretend they are anything even resembling profesional. Always plenty to work on and improve. I dove in and started throwing parts at the car to compete in STU this year...if auto x ever starts back.

So here is where I'm at so far:

Whiteline Offset Top Hats

Braille 15lbs batter

Super Pro Front A-Arm Rear offset Bushings

Group N motor mounts, transmission mounts, pitch stop, differential mounts, front a arm forward pivot bushing, rear subframe bushings, and all rear end bushings that STi offers for group n replacements.

GTWORX Bilstein Trophy Cut Coilovers (Big thanks to Myles at Racecomp Engineering for answering the million questions I bugged him with. I can't overstate how happy I am with his customer service and the product I received.)

Proform Wireless scales are on their way and I will be corner weighting the car soon. After I got a quote from the only reasonably close shop, it seemed like a much better decision to buy the scales and learn how to do it myself. I'll be continuing to modify the car through the year and the scales will pay for themselves the second time I corner weight the car. 

I run on Bridgestone RE-71s for auto x

Anyway, here are some pics from some of the work and I'll post on any success once the season starts back!

Sweet, I bet that thing rips!

Jake Harris said:

What is this sorcery with the stands and such?  Please tell us more!

I used to autocross my Impala SS with the San Francisco region back in 2008 in STU and then STUN.  I had run some events with a bum 4L60E that had no engine braking on decel.  The last event I ran with a new transmission and it was a lot more fun being last place than all the other times I ran.

Haha, it's just Paco Motorsports' alignment hub stands and a quick jack. I had just raised the car with the quick jack to put the stands on and then lowered it back down. It's great for working on suspension components with the suspension loaded. My garage isn't level though, so I'm working out a plan for some platforms to dial in the alignment. I figure I was able to get it close enough for now that I don't destroy my tires. It's also not daily driven and even more so right now with lots of tele working. The alignment stands are a bit pricey (just under $1000), but they are already proving to be worth it!

Proform scales showed up yesterday and I took them for a test run today. Not that I have any experience with scales, but these seem like a really quality product. If there is anyone out there that is experienced doing corner weighting and see anything wrong with my home rigged set up let me know. I didn't bother adjusting anything yet, as I need to figure out a better slip plate plan. My first attempt at slip plates didn't work correctly, so the suspension wasn't settling. I could also drive the car on with some kind of ramp, but if I get slip plates working I figure it will be much easier to just lift the car and make adjustments and then lower it down again. Plus, as you can see there is a significant slant on the back half of the floor that requires a fairly tall stand for the scale, which could be problematic for the roll on and off technique even with ramps. I also need to get a better straight edge to triple check all the scales are as close to level as possible. I'd rather take my time and get this right the first time than have to do this several times trying to get it right. 

I haven't done this before, so I'm not sure how bad 2.6% off of 50% cross weight is, but I certainly have some adjustments to make. 

I bought the same scales and corner weighted my car a couple days ago.  I think you should be able to get pretty close.  Just google "corner weight calculator", you can plug in your weights and it will give you target weights.  It only takes a couple turns on the coilover to get it dialed in.

Remember that adjusting the coilover "higher" puts more weight on that corner AND the opposite corner.

In reply to Patientzero :

Thanks for the calculator recommendation. I'll check it out. 

Welp I think this is as good as I'm going to get it. I'm probably chasing inaccuracies in my home built set up at this point. I was meticulous as I could be leveling all my platforms, but a novice in his garage has his limitations haha. I'd like to get the front to rear balance a little closer to 50%, but I don't have a lot of options to move stuff around for STU class. Any suggestions?

STI and a 500 abarth? It's a hot hatch party! 
I wanted one these badddd but ended up with a speed3 instead. 

In reply to spandak : It's true, I have a type haha! The abarth is primarily my wife's car but it might be my favorite. It's impossible not to laugh the entire time you drive that tiny dragon around! I always wanted a Mazda speed 3, unfortunately it never happened though. I'm going all in on the STi, so no new cars for me for a while.

Corner weighting won't affect your front to rear weights.  Like you said, without the ability to physically move the weight around there is likely nothing you can do.

Can you replace parts with lighter parts in STU?  I haven't looked at those rules lately.

I already swapped out my 44lbs battery with a 15 lbs brallie, which is the low hanging fruit in the front end. I can swap out rotors with aluminum hub rotors and lighter calipers as long as they bolt to the factory mounting points. There are some kits I have my eyes on, but the weight to price savings keeps it on the wish list for now. The other easy weight savings I can do is a titanium exhaust, which is probably in my nearer future, however this is mostly going to lighten up the rear end more than the front. Those are pretty much the only realistic options for STU. When I start moding the engine I might save a few pounds replacing the stock intake with an after market one, but I doubt it will be a significant difference. My front ratio is 58.3% and rear weight is 41.7%, is that a big enough split to be concerned about? Should I really hope for anything much better?

After installing the coil overs, corner balancing and aligning, my rear tires have -2.0 degrees of camber. I only lowered the car 1/2" so I didn't think the rear camber would change too much, but it did. So I got the Super Pro rear camber kit. I looked at some other control arms that seemed easier to adjust, but they all replaced the inner control arm bushing with an all metal spherical bushing, which is not permitted in STU. I've had good experience with Super Pro in the past, so I look forward to getting these installed. 

It seems unclear in the SCCA STU rules if I can use the tow links in this kit. I believe I can get the alignment I want with the OEM tow links, but I like having the super pro ones just in case. And if they are permitted then it wouldn't hurt to get a new ball joint to replace my 70k miles one. 

After having done so much work already, I figure I might as well replace the last few things that aren't now new in the suspension such as the front ball joints and rear OEM top hats. While I'm at it I'm going to go back to OEM top hats on the front because it looks like I can get the camber I want up front (~1.8-2.0) with the OEM ones. Don't know that it will really make much of a difference, but I figure if I can maintain the factory strut alignment and get the same camber then that would be better. It might be another week are two till the rest of the parts come in, and then I'll do the alignment and corner balance all over again. 

Ok, I think I'm finally done...for now. And Autocross is finally starting again in my area, so we'll see if I got any of this done correctly. Turns out if I had just done this right the first time, it would have been way easier. OEM top hats and Super Pro lower control arms are now installed. It seems like i can use the super pro tow link, but I don't need them and just want to be sure I stay in class for now. I was able to get the desired 2 degrees of camber up front with the OEM top hats and a 1/2 inch of lowering. After I got everything installed and aligned the car, I realized I set the ride height wrong and then started all over again with setting a 1/2" drop, corner balancing, and aligning. Here is what I ended up with:

Ride Height Dropped 1/2"

Alignment:

Front Camber: 2.0 degrees

Rear Camber: 1.3 degrees (plenty of ability to add more if desired)

Toe: 0 front and back

Cross Weight Left rear to Right Front: 50.5%

The Front/Rear Weight Ratio is 58.7%/41.3%. Based on that weight distribution I calculated the ideal weight at each wheel:

Front Left= ((% on front tires) x (total weight on both left tires))/100 = 1053 lbs

Front Right= ((% on front tires) x (total weight on both right tires))/100 = 983 lbs

Rear Left = ((% on rear tires) x (total weight on both left tires))/100 = 741 lbs

Rear Right = ((% on rear tires) x (total weight on both right tires))/100 = 692 lbs

If you compare that to what I was able to adjust too, I'm within 13 lbs of perfect weight on each corner. Considering I'm working from my own home made leveling platforms, I figure that's about as close as I can get. In the future I might look for some static weight I can move around to properly balance the car further.

Ride height at each corner measured from the center of the Hub to the fender post cross weighting:

Front Left: 355mm/14 inches  Front Right: 355mm/14 inches  Rear Left: 351mm/13 7/8"  Rear Right: 352mm/ 13 7/8"

The rear heights were so slightly different I couldn't really differentiate in inches, hence the 1mm difference. 

I also replaced all the lock nuts on the suspension, since they are only designed to be used once and I had loosened and tightened them at least three times each at this point. It was almost $70 of nuts from the dealer, but cheap insurance for the track. I also replaced the front lower ball joints since everything else is now new in the suspension. The old ball joints were a huge pain to get out, but I guess that's standard for ball joints. 

Seat of the pants judgement is that the STi feels the better than ever. Very flat in corners with much better roll resistance. Feels very balanced and controllable in corners. It felt like I got a little power on oversteer at one point, but it may have just happened from the undulations in the road causing the rear end to loose some grip. I guess I'll find out at autocross. I wish I had a place to do some objective testing, but I'll make due for now. 

After nearly a month of the car spending most of it's time on the lift, it's great to have it back to drivable and feeling better than ever. 

I got out to a few autocross events the last few months and I love the suspension. Overall I don't think it made me much faster, but it did allow me to be incredibly more consistent. Other than my first run, every run was withing .5" of the others. The coilovers have made the car much easier to drive at the limit and the feedback from the car is excellent with all the new Group N bushings. The rear end had previously felt vague and it was a bit of a guess as to what it would do when cornering, but that is no longer a problem. 

On the way back from one of the events I popped at P0171 code for Bank 1 running lean. I had replaced my O2 sensors as a preventative measure, but after extensive trouble shooting it appears the problem was the forward O2 sensor being faulty. I swapped the old one in and I haven't had a problem in over 400 miles. I leak tested the intake and exhaust with a smoke machine. There was one small leak in the intake, but fixing that did not prevent the code. The only thing that has gotten the code to go out is putting the old O2 sensor back in, so I will continue to monitor. 

I found a leak in a broken weld on my SPT exhaust, so obviously I talked myself into buying a titanium exhaust to replace it with. I'd been looking for an excuse to get the exhaust and save 30 lbs. I went with the Tomei Extreme Ti since it is one of two options for a GR titanium exhaust. The other option is $500 more. It was a straight forward install. 

So I think I over did it with this exhaust. It is only 15.2 lbs, but Woof is it loud! The rest of my power train is stock. It does sound good at WOT, but it sounds like I'm raising hell when I'm just putting around town. Personally the giant can exhaust isn't my style and neither is excessively loud exhaust. I like an aggressive sound, but this is a bit much for me. I prefer some subtly. I'll keep it on and see if I grow to like it. I doubt the 30 lbs of weight savings will truly manifest in dropping my run times. Or perhaps I'll swap the exhaust back and forth between periods autocross/track events.

My noise complaints aside, this is a really quality product. I was very impressed with the build quality and easy assembly. Although the joints do leak some air. I smoke checked the exhaust after install and no matter how I adjusted the slide over fittings, springs, and clamps some air leaked out of the two slide on joints. 

There is an event coming up and I'll see what I think. Also a STi front upper strut bar is being delivered tomorrow. The front end of the car is a bit soft, so I'm hopping that the strut bar will help get the desired result.

The strut bar showed up a couple days ago and it would not fit because of the COBB AOS. It sadly took me a day to figure come up with the idea, but with driling a couple holes and adding some spacers, I was able to lower the AOS and keep it clear of the brake lines and other hoses/harnesses in the area. Inital impression is that it gave me the increase in front end stiffness I was looking for. Also the benefit of the STi strut bar is that I didn't lose any ride quality.

The STi comes with some stout brakes from the factory. I haven't had any issues of pad fade or brake fade while doing track days at Button Willow or the Streets of Willow tracks. However, at Laguna Seca I have had some brake fade which I believe was mostly the pads being overheated. I always flush my brake fluid with a racing fluid before every track day...and that's it. In stock trim the OEM pads hold up well. I did swap on a set of Hawk street/race 5.0 pads once for Button Willow. The bite was pretty incredible, but they were almost too aggressive for me and squealed real bad during street driving. I know there are trade offs, but the goal is to keep the car tolerable enough to street drive to the track and once or twice a week. 

In what is probably the most unnecessary mod I've done so far, I swapped on AP Racing's front brake kit. This should increase thermal capacity a significant degree, but also shed 15 lbs off the front end. They are expensive, and the gain likely doesn't justify the cost for my use, but at the end of the day I just wanted them. 

I weighed the pieces separately and all together. Ultimately I found the total savings to be 14 lbs, but given that my oem pads were worn out that likely accounts for the 1 lbs discrepancy of the advertised 15 (the new pads weighed one pound).

DBA 4000 Rotor: 20 lbs

Essex Rotor: 17lbs

AP Caliper:  6lbs (7lbs w/ pads)

STi OEM Caliper: 10lbs (with old worn pads and brake line attached)

AP Racing Kit all components total: 23lbs

OEM Caliper and Rotor: 30lbs

I got the Ferodo DS2500 pads with the kit and opted for the pre-burnised service. I put a set of the DS2500 pads on the rear and bedded them in. I haven't made it to the track yet, but so far the pads seem fairly mild. Slightly more bite than OEM, and mostly quite. They don't squel much on street driving. So far they seem like the right pairing for my goals. 

Prior to getting underway with power mods I went down the Antspec in LA (Former LA COBB shop) to get a compression and leakdown test. Compression is good, but cylinder 2 is weak on leak down at 13%. 

So, I've decided to bite the bullet and just build a motor with an IAG short block with Antspec doing the assembly and tuning. Seems like I will just grenade my motor doing mods on it now and it will end up being more expensive later. Since I'm going for it, I'm likely going to put a new turbo in and class myself out of STU. Figure I'll build the car I want and firgure out where to class it later. 

It has begun!

The motor is out and the build is underway! The shop ran a baseline dyno that showed 226whp and 247 ft-lbs on a mustang dyno. Seems fairly healthy for a 10 year old STi.

The engine is progressing along.  Antspec has been awesome through this process. They have stayed engaged, keeping me updated as the build comes together.