94boosted

Hey Guys,

I've been autocrossing my 2010 GS Coupe in SS for a couple years and and a year in SSP (due to headers). Now in order to be more competitive (local level not national level) I think it's time for some more mods and here is where I need some advice.

This car is my summer daily driver and occasional HPDE and Track Day car but main focus is on autocross.

Current Mods
PFADT Headers
Vararam Intake
TB Spacer
Hotchkiss Sway Bars (Stiffer in Front/Slightly Softer in Rear)
Polyurethane Sway Bar and Control Arm Bushings
Bilstein Sport Shocks
Slicks (Continental Extreme's) on Factory GS Wheels
PFADT Street Alignment
SS Brake Lines
MGW Shifter

Mods Planned For This Winter
Hawk HP Plus Pads
Corbeau FX1 Pro Seats
T1 Adjustable Swaybar Endlinks
Corner Balance
More Aggressive Alignment

Mods Planned for Future
Hyperco or T1 Leaf Springs
Hoosier A6 or A7 Tires
FAST 102 Intake + TB
Lightweight Battery

Mods Planned For a Long Way Down the Road
QA1 C or Penske Shocks
PFADT Heavy Rate Adjustable Swaybars
Aero?

Is there anything I'm missing? Is there any one or two big things that would knock some significant amount of time off? I'm not at the level where I'm prepared to spend thousands of dollars to shave a tenth or two.

Thanks in advance

ratt_finkel

What level of competitiveness are you looking for?
What size wheels and tires are you planning on running?
How much streetability do you want to retain?

As a side note. The car can certainly be used dual purpose for auto-x and HPDE. But you will need different brake pads and alignment setting for each venue.

94boosted

Well right now I'm almost always finishing in the top 10 (raw) out of about 40-70 drivers, my goal is to finish in the top 5. So that means I need to shave 1-2 seconds off my time.

Right now my track wheels are just a second set of factory GS wheels so 18x9.5F and 19x12R with some 285F and 325R Continental Extreme Slicks. Yes I know they're not as good as a Hoosier A6 but the price is amazing.

I realize that the point where the car will need to be trailered to autocross or the track is coming but if I can hold off on that for 2-3 years that would be ideal.

dhowdy

Why are you comparing raw times when your car presumably has one of the tougher PAX indexes in the field?

Are those even legal in SSP? Non-DOT tires would bump you to P right? There's also been some interesting discussion recently about Pfadt so you may be well served to look into that. Just email Sam and he should be able to set you up.

94boosted

I'm comparing raw times because a better raw time will undoubtedly lead to a better PAX time also. I don't want to go back to SS and I'm not ready for the financial commitment involved in SSM. Besides nobody else competes in SSP at my local events. And I don't think there are any other classes for me.

Yes technically I'm not allowed to run the Conti tire but because it's less competitive than an A6 in autocross nobody really cares.

Look into PFADT for what? Sway bars?

Who is Sam?

dhowdy

Well there's always CAM-C I kid, people would definitely complain about that pretty quick. I've actually been wondering recently how competitive a vette could be in SSM against the RX7s. Can it be made nationally competitive? I don't know...

https://www.corvetteforum.com/forums...fadt-back.html

Sam Strano
www.stranoparts.com

Supporting vendor... I'm sure he'll be in here soon.

strano@stranoparts.com

That'd be me. Can help. Have parts. Know the cars (have a C5 and a C6 myself). I have setup many, many National Championship stock and SP class cars (including Corvettes). I've got 7 Solo National Championships, 7 ProSolo Series Championships, and was the 2009 ProSolo Overall Champion. I've been in Super Stock/SSR since 2011. I've been 2nd twice and 3rd twice. No Corvette has won in that time, it's been a Lotus and then the same GT3.... Seeking to change that next year but it's a tall order to beat that's well driven.

Looking at your list there are some things that stick out to me. First the tires you've been running aren't legal. The shocks are lacking and you mention those but I'd not go with either option you list myself (and haven't). QA1's are terrible shocks honestly with cheap adjusters and no gas charge to help with fade. Penske's don't suck but frankly I prefer MCS if you looking high, high end (and have used them myself) because of the range of adjustment and supreme durability. But there are a few other viable options we can discuss. The bars are ok, but frankly the car can use more front (we have options and many guys are running my bars).

HP+, NOT my favorite brake pads... in fact here's how much I don't like them. If you want a full set for your GS, I have a set that have less than 300 miles on them and they are for sale because they are not what I like. Again that's something we can discuss.

Different wheels would be a good idea, going to 18" all around with wider fronts as a start. I'd build a set of Forgestars (I am a dealer for them too) because there is not a better deal out there for light wheels that aren't a zillion bucks.

The GS front spring is VERY soft, despite some of the claims. See I owned a GS myself and raced another one too. 2011 and the first half of 2013 were run in GS's, and I went back to a Z06 for "stock" because the front spring is better. In a non-stock class I'd definitely change the front spring. I would not change the rear, at least not for a while.

Your alignment is certainly not up to scratch, you will have to be ok with running that more aggressively.

Anyway, aside from the fact I'm pretty good autocrosser, I am also a supporting vendor here too. I've got quite fair pricing,and some things I'm even better than most on. I can do the one stop shop thing that's for sure. And I'm working on Delrin bushings (bigger, tougher, better located ones) right now too.

You can call me at the number in my signature. But I'm just one guy, and it takes time to talk to everyone who wants, plus to regular day in and out work. So sometimes it might take me a little bit go get back to you. But I think you'd find it worth the call (and whatever wait there might be).

ratt_finkel

If you have the chance to speak with Sam, I highly recommend it. Just remember everyone has preferences.

I think for the sake of this thread, it's probably best to focus on the build itself. Rather than discussing your driving ability or national competitiveness. Lets get the car right, so to speak.

Since it sounds like you don't want to go with an all out SP build. Let's pretend like we are starting with a blank slate. And figure out what mods are really going to be the most important.

Stage 1:
Wider wheels and tires. 18x12 Front and 18x13 rears. 335 or 345 front. 345 rear. Hoosier A6's are really the only option. I don't think the A7's are out in those sizes yet.

Springs. Being able to customize (stiffer) rates will help dial in maximum grip.

Shocks. This really should be done in conjunction with the springs. Moton, Penske, MCS all make strong options for the vette in a double adjustable. LG makes two kits based off of bilstein shocks. Which can be valved to whatever you want. The non-adjustable option is great for someone who doesn't want to mess with *****.

I personally have a preference for coilovers over the leaf springs. Though either option can be fast.

Alignment. This is a no brainer. You should be maximizing your foot print with proper autocross oriented alignments.

Tune. The stock tunes are not great. They are a compromise. Even with a stock motor, this is worth the time. Rather than aiming for peak power. You'll want your tuner to improve area under the curve. With a focus on driveability, both WOT and especially at part throttle conditions. As you need a car that is consistent at %25-%75 throttle.

Those are going to be the biggest gains out of anything else you can do.

For stage 2. I would look into the following:

Weight reduction. Do the simple stuff first. Seat, exhaust, battery, Etc.

A good clutch and lightweight flywheel. This will help more in an auto-x setting than elsewhere.


Stage 3:

This is where the return for your investment starts to diminish. And you will be spending lots of time and money for very little gains. But up to this point you only have a car that's %90 prepped.

Bushings, weight reduction in all areas, suspension optimization, upgraded rear diff, aero (yes this is effective in SP) and finally power.

strano@stranoparts.com

We mostly agree. But remember that coil-overs are not SP legal.

As for non-adjustable dampers. Well... that's one of those things that flummoxes me when folks spend so much on other things that they skip that. Sure you can revalve other shocks, but that takes more than 5 minutes, and costs a lot more too with labor and shipping involved. And while you sometimes hear something akin to "be definition there is only one right setting" that's not really true. If it was you'd not see adjustable dampers on all kinds of other cars ranging from other race cars to street cars that are not race cars.

A tire change alone can dramatically change how the car reacts to inputs, and how it feels. You can use shocks to dial things in. You can alter the ride. You can change the roll/response rate to suit your personal taste. And shocks are what rule the roost transitionally. That's why you see so many autocross cars with high end shocks, because if you think about it we transition, a lot.

94boosted

Sam and ratt finkel thank you both for the responses.

Shocks
The shocks I put in are definitely an improvement over the stock shocks but thinking about it now I should of never put them in, I should of saved up some more money and bought a better shock right from the start. We'll see what the budget is for this year but if I can get away with one more season on my Bilstein Sport's I'd be happy. How much time realistically am I giving up between a Bilstein Sport and a high end shock like a Moton or MCS? Are we talking a couple tenths or a second plus?

Wheels and Tires
Wheels and tires are a similar story, the deal I got on the Factory GS wheels and Conti slicks were too good to pass up and they are definitel better than any street tire I've ever run. Right now I don't really have $5000 to pick up a set of Forgeline wheels and Hoosiers.

Springs
Coilovers are out of the question as it's SSP but if upgrading the spring (especially if it's only the front one) will help substantially then that's something I can do this year.

Sway Bars
Right now the Hotchkiss bars I have are setup about 30% Stiffer Front and 15% Softer Rear and I really like the way the car feels, very neutral. I had the rear bar at 15% Stiffer than stock and the car was very tail happy.

Tune
The car is already tuned for solid mid-range not for peak power.

Brake Pads
Brake pads, if not HP Plus what's a good pad that will be great for autocross but still ok for street and HPDE?

Alignment
I definitely will be going with some more ngative camber this year.


Like I said right now I'm looking for any great bang for the buck type mods. If scrapping the Corbeau race seat idea and getting some better springs will shave a second that's what I want to do.

Sam I will be calling you for sure to discuss some things.

strano@stranoparts.com

Think about the difference you saw in the Bilstein's vs. the stock, shocks do matter, a lot. Can I quantify a time? No, but I'll tell you I'd rather have good shocks vs. tons more power on an autocross car. The thing is, personally I'd not go MCS or Moton. I'd go (and can back this up as it's what I run) Koni's with spherical ends which is $1600 a set. And no worries about your Bilstein's, they tend to hold their value well for resale.

Wheels. Not I said ForgeSTAR, not ForgeLINE which are super nice, but $$$. $1600 or so for a set of those in hand depending on options. Add tires, which you need to add anyway... and even $3200 if you get new vs. take-offs that's a far cry from $5000.

Spring, I'd DEFINITELY do a Hyperco Track front spring, no doubt. Again the GS front spring is soft. Even if you got a take-off Z06 front, that's better.

Bars. This depends on what spring. On GS's I use a 35mm front bar, SOLID and two way adjustable and run it full stiff, even on the stock 9.5" front wheels. But on the Z I use a hollow 33.3mm bar I make (I make both in fact) because of the differences in spring. Either way I think you want more front bar than Hotchkis, I've moved a lot of folks from the Hotchkis to my bars, and not only are they happier, but they win stuff too.

Tune/Power, etc. Your call, the cars aren't slow, but they do pick up a LOT of grunt with better tunes and headers. A light flywheel wakes things up a huge amount as well. But certainly I'd work on the suspension stuff as a more "to-do" thing for an autocross car first.

Pads. something to discuss. But realistically race pads aren't happy on the street or autocross, and street pads aren't great track pads. There are a couple that might work, but frankly I'd recommend different pads for each use. HPDE is not a certain thing. Some tracks are harder on brakes, some drivers are. Some are easier. You can get two guys running similar times but one is a terror on pads the other isn't. Too many variables to say "absolutely this".

Alignment, yes that nees to be more aggressive (but not too crazy especially on toe unless you like to shred tires and wheel bearings.

I'd get a seat of some sort. It's a huge help if you know what's the car moving vs. you. I have seats from Cobra, Sparco and Corbeau, and others like NRG too. We don't need to go broke on a good autocross seat. But the more you track the better the seat should be as you don't want it to break should you hit something (meaning you want FIA approved seats which do cost more).

Please do. But note that at this time of year I go to California to see my girlfriend and friends out there. I do it now because I can close over Xmas and New Year and not lose so much work time. The shop is open but I'll be gone. I will have access to email and if desperate I can probably call a few folks. I just want to put that out there....

HC Mechanic

Do you have any experience with the H&R coil overs?

I'm looking for some sway bars to tighten up the car
C6 Z51 - stock sways currently, recently put on some Pilot Sport Cups.

HC Mechanic

21 pound battery...how about a 5 pound one?

http://shoraipower.com/lfx36l3-bs12-p130

I just installed mine last week, installation was super easy with some industrial velcro.

troyguitar

Will those things start a Corvette? That is a lot of weight savings.

HC Mechanic

Hell ya it will

HC Mechanic

Who makes a good set of sway bars for our cars?

t.renz791

See post 7 and 11 in this thread.

strano@stranoparts.com

Sure. I sell H&R, as well as a lot of other brands. I have a number of coil-over options, and and a number of non coil-over options. Some are better than other.

Personally I'm a stickler for wanting adjustable damping on the shocks (and not all adjustable dampers are good, and some non-adjustables are better than others, etc). But I want GOOD adjustable dampers, coil-over or leaf spring.

I'd recommend shocks and bars, particularly the front bar, first for anything except a base car as their rear bar is just too small. The Z51's and up have better bars. We can play with rears, but I always start with the front first.