ldstang50

iTrader: (2)

SCCA has come up with a new supplemental ( I think ??) class this year called STR, or street touring roadster. I'd like for members on here to come up with ideas of what one should do to make the car competitive.
We are limited to 255 tires with 140 treadware.

Mods:
Wheels Enkei RPF1 (lightest wheel possible)
going by STU rules, 2pc aluminum hat rotors
both will reduce unsprung weight and rotational mass
light weight single exit exhaust
intake(s)
ECU tune
replace both seats
front/rear control arms
what suspension?

I'd like to pull out about 100lbs if not more from the car

sublimemoment

iTrader: (1)

Can you change the hatch?

guitarist

iTrader: (1)

From the thread over on SCCAForums, the brakes/rotors rules are following ST/STS, not STX/STU, so 2-piece rotors are not legal, but I don't know that for a fact.

Sublime: you can't mess with any body parts except the front & rear bumper covers, side skirts, and you can add a wing or a spoiler, unless your car came with a spoiler/wing, then you can only upgrade to a different spoiler/wing (really only applies to Nismo Z, weird/dumb rule).

To consolidate, I'll post up the info on my build I've posted elsewhere (what I've done and what I plan to do) so we can keep it all in one tidy thread.

Done:
17x8.5" SSR Type C-RS wheels
Kumho XS 255/40/17
Koni TrueChoice DA front/Koni Sport rear shocks
650lb/in Hypercoil coilover fronts, 500lb/in unknown brand rears on adjustable perches
Custom modified stock upper mounts for the front shocks, stock rubber uppers in the rear
Front upper control arms
Custom single exit exhaust (Y-back only so far)
strip engine compartment of aesthetic/acoustic plastic (2-3lbs, but it's free and legal)
Alignment: -3.0 front, -2.5 rear, 1/16 total toe-in rear, 1/32 total toe-in up front.

To do:
Headers (focusing on weight)
HFCs (again, weight)
Y-pipe (weight)
battery (lots of weight)
seats (note: 25lb minimum per rules, so only about 12lbs savings per seat if you have the cloth ones stock)
aero (maybe, but it adds weight so it'll need to be effective to bother)
Intake (esp. for weight; can maybe drop a couple pounds high on the nose, also worth a little power maybe with a tune)
strut bar (if worth the weight savings)
tune (raise rev limit to get more mph in 2nd, adjust WOT behavior, remove throttle cut under LFB if possible (need to research that))

And that's all I've come up with so far.

ldstang50

iTrader: (2)

I figured a build thread would be easier to nav and find.
I hope they allow 2pc rotors. Thats a nice mod to have, esp if you track your car.
But knowing SCCA and their love affair with Mazda/Honda, I doubt that'll happen

guitarist

iTrader: (1)

lol don't let Isley see that mazda/honda stuff or he'll jump up your *** about it being complete fiction. I share your view of it though.

I agree that the S2K/Miata are the cars for the class, though I think the dark horse is the MR-Spyder. If you can get enough tire under it and enough power/gearing out of it, it's the best platform to build on (light, mid-engine, balanced).

I kind of hope they don't allow the rotors,as that's just another fairly big ticket item I'd have to buy to cut weight. I kind of hope they do, however, as I've only got another 100-150lbs MAX to lose, and at great expense.

Here's a quick roundup of the stuff I haven't done yet:

HFCs: 26lb total savings, $500+ (est)
Headers: ??lbs (not likely more than 8-10, if that), $900?
y-pipe: ??lbs (again, not likely more than 10) $200+ (est)
battery: 25lbs, $80-100 with bracket
seats: 24lbs, $500-700+ (est)

best case total weight savings: 95lbs, total money: $2000-2500 or so.

With all of the mods on the "done" list above plus 1/4 tank of gas and the rear hatch area stripped of all legal bits, my weight = 3,108lb (2003 enthusiast), so that puts my best-case weight around 3,013lb. Better, but not great, and it's probably more realistic to think weight will end up around 3,030-3,050lb.

Could maybe save some weight with lightweight bumper covers, side skirts, etc, but you're talking big $$$ for small poundage.

ldstang50

iTrader: (2)

I heard switching to a coilover suspension we should be reinforcign the strut mounts on the car since they become a higher stress point. Any truth in that?

halfrice

iTrader: (30)

only if they combine the shock and spring in the rear (ours being separate stock) or as some companies call it "true" coilovers. The rear strut mount isnt made for handling the spring as well and should be reinforced.

guitarist

iTrader: (1)

I've heard that as well as some pretty good arguments from the Grand Am guys that the car works better with the spring in the OEM location. They also say it works best with 500/425 f/r spring rates, but that works out to a NF well below 2.0hz, and that's not quite up to snuff for quick offsets or high-speed slaloms, imo. Probably works good in 100mph+ corners though.

Mine are in the OEM location, just on adjustable perches, and I'll let you know tomorrow evening how it works out. Feels really good on the street, but you can't do anything to really feel them out on public roads.

AznSky

iTrader: (12)

subscribing......but not saying anything cuz i'm still a noob

ldstang50

iTrader: (2)

I'm still a noob too, no worries here.
What do you have for mods currently?

guitarist

iTrader: (1)

I'm definitely a noob. Only my second year of autocross. Don't let that stop you; being wrong is the best way to learn new stuff.

betamotorsports

iTrader: (1)

Funny how the Nissan engineers got it right... The lemming like installation of aftermarket bling is a real racer's best friend. I always encourage those racing in my class to buy and install the shiniest, flashiest, most JDM blingy parts sold at Super Autobacs.

ULLLOSE

Regardless of yours, and others, delusions about a SCCA/Mazda/Honda conspiracy... How does not allowing two-piece rotors screw you more than the rest? You think the S2K and MX-5 cant get, and wont benefit from lighter rotors? A car with less Tq has more to gain from them.

It is funny how every track day hero thinks they need a two-piece rotor. How the hell do all those Showroom Stock and Touring cars survive on stock brakes? Dear god, a T2 350Z must be a death trap, having some of the biggest brakes in the class. Drive a 3800lb T2 F-body and then lets talk about brakes on the track.

For the record, I think the Z is effed in STR. While it is nice they saw fit to give it a place to run on ST tires, they did it no favors with a 255 limit and much lighter cars to run against. I would start getting some data next year, and ask for a move to STU - at least then you could run a suitable sized tire.

ldstang50

iTrader: (2)

My car is set up for B stock
2007 Nismo
Cobb front bar at full stiff
Stillen catback (actually GAINED weight with this exhaust) Looking to replace with a custom hand made exhaust this year.
295/18 315/19 Hoosier A6s

I ran used tires all season as I never planned for a $3000 tire budget. With corded tires the car raw timed Finger Lakes National Tour, but a cone negated me to 2nd. And the car placed 2nd at DC Pro .068 behind this years 4th place finisher at nationals, Jason Ruggles.
The car is on stock shocks. I'm very confident with fresh rubber I (or the car) would have trophied out at nationals.... if I went.
I'm debating at an STR setup but I know my car is different from regualar z's. The only thing I would really address is the rear diff and upper control arms.
Other than the normal power mods, thats all I would do.

betamotorsports

iTrader: (1)

By learning how to brake properly? Just a thought...

I've raced an ITS (E2) Datsun 240Z with two piston front calipers, solid 10" OD front rotor, and rear drum brakes at the CalClub 3 hour Enduro. Talk about having to manage brakes!

The stock brakes on the base 2006 350Z are great (I do HPDEs with them) and the Brembos are frickin' outstanding.

BTW... see my bling post above.

ldstang50

iTrader: (2)

I was waiting for you to jump in Jason and provide your colorful reply.
I know if they allow 2pc rotors that msr and s2k guys will be doing the same thing. And am very well aware a lower torque car has more to gain from it. I don't NEED 2pc rotors, I would LIKE 2pc rotors.
I'm thinking in the overall regard of reduced unsprung weight and reduced rotational mass. Being my car has 12.8 fronts and 12.7 rears, the reduction of rotating weight would be nice. How much would an s2k or msr gain from this being their rotors are already smaller and lighter than the z's?

ULLLOSE

Shut up. There is no skill involved. Floored all the way till the last marker, hammer the brakes, turn and repeat. How hard is that.

guitarist

iTrader: (1)

I agree pretty much completely here. Part of my plan is to do exactly that. With a solidly documented build and a fairly wide range of events, I'll have a good case for the inclusion in STU. It's not like there aren't many other cars that fit into multiple ST* classes, though I won't mention brands...

And you're right. With 10-inch wheels and 285s, the Z would be a hell of a lot better street tire car.

ULLLOSE

The weight reduction on a two-piece rotor comes mostly from the center, which regardless of dia is often very similar from car to car. For a given bolt pattern and hub dia you can only make the hat so small. The RX-8 and MX-5 hub is the same bolt pattern, and are actually interchangeable - they use the RX-8 hub on the MX-5 Cup cars. So while the MX-5 already has a lighter/smaller rotor than the RX-8, the center mass weight savings will be similar.

This year I went to bigger front brakes on the RX-8, 13" up from 12.5", and still saved 3lbs per corner on the rotor. The real weight saving on a Mazda is the caliper, which is cast iron, switching to a four piston aluminum unit saved 6lbs - you want to let the MX-5 pull 9lbs of unsprung weight off each front corner?

How much weight can you lose from a Brembo caliper?

Sorry, the small car gains more here.

ldstang50

iTrader: (2)

You lost weight by switching to a bigger rotor? I, like most people, thought you would have gained weight. Did you do the swap for that reason, or was that an added bonus you gained because you wanted bigger rotors?

How much can be lost from switching out the Brembos? I have no idea. You have a lot more research in this than I have.

Hearing all this and knowing how inferior the z already is to both cars, do you think the z should be allowed a larger tire, like the M3 is in STU, to hopefully keep up with the msr and s2k?