sjfehr

What's a digression knee?

burglar

Looks like at what velocity you want the 2nd stage of the shock valving to blow open and to what slope. It's beyond me.

Doesn't look like any new ST worthy tires debuted at the SEMA tire expo this weekend, bit of a surprise? Anyone on the up and up of how / when tires get released?

Auto_Werks 3.6

Shock valving is not really ever "top secret". SCCA offers shock dyno service to members that is not overly expensive.

edfishjr

On a shock dyno plot of force vs. velocity the compression force is often set to rise quickly in the range of 0 to 1 in/s or so, then "bends over" on a different slope thereafter. The bend is the "knee" and a shock that does this is called digressively valved. This gives you good compression damping at slalom frequencies but keeps the forces from going really high on bumps, which are higher frequency/higher shaft velocity disturbances.

I'm told that such valving is particularly important for autocross at concrete sites where the basic layout is smooth but there are sharp impacts where the concrete slabs have tilted and no longer meet up at the edges.

burglar

Well, what I meant was, it would be specifically uncool to pay the premium for, say, Elephant's or any other shop's proprietary shock valving and then post the dyno charts up here. Not that everyone has access to shim stacks and a shock dyno, but some people do.

Auto_Werks 3.6

I wasnt suggesting you should publish the data, but once the shocks are yours there's no reason not to find out what you've got. If for no other reason that to use for your own tuning information.

burglar

Update.

Recommendations were all over the map, so I threw a dart and pulled the trigger on 23/30 bars. It's virtually the same as stock balance. I can't get as much front bar as the through-body guys, so I figure I can tweak balance with more rear bar if necessary. Also, this just happened to be the biggest I could get in the economical Sway-A-Ways. Price would be almost double going any bigger.

I found out that a local autocrosser revalves Bilsteins. He knows what it takes to make an autocross car fast, and I'll be supporting both a local business and someone that is involved in the sport. They won't be on the car adjustable, but he'll be able to make tweaks for me based on feedback at any time.

Also, some Dunlop Z2 info and pricing popped up from a Tirerack rep on a Miata site:
http://forum.miata.net/vb/showthread.php?t=479343

Heidster

Hey burglar, Just skimmed through your posts. I used to do some AX with my SC. Did these mods:

Suspension: Bilstien Sport shocks, 22mm/28mm torsion bars, 19mm-F/22mm-R weltmeister adjustable sway bars and shock-tower brace. Turbo tie-rods w/bump-steer correction. Poly bushings. Properly aligned, lowered and corner balanced.

Wheels/Tires: 8”&9.5”x17” HRE-525 3-piece (RUF style center) w/225&275 Hoosier track tires.

I needed to go full stiff on the rear sways and fairly loose on the fronts to get good low speed turning. (for track it was opposite.) I think your torions are sized fine. If you get a rear adj sway...that will be key to getting the thing to turn good at an AX. I remember a guy who used a larger front sway (not a through the body) with, I think, a rear 19mm adj weltmiester and he liked it.

Good luck, Heidster

burglar

Thanks for the tips! Speaking of, do you happen to have recorded your alignment specs? I'll be doing my own, and again "proper alignment" opinion tends to be all over the map.

Heidster

I have no records as I sent all paperwork to the new owner.
Strictly from memory...Camber ~ -1.0 to maybe 1.5 front, ~-2.0 to 2.5 rear, probably closer to the lower #'s as it was a part street car too. I forget the caster but = both sides. Very little toe-in...just enough to keep it from getting darty during "normal" driving...whatever that is/was.

burglar

Today I'm starting on the suspension. I went with Neatrix spring plate bushings, and polygraphite everywhere else. Those are eBay offset monoball camber plates, I figure I'd give them a shot. They seem pretty decent quality. So far, it's going smooth, but I only have one front corner apart. Plenty of time to get stuck on something...

burglar

The car is back on the ground. She's dirty, the side skirts aren't on, and the "alignment" is however I bolted it back together. Rides stiffer, makes a little more noise (no squeaks though) and the original shocks can't quite keep up. The front end needs raising too. Took 10 days of an hour or two here and there, and lots of beer.

ToSi

Looks good, which tires did you use? Are the new star specs out yet?

burglar

Those are still the original 15"s. The 17" wheels are sitting in boxes waiting for the Z2 to come out. I did go on the internet and find this:



Don't know if it's accurate or anything, but it suggests a staggered release. If it gets too close to the wire, I really don't have a problem with running the RS-3 for the year as I try and figure out the car.

BisimotoSales

Great build thread, keep the updates coming! Have you considered investing on coil over suspension for your rear?

We have been working in collaboration with the engineers at Eibach Suspension and have developed a fully integrated coil over suspension kit that can be used in combination with torsion bars or as a complete rear suspension replacement. With a completely rebuildable damper, inverted design for lower unsprung weight, and fully plated for corrosion resistance it would be a great option for your build.