Nathan Atkins

Welcome, Tamra, looks like you've got a better foundation of skills than most people start with.


Everyone chastised me for using Bilstein HD's on my CS car and I heard from all directions that the budget shocks to have were in fact the degassed koni yellow's. So if you don't have gobs of money to throw at it, they wont let you down.


I'm not sure what Rachel was using on her car, but I cant imagine that even with something super high dollar that she'd be uncatchable in CSL.


The rest of the formula is pretty straightforward: Nice light wheels, Nice light exhaust, a healthy engine, front swaybar, alignment is important , alignment is essential, alignment is crucial.


Good luck, and keep posting video, not many of us seem to be doing that :-)

wankelbolt

iTrader: (21)

I own a unicorn!

Welcome to the RX-8 addiction.

I'm surprised it didn't push like a pig with +1 whole degree more negative camber in the back. I had slightly more camber in the back once after a bad alignment and it just wouldn't turn. I had to adjust it at the track (VIR). I forgot to reset the toe link and ended up with toe-out in the rear, to hilarious effect...

So, just checking, but are you saying alignment is important?

Tamra

Thanks, Nathan! Degassed Koni Yellows may be the way I go then, unless others speak up. We actually have a set of the Oz Alleggeritas that we picked up for a crazy good deal awhile back (like, 4 for the price of 1, with tires!). I weighed them against the stock wheels with tires, and they came in at exactly 10lbs of savings per corner. That's 40lbs off the car!

Exhaust wise, I've read it's only 15-20lbs savings for quite a bit more noise. We race at NER, which has really strict sound, so I'll probably stick with the stock exhaust for now.

Healthy engine... well she still starts when hot... good enough for now. Haven't done a compression test yet, but I went through and did plugs, wires, coils, and an Optima Red Top battery as soon as I bought her. I got a good enough deal that I can afford a future engine replacement (if necessary) and still break even on the car

Based on my experience this past weekend, I'm tempted to try a nontraditional alignment and go for more rear camber than front camber, and leave the OEM front sway bar, at least initially. Because honestly, the balance felt pretty good, and I was just wanting less "flop" and more grip, and a touch better front end bite.

I had the opportunity to drive another RX8 there, an R3, that had the traditional formula of parts (-1.7f camber, -1.3r, front sway bar, etc.). It transitioned significantly better than my car and was ultimately faster, but I was surprised that it was actually a little pushier than mine. I'm guessing the front bar gave it more transitional stability and better ability to power out of corners, but at sacrifice of pushiness. The owner is a great driver though. I hope he will drive mine sometime to compare times and setup notes (once mine is setup).

I would like to see what better shocks and alignment alone (non traditional, -1.7f, 2+rear) can do for my car, and then experiment with the front sway. Anyone tried this?

Here's a photo of my new girl:

jrose29

I really like the de-gassed Koni doubles from ProParts that came on my car. Compression adjustment is really nice have and the car drives pretty easy on them. I think new they run about $2200 new but there is a set on Ebay for much less. Koni Yellow for RX 8 Double Adjustable | eBay However if you plan to drive your car a lot the de gassed koni suck daily. Great for autocross but are super harsh day to day so consider that. I would imagine a properly valved bilstein would be a great option as well. The other key is bumpstops. Swap in the fatcat style stops with a stiffer rate in the rear to help steady state balance.

I have the Progress MX-5 front bar and love it. Struggled with some weird bushings issues but progress shipped me bushings made from a harder material and its been great so far. The 949 endlinks work well and are on the cheaper end of adjustable links. I have ran it on the middle setting all year.

But before doing any of the above get the alignment fixed. If you bind the bushing you should be able to get around -2 degrees up front.

Tamra

Hey guys, couple of CS specific questions for you.

I just ordered my Koni Yellows. Got a killer deal and paid $510 shipped for all four. We'll de-gas them. For the bump stops, I can't find much on RX8club.com. Which ones do you guys recommend? Replacement OEM's, Ground Control?

My catalytic converter is questionable. Since my car is an 05 I don't need actual OEM. Any recommended OEM equivalent replacements that are CS legal?

For exhaust, I'm looking at the Borla XR-1 with a custom single exit starting at the rear cat flange. I see they make a rotary specific model for quite a bit more $$. Is it worth it to spend the extra, or is the regular XR-1 good enough/quiet enough and holds up to the heat?

I picked up a Mazdaspeed FSB. Which end links would you guys recommend?

I'll also be replacing the upper and lower front control arms in the spring. Are rockauto replacements sufficient/legal?

Final question - for my lightweight starter, what is the weight difference between it and the newer faster starters?

Nathan Atkins

I use the fatcats, they can be bought from Goodwin, help to stop steady state understeer:
FCM 36/58 White Bump Stop Kit SPORT version for LOWERED 06+ Miatas for MX5, Lowered
this says its for the 06+NC, but its what you want

lots of serviceable OEM cats lying around garages around the country, I have one, I'll sell it to you :-) They flow well enough, I'm not sure about CS legal options, I haven't heard of any.


I would get the rotary specific one, I think they both use stainless packing but the rotary specific will resist burnout better, that said the 'spiral' BHR resonator works very well and has no packing


Stock is adequate, but it doesn't hurt to have spares on hand, I've been using stock endlinks with a 32mm progress FSB for 2 years now and no issues


get in on the "mazdaspeed motorsports development" parts program, its easy to register and submit "race results" (any SCCA sanctioned thing, including autocross) you can order the OEM parts at dealer cost, awesome awesome program.


I know nothing on this, but the newer starter sure is nice to have, I wouldn't sacrifice strength of the battery or starter as an opportunity for weight savings.

Tamra

Thanks for the response, Nathan!

Nathan Atkins

I definitely recommend the fatcats over OEM, if youre really on a shoestring budget you can trim 0.25 inches off the top widest part of the OEM front stops and get similar balance effect, but youll appreciate having the higher durometer of the Fatcats.


If you don't have a CEL I would just continue using your own cat for now, I'd ask you to pay $150 for mine+shipping cost or we could meet at a NJ event or something and I could hand it to you. but if yours hasn't thrown a CEL yet its probably not clogged. not to much trouble to drop it down and look inside. If you have a borescope you can look into the O2 sensor hole and inspect both banks of catalyst media.


the sway bar doesn't really 'preload' the idea behind the change in end link length is to get the arm of the swaybar perpendicular to the travel of the suspension. unless you're radically lowered its already pretty close, it just changes the moment arm of the sway bar force to the cosine of the incident angle for the arm, but you still have 95% of the sway bar force at an 18 degree angle and 90% at 26 degrees so it has to be pretty extreme to matter, basically at ride heights you wont see in CS anyway.


The starter is light enough to hold in one hand, and is basically as low and centralized a piece of mass you will find on the RX8 :-) 10/10 would choose strength over weight savings here. the whole starter assembly weighs about the same as a gallon of washer fluid

Kennetht638

iTrader: (2)

I've been using a regular XR-1 for 7 years and it works just fine. The rotary specific one is ridiculously expensive, so I wouldn't waste money on it. When I had it in stock trim, it was pretty quiet once I pointed the exhaust out the back. I started out with a turndown and it was quiet outside the car and really loud inside. It wasn't until I went to a high flow cat that the car got obnoxious. You should have no problem passing sound though, and that's probably still true even if you have no muffler because the cat does a lot. It's also easier to cut up the stock catback than to build a new one all the way from the flange.

I'm also running stock end links on an STX/DSP/SM car. I'll probably switch eventually, but I haven't had any issues with binding up the bars even with the car corner weighted.

The angle of the end link to the bar doesn't actually matter this way until you get WAAAAY out to the extremes. Regardless of the end link angle, an inch of suspension travel = 0.6 inches of sway bar travel (or whatever that motion ratio is). I wasn't so sure of this myself so I made a geometric model to check it and any change in end link/sway bar angle is pretty much negligible as far as sway bar load is concerned. So long as the bar is not twisted at ride height and it won't run into anything in its travel, it should be totally fine. I've actually always wondered why nobody sells just a single adjustable end link because that's all you'd need in most cases.

Nathan Atkins

ooooOOOOoooo.....for sharing?

Tamra

Thanks so much for the responses!

Nathan, I'll probably take you up on that cat at the first NNJR event next season, if you still have it. We'll touch base when it gets closer. I'd also love to have you in my car at some point once its set up to give some feedback, if you're interested.

Sounds like I'll be picking up some stock end links based on both of your feedback. Kenneth's review on the regular XR-1 sounds great, so I'll also go that way. Hopefully it will make sound at NER. I'll also do a little more research on the FCM vs GC and go with one of those, I know in some instances they are one and the same.

One other question for you guys - in your experience, what are the weakest links of the RX-8 in stock trim? Do you bring spare axles, diff to big events? Coming from both Miatas and S2000s, they have very different launch styles. Miatas don't seem to care about wheelhop, whereas S2000s have a diff made of glass so you do everything in your power to avoid wheelhop. Where does the RX-8 fall?

Kennetht638

iTrader: (2)

I don't really have anything to share. I just took a couple minutes and drew some lines in CAD, so I didn't save it. It's pretty straightforward to reproduce though, even if you just use a ruler and paper and pencil or it can be done in Excel with some simple trig. The other commonly held myth about sway bars that I'm never sure if I'm wrong about because so many people attest to doing it is using "half" settings on adjustable bars where you use different holes on each side. While it's true that it produces bar torsion that's somewhere in between the stiff setting and the soft setting, it creates unequal loading on either side because the end link reacts the sway bar torsion at a different moment arm length. To have a moment balance, the force on the stiff side is greater than the force on the soft side.

I've had some pretty mean wheelhop in my RX-8 and aside from the catback exhaust flopping around a bunch (must be resonating at the wheelhop frequency), I haven't had anything go wrong with it. I've been autocrossing/rallycrossing/tracking/road rallying mine pretty steadily since 2008, and I haven't had anything actually break on me except when my high flow cat fell apart and lodged itself sideways in the catback. I had a front wheel bearing start to come loose in 2013, and my front lower control arm rear bushings were both totally demolished when I pulled them out at the beginning of this year. Those are wear items though, and should just be checked regularly. Just don't let your bushings get to where mine were before replacing them!

Nathan Atkins

Recently realized Tamra is our reigning CSPL National Champion, not surprised at all by the skill apparent in your video as well as your obvious volume of car knowledge. I'll be looking forward to seeing you take the fight to Rachel next season :-)

Tamra

haha, thanks Nathan Most of the car knowledge has come from building a Factory Five 818 in our garage over the past year. I still feel like I have a lot left to learn, but it definitely has taught me a lot. We have a lot of development left in this car, but it's a blast to drive. Over 300whp and less than 2,000lbs

fossumja

iTrader: (4)

Touching on a few recent posts:

More CS RX8s have won on OTS Koni SAs than any other shock. Nothing wrong with the DAs, etc, but IMHO not needed, and it's hard to argue with a winning recipe.

Never had any trouble with parts failing at an event except a belt that I should have replaced ahead of time. Since they are a hard to find size, it doesn't hurt to have a spare available. Same goes for coils and wheel studs, though these are unlikely to keep you from getting home. Mazda either did a really good job designing the drivetrain, or it just doesn't have enough torque to break anything :-)

Personally I think the Hotchkis front bar for the MX5 is the best CS option, but almost anything (including the stock bar) will work. Only reason for aftermarket endlinks to fudge the corner weights, but they should be pretty close with stock springs.

Jim

JP-X

Late to the party here, but I'll throw in a couple quick points before asking my question.

I built a catback on mine using the 16" XR-1 (40942) last summer. Just for a reference point, I peaked under 90dB at the Wilmington Champ Tour in August. What I have works well on the street. It has that extra sound to it without being annoying.

Drop your midpipe and take a look at the front face of the cat. It's probably fine. Rotary's burn oil, so they do smell a bit different than you're used to. It doesn't mean the cat's bad.

As far as parts go. It's never a bad idea to have a spare set of plugs wires and coils along. ALWAYS have oil with you, and check it frequently.

Also ... that FFR is sick ... I've wanted to try driving one of those since before you could even buy the kit.


Now on to my original purpose for coming here. I also happen to have the unicorn model, but in the 2004 variety. Some of you may have seen the start to my build thread that I just never bothered to update after a short while into the build ... Sorry about that.

I drove it this past year in STX in very light prep. Basically I wanted to tinker with springs and bars and so forth. But I also tried my hand at my first couple national level events this year. I liked it enough that I plan on doing more of them next year. So with the need for a better prepped car and my budget constraints I'm doing the few things I need to take it back to CS.

One of the things that I've been searching for for a little bit is what the actual lengths are of the OEM bump stops. Hopefully someone here has that info handy. Until then, my search continues.

Cheers,
Josh

Tamra

Josh,

Thanks for the tips on the exhaust and cat. Our FFR 818 is a blast to autocross. We are in process of stuffing a 275/315 Hoosier A7 combo on it this winter, so I can't wait to try it out again next season. We've also got it into the under 1900lb range range now, so its power to weight is even better (currently making a little over 300whp). Considering we have around 700 hours of garage time into building ours, I imagine you'll have a hard time convincing anyone to let you drive one - maybe you should build one!

As for the bump stops, I don't know what the actual lengths are, but I did find a photo on this page showing a measuring tape next to one, and it looks ~2.5" which is a little over 60mm. I believe the SCCA rules just say that we can't use taller than OEM bump stops in street class, but we can shorten them.

I did do some research awhile back on bump stops that will hopefully help you and others.

I was actually warned away from the FCM 36/58 Bump Stop kit that Nathan recommended, due to the 36mm bump stop that is included being the "blue" material, which is the 300lb rate (red = 100lbs, white = 200lbs, blue = 300lbs). Due to it being so stiff, it will cause a very abrupt transition when you hit it, which can induce sudden understeer.

I intend to go with a soft front and cut it down to 36mm (for slightly later, but softer engagement), and leave the rears at 58mm. I'm not sure if anyone has ran this combo before, since it sounds like most people opt for the kit Nathan recommended.

Per my understanding (someone correct me if I'm wrong here), if you run 58mm all around, the fronts will engage before the rears which will cause some understeer problems (which is why the 36/58 combo is popular). By cutting down the fronts you can get them to engage later and change the point at which the front lets loose. Just be careful that you don't cut them down to the point where the shock at full compression is taller than the bump stop.

Nathan Atkins

My cut down the OEM fronts on my buddy Aaron(denim on here)'s car about 3/8" from the widest part at the top of the front stops and it seemed to kill the factory tendency to fall into sudden understeer with bumpstop engagement, I think if I had it to do over again I might have just opted for shortening my OEM bumpstops but mine were deteriorated to the point of being unserviceable and the price on the FCM wasn't to bad compared to new OEM.


my 36mm/58mm stops are both the "white" material.


either course of action will get you similar results, only one of them is free!


In my experience equal length bumpstops all around will understeer on engagement since front loading happens earlier with a stock bar. If you use a stiff bar, even though you have a higher FRC, youll get less sudden onset understeer because you will stay off the stops.

Kennetht638

iTrader: (2)

Has anybody measured where the bumpstops engage and what kind of rates they see? It might be edifying to pull out the spring and run the suspension through its travel with a bathroom scale and a jack. I did this before but only to test the torsional rate of the bushings so I had the bumpstops out, but it's super easy.

I haven't been stock in a LONG time, but I'm pretty sure that the rear bumpstops engage first with very little travel (like 1/4") and the fronts hit at about twice that so any autocross maneuver would be on the bumpstops. However, the nose of the bumpstop is super soft so it doesn't give an abrupt rate change. The FCM bumpstops appear to be designed similarly so I wouldn't expect snappy behavior from running the 58mm units all around. Nathan, you might just have a reduction in understeer because you have 200 lb/in less rate in the front most of the time, as your front bumpstops probably only engage over bumps.

But like I said, I don't have firsthand experience in this arena and Nathan seems to be doing quite well, so I expect it's going to largely be up to driver preference (like most setup-related things). I'm just offering up my thoughts based on the physics of the system and my knowledge of the configuration.

Edit: Looks like Josh responded below at about the same time and his last paragraph is the approach that I'd be most interested in. The car is designed to corner with rate assistance from the bumpstops. To me, that's an advantage because it means you can pretty much treat them as springs.

JP-X

I'm not holding my breath on the driving an FFR front. I grew up building street rods with my dad, so I'm well aware of the kind of time/work that a real car build takes. I'd love to build an FFR either the 818 or the 33 Ford, but neither of them are currently within my budget for car stuff. So I'll just have to wait the 5+ years until it is.

As far as the bump stops go, I'm currently on the FCM 36/58 setup. It works really well with the koni yellow and progress tech springs and bars that I currently have on the car, but I know that is something I will need to change when I go back to factory springs. I have a friend locally with some fresh OEM ones sitting around that I can measure.

I'm going to take a slightly different approach to my setup as well. I'm going to order some 58 Reds to go with the 58 White that I already have. Then I'm going to make a handful of spacers to bring them up to OEM length and play with the spacers a bit until I find something that I like. I want to get my car to settle on the stops as quickly, early, and smoothly as possible to limit body roll and speed up transitions. It'll be some interesting experimenting to say the least, but I hope with that approach and the other adjustments I have available to me I can get the car to settle in quickly and well without snapping over/under.

Tamra

I had my OTS Koni Yellows dynoed. I'm pretty impressed with my $500 shocks. Koni has fantastic customer service- really impressive company to work with.

What do you guys think?

NotAPreppie

Can somebody help me understand how to interpret shock dyno plots?

Just based on the axes of the plots, it looks like we're plotting the force (dependent variable) vs velocity (independent variable). So, at a given velocity, the shock resists with the force measured?

I also see that the force is measured in both positive and negative so I assume this is compression and rebound. Doesn't that sort of imply that the velocity should also be both positive and negative (unless it's supposed to be labeled "speed").

Allow me to answer my own question in a snarky but effective way:
http://lmgtfy.com/?q=how+to+read+shock+dyno+graphs&l=1

fossumja

iTrader: (4)

Yes, speed would be technically more accurate, but shocks measured in force vs. speed are cheap, offshore junk. The only thing worse would be if they were measured in imperial units.

Tamra

To confirm your semi-self-answered-questions:

The upper lines are compression, the lower lines are rebound. Each shock was measured at full soft and full stiff rebound. You can see that compression is mostly independent since it doesn't change much (hence why they are single adjustables). The left and right shocks are pretty similar to each other at both full soft and full stiff, with a small amount of low speed difference on the rears at full stiff.

xfz

I think it might be time to get off my stock bilsteins