Nathan Atkins

I scientifically bounced off my rev limiter, OBD output said 9300 and fluttered about +/- 20 rpm, interestingly, the tach read 9600 at that same time

ABQautoxer

Thanks! I'm going to use 9200 in my spread sheet for some fudge factor.

Carbon8

iTrader: (4)

Peak power is at about 8500, going past that point is useless.


Best advise would be get and OBD plug, get your car dyno'd and cross reference your peak power with what the OBD logged. That should be your max RPM.

ABQautoxer

While I appreciate the importance of the power band, I'm looking at autox gearing choices for local sites as I use a different car for national events.

marka

Howdy,

FYI, for 2014 C-Street will NOT be indexed at ProSolos.

That's great news for us & twin owners.

Mark

ABQautoxer

A bit off topic but I'm not dumb enough interested in running an RX8 against a 370z at a Pro. So off to STX we go for 2015.

TeamRX8

iTrader: (25)

So many helpless n00bs, so little time ....

http://www.roadandtrack.com/cm/roada...a-RX8_data.pdf

ABQautoxer

That doc is part of the confusion saying 9k, other docs say 9400. Mazda's doesnt seem to document it (though I swore I thought I saw a Mazda doc say 9400).

Ah yes, another Mark Sipe congeniality lesson.

MikeTyson8MyKids

iTrader: (1)

Does anyone know if stock NC Miata rear end links are shorter than RX8 end links? Lowered the car a bit more and don't like how the rear bar is oriented.

TeamRX8

iTrader: (25)

guess I should have said so many people who can't take a lil' ribbing you're welcome btw The OE rev limiter is 9000 rpm>period<

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Given that the rear bar arms are not straight I'm not sure what the basis for the concern is? The car is lower, but the springs stiffer. Are you sure it is even moving as far as the OE would be in a turn?



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MikeTyson8MyKids

iTrader: (1)

Because a sway bar works best when being in torsion, not bending..Lol. When the end link has the bar oriented at a higher position, there is less movement in the z-axis. Linear movement in the z-axis is what twists the bar most efficiently. I'm not slammed by any means. I've initially set the rear ride height at 14" and the front ended up right at 13.8".

You yourself recommended shorter links a few years ago for that same reason...I can dig it up if you'd like.

TeamRX8

iTrader: (25)

I was wrong about any number of things over the years, my opinion and experience does not go without change over the years

unless you are running ultra short shock lengths the rear bar will never hit the subframe at that ride height, if you are running ultra short shocks at that ride height they must be in full extension with no droop capability

I'm not even sure what you're trying to get at regarding Z-axis etc. The endlinks rotate freely in all three directions and it's unlikely you are trying to rotate them beyond their limit Shorter can create problems too, like rotating to extreme angles. They actually should be as long as possible to have the highest rate of effectiveness. Someone made a set on here that was the ultimate short link ...and also the ultimate mistaken effort of total fail

JeffH

Wouldn't think the Miata links are shorter based on measurements taken in the past. You could always try calling Mazda for part numbers. My rear bar was hitting the sub-frame on compression so I looked into something shorter. Built a set using 1- male and one 1- female end link from McMaster Carr. Chose the cheapest self lubricating ones and they work fine.

Not sure what you're trying to accomplish by changing the axis as discussed though. Would be surprised to see rear suspension operate in a linear fashion in addition to effects from bushing compliance.

MikeTyson8MyKids

iTrader: (1)

I actually just looked into that last night. I'll go that route, and its inexpensive.

That point I was getting at was at really low ride heights, the amount of suspension movement isn't translated into the rear bar at those more extreme angles, so you're effectively running a softer rear bar. To get the maximum amount of torsion into the rear bar, the end link movement needs to be tangential to both the bar and suspension link.

Hard to explain in words...Lol.

Anyway, yes thanks for help.

Kennetht638

iTrader: (2)

Other way around. Think of the limiting case where the sway bar arm is parallel to the end link. It's infinitely stiff. When the end link is normal to the imaginary line from the end link attachment to the bar pivot, the bar is effectively at its softest. The issue is more one of linearity than it is of rate though because at that softest case, the effective length of the sway bar arm changes the least with travel. The change of rate matters less because it's just a deviation from the published rate which you likely didn't specifically choose anyway. You could theoretically use the end link length as a tuning tool, though I haven't heard of that being done before.

Also on the redline thing, the stock tune on my AccessPort says it's 9000 with 200 rpm allowable hysteresis. For how long the data has been available, I'm surprised this is still a question.

ABQautoxer

The redline is 9000 stated everywhere. The rev limiter has conflicting information. I realize you mean the same thing in this case, but considering how many RX8 owners I asked and they gave the wrong information I trust autocrossers to know since we care more than most. I appreciate clearing it up so hopefully the next person that searches finds this and they don't wonder like I did.

TeamRX8

iTrader: (25)

The same argument/conflicting info/mentality has been occurring for 9 years. The next guy won't believe it any more than you and we will rinse & repeat forever.

Jeff was running extremely low ride height and has shortened shocks. My whole point was for you to not assume, but to physically evaluate and confirm. This would mean pulling the springs, bolting it all up, and compressing the suspension through it's range. At best you can line up the end link and bar on some theoretical plane in a static condition. On e real world dynamics come into play; bumps, pitch loading, etc. all that is out the window. Or in a case like Jeff or depending on the bar design the height may be determined by what it takes to avoid interference. IMO the subject is overplayed to the theoretical level of extreme silliness. In an extreme case it can matter a little, but in general it is much ado over nothing. The exception is an interference, which mounting the rear bar upside down will create and has happened.



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Nathan Atkins

Hey guys, I wanted to get some opinions:
So I can essentially build myself a bad-*** suspension kit for less than a grand:

4ea Hypercoil 12B0300 best springs in the business and will lower the car about 1 inch and give natural frequencies of 1.75F and 1.79R which is good for autocross without throwing street-ability out of the window, $296 shipped

Koni Yellows, the best adjust ability this side of Penskes without the heinous price tag, so i'll be able to dial in ~65% critical damping, $525 shipped

FCM Bumpstop Kit (F:36mm/R:58mm) from Good Win Racing, the shorter stop up front will remove the cars tendency to understeer on hard transitions, $145 shipped

$966 all in, and I get basically the same thing as i would've gotten with a good quality coil-over kit, except for the ride height adjust ability, which I don't really feel like i need. What do you guys think? Is 1 inch of drop too much for a DD? I use stock wheels with 245/40/18 Rivals.

ABQautoxer

Are you making your own perch and top hat adapters for those Hypercoils? I didn't see a cost figured in for that part.

Kennetht638

iTrader: (2)

It's probably in this thread somewhere already, but I basically did that minus the bumpstops. As Tom mentioned, you can't just drop race springs onto a factory-style damper. I modified a cheap eBay coilover kit and made upper perches on a lathe. I also modified mine to take spherical bearings. I think my setup was about $750 all in and it worked very nicely. Also, how did you decide on 300/300 spring rates?

Nathan Atkins

Hmmmm, I guess i thought they would go right in place of the old ones...the RX8 was listed as an application but i know what that means ;-)

Anyway I saw these Delrin upper adapters on Good-win for $40 each for the rear, FCM says their kits reuse the OEM upper Hardware, but they use Eibach Springs, so maybe theyre made to go right in. Also I measured the front lowers at 2.5 while the rear lowers are 70mm, and theyre both 3.75inches up top. So i guess i could mill upper perches like Kenneth did.(if i wanted to stick with the hypercoils)

Anyway, i guess i need to read more, i thought it'd be more plug-and-play than that, i just think i could circumvent paying $2500 for something quick, and maybe get away with half of that if i put in some due diligence.

Thanks for the replies, let me know if you have any other suggestions.

Nathan Atkins

how I arrived at 300/300:

about 1/3 of the way down the following page is the part about spring selection and natural frequencies, "Street car: 0.8 Hz. Occasional autocrosser: 1-1.5 Hz. Full-bore autocrosser: 2.2-2.5 Hz" I'm using the car daily, but i'm taking my autocross more seriously these days and am looking to become competitive, so i thought that a natural frequency of 1.8Hz would split the difference from Occasional to Full-bore for my Daily Driver.

Autocross to Win (DGs Autocross Secrets) - Suspension

So I used Fat Cat's spreadsheet (below) to find a spring rate that will do just that and settled on 300/300, a 12 inch (300mm) free length at that rate gets me about 1 inch of drop compared to stock front and rear:

FCM_MSDS_RX8.xls

ABQautoxer

I'm new here but naturally not to SCCA autox (I recognize a few names on here, some of you know me from the SAC) so a grain of salt and all:

Race springs come in standard dimensions: diameter, length, rate. Qualities vary from one company to another such as Swift, Eibach, Hyperco, etc. I haven't yet owned or worked on a car where those just bolt up without an adapter, Ground Control makes a nice living primarily selling adapter kits. So when you see applications, usually that is for a lowering spring set specifically meant for one car type only. Not sure why you'd see RX8 listed for standard race springs.

I've saw that calc from FCM when I was doing my research for STX awhile back. I couldn't find anyone that seemed to know what they were doing running similar to their package so I ignored it. I'm boring that way in that I'll usually adapt a known good for a class and get some experience before I go looking to reinvent the wheel. More times than not I find it's just minor tweaks to my preference/sites than major setup changes. FWIW, reinventing the wheel, while it may be faster, could potentially cost exponentially more because you have to test a lot more. Budget builds are generally not a great place to do that.

Kennetht638

iTrader: (2)

Here's a picture from FCM's website:



They do reuse the factory top mount hardware but with an adapter. Notice also that there are coilover sleeves on the damper bodies. The rear is just like the delrin adapter on Good-Win. The front one is similar to the Bilstein PSS9 top mount adapter. Here's a better view of that (2nd one from the left):

Nathan Atkins

Hmmmm, I'm feeling a bit discouraged, like maybe I have alot more to learn than i thought, especially since from what ive read, not many people are running as 'square' a spring rate as what i suggested.

That said I'd like to soldier on and maybe make adapters, should be easy enough to mill them so i can use the spring rates i had in mind.

I thought about putting the sleeves on too, as i saw a new set for sale for 80 bucks, but with the costs of parts accumulating like this and maybe more to come i might be best off just buying a set of pre-engineered coilovers *sigh* that's economy of scale for you...