Matching My budget with desire for more speed whenever possible.
 

If I were to spend another few grand or so on parts for my car what would give me the most benefit.
First off my car is pretty good for what it is already.
It is a regularly street driven car that gets driven on long road trips as well while it is near the extreme upper end of performance level for most Miatas.

I can lap most any road course in it significantly below spec Miata lap records. I hold the track record for a street car with doors at a couple outdoor go-kart tracks with it.
And I also kind of went overboard autocrossing it in 2010 with several overall FTD’s in route to several titles.

2010 Western Washington slush series champion – Open Street
2010 Western Washington Series champion – Open Street
2010 SCCA NW region series champion – Street modified Group NS6 (SSM)
2010 SCCA northern Pacific Divisional champion – (SSM)
2010 SCCA Packwood NT 1st – SSM
2010 Chuckanut sports car club series champion – C2 (SSM)

Car has a lot of my own custom handiwork and would take a book to describe everything I’ve don. Basically it is a fairly well sorted 90 Miata with ~360 rwhp ~320 ft-lbs of torque, a decent all around setup suspension, brakes that truly handle a 350 hp Miata on the track, and a bit of aero work. I did autocross to feed my competitive urges but my real joy is on road courses with it though.

Items I’ve narrowed down to more immediate want level.

1) 15X10 ~10.5 wheels-- I ran 275’s on 15X9 6ULs but the wheels really aren’t wide enough. I think the edges are wearing faster due to being pinched on the wheels and I know they would be faster on wider. Drawback is they would only serve autocross duty. It is looking like cheaper alternatives won’t fit my 11.75” brakes so Bogart or Kodiak custom wheels are likely needed. ~$1,800 -$2,000

2) OS Giken Diff – currently running a type 2 Torsen with a 3.909 and six speed. I will be switching to a 3.636 so I’m pulling it apart anyway. I will say at my power level the torsen is severely lacking most notably on the go-Kart tracks and road courses where you touch curbing. A good bump on the inside wheel at an apex while applying power and all the sudden it behaves like an open diff. ~$1590

3) XIDA coilovers – I spent a lot of time 8 or 10 years ago and have developed what I have on my car now (Revalved Koni Sports, 700/400# 2-1/4” hypercoils, custom spherical ball extended travel shock tops, NB bump stops, ISC Racing sway bars, urethane bushings) but the shocks are 10 years old. And I think there is better stuff available now. I’m really liking the features and apparent performance of the XIDA-S or XIDA from 949 can’t see putting anything else together as good for a better price. I got a test drive in the 949 rental to know they are good. $2389 - $3949

Might be able to squeeze out one of these Items from the budget, what’s the biggest bang for the buck? When logic in me starts computing the Diff starts looking better.

Bob

I know you're not dumb, but have you played with tire pressure much? And/or do you really need to run 275's? Plus, as you said, that's two grand for autocross only.

Sounds like your diff performs decently most of the time, no? This option, although the cheapest, just doesn't sound like it would benefit you enough.

Me likey this one. You're going to be on that suspension all the time. Straights, turns, curbs, you'll feel the benefit every where you go.

The OSG is supposed to give 1-2 seconds on a 2 plus minute track. I also think at your power level the OSG would be needed more. As much as I love the XidaS, I think the OSG plus a revalve on your front shocks (since there older) and your dropping seconds. I dont think you"ll see a big improvement with the Xida over your current setup, maybe .5 second average and way easier to drive at the limit.

This is what I am thinking. Kieth from FM put one in his Targa car and took a second off his best time on a track he has a gazillion laps in that car on. The more power you have the more difference it will make I think.

FWIW I think I still hold the Miata record for that Grand Junction track though. My first and only time there at the FM open house and I was on the same full tread RA-1's I drove 1000 miles both to and from the event on. The tire trailer was loaded with camping gear rather than tires.

When I drove Emilio’s rental car it had just a torsen in it we had the same spring rates and pretty similar alignment. his car felt tighter and hooked to the track better in the corners but mine felt like I could put power down better off corners even though I had allot more power to put down for some reason. I drove both cars back to back in the same session.

Bob

Honestly, if you have the cash the OSG and XidaS combo would be mint. How much can you sell your torsen's, ring gears, coilovers for? :) I bet the OSG gets the most time but the Xida's would be a joy to own esp since you daily your miata. Forget the rims since you"ll probably be on 245 NT01's soon.

I've got a set of 4:10's I will be swapping out my 3.909 from an 80's RX7 for a 3.636 from an 82 626 that just arrived today.

Another issue I have though is I seem to already be dam fast on the track and there is not much competition it's just for fun. Autocrossing is hard and I have some very competent competition so going faster autocrossing brings more glory unless we get some sort of Miata challange going on up here. I think the OSG will be the ticket at the local Kart track lap attacks though. putting down power is real difficult on it. The only street licensable car that has beat me so far is a 300 hp Areal Atom on 275 hoosiers.

Bob

Sounds like OSG and a cheap front revalve/refresh is the ticket.

here's a crazy idea and I'm not sure what the bang for the buck is but you said "road trips"

swap everything into a 2001-2005 shell. oh and seam weld it first and get all the bracing.

What? Have you been drinking?

What would that achieve?

I've already seam welded and replaced welded in some of the extra unibody chassis bracing from an NB. I welded in stout backing plates for my roll bar and door bars so they are much stiffer as well. I have also added stratigic bracing to the chassis. If people didn't like me or knew id likely get protested for this stuff that was done to make it a better track car with less shakes and rattles on the street that is not quite legal for SSM at the national level.
I dont think any of it makes me faster at an autocross most of it just adds weight for that use.

Bob

One downside to the diff option is no visible bling.

Bob

2 sec a lap isn't bling?

:dons flame suit: Torsens suck :flame suit off:

Xida, then the new diff. I've driven Johnwag's car with the Cusco diff and it's pretty awesome and amazing how the car turns. However, the (non-xida) AST 5100's let me put the power down at what felt like similar positions and the car is damn faster.

I was talking the Brian who runs AST-USA. He told me Stevenson Racing (Grand AM) had a set of AST's made with an idential shock dyno to their Koni shock. I don't remember the numbers but the team was happy and went substantially faster. Piet Kreeft (AST HQ) watched the car on the track and ordered a few more changes (shims and valves) overnight from Holland (nobody likes the tuna) and the car went even faster the next day. AST is doing something special apparently and 949 has done all the fine tuning.

I know I jock these dampers pretty bad, almost embarrassing to be posting this again, but the stuff I'm doing on track with these shocks is amazing. A local BMW switched to AST and set 3 class records in TT on the 5-tracks we run in the season. I was within .2 to the Miata record set by 290whp and 275 Hoosiers at Hallett this year, and he and I both have tons and tons of experience on that track...I was making 232whp, ran 225 Nittos. There was some discovery going on with me (fear of grip), then John got in the car and bested that record by 1.1-seconds. Also, I'm not that good of a driver, my lap times really started to take off at the end of this season though.

Badass instructor guy in a C6Z recently let me know that I was "turning in way too early". What he didn't realize was that I was going 3-seconds faster than him at ECR, and doing it with overheated brakes. I think I'm hitting more corners 1-gear higher than not.

I'd go for a ride in a Xida car before I dropped the coin on anything.

I already mentioned I drove Emilio’s track rental car back to back with mine at Laguna. It felt freaking awesome but the very one thing I felt my car did better was putting power down coming off the apex of corners. I’m not sure what subtle things we had going on that made this so but the most significant thing was probably dampers might have been somethig else I got right by accedent. My car had significantly more power to put down as well. My car felt more floaty and skippy on steady state cornering with a slower turn in and tended to skip more on the curbing and feel unsettled on uneven surfaces but setting that ass down under acceleration it would stick very well. I also noticed it watching youtube in car videos of Emilio and Bellwilliam and VegaXt all on XIDA’s Most evident in VegaXt’s video trying to follow me I’m launching off the corner in front of him while he is struggling to put power down with the rear end itching to step out and having to do a lot of correcting. I watched Emilio and bellwilliam fast laps and it looks like they having the same issue. And that is what I felt in Emilio’s Rental car prior to seeing any video. My car also felt like the suspension had a smoother ride even with the same spring rates.

Bottom line is I know they are better but my current setup aint too bad either. Fastest car there was Savington on Koni Race shocks probably not hugely different from mine other than being more stroke challenged in the rear. I might have been second if my lap timer hadn’t gone tits up I could tell. So I am not sure how much better.

Bob

Bob,

VagaXT was on MonoFlex. William's car had an OS Giken diff with some experimental diff settings. Fast but edgy. The Rental is set up to be driven through the apex with the tail a little out under power similar to a Spec. With me driving it at least, it does 1:42's there without a draft. If you are accustomed to driving off turns with no slip angle at the back as you would want in a higher powered car, then it's no surprise the Rental's set up would feel loose. That is not a strength nor weakness of the Xida's. That's just the way I set the car up as that's what's fastest at that power level with no aero and that tire/wheel combo. Double the power, add aero and that is no longer the fast way around a racetrack but I'm sure you already knew that :)

Any corrections you see while I'm tracking out at full power in the youtube videos I post of the Rental are because I'm generally driving the snot out of it and uh, sliding a bit.

Well, you're not going to go wrong with the diff, that's for sure. I've found my Torsen does a pretty good job until I'm turning while going up a steep hill...and then it's all or nothing. I was really surprised to see how well the torsen still works after putting real shocks in the car even over curbing.

Honestly where the Torsens weakness really shows up for me is on the little go-cart tracks. Quick second gear turns on a race course like track that has different banking and curbing and such and it feels like a open diff sometimes. You feel like the car is not at the limit of grip or slip angle and you apply power but nothing happens just the inside rear tire spins up and the engine revs the car doesn't speed up or get tail happy untill after you are fully off the corner.

Bob

Here ya go! This plus Xida...

I figured the edginess on power off corners was setup. It just wasn’t obvious to me what caused the difference in our setup. Shocks are different, I think I have bigger bars both front and rear (ISC 1 notch from full stiff up front and ISC full soft in rear) plus some added aero. I am quite confident I could get the XIDA's set up too my liking on my car. My best lap where my timer work in session 2 was a low 1:40 but I am also quite confident that wasn’t my best lap time. My lap timer quit working. Perhaps a Data acquisition system should be in my toy budget in the near future.

My car rotates under power it just didn’t seem as edgy. I did manage to do a nice controlled drift in the rental without lifting coming off turn 2 and I’m not much of a drift driver so it definitely gave me confidence control wise just seemed like it did it with less power level than I felt I could be using to go faster. Maybe with my driving style just wasn’t entering the corner fast enough to begin with however, the rental car gave me a lot more confidence in the first part of the corners than did mine. In my car however the biggest drops in lap time I have seen once I got the general setup working pretty good for general high cornering grip have been in trying to get it where I can apply more power sooner coming off corners. The current aero setup seems to make it push a bit more the faster the corner is but it seems like it just allows the use of more power and the car is still faster with a bit of steady state push at high speed corners with a bit more rear end grip for the slow speed corners. I seem to have enough power to overcome a bit of extra drag.

Anyway you didn’t answer the question or take a guess. Which do you think would help lower my lap times more the OSG or XIDA’s.

Bob

OK where did he post this?
I have a Torsen II with a 3.909 and a spare 4:10 gear set that might work as a trade.

Bob

I'd say Xida by a small margin over the diff.

Lowering lap times in a 160whp track Miata is all entry speed. Exit speed doesn't change much.

miata.net, track section

Damit

3rd in line.

Didn't realize I needed to get up befor down on Christmas moring and spend all my time monitoring various internet forums in hopes of finding deals on stuff I want.

Bob

Bob,
Get the data now. Save the slight improvements to your already-capable diff and suspension for another time. In-car predictive segment & lap timing can really help drop lap times, and post analysis can help even more. I have found the data can help both car and driver development. It is fun too.

I like the Race-Technology DL-1 and Dash3. The Dash3 is small enough to be mounted directly in your line of sight on the dashboard, and big enough to be easy-to-read (with 3 different font sizes). I really enjoy the predictive segment and lap times, and the ability to set the track markers in advance or while on-track. If you have local guys & race buddies to share data with, find out what they are running.

That said, from a purely selfish perspective, get the full-blown XIDAs! I'm running the Ohlin DFV's with custom spring rates, ISC sway bars, custom spherical suspension bearings and such. IMHO, I find the Ohlins to be an incredibly effective package. I have the shocks rebuilt at the end of every season. Most of the reviews I've read about XIDAs have come from owners who upgraded from Teins, Ground Controls, or Bilsteins (SM). I would consider your custom Konis on par with my Ohlins, and both of them significant upgrades over Teins/Ground Control/Bilsteins.

I've been wondering about double or triple-adjustable shocks, and whether or not the grass is actually greener, and if so by how much, with a more adjustable and dedicated motorsport coilover. I've looked into rolling my own setup (based on Penske, etc), but as you've also concluded, the XIDAS already seem to check off all of the boxes of features I would want.

So anyway, go with the XIDAS and tell us all about how they work with your setup...!

I also have an OSG diff that I bought from 949 a year ago, but still have it sitting on a shelf. So, if you decide to go that route, I'd still be interested in how it affects the balance of your setup.

...But honestly, I would go with data first. :)

- Will

Currently weighing data (Racepak IQ3) vs. Giken myself. Irrationally, I want the Racepak since it will let me eliminate my abhorrent gauge setup and make me better as a driver, but I'm pretty sure the Giken will make the bigger difference in lap times. :(

I kinda wish I didn't blow a wad of cash on the OSG (but I'm sure Emilio didn;t mind :)) to better determine what actually made/makes me faster - shit, as far as I know I could be 3 more sec faster at my local track if I had a set of nuts to push it harder in the corneres. But I went from a viscoud LSD straight to the vballer of LSDs. excuse the typos - i'm 7 beers in to this thread :friday:

But, seeing how I have the OSG, my next step is the Xida sports - i don't have the cash to get the race. I shoud be able to tell the difference now with some experience under the belt.

Sure you wnat the race pack? The AIM systems look pretty tempting - but at twice the cash, dunno

AIM is twice the cash and Racepak has a superior featureset. 3-axis internal accelerometer, standard GPS, three times the sensor inputs, predictive lap timing, GPS-based lap timing, and the list goes on. The Racepak is way superior.

Sav - I don't know what the hell I was quite trying to say - if anything? Thanks for the input on the racepack - It was the Freedom Autosport guys tyring to sell me on the AIM. They had one in their SM I was playing with.

But Bob doesn't need one here, so - I'd say go with the Xidas 1st, power aint nothing until you can control it, assuming your T2 is still working.

Yes, I win Jake! Plus, you could sell your koni setup to me Bob! Help fund your xida s, or use the cash to get the top xida.

Well on closer inspection to funds it looks like the OSG is doable and the XIDA not really. And I am pretty set on the high end XIDA double adjustables because one thing I have learned about myself when it comes to spending money on my hobbies, buying the lesser product due to slightly less cost pain almost always ends up costing more in the end.

Bob

You pay a small penalty for the upgrade path, but you can go from Xida Clubs to Xida-S to Xida doubles without buying new shocks each time. I've driven doubles and Clubsports, and there's not a massive difference between the two.

That's actually the only benefit of the AIM - user base. If everyone at the track has the same system, you can swap data between cars and see where you can be faster.

I have a MyChron3 on my shifter kart, it's awesome, and AIM is an awesome company to work with (at least for karters) but I bought it in 2004 and the Racepak is definitely a big jump ahead at this point.

Honestly, I'm just excited to have a rev counter back in the black car - 18 months of shifting by sound ;)

zOMG us California guys all have AIMdashes in our awesome racecars vote yes on prop 19 free Tookie I'm the Governator blah blah blah blah

I'd kill you all for an AIMdash.

Tired of the loud bang signaling shift tyme?

The XIDA Clubs look like an incredible value but one single feature, the shock tops are a step back from my current setup. I realize this feature will have very little effect on how well they work but it goes against my goal of having every single thing I change on my car to be better in some way than what it replaces. They are my rules and I make them up as I go along.

So the XIDA-S single can be re-built into an XIDA double? What’s the cost of doing that after purchase?

Bob

Best to call Emilio on that one - it's whatever the price gap between singles/doubles is plus a couple hundred bucks, but I'm not sure exactly how much.

Bob- I understand your pain on the LSD aspect (I can't say much on the suspension). But after having been at the FM SC with you, I think you'll get more use from the OSG. Even with my fancy suspension and V710s out there, I was losing a fuckton of time to wheelspin....pretty much the first half of the track...esp. the hard left after the chicane that killed Elvis. It was a constant feathering of the throttle to try to regain traction. If my Ohlins weren't able to help me on this, then the answer for you should clearly be the OSG LSD. If I hadn't been fighting my LSD, I might have been damn close to your times....but only 1.8 sec off wasn't too bad for 130rwhp less than you ;)

Gene- Bob's got the balls.

FYI, your Ohlins have almost an inch less rear damper stroke than the Xida. That's responsible for as much of the wheel spin as the Torsen is.

Same problem I have experienced with Tein Flex. Can't get the stroke range set up right. Stroke is the one thing I think I have I think almost perfect with my current setup. Much better to have too much stroke and helper springs than preloading already stiff springs to get enough bump travel at the expense of precious little rebound travel

I will say I have driven an NB on Ohlins and I was impressed with how well they worked though.

Bob

Bob, the top hats you have should carry over to the XidaS right? What is the shaft diam of the Koni vs Xida?

What exactly did you like about the Ohlins on the NB? I'm loving mine, just looking to confirm my gut feeling.

Xida shaft is 14mm, shoulder is tapered to 12mm where it goes through mount.
If one has nice mounts already, it's not difficult to figure out a bushing config to run them with the Xida's.

I'm assuming that Xida CS are cut to 10mm to work with NB bushings and top hats.

Nope. Proprietary MCU bushings and a few other bits. NB mount id is actually about 15mm. The special bits ship with the XCS for orders w/o mounts. So you just supply the stamped steel OEM mount.

The new spherical bearing extended billet mounts we're working on will not only fit the Xida, they'll come with adapters to work with 10mm shaft OEM replacement shocks. They'll probably sell for about $300/4. No ETA on them yet. Currently, the extended mounts are a $550 upcharge and only work with the Xida.

Woe, now there is a thought.

That is the same dimensions as Koni. My shock tops have ½” ID spherical bearings in them to work with those dimensions and I’m already running 700/400# 2.25” ID hypercoils 6" long in the front 8" long in the rear. If they have enough stroke to work with my shock tops I might could get bare dampers with just the lower adjusting collars.

My shock tops move the top mount up about an inch higher than the stock NB location. Do the shocks have enough stroke to deal with that? I suspect this would eat up rebound that the helper springs are used for and may not hurt that much. Id also need to check how the body lengths compare to my Koni sports to get the bump stops in the right location.

Picture shows a cutaway of my shock tops. Note the location of the 12mm to 14mm shoulder. It sticks all the way through the center hole of a modified NB shock top. other picture shows where the shoulder ends up on an NB stock mount.

Bob

You mean shaft length I assume. The shaft length of the Xida puts the top nut about 20mm above the NB mount. Just enough room for the MCU bushing. Probably a tad too short for your use. The Xida-S billet mounts end up with the top nut in the same place. Your stack looks a bit taller. No guarantees it wouldn't be too tall for the Xida shaft length.

I’m not sure how to describe it other than the tires felt as though they couldn’t be separated from the ground easily. Same feeling I got with the XIDA's. I didn’t feel the limited rebound travel as much as what I felt with Tein setups I've tried but I suspect that having high enough spring rates on the Ohlins helped that problem a lot. A lower spring rate and no rebound travel feels awful in the rear but having very little bump travel feels even worse so Tein’s usually get set up with very little rebound travel in the rear to counteract the lack of available shock stroke. Upping spring rates reduces the stroke required for the suspension to take a set in a corner so it helps reduce the run out of stroke feeling where the car transisions behvior at a set level of cornering force.

Bob

It sort of looks like the 12mm section is long enough I could put a sleev on it to space the shaft down and have the nut about the same spot relative to the mount as the clubs.

On the Xida-S pictures it shows the front and rear tops have different offsets. I would guess the nut would end up similar location relative to what the one shown for the rear does.

Shock bodies look like they might be shorter. Might need to add spacers to my bump stops to keep tires out of metal bits of the car.

Bob

Bob, can you cut and weld your hats shorter. Any fab shop with a decent wellder can weld that od in about 5min a hat tops. Then if your hats can be lowered will the Xida shocks and collars work with your springs? If not I'm sure your koni/swift setup would bring a decent price.

I hav the skill and the tools to do that. Actually I bet I could duplicate the geometry of the XIDA-S mounts. Not sure that my sperical balls are the same quality or load capacity where they could handle both the spring and shock load like the XIDA-S mounts do though. I don't think those are cheap bearings in those things.

Bob

Original version pictured on site. Current version used the extended hat (longer shaft) front and rear in order to be compatible with NB mount.