Z_WAAAAAZ

Holy sh*t it's gonna be a busy week. I'm gonna keep the exposition short for anyone new here who wasn't following my NA build on here over the years.

This all started four and a half months ago, at a WSIR track day in my built-motor turbo NA time attack car. It was a killer track day, I was getting some practice sessions in for an upcoming NASA TT there in a couple weeks. I'm much more on or even quicker in pace at WSIR compared to the rest of my class (this is the opposite at most other tracks around here), and was hopeful that I could snag a podium in TT3 at the upcoming TT. The car was running spectacular, and I was running consistent sub-1:30's, even putting down a 1:28.9 in one of the later sessions. I was feeling on top of the world. My car was finally sorted, I was running a safe power level (270whp) for the drivetrain, and then I went out for my last session and blew 4th gear out of my new-to-me 6 speed transmission.

F*ck me. I had just bought the trans the month before after my last 6-speed developing issues after ~5 months at 270-300whp. My mindset changed a bit, I didn't want to keep going through 6 speeds on track, and figured I'd ditch the GT2560r on the car for something bigger. Might as well do a non-Miata transmission swap now and bulletproof the car for later. This was basically the downfall of that car. I procured a BMW ZF6 transmission and KPower's swap kit to put it and also had the exhaust modified at a local shop to clear the new transmission crossmember and differential brace. Not a cheap or low-effort endeavor.

The car immediately developed the dreaded 65mph death-vibration that many ZF swap users have experienced. I thought I found a smoking gun when I noticed the driveshaft KPower supplied had a wild amount of runout. I got a driveshaft made but it only slightly helped the concern. I spent the next three months fighting the vibration, trying every diff and pinion angle imaginable, running a softer trans mount, modifying my PPF to mount to the trans crossmember, swapping diff bushings, checking components for runout, eventually installing a Getrag differential. You can follow along with that escapade in this now 8-page thread I made specifically for it:

https://www.miataturbo.net/suspensio...ration-109305/

I was getting closer to fixing the vibration after the Getrag swap, actually having the car vibration-free up until about 100mph, when one of my water pump bolts backed out. I'm assuming this happened over time and was partially due to the death-vibration, as the bolt was profusely loctite'd in and couldn't be rotated by hand when I tried to pull it out afterwards. The bolt caught and wrecked the timing belt, which resulted in P2V contact on cylinder 3, bending the beautiful oversized inconel intake valves. At this point, I was pissed, although I know it wasn't the end of the world. I'd just been wanting to run track laps again for months, and now I'd minimally have to pull the head and toss on a new one, just so I can continue diagnosing and trying to fix the driveline vibration that's still keeping me from tracking the car. After pouring countless hours into this car, I didn't want to ditch it, but it felt like I was hanging onto barbed wire the longer I spent on it.

I'm being dramatic, but you get the point. I started doing research on other options that might be hitting the easy button: Corvettes, Mustangs (I'm a Ford mechanic), 370z's all seemed like potential candidates, but all seemed too easy and none of them got me excited. It only took a couple days to come to a conclusion I got stoked on. The obvious answer, an NC build! More potential than my previous car, more refined, but still a quick-handling roadster.

And so it begins. I scoured Craigslist and FB marketplace over the weekend, went to look at a couple different NC's, and ended up bringing home this little number last night. An '06 with 162k on the clock, a Blackbird Fabworx rollbar already installed, hardtop, LSD from a 2012, 5 speed trans, 17x8 PF01's, Tein Coilovers, RX8 sways, and absolutely f*cked paint (and some surface rust on the hood). It's perfect.




I figured I could look for something newer but it was basically a given to me that I'm going to eventually do a 2.5L swap and late-gen 6 speed in this car. My plan is to avoid the blunder I made with the last build. Keep as much sh*t as possible able to be replaced with off-the-shelf parts. No crazy trans or diff swap (not that these need diff upgrades for high HP), no fancy built motor. Just a stock drivetrain, and 2.5L engine with cams that can be replaced all day for $6-700 on eBay. Forced induction eventually, but I'm kinda stoked on the idea of running this thing N/A on e85 at close to 200whp for a bit. The upper limits of the stock bottom end and late 6 speed trans in this thing seem to hover around the low-300whp range, depending on who you ask. I'll likely cap it in the 200's if/when forced induction comes along.



For now, it obviously needs paint work and some body work on the passenger side door. I'm going to talk to a couple buddies and see how much they'll charge me for a MAACO-level spray if I strip the car down. Then it's onto brake and cooling mods before starting work on the 2.5L swap. I've still got more research to do regarding the ECU side of things. Since tuners were able to crack the NC ECU, there aren't many standalone options available, and everyone with the swap seems to go through ECU-TEC for tuning whether they're boosted or not. I was never great at it, but I'll miss messing with my car's tune a bit.
There's also the option of just boosting this motor until it blows up, then going 2.5L. The NC1s did not get the forged bottom end that the NC2s and 2.5s did, and are rumored to give out around 240whp. I'd be happy well below that. Gotta sleep on it more. Mid-power N/A build sounds like it'd be a cool change of pace and I still have much cleaning up and peripheral mods to do.



I'm super bummed to part out my NA, and understand if some of you guys want to grill me for giving up on it. That being said, I hope all you guys know I'm still glad to be on MT.net and hope you'll enjoy following along on this new project! No joke, this forum played a measurable role in deciding what to do next after my recent debacles. I appreciate all you guys!

SimBa

LMAO, that was fast. Looks like a good starting point with the hard top and roll bar.

I'm in for seat time, boring OEM parts and paint correction

Fireindc

iTrader: (13)

Holy ****, this is gonna be fun to watch. If I weren't so sentimentally attached to my NA (my first car, have had it since 2004 and in the family since 2001), I probably would have jumped to an NC years ago. The NC chassis is better and faster than the NA/NB in just about every way, other than perhaps "feel", they just have so much mechanical traction and room for tires. Not to mention rigidity, and cost of entry now days, no brainer.

I'll be interested to hear your thoughts on the 2.5 when you go that route. I've heard of enough of them blowing up on track that I think I'd be sticking with the 2.0, but I'm no expert. Just seems like the 2.5 econo car motor is worse in every way other than displacement (and power/tq ofc). My idea of a dialed track NC would be the 2.0 (ideally the later forged crank version) + rotrex to make power. If going 2.5 definitely look into balancing the rotating assy, or adding a fluidampr or similar to help smooth things out at high RPM. Not trying to discourage you because I love the idea of junkyard motors and 200hp bolt in swaps, and maybe it's not as bad as I've heard. The NC transmission is great, and pretty damn strong, so I think you'll be safe there.

I love the car you picked up, looks like the perfect candidate for a track build. Again, really excited that you are staying here with us and building out this NC, it will be fun to watch.

Satisaii

We have a complete NC Quaife transmission setup for sale. You know, just in case.

Z_WAAAAAZ

Thanks for the support guys! Yeah, it doesn't feel quite the same as having an NA/NB like most everyone else here, but I hope we can see past our differences and continue to be friends

That's what I'm going for! Boring OEM parts may unfortunately be boring, but the car itself should prove to be exciting once on track lol.

Thanks Nate, I totally feel that. After that period of time, the car's practically a part of you haha. It feels sh*tty to tear my car apart and I've only had it for 2 1/2 years.
On the next token, though, yeah the capability of the NC chassis is wild in comparison to the early generations. My thought is that with the money I get from the part out, I can build the NC to be roughly as fast as my last car, and eventually faster. There's a couple guys running ~190whp 2.5L swapped NCs on street tires that were still putting multiple seconds into me on tracks when my car was making 240whp. Entry cost was pretty rad too. I paid less for this car than I saw some clean-ish NBs going for.

In reference to power adders, I spoke a lot about the 2.5L swap but in reality am still undecided. The durability seems to be all across the board depending on who you talk to. I've heard of failures happening, but on the other hand there's so much support for and documentation on the swap that it seems like most still consider it a viable option. I still have more research and milling to do. Tossing a Rotrex on this motor and making 200whp until I can buy an 09-up motor wouldn't be an awful way to go about things either. Still have time as there's plenty of peripheral upgrades to do on this thing in the meantime.

Oh hell. I'm probably a ways out from needing a sequential but I'll keep that idea on the backburner. It's not going anywhere soon is it? Lol.

SimBa

Fireindc

iTrader: (13)

I haven't priced any of this out, but I do think the rotrex power delivery to be excellent for track use, soft on gearboxes, etc. Similar powerband to an N/A build. I suspect it would have good longevity and easily make 220+whp out of the 2.0.

Then again, the 2.5 could be fun. IF you go that route I'd throw a junkyard motor in there to get it going on the cheap and build a nice 2.5 on the side. Forged, higher comp, lightened and balanced rotating assy and have a bulleproof motor that makes 200+whp.

These are just my opinions, I'm no NC expert, though my best bud does have one (and it ******* rips). He's no more than 3-4 seconds off my pace (runs sub spec miata record times) on his bolt-on and track setup NC2.

lsc224

iTrader: (13)

I don't know if you have ever seen this YT video

OptionXIII

Oh hellllllll yeah! When I saw the notification email for your post on the Montego thread I was really feeling down.

If I suddenly had to start over in the car world, an NC would be my most likely purchase. I think they represent the value NA/NBs used to be, and of course a lot more capability as you pointed out. NAs got a massive price spike from nostalgia and weebs, and I'd say the NB prices sort of rode on the coattails due to being so similar as prices rose. Being the standard "first project car on social media" during the tiktok boom didn't help either of them.

Regarding how built your last car was and your goals for this one... Welcome to.. the dark side? Or, I guess, you've seen the light? Whatever, weak metaphors. Sure, there's a lot less glory in how cool your car is when it isn't built to the absolute limit. There is, however, immense satisfaction in knowing you overbuilt your car for reliability. Knowing you could drive your car a thousand miles to a track day, beat on it for hours, then drive it home, and only worry about tire wear. Or commute in it to work, comfortably. When stuff just works, it's really neat. Being one of the last guys out on track as everyone else packs it in is awesome.

Can't wait to see where you take this thing!

redursidae

I too was super bummed about your last post in the NA thread, but the boating comment gave me hope! I'm a fan of NCs and what you've got there seems like a great canvas. Man, I hear the slightest mention of maybe keeping it naturally aspirated and just want to direct your attention here: https://bbrgti.com/products/bbr-mx-5-nc-super-225

Sometimes a snort is all you need to crack a smile, I promise. In all seriousness though, I support this decision, as difficult as it may have been. And those 2.0L are cool engines.

douginjenison

iTrader: (1)

Trying not to clutter up ur thread too much, but https://www.beermoneymotorsports.com has an NC ecu in the works.

SimBa

This seems to be quickly transforming from being Z's NC build to being the MT.net Community NC build lol

Maybe more of us need to jump on the NC bandwagon. Z, lead the charge.

Satisaii

It just sold. That was fast, I think we put it up yesterday.

Z_WAAAAAZ

By all means everyone, keep pouring in the input! As stated, I've been doing fervent research the last handful of days but am far from having conclusive thoughts as far as power adders go. It's worth noting that the NC1 got the non-forged bottom end that the NC2 and 2.5(3?) received. I could bolt some forced induction onto this one but would probably be limited to the low-200whp range. This wouldn't be the end of the world and I could always toss in a late-gen 2.0 later and turn the boost up.

Here's my current mission statement: Make a fast car that can run track laps all day and be back up and running using off the shelf parts if something sh*ts the bed. The idea of having a late-gen 2.0 or 2.5L swap making 260-280whp with forced induction, that can be achieved with a relatively-cheap unopened motor (maybe cams at most) really appeals to me. It seems like with the powertrain options available, this should be easily achievable.

Got the car up in a lift for an inspection during lunch. Didn't find anything noteworthy under the car. Everything looks good, no fluid leaks, no hanging hoses or wiring. I will have to do a bolt check on it this week, change the oiland bleed the brakes. PO said he just got all the fluids done. The oil and coolant look brand new but better safe than sorry. While it was in the air, I decided to remove the plastic rear diffuser ornament that was hanging off the car. Then since I was already working on that, I figured I might as well get on with it and take an angle grinder to the rear bumper. I know the bumper cut is polarizing for some but I love the look of it. Went mellow to start out, might chop more out at a later date.




Also ran the car through the wash and gave the headlights a good polish. Those suckers were YELLOW. They're not perfect but they're better now.




I can't remember if I mentioned it but the PO included a PCI seat bracket and the original open diff as part of the sale. Next step will be getting my Sparco Pro2000 seat and steering wheel mounted in the car.

OptionXIII

Forgot to mention that I absolutely love the NC removable hardtops. A red NC with a black hardtop is just so choice, if you're looking for paint recommendations for that Maaco job. Sounds like you've got a fantastic base with some good parts ready to go like the Blackbird bar. I really can't imagine a much better starting point for a track build.

I'm not certain on this, but aren't the NC transmissions basically revamped versions of the same 5 and 6 speeds that you'd find in the NA/NB? I've heard the primary weakness of the NA/NB 5er is case flex, so I would guess that improved a bit on the NC version? Pretty sure the 6 is the Aisin AZ6 basic design that is shared with a lot of other cars, even if it's more of an engineering platform than a shared design with lots of parts swap options.

Gee Emm

I don't know what the NC scene is over there, and the scene here may have changed over the last few years. No doubt NCs are quick out of the box compared to NBs, and 2.5 conversions are (were?) popular here. However 2.5s were not trouble-free, nothing like dropping a VVT or !.8BP into an NA. Tracked 2.5 NCs here were not built to the sort of 'formula' that we apply to NA/NBs to make them (relatively) bulletproof, and I am not aware of whether the failures are now being eliminated by a similar sort of program of development that benefitted the NA/NBs.

That being said, running a stock 2.0 NC on the track would be viable as a fun car, I would suggest using that time to get some bugs out of the car, maybe do some basic work on the handling, and doing a LOT of research into upgrade paths for the 2.0 and 2.5.

I think the platform has great potential, my question is potential for exactly what, and what is necessary to achieve that potential - and how doable/affordable is it.

Good luck I will be following with interest.

Z_WAAAAAZ

@OptionXIII Red and black is being considered for the future color combo! Whatever I go with, the hardtop is gonna stay black for sure. I’m debating doing a black hood as well.

From all the reading I’ve done, the 5 speeds are basically an NA/NB 5 speed in a different case. The 6 speed is different, and the NC2 6 speeds have improved survivability at high horsepower over the NC1 6 speeds. Mazda Motorsports also makes a more durable 3rd and 4th gear for the 6 speed, and maybe some other mods? I didn’t get that far into researching it. At any rate, the NC2 6 speed is supposed to be pretty stout.

@Gee Emm Yeah the more I read, the more it seems like the 2.5 is meant to be more of a truck motor than a high-rpm screamer. There’s a few guys ripping them on track around here that seem to be having good luck, although “a few” probably isn’t the greatest test sample ever.

I agree with you regarding getting some track time on the stock 2.0 first. The car is already less slow in a straight line than I expected, and I’m definitely going to have to get a good baseline for suspension and handling. Im gonna have to learn how to drive the thing, too. I took it through our local canyon road at a mild pace today and it handles way different than my NA. Turn in is insanely quick and I’m not used to power steering or electronic throttle control. I’ve got a lot of parts to rip off the NA this weekend but am hoping I can get my bucket seat into the NC and take it up to the mountains for a preliminary shakedown.

Hopefully I can provide some good data for all in the coming months.

Roda

Sorry to hear about your NA, but great choice on the NC! Like others have said, if I wasn't neck deep in an NA I've had since forever, I'd be building an NC. It's a great chassis! We had an NC3 Club PRHT for a few years, and would really like to get back into an NC2/3 PRHT for our 'street' Miata, but it's a great basis for a track car as well. More power, more tire, better brakes... big upgrade on the NA.

The 2.5 swap was a new thing when we had our NC, and it's come a long way, though I'm still not completely sold on it. A stock 2.5 makes better power than the 2.0 but is pretty boring to drive. From most of the folks I've talked to, cams and compression are needed to make it really shine, and fun to drive. Rotrex would seem like the easy button.... but, FM had a Rotrex NC car that they were developing for a couple of years, and they never brought a kit to market. I was interested for our NC, but every time I talked to them it was like they were holding something back, some issue that they didn't want to talk about, and then the project went away. I know something really turned them off the Rotrex on the NC, but I never found out what it was. I also know a lot of guys had to re-work the Rotrex kits for NA/NB to make them work properly and reliably for track use.

And K-Power just announced their K swap for the NC... Expensive, but the really attractive thing is the swap retains the stock oiling and balance shafts on the K engine. IMHO, removing the balance shafts is the biggest drawback of the NA/NB K swap. Since you're starting from zero, the cost of the swap may balance out with a built 2.5/turbo, whatever.

Whatever you decide, I'm looking forward to following the build!

Midtenn

iTrader: (15)

because I am really sure he wants to give more money to KPI after all the trouble with the driveline swap in the NA....

Ryfrog

DANG Going to miss seeing about your awesome NA, but excited to see you make the boat generation fun. Jokes aside awesome to see you're sticking with a miata and can't wait to see what you do to it. If it's 1/2 as cool as your NA was it'll be a sick little track car. All your bmw problems makes me want to lean towards 6speed or WALTERMOTORSPORTs built trans over the bmw swap especially for the money.