I ran an airdam w/o splitter on my car, then added a 4” splitter later on, then a 5.5” splitter after that. It’s obviously gonna depend on the roads you drive, but having the airdam only will be perfectly streetable for most people, depending on how low you cut the thing. I think mine had around 3.5-4” of ground clearance. Could have made it lower, but that would’ve made it scrape more.

Adding a splitter made a substantial difference in aero, but also resulted in contact with the ground on driveways and pulling into parking lots/gas stations/etc much more. Guess adding one just depends on how much that bothers you. I used to hit the underside of my splitter with some black spray paint just about every time I put my car in the air lol.

I only ever ran the airdam-only setup with a 59” NRG rear wing, which has similar dimensions to the APR wing but is probably less efficient. The pylons also mounted directly to the center of the trunk so it wasn’t as stable as the APR or 9LR-type mounts. The balance with that setup was actually very good though. After adding a 4” splitter, though, the car needed more rear aero.

 

Thanks for that info Zak. At this point I'm thinking of doing some kind of rear wing but honestly not sure which. I think cosmetically the APR gtc 200 with risers looks the best, followed by the 9LR street **** for the street. These wings are a bit much for the street already, but are passable to me. the 9LR big **** is gigantic, and I saw someone selling a giant singular version of the gt250 locally for a good price but dayom that thing is monsterous. A little rear aero would def tame the rear down a bit at higher speeds.

Jumping back to the alternator issues.. I oredered an ACDelco remanned from rockauto and I put it in today. I thought it'd be a remanned unit but I'm pretty sure it's just a new China alternator, not even a remanned.. :/ I did some googling and it looks like good reman options are simply no longer available (Denso and Bosch) which sucks, so I installed the China alternator. I plan on getting a spare but I'm gonna be pissed if this thing leaves me stranded one day. Over on the BMM Discord, one member did mention this high amp version by powerbastards.. It's $395 but if it's a brand new quality piece.. honestly that's not bad. https://www.powerbastards.com/prodde...3895-160-HD1-1 There are such limited options for alternators these days. I will bring a few alternators back to the local guy to rebuild me a good one but it's a shame there aren't more options anymore. A few shots of the alternator. Pretty sure it's a Wai/DB electrical with an ACDelco sticker slapped on it and they charge $40 more. I didn't think they remanned these in China but in Mexico and the US. If someone knows better I'll be happy to be wrong.






At least the alternator works (for now) and the car is moving.

 

Question for you guys. I picked up a 6 speed tranny from a certain "prestigeous" seller, and I wanted to know if there's a way to identify if it's an NB1 or NB2 6 spd? Can you tell just from the outside or do I need to remove the shifter? If anyone has any tips or could point me in the right direction of how to identify the differences I'd appreciate it. I will likely just replace the driveshaft seal, shifter bushings, and install it. I know there are different shifter bushings depending on if it's an NB1 or NB2 shifter. There is a sticker on the top but the ink is all washed out and it's unreadable. I thought about getting a miataroadster shifter but I'm not sure it's worth the money over just refreshing the stock unit. Any input is appreciated!




These guys shipped it across the pond just wrapped in layers of cardboard and plastic.. lol Seems to be ok and no cracks in the case. This is after I started unwrapping it. Not the best packaging job but if it works..

 

No vin # on the case? Eh, identifying it by the shifter bushing is easier anyways.

I had lots of trouble running the stock 6 speed shifter on track (even with a brass bushing and poly motor mounts), mainly downshifting into 4th. I swear the gate would just disappear. I've got multiple videos on track where I can be seen struggling with it. Money shifted more than a few times with it too. On my NB1 6 speed, I ended up modifying an eBay 5 speed shifter to fit (lower ball is the same as the early 6 speeds), added a generic 2" shift extension, and it worked great. Probably not the prettiest solution but I stopped missing shifts and the whole solution cost me under $70.

 

Most of his parts will ship without a VIN tag, unsure if that's a UK thing or if he removes them. No way to tell without the VIN or by looking at the shifter.

 

Appreciate that info Zak. I guess I'll just pull the shifter and measure some parts with a caliper to figure out what transmission I have. Honestly for the time being I'm just going to get it freshened up and after another event I'll cross the bridge of whether I want to change anything (if I have a problem shifting/etc). I'll be honest, my first track day this past spring I found myself missing 4th a bunch with the stock 5 speed tranny. It was bugging me a bit but by the end of the first day I got a good feel for it and started missing 4th a whole lot less. I can't remember the exact "technique" per say, but I eventually figured it out. I think the tranny moves around a bit due to no transmission mounts. I'd say that's honestly my biggest "complaint" about the miata platform compared to others. It has a good tranny, but the way the tranny is mounted (or rather isn't) allows it to move quite a bit. Once you get the hang of it it's not nearly as bad. Hopefully the 6 spd won't be too bad, but I'll definitely be conscious/careful with the shift to forth and not pull towards 2nd to avoid a money shift.

Ya, I just did some googling and apparently VIN tags are a US thing..? Thanks.

 

I'm about 99% sure its a NB2. The protrusion circle below showed up on NB2 transmissions. Its houses the fore-aft detent for the shift rod. The fore-aft detent on the NB1 transmissions is down in the main box.

 

Fwiw, I got a tall angled miataroadster shifter for my six speed, and despite the fact it is horribly expensive (over aud$600 landed here in Oz) it made a massive difference to shift quality and imo was worth it. Ymmv.
moving from a silky smooth 5 speed tranny to a notchy 6 speed that was terrible to get into reverse and missed shifts regularly and now back to accurate shifts, no reverse fumbles and the bonus of better lever location.

 

Big thanks for chimin in. I found your post about the differences with the 6 speed trannys so sounds like you've messed with them quite a bit.

I will definitely keep that in mind. For the time being I will just refresh the stock shifter and see if the 6 speed is really as bad as everyone says it is. Hopefully not, but I can always change it down the road. Most people seem to love the MR shifter. I'm personally not a huge fan of the tall angled shifter (never driven one maybe I'd change my mind if I tried it).

So the last mods I see doing to this car (for the foreseeable future) are swapping in the 6 speed, a 3.6 torsen (and welding in some reinforcement plates for the arm), xida coilovers, fluidampr (hopefully it helps), and a 9LR street ****. Going to keep power down so the motor doesn't pop and hopefully just drive it. I definitely didn't "need" the 6 spd, but figured if I need to swap the diff out for a torsen anyway, might as well put in a 3.6 and get the taller 6th for highway cruising (and hopefully the 6 spd will live happily at a little over 200whp). I originally chose a miata because I thought a turbo miata would be an "affordable" track car. lol I guess it sort of is, but everything always adds up and costs more.

 

FWIW, I have the 6 speed with the MR shifter. It's a big improvement over the stock shifter and worth the investment, IMHO. I do prefer the tall angled shifter for a track car. Puts the shifter close to the wheel which is nice on track.



5sp vs. 6sp is a different discussion. I tried 4.3 with the BP engine and didn't like it with the 6sp, and I'm not running the K to 8000, so I stuck with the 4.1. On most of the tracks I've run so far the 6sp is a pretty good match with the K24 and 4.1 diff. The last track I ran was not a good match with the 6sp. I compared video with another K swapped Miata with a 5sp... he was shifting 4 times per lap, I was shifting 12 times with the 6sp. I talked to another driver with a turbo NB making a little over 200hp, and they swapped in a 5sp specifically for this track. That's more trouble than I'm willing to go to, because the 6sp works for me at most of our usual tracks.

TLDR, my point is that the 5sp may be a viable option, depending on your typical tracks, especially with turbo torque. Keeping one alive could be a challenge though. With a turbo I would definitely use the 3.6 diff with the 6sp.

 

Woah, been way too long since I checked in on this thread, especially considering you're somewhat local.

I meant to get out to Dominion this year and completely dropped the ball. Man, you weren't kidding about the lack of runoff. It's weird to me because there are spots on the outside of the track where they obviously cleared more land and have trees growing back up, but put the concrete barriers right up against the track to the point you couldn't pull off track completely. I understand the wall being right there on a tight infield section, but it's that way even on the outside of the track limits.

I've had no issues with my parts store reman alternator over the past 6 years or so, which is way better than I was expecting. There have been lots of track days since, including a few sessions in there where I was going for 1hr straight, coming back in for fuel, and going back out. I believe I've read a post from @curly where he said giving the alternator a fresh air duct fixed their issues with alternators going out on endurance cars. I haven't done that, but I also don't have to worry about turbo underhood temps. Also, I really like how you've focused on air management! Very clean work integrating new parts with original.

For rear downforce, I couldn't bear with the idea of having a massive wing either, despite my own disconcerting wiggles through the uphill esses at VIR. I picked up a Carbonmiata rear spoiler and am quite happy with the fit and finish. I haven't installed it yet as I am trying to add threaded nuts into the structure of it so I can bolt on different height lexan blades to adjust downforce, much like you see on a lot of the domestic track cars these days.

 

FWIW, my stock engine ran noticably smoother after I installed the Fluidampr. Seems worth it to me for that alone, given these engines aren't known for their spectacular balance from the factory.

I also feel you on the thoughts of a turbo Miata being an affordable track car. FWIW again, though, if you keep the power under that magical 250whp mark (I.E. no built motor, drivetrain swap, etc), I think it's still pretty killer bang for the buck. Once I got into the built motor, I was probably still on the quicker end of what could've been built for the same cost. Post-drivetrain swap I think I could've built a faster car, with equal or better reliability, for less money (although consumables may have been more expensive depending on the chassis). That's just my personal experience, though. It's obviously gonna vary from person to person.

TL;DR, If I were smart, I would've kept my car exactly where your current build plans are. No regrets, though. I guess you gotta factor the fun and learning experience into it as well haha.

 

Also, I'm glad to hear you're having a good experience with the BMM ECU. The low buy in price and on board support for wideband among the other features has me really thinking about dipping my toes into the standalone world again, even on my daily. Could you PM me a link to the discord?

 

Thanks for your thoughts Roda. I'll definitely keep that in mind. The shifter is fairly easy to swap out so I think I'll have to give the stock 6 speed shifter a whirl to see what all the hate is about first. I've also dropped a bunch of money ordering all the parts on my final list so I'm in no rush to burn more money.. lol

Regarding the tranny swap, considering the poor shifting of the 6spd, I have no "desire" to move to the 6 speed except for the increased reliability (hopefully). Shifting wise I'd say the 5 speed with 4.3 was JUST RIGHT for my power level and I see no benefit of moving to a 6 speed in terms of faster times. It's solely due to reliability at this point and if I'm replacing the diff with a torsen unit, might as well just do it once with the 3.6 and switch to the 6 speed now (I used the Kmiata gear calculator, and looks like the 6 speed with 3.6 is just a hair shorter in 3-5 than the 5 speed with 4.3). I'd rather not switch to a 4.3 or 4.1 torsen, bust a 5 speed, and then have to swap the final drive in the diff AND the tranny. I'd rather just not roll the dice with the 5 speed lasting on track and bite the bullet now. That's my logic at least. Despite what some might think by this build thread, I much prefer driving the car than wrenching.

 

Ya.. while it's easy to poopoo Dominion, ultimately it is a fun track. The mini uphill esses are definitely fun (haven't done the real ones at VIR yet). The negativity comes from the fact that it's a brand new track (build in 2016 I think) and the poor planning and layout which could've made it really good. Due to the design I don't think it's used for any sanctioned racing (which makes sense), but it limits more clubs from doing events there, less money going to the track, etc. For an HPDE track it's still fun.

Hmm that's good to hear yours is holding up fine. It's an interesting thought with a fresh air duct to the alternator. Honestly I'm not sure how I'd run one, but I'm hoping the hood vents keep underhood temps down a bit to maybe make a fresh air duct unncessary..?

Ya, the 9LR street **** isn't small either but hopefully it'll help a bit. At higher speeds I can definitely feel the rear being a little more unsettled (like through the mini uphill esses at Dominion) and if I could tame it down a bit that'd be nice. Sent you a pm. So far so good with the BMM ECU. The discord is fairly active and people are very helpful. The community makes it totally doable to tune your own car for someone with some experience and a willingness to learn/tinker. I haven't poked around how much support the other standalones have in terms of community support like the Link or Haltech.

 

My trans/diff plans are identical to yours. 6 Speed + 3.6 keeps the top of second about the same MPH as 5+4.3 which is a big deal for autocross. Once I bump the power up then the 5 speed's going to grenade, but FWIW I've been running ~225 WHP through it for a while without issues. I'm half tempted to keep bumping the power up to see when it fails. I think their limits are pretty well established on the forums, but I'd be interested to get some data first hand. Granted, I also don't want to clean up the aftermath of a transmission blowing up.
Another friend runs around ~250-270 WHP on his 5 speed. He runs Hoosiers on that and has had the 5 speed in there for years (I wanna say 5+ years at this point).

Similar to what Zach said, I've realized more and more that the jump past 250 WHP really opens a can of worms. I'm still going to do it, but it does add a ton of cost.

 

Thanks for that note on the fluidampr. Good to hear it made a perceivable difference. I have one on my honda for the same reason, a few people's opinions I value said it seems to help. Ya, a built motor definitely adds a lot of cost. At some point I will buy a spare longblock to build, but I'm hoping this one stays together for a while. At some point the rings will get tired and it'll need a refresh, but if that's 2-3 years from now and a lot of track days *fingers crossed* that'll be a-ok by me. On that note, I really ought to get off my **** and do a compression test and leakdown on this motor so I can get a baseline of how it's doing. It has ~120k miles on it, and seems to have been well taken care of by the previous owners so I'm hoping it'll last a while. It seems to burn a touch of oil on track, maybe i put in about a quart for the weekend (I also need to check my catch can) but I'm pretty religious about checking the oil every session or two. That's a surefire way to kill an engine quick on track.

Bang for the buck in terms of simply going fast you definitely can't beat domestics, but these miatas are fun on track and really make you work which makes it a lot of fun.

Another sort of random thought, but one thing I like about the miata is the kraken 3" exhaust has a really nice tone. The large rear muffler and good sized resonator in the exhaust make it far from quiet, but definitely not loud/obnoxious/droney on the highway either, which I can appreciate these days.

 

Ya I admittedly may have jumped the gun when switching to a 6speed. I was chatting with someone a little while ago who said 5 speeds should do fine on track for low 200whp, so maybe the stories of how "fragile" the 5 speeds are is overblown. I figured better to have a little more leeway in case I want to turn up the boost even a little bit.

 

FWIW, all my 5-speed failures have been internal, no mess. A few gears strip, either while driving or just after a shift you find you can't get in the next gear. Thankfully 4th has held together, often requiring stopping the engine, putting it in 4th, and starting it again. This was a 2.4 ecotec, making 180ftlbs. On a BP, 200hp is probably only making 150-160ftlbs, and on track at higher RPMs, hp is great, but torque drops after 5000rpm, which is typically some of lowest RPM you'll see.

 

Really? That number sounds lower than I'd expect. Mine was making roughly 185ft/lbs at 210whp with the same kit as OP.
Actually, I just went back through my photos and found the dyno sheet from that day. Made 181ft/lb at 197whp before we "turned up the boost" one psi.

The 5 speed that was in my car survived 200k+ miles, ~10 track days N/A, ~8 track days boosted, then I put it back in later on after blowing my 6 speed and ran it on the street/mountains for a month or two at 240whp. It's still very much alive and sitting in the corner by my workstation, actually. Everyone's experience varies, obviously, and I feel like I may have been lucky.

I'm tempted to say send 'er till you bend 'er but would feel really bad if you did that and then blew the poor thing on the first session of a track day