Ok so I'm thinking of coming back to Miata's from BMW's and Porsche. Cost to run is just soo much better.

I've narrowed down what I'm looking at to three options. There are alot of plusses and minuses, what do you think? This would be a 90% track 10% street car, but would be street driven some. All would have OS Giken, top shelf coilovers, bigger brakes, max safety equipment, etc....

1) NC with turbo K24.

• Keeps balance shafts, and fits nicely.
• reletively low boost needed 10-12psi
• Support for transmission and rear end avail
• Knowledge base exist, but could be fragile?

NC with LS

• Good support
• N/A simple power, aka bulletproof after teething time
• Heaviest option +100lbs

ND with EcoBoost

• New Ford motor, trans, and ecu with tune no junkyard
• ND is light, gets rid of trans issue
• Rear end questionable at 400whp
• Very light 2380lbs

 

I see you and I both live in Aliso, small world! A few tidbits I think might be worth sharing:

Factory EcoBoost rods nuke at around 400whp, sometimes a bit under, so that might not be the best option for 400whp if you want to run unopened motors.

I was under the impression that the ND trans was absolute glass, unless you're talking about the auto?

To further complicate things for you, Andy Bui at Epsilon Motorsports up in the Silicon Valley is currently working on putting an EcoBoost motor in him and his buddy's NC W2W car. Can't remember if he's doing a 2.0 or 2.3L in his car. I think he said he was gonna detune it to 210whp due for class restrictions. Dropping an EcoBoost into the NC requires cutting of the firewall to facilitate room for the high pressure fuel pump, so probably not ideal for anything but a track only car.

I'm obviously biased but I have a similar goal to you long term (minus ~60-70whp) and am pretty set on the path of 2.5-swapped NC + boost. Dollar to horsepower ratio on that path means you can do a transmission swap if need be (TKX? 8HP?) and still be in the total dollar range of an N/A K swap running a stock NC trans. Again, very biased, but that's my personal path haha. Also sorta off topic but my 2.5 without balance shafts has yet to rattle anything loose after ~7k miles and 16 track days.

Selfishly, I want to watch an NC LS build thread, so I think you should do that

 

Interesting. So the 2.3 is what I was looking at. GeauxMoto has a full swap for it and are running it in their shop car at 400/400 at the wheels.. No rear end options for the ND out there I'm aware of, so probably Puddymod, OS Giken, and a cooler. Transmission for the ND would be the Ford from the Mustang. For the NC transmission there are a few options, Getrag, T56, and there is a kit being developed for the BMW DCT, which is heavy, but super cool.

I've also talked to KMiata, and the ND kit will be out very soon, but not sure I want to be 1st in line with KMiata's reputation in that regard. It sounds like it will be reasonably straightforward though.

I think there would be a teething period on any of the options. Biggest issue with the LS is I'm not convinced that it does not need a dry sump. So many anicdotes of blown motors. Dry sump in a Miata is just such a huge pain with the tank in the trunk.

 

Interesting on the GeauxMoto car. I'll have to look that up and see what they're running. The 2.0 is generally favored over the 2.3 for super high HP builds due to its closed deck design vs the 2.3's open deck. I work in service at a Ford dealer and we've seen plenty of 2.3 Mustangs come in with a hole in the block pushing the unopened motor with just a tune. Generally seems that the rods fail on a stock engine before the block has issues. That being said, the stock turbo is tiny and spools at super low rpm, so it's easy to create a bunch of rod-bending low end torque with that setup. Maybe GeauxMoto got around that with a really progressive boost curve.

I saw GeauxMoto's DCT NC swap was in the works. Cool stuff. The fact that it retains the PPF is stellar too.

You're familiar with Ryan Raduchel, right? He's got a dry-sump'd LS swap NA and comes down to Buttonwillow a few times a year. Might be worth hitting him up on FB or IG if you have either of those.

 

If I didnt already have a really nicely built NB(cage, xida's, brofab hubs and brakes, 9 lives aero, etc...) I would be building an LS powered NC. The form factor is so much better than the NA/NB. while not a "big" car obviously, its so much easier to fit stuff into. 17" wheels means much easier time putting big brakes on them, much more room under the hood, trans tunnel is larger, etc...

LS, TKX, Ford 8.8... V8R front sub-frame... Kiesler 8.8 mount and cv shafts. Choose rear gear and trans gearing wisely.

Weight is not really an issue with the LS swap IMO since you have so much overhead for more power. 400whp an LS is just starting to come into it... 450whp or 500whp overcomes the +125-150lbs over a K swap pretty easily.

Im not doing a dry sump. Kevko baffled F body pan, 3qt accusump, Johnson axle oiling lifters, Manton oil restricted push rods, improved racing crank scraper/windage tray, Melling high volume pump, big Setrab cooler. You have to keep the oil out of the heads where they have no chance to return to the sump under high g turns. From everything I read running an oil restricted push rod is one of the keys to keeping these motors alive on the road course. Theres other ways to do it such as bushing the lifter bores and controlling oil there, but thats $$$$(my shop quoted me 100-125 per bore x 16)...

 

Hello. I'm in Mission Viejo and just bought an NC. Would love to see where you go with your build.

 

So with Z_WAAAAAZ's info (thanks btw) it looks like you'd need to build the Ecoboost to be reliable. I think GeauxMoto is running a bigger Garrett which is why the rods are probably living.

So maybe the NC is the better bet. Especially being able to swap the RX8 suspension, diff, wheel bearings, etc... into it to make it pretty bulletproof. Use the K24 Turbo and then just need to decide the transmission, but I think the DCT would be the best / coolest bet. Carbon Miata flares, 18x10 with 285's. The electonics, power steering, and even AC are all already handled. No way I'll ever get it registered in CA, but that's a different issue.

I know the LS would probably be more reliable, but I'd need to be convinced it would live with slicks at 1.4-1.5g, and I suspect it will not. Heck, the K24 might not either!

 

The oiling on an LS is really not an issue. Its very well understood.

Hell you could literally throw a set of oil restricted pushrods in a stock motor and solve 90% of the issue. A baffled pan and a 3qt accusump thats always open to the system solves the rest. Even with a K motor or an expensive built BP a 2-3qt accusump is good insurance.

The LS head is the problem and the oil return ports are so damn high that under sustained high g's you fill the head with oil. So you restrict the oil from getting there in the first place. There's also guys that have drilled into the heads and run drain lines back to the sump, but I think thats overkill.

Bronson does nothing special with his LS outside of an accusump and he is probably on the ragged edge of Miata LS development and he can drive his damn car. After talking with him at length about the oil system I feel pretty confident I can keep a wet sump LS alive on the track.

 

The GeauxMoto ND is running a built motor, so that makes more sense.

 

Ok, so prety much decided to start with an NC and an LS motor. Probably a crate motor, as new from GM is hard to beat, but maybe something built as I'd rather have forged pistons and rods, but not at a 2x price point.

The NC also has a lot of advantages with the RX-8 offering a lot of "upgrades" as the parts interchange.

 

What swap kit will you go with? The only one I know of is V8Roadsters and people have variable opinions on the quality of their parts and almost universally say their CS sucks.

My dream miata build is also an LS NC, so I realllly hope you do it and document it very well!

 

Ive done the math on GM crate motor vs. fresh build... its close, but like you said with a build you get to pick your poison. I think an LS3 crate motor can be had for like 11k, but you will still be in an oil pan for another 500 bucks.

Im going to be about 14k into my motor and im buying EVERYTHING...sensors, gaskets, pumps, oil pan, etc... and will have all forged everything except the crank and GM cranks arent known to be weak.

If you can find a good deal on a block and heads on marketplace you can find cranks there also. Im in my 6.0 aluminum block 500 bucks. LS3 heads(with the lightweight intake valves) for 550 bucks. Crank for 90 bucks. LS3 intake manifold/injectors/throttle body for ~$500.

My build at the machine shop is going to be about $5000 including Callies h-beam rods, Wiseco pistons, line bore the mains(upgraded to ARP studs), balance crank, etc... Only head work I am doing is a clean up pass. Machine shop assembling short block, but ill put the heads on and dress the motor.

Cam motion cam, BTR springs, rocker arms, Johnson lifters, etc....

You can build a "better" motor for about the same money, its not going to be double. You will have to do some of your own sourcing and work though. I can send you my build spread sheet that has every part I have purchased so far...

 

Im building an NB and were collecting parts for my buddies NC build also.

I believe the only V8R parts were going to use on his NC is the front sub-frame because thats all thats out there. Probably will run their clutch master setup as well.

Kiesler 8.8 rear setup. We will build the 8.8.

TKX with a custom mount, custom drive shaft.

Gen 5 camaro manifolds(all of the NC swap headers are NLA from what we could figure out) and a custom exhaust.

 

Build sheet would be great. Also thoughts on the Kiesler 8.8 vs the AAM from v8roadster? The tkx is my backup if the DCT doesn't workout.

I was looking at the crate for about 11, but then I'd want a different cam, restrictor pushrods, pan, lifters, springs, rockers and then you should have just built it. I think done right about 15k from someone like Texas Speed.

I have a good budget, so build is this:

NC Chassis
Roadstershop subframe
LS3 V8 tbd
Kiesler 8.8 with OS Giken
BMW DCT
18x11 with Carbon Miata flares, 285's square
DG hardtop
Brakes tbd, but want something nice
Probably add MK60 abs, but will wait to get it running first.

 

You know if you're gonna run a crossmember across the frame rails or adapt the PPF to the TKX? Curious as I've seen almost everyone deciding on PPF adaptation in the NC instead of solid mounting the trans.

 

no way to use a PPF with the Ford 8.8 setup...

I dont know how we will do it until we get it put in. Will fab something up. Most of the NB mounts are through bolted to the trans tunnel with backing plates so guessing something similar, but i've never been under an NC to understand how the trans tunnel is shaped.

 

PM me your email address and ill send over the spreadsheet.

My motor is being built by Horse Power Research here in Dallas. Its the first de-stroker they have done, at least that they can remember doing.

Ford 8.8 is the way to go. EVERYBODY that I know with the AAM from the Cadillac hates them and says they are disposable junk. No gear choices, basically no LSD options(outside of the OS Giken I believe is now available), rattle badly, etc... Axle shafts become an issue as well and I think you have one source and thats DSS which doesnt have the best reputation. Kieslers axle shaft setups with the Porsche 930 CV's is the way to go. Im going to be running a similar setup in my NB.

Ford 8.8 has "unlimited" gear ratio's basically from like a 2.93 to I think a 5.11 and mostly everything in between. Hell I think you might be able to find an old like 2.56 ratio. Like 10+ LSD carrier choices. Im just running a cheap trac-lok clutch LSD with carbon clutches. Then you can go all the way up to the OSG. Several torsens in between with different ratio's. My spread sheet has my full 8.8 build setup in it, slightly different with the Explorer diff that the Kiesler setup uses, but the hard parts are the same. Stud the caps, Chromoly 1350 input yoke, crush sleeve eliminator, etc...

BMW DCT is what I was contemplating for the NB, but it hangs to low for me to be comfortable with it and not ripping the damn oil pan off. I think the NC trans tunnel is larger and it fits better. Going to want to run like a 3.08 gear in the rear end if you do once you start looking at the trans gear ratio's... unless you only want to use like 4&5 or 5&6 gears. Even my 3.31 ratio was getting a bit far off and I was only going to use like 2 or 3 gears. I decided it was a lot of work for no real gain over a TKX. Most LS guys will tell you they basically run 2 gears on track. It became hard to justify the DCT outside of "my LS miata has a 7spd DCT"...

Brakes were looking at to put on my buddies NC is the Sakebomb trackday kit.

 

Ahh, I'm an idiot. The 8.8 comment didn't even register in my head. Never mind me.

 

Guessing the NC rear end will hold more power than the NB rear end if you are discussing it in a 400whp thread. MAYBE with a turbo 4 cyl that doesnt have much torque. But an LS will blow an NB or NC 7" ring gear pretty quickly.

The great thing about doing an LS swap is that all the parts will withstand 6-700whp so with 400ish WHP you are barely stressing the motor and driveline so longevity is fantastic. There's Cobra guys putting 1000whp through the 8.8 IRS.

 

I think what Z is referring to is that Fab9 is making a NC TKX kit that adapts to the PPF. So I think he was visualizing running that, but with a bellhousing on the TKX to fit an LS up front.

It seems like a ton of money for someone to keep running the stock rear end. If someone plans on running big power, they will probably also spring for the AAM or 8.8 rear diff setup. I wish Fab9 well with their kit, but I think it won't sell very well. It was initially advertised to go for $4400, but the latest posts from Fab9 indicates 6-8k.