I’ve wanted to LSswap just for this:

https://dealers.linkecu.com/G4X_Xtreme_LS_Bundle

 

I've gotta agree with the LS choice, if looking for that kinda power. I think the K's sweet spot is 220-250 N/A whp keeping the stock driveline (and is a GREAT choice for a high revving not overpowered track day toy), beyond that LS is the way.

And that Link LS solution looks great. Though with an LS theres a lot of options..

 

This may or may not be exactly what I already have earmarked for future engine management in this purely speculative scenario

 

 

...and so we meet again 33 pages of wiring bliss. Hopefully this is the beginning of the last round of anguish with you.

 

Hahaha, you like it!

 

So does the title get another "and build the NB1 again", again?

This'll be fun to watch. Can't wait to see how clean you'll do the swap and I'm sure I'll learn some great stuff along the way. Your thoughts on the "why" of an LS swap vs a turbo K24 are exactly what I was thinking. Sure, a turbo K24 with DCT may be less of a "cut a check" build, but anyone who is so jaded that they find an LS swapped Miata boring needs to do something besides watch Youtube. Besides, if we're going by the "please the comment section" standard, a turbo K swap is becoming fairly common itself for builds posted on social media.

I'm in for more! Make that modern day Cobra.

 

...to be completely honest, I don't mind it. Every time I do it, I learn better ways to do things. The tediousness of it all and getting to a motivational kickoff point is the worst of it.

I'll be sure to document what I'm doing, but for now it's a big ole stack of busy work in photoshop to keep everything tidy.

I didn't buy another CTS-V (again) so I think I can just continue on my previous "...build the NB1 again" thread title suffix

I'm already learning some things and I've barely cracked the surface of it all. I won't beat the LS vs turbo K24 vs "literally any other swap combo" topic to death too hard. They are all universally fun money pits. It is just a matter of which pit you want to play in yourself for your own selfish reasons.

It's funny how you mentioned the cobra comment. One of my best friends runs a 427R powered Cobra that is deep in the 3.xx lb/hp power/weight ratio. Watching and helping him successfully run that car has been fairly influential to the "big n/a power, light car, fat tire" recipe that frankly just works on track without major hiccup. Taking some of his learnings on the cobra coupled with copying what seems to be working well for other miata-specific guys I've been in chats with will hopefully lead to similar successes.

 

So I guess I'll spill the beans and formally kick off what is going to be a long haul effort and TONS of new content to add to this build thread. After years of contemplation and second guessing the right move to make, I'm just committing to this regardless of how long this takes me. I'm removing the Kswap package to pursue a swap that enables more naturally aspirated power: The small but mighty LSx



It took some patience to find the right person, but I found a buyer that wanted my full kswap package for a price that I felt is fair for all involved. He is taking, quite literally, EVERYTHING related to the kswap drivetrain and what controls it to install into his NB rolling chassis. The wiring, ECU, engine, 5spd transmission w/ notched bellhousing, subframe, exhaust, custom over-radiator intake, custom dual pass radiator, oil pressure / coolant temp gauges, and front bumper support bar are all part of the deal. I just finished providing videos to the buyer of the car running, and he gave the thumbs up approval that all is good to have me start removing the parts. Everything should be removed by this weekend, and the buyer is driving to grab it all on the 26th. So without further ado, here is going to be the last photo you see on this build thread of this NB with the K24 in the engine bay.



You may be wondering.... "Matt, why not just sell the whole car and start over?" Well, the answer boils down to 3 reasons really.

1. Believe it or not, this stupid car has sentimental value. My wife and I started dating shortly after I bought it so there are fun memories there. Many people also know Left Lane Designs exists because of parts I initially developed on this car (...and more ideas are coming!)
2. There is also a TON of money in the chassis/suspension that I know I'd never get back out of it if sold, so rather than take a big loss on selling the car and starting completely over, I'm making the call to keep this honestly great handling chassis package in my possession and KEEP ON BUILDING (regardless of how awesome NC's are...)
3. I can't hide the fact that the engineer in me likes building things nearly as much as I enjoy driving them. This next phase of the build will scratch that builders' itch that has been there for a while

So what am I tentatively planning on? The high level breakdown is this:

• L94 (Aluminum 6.2L) junkyard engine w/ valvetrain goodies: This is known as the 'poor mans LS3' that came in the premium GM SUV's of the era. Reasons for this will make more sense later...
• TKX 5spd transmission
• Getrag Diff
• Accusump Oil System
• Link G4x Standalone ECU w/ DBW Capability
• MK60e5 ABS system
• AIM PDM32 w/ 10" Display
• ....lots of other little sh*t that I'm too lazy to list or don't know of yet

What is my goal?

• 500whp N/A
• <2500lbs w/ driver, full fluids, and same interior features that I have now

So now that the admission of what I'm planning to do is out of the way, where does a guy start with this? well, other than the obvious fact of removing the Kswap stuff first, the next most obvious thing is, I'm basically starting over from a wiring perspective. As mentioned above, the NB chassis harness that I have now has been heavily pruned from front to back. During the Kswap I removed 7lbs of wiring from the factory chassis harness as I showcased years ago in this thread. It was nice to get rid of so many unused wires, but the factory harness is cluttered with ground splices in places you wouldn't prefer and I'm currently using 2 OE fuse boxes when I believe I really only require 1. The PDM32 that I'm planning on will likely vastly reduce the number of physical fuse circuits that I need, but due to my desire to maintain multiple street car features (wipers, power windows, and exterior light circuits) this 32 channel PDM will quite easily become full, thus warrant a standard (smaller than OE) fuse box in conjunction with the PDM.



To figure out how big of a fuse/relay box that I'd need, I first need to lay out all the circuits that I intend to keep. That brings me to the below image, which is the 33 page OE NB1 harness diagram pruned down to 14 pages all of the key OE features that I want to retain for this car. I have the PDF version of this attached to this post if you'd like to check it out in more detail. The online tool that I used for this is a free photoshop website called Photopea. It honestly works great for this as I just "white out" any circuits that I don't need, delete sheets that I don't need, and therefore am only left with what I'd like to keep. Keep in mind, this does not include all the Link ECU, AIM dash, or MK60e5 ABS system connections, but it at least captures the OEM side of things in an easier to follow manner. This took me about 4 hours to modify from start to finish and has already been immensely helpful in understand how to approach this issue. More to come here...


As soon as the Kswap sale cash is in hand, the goal will be to get the car off jack stands and back on the wheel stands as a rolling chassis to stay organized, which means sending an order in to V8R for a LSx subframe. It does seem that V8R is the only place to get long tube headers that fit in the NB chassis, so getting that order placed at the same time likely isn't a bad plan knowing V8R lead times can be awful. I'm hopeful those are the only 2 parts I will need to buy from them. I will be chewing this off one bite at a time from there!

 

It was bittersweet voting against keeping the K when consulted, but I think for your needs the LS is going to make you a very happy owner. Congrats on "ruining" the car with twice the amount of cylinders then Mazda intended for, I can't want to see this happen.

 

I was curious to see how your build was guna go! Should be a blast.

However, I would 100% LSx an RX8 over a NB nowadays. It has nothing to do with the fact that I got an RX8 and figured out how good they are, lol.

 

The RX8 is pretty much a 4-seater NC. Trust me, I deeply considered it as an option given how good I know the NCs are and 4 seats with kids would be cool. Here is what convinced me against it though... Given the RX8 2900-3000lb OEM curb weight with super light rotary drivetrain, by time you are done adding LSx drivetrain weight to one I have seen many reports of LSx RX8's in the 3100-3200lb curb weight range. It seems a LOT easier (and MUCH cheaper) to just go straight to a 3200lb C5 when focusing purely on performance capability... and turning into a "corvette guy" feels boring... The NC is ~400lbs lighter than the RX8 mod-for-mod, which makes it a bit more attractive in that C5 comparison, but the NC being a convertible forces me into spending cash on all the auxiliary safety items again (rollbar, seats, harnesses, etc) which sucks financially on what will already be another big money deep dive here.

Soooo.... deciding to build the prepped NB chassis that I've got and be an estimated 300-400lbs lighter than a similar LSx NC build would be (and ~800lbs less than a "boring" C5) is where I ended up landing on the whole dilemma. At least the "PWR2W8" vanity plate will continue to make sense. If I was starting from absolute ground zero with no car, an NC is probably what I would be swapping, but I can live with avoiding the yacht jokes and not being as cool as an LSx NC.

 

Rotaries aren't actually all that light by modern standards. They were considered light in the 70s when compared to iron block / iron head V8s, but modern aluminum engines have more than made up that difference.

They are small though. There's just not as much air in them as there is in a "boinger" engine.

I agree with you about picking an NC over an RX-8 though, if only because the RX-8 is ugly. Just don't bring one anywhere close to an FD

--Ian

 

Fair point.

I'll admit, I actually haven't spent the time looking at renesis weights on their own because I have zero desire to know much about that lackluster engine. I know they aren't THAT light, but they are small and relatively torque-less with a trans and diff sized appropriately to meet those mild requirements. I did reference a lot of renesis vs LSx RX8 published scale weights and seemed to always find close to 200lbs be added with the v8 swap (granted that addition is shared between rear diff, transmission, various mounts, cooling system, and engine upgrade differences that come with the swap).

 

NB + lsx is going to be a way more thrilling, visceral ride. Much more akin to the cobra mentioned here. Rx8 more capable sure, but nothing like a drop-top 90's miata with a 400whp v8.

And I'm not hating on the 8, with the price of shells now days I've considered building one too. Very capable track platform too.

 

Quoting and posting this for future me's frustrations.

 

I definitely understand a slight sunk cost fallacy on the NB, I've got it going with mine for sure lol.

In the real world, RX-8s that are modded aren't usually 3000lbs. Most STX/DST RX8s are in the 2750-2800lbs range, so that's full interior a/c, radio, etc. I'd be super surprised if an LSx RX-8 ended up over 3000lbs.

I also would rather have an LSx NB over an NC, though, just to confuse my argument some more

 

Just realized I haven't checked your thread in a long time. Holy hell, looks like I came back at a good time! Sub'd for updates. Can't wait to see you work your magic on this swap.

Does this mean there'll be an eventual battle to the death with @Wingman703 for nastiest east coast Miata?

 

You may have tuned back into a reasonable time...

I don't know what a east or west coast is, but I can tell you what a cornfield looks like?

 

...one step forward, errrrr, actually it feels like mostly steps back here, but I'm going to still call this PROGRESS!! Removed the engine/trans/subframe as one complete assembly and dropped it out the bottom. Was able to rest the assembly on 2 wooden dolly assemblies that I typically use for rolling wheel stands and the whole process went pretty fast with an extra hand from a buddy of mine. It was a little tedious to get the depowered steering rack out that I plan to keep (because it's so nestled in-between the subframe and oil pan), but pulling the 2 engine mount bolts out and allowing the subframe to drop from the engine did the trick. Not shown, but I have the driveshaft, PPF, 4.3 torsen, and axles removed (and posted for sale). While I was here, I took the time to remove the xidas and plan to clean them up... this is just the beginning of cleaning it seems as everything has gathered a nice layer of dirt that come with daily driving through rain and gravel roads. I should buy stock in shop towel companies for what is about to come...


Intake, cooling system, exhaust, master/slave cylinder, and front support bar are all off and in the "sell pile" as part of this deal to the buyer to easily go from a rolling chassis to a running car. One solid weekend and he should have the car back up and running with these parts!


Goal for tomorrow is to tackle all the interior bits, which is really related to pulling the dash and removing the longacre gauges, AFR gauge, adapter harness, engine harness, and ECU. Only small bits remain from there like the fuel pump, braided fuel line segment from OE hardline, throttle cable, and overflow bottle as NONE of that will be reused on the next phase of this build. A little bit of this is bitter sweet, but I am excited about the idea of having a blank canvas to start from shortly.