I do.... but... I'll defer to Phillip's response as we all can't be rebuilding miatas from major self-inflicted situations in a couple days

 

Many given, and laughed at Josh's comment.

 

Rolling off of the dyno, the car felt perfect, zero issues. The next event was two weeks out, and I almost didn't drive it before loading it back on the trailer for said event. Buuut thankfully I did decide drive speedily around the block as part of my normal event prep, or rather, I attempted to drive around the block, but found the car had developed a nasty vibration above 20mph that was so bad, I couldn't even maintain a steady throttle and speed would oscillate up and down rapidly, VRRRRrrrrrrrRRRRRRrrrrrRRRR style. I spent a few hours double checking driveshaft bolts, diff and transmission alignment, swapping wheels and rotors, but it wasn't until I stuck it on jackstands and ran it in gear that I noticed my drivers axle shaft was doing an oval orbit inside the CV joint. Yikes. Closer examination showed there was a CV ball halfway exited from the grease boot, and something inside the CV was NOT happy.



Yup, CV definitely spat a ball. What timing, as this had to happen during one of the two pulls I did post dyno before it rolled onto the trailer. 10 minutes earlier and I would have felt it on the dyno, an hour later and it wouldn't have happened until I was hours away from home at an event with no spares on hand.
Running theory is this CV was damaged when the diff fell out of the car at Norton, and then doing 20 pulls at ~600whp on the dyno finished it off. The 930 CV's don't really like extreme angles, and it would have seen upwards of 20* when the diff attempted to exit.


The good news is these axles from Bronson are 100% off the shelf parts once you're inboard of the upright, with the only custom part being the Miata axle to 930 CV adapter. He sent me a slew of part numbers, and the 930 CV's I can actually source from rockauto, being an OE Porsche part. The shaft itself was salvageable, and the only other item damaged was the grease boot/CV cap which was easy to get from Pegasus. Cut it a little close, but Thursday morning before the event weekend I installed the rebuilt axle into the car, reassembled the upright, and took it around the block before loading it onto the trailer, vibration completely gone.
It's currently cost prohibitive to point blank order a full set of replacement axles as spares, but with the full parts list on hand I can slowly assemble parts for a set over time. I don't anticipate going though these often, and I think the only reason this one spat a ball was due to the extreme angle the CV experienced when the diff fell partially out of the car at Norton.

Thursday night I received the unfortunate news that a friend and hillclimb competitor of mine, Seth, blew a headgasket in his car less than 36hrs prior to event start. He drives a Kswapped, supercharged BRZ with a ton of fancy tech packed into it, which is kinda the Ying to the Yang of my Kswapped, supercharged, minimal assists Miata. You might remember his BRZ having headgasket issues at Norton, so there was something seriously hurt in his motor that just slapping another headgasket in wasn't going to fix. It just so happens we were in a championship fight for 2nd place in the Appalachian Hillclimb Series Outlaw class, but if he wasn't able to run in the final event of the year I would take second place without contest. A win's a win, but also kinda anti-climatic after the battles we had at Pine and Norton, so I offered him my car for the event. And he said yes. Ohhh boy.


Chasing the Dragon Hillclimb 2025

Dragon is my favorite hillclimb on the AHS callender. It's a fast, bumpy, momentum course that the car really does well at. It's also BUMPY and FAST. I think average speed in a stock miata is low 70's, and in my car, top speed is north of 100mph. All on a super bumpy course that rivals Sebring. Mind the bumps.
It's not a course I would normally extend a codrive invite at due to the high chance of any off being the end of a car, but Seth let me co-drive his BRZ in 2024 when my car had freshly put an inspection port in the block so I felt there was a favor to repay.
I was also pretty nervous about mechanical reliability, even in a stock car the bumpiness of Dragon loves to knock bolts loose and items off the car- I think 2023 the bolts for my steering column actually rattled out, and 2022 the bumps tore the wing mounts out of the trunk. Its some serious ****. The wiring and diff mounting issues were fresh in my mind after Norton, so hotlapping this knife's edge car with minimal time for inspections between runs was going to be a real test of durability.



If you ain't trimming the clibbings at Dragon, you probably ain't fast...



Well I'll ruin the suspense now, despite a cumulative 18 runs between the two of us, we had ZERO mechanical issues. I literally did nothing to the car all weekend except rotate tires and drive it. I ran the car on "high" boost all weekend(turned down to mid 500whp), Seth ran it on "low" boost(mid 400's) for his first 4 runs, tried out high boost once, almost spun it into a ditch, and vowed never to turn it up again. Turns out the powerband of a turbo K is quite different and more violent than a Rotrex supercharged K.

I never quite had the pace to challenge first place, who maintained a steady 2 second gap over me though the entire weekend. Seth had a nice tight battle for third step on the podium... that he eventually lost by 2.5 seconds. This may be partially due to the fact that neither of us got our final run in on Sunday. Second to last run as Seth was sitting in the stageing line, I noticed a little white line on a rear tire that, upon inspection, turned out to be the first line of cord starting to show. I let Seth know this would be his last run and I would take my last run right after him. When loading onto the trailer later it turned out to be a good thing I shut us down there, as the single line of cord was the smallest amount, and other tires had much worse.

And actually it was even worse than that, because when I pulled the wheels off at home EVERY tire was corded, and one tire was down to bands. Dragon's surface definitely isn't smooth, but I had forgotten how much of a cheese grater it could be on soft tires. The good news is that these were 2021 date code A7's that had already served 85% of a season under my use, so not the biggest of losses.


Anyway, boohoo soft tires wear fast on rough surfaces, holy **** never though the car would be to the point of reliability the only thing I can complain about is tires wearing out. Maybe I'll complain about brake pads wearing out next...



While I never quite had the pace to challenge for 1st in class and ended up 2nd in class, 4th overall as is tradition at Dragon(seriously that the third year I've ended up in those exact spots), Seth had a nice battle for third step on the podium... that he eventually lost by 2.5 seconds. He ended up only being 4.5 seconds off my own time, which isn't half bad for 8 runs in a completely different animal of a car.


Funnily enough this events podium was also our finishing order for the season standings, 1st place "Camaro"(its tube frame), second place "Miata"(what's left that's Miata? dunno...) third place... parts of a Miata(Mr Bearded sunglasses drives a supercharged miata kart with a chopped up hood being the only remaining body panel).








With the closing of the Appalachian Hillclimb Series 2025 season, my 2025 season is also coming to a rapid close. I *might* squeak in two events between now and November but those are TBD, and I'm going to need all the time I can get during the off season. This has been a terrific year of bug squashing and problem finding with some good results along the way, so there are a LOT of temporary fixes that need to be replaced with permanent fixes on this car. Brake ducting, heat shielding, rewiring, tire clearancing, body repairs... Oh and of course upgrades. Because I can't leave anything alone

 

Dude hell yeah! Congratulations on a successful weekend and very glad to hear you had an issue free weekend. That seems like an insane course.

 

Can't be mad about that! Glad the car held up for you and judging by the proximity to the grass in those photos it looks like it performed too! Congrats on the podium!

 

Had a mini heart attack watching that oversteer correction in your final turn. Congrats on the result and not having to spend hours under the car! This thread continues to be one of the most entertaining on the site lol.

 

Duuuuude I was shitting a brick in the car during that. The car went from being fully loaded on the LH side to just scooting across the entire road and into the grass in the blink of an eye. Was absolutely nuts

So originally the plan had been to make the trip up to VIR for a HPDE day late September, and then finish off the season with a local event at Road Atlanta. Unfortunately due to circumstances, the day at VIR didn't work out, so I was going to be sitting around till November. Big espresso depresso for a few hours until I started shopping around to see if there was another event I wanted to attend in that timeframe... bingo, Gridlife was having the season closer at Pittrace middle of October. Long drive, but I've done similar.
This did give me an extra month of time to work with though, so I hopped into something that's needed to be tackled for awhile.. the electrical side of things.


I built the original wiring harness for this car back in 2021 when I first Kswapped. Over the years I've added and modified things to it, and over time the wiring kinda got to be a mess. "oh I need to power a boost controller, just tap into the ECU power" "I need to add a 50amp supply for ABS, steal one fuse from the bussman and throw an additional relay somewhere else in the car" "Hmmm I went from a walbro 250 to a 350, hope the wiring is fine with the extra amp draw..."
Anyway as you might remember a few things in the car have smoked themselves this year so I decided to put an end to all that. Ripped out the entire body harness and upgraded to a PDM


I already run the Maxx Race ECU, so while I did look at an ECU masters or Link PDM, the Maxx PDM20 was the easy choice for integration. The ECU and PDM talk to each other through canbus so controlling things should be fairly seamless. And since I was moving from old fashioned relays and fuses to a solid state PDM, I also deleted the old-school switch panel with its single use switches and buttons, moving to a programmable canbus keypad.

I ended up mounting the PDM behind the passenger seat. The "normal" area up by the firewall is already filled with brake lines, ABS, an ECU, and the power steering motor. Locating the PDM behind the seat means some additional wire length was needed, but access was maintained and its out of view while driving. The main power cable already went through this area so tapping it for the PDM was easy and didn't require me to fully rebuild any cables, just cut and add two connectors.




After the PDM install I had the weirdest issues... the engine would keep cutting out under load/higher RPM. I initially figured it was probably an ignition misfire, so pulled a few logs and realized it was actually a full sync loss. Doing a deep dive showed the ECU kept missing a few teeth from the crank trigger, but the signals from the intake cam(VVT) were solid, as was the exhaust cam(Home). The Maxx has a built in oscilloscope so I was able to look at the raw signal voltages in real time without any kind of filtering or smoothing getting in the way, one of the very handy features of the Maxx. And yup, it was just straight up.. not seeing a few teeth.
Each spike is a tooth going by(or the voltage "going high"). The voltage collapsing to ~zero is the end of the tooth(and is where the "falling edge" term comes from), and you can see this one was both missing full teeth(as indicated by the half/zero spikes) and then reading two teeth as one(the spike that flatlines high). Very weird behavior, and coming off doing a LOT of wiring work I figured it had to have been something I did.


So I rang out the entire engine harness, induced vibration to everything, checked for bent/loose pins, loose connections, bad grounds... nothing, all checked out. Ulgh, this ment it was probably the sensor itself. Since I have an R40 block, the crank sensor isn't on the front of the motor like a normal K, its buried next to the MBSP/crank gudle/upper oil pan(whatever you prefer to call it) at the rear of the motor reading a 60-2 trigger wheel bolted to the crank. In a Miata with stock subframes this gives you about 1/2" of room between the motor and subframe to get at this guy, so I had to pull the lower exhaust, loosen one engine mount, jack the motor up, and cut down a 10mm socket to get at it. Not fun.


The spare sensor in my bin was a brand new Delphi, bought new back in 2021 and had never been used. Threw it in and.... SAME THING BUT WORSE! Instead of missing teeth at high RPM it would do it at idle. wtf??? So I grabbed a used OE sensor I had laying around in an old block and threw that in... runs great. Whats the chances of having 1. An OE go bad in that manner, 2, a brand new aftermarket sensor go bad in the exact same way???
Anyway put the car back together and bought a brand new OE sensor to go in my spares box.

Oh and while doing all this work around the FR of the car, I realized my lower ball joint though bolt had pissed off at some point. Probably during Dragon. It also wallered out the lower control arm during its struggle for freedom so I had to pull the whole arm and repair that. Yes it looks bad but with some welding it's a roundish hole again, not an elongated oval.



So with the rest of the suspension bolts checked and locktied(before they were only torqued...) This car should be ready for Pitt. Which is great news, because just a few days ago we received word Pittrace has been sold to land developers and will no longer function as a racetrack after 2025. So Gridlife there will be one of the last events it ever holds.

 

Built in O-scope on the ECU is pretty awesome. I had no idea Maxx had that. I'll throw that video up on the garage TV when I'm swapping out my master/slave cylinders tomorrow.

 

*Final boss music plays*

I'll be at the track as well the weekend of Pitt, but I'll bookmark the livestream to watch in the garage the following week. Can't wait to see this thing on track again!

 

Enjoy the extra content you give here for the MT folks. Good work as always. Nice seeing some continuous improvements

 

 

F

 

I might not be tall enough to ride this rollercoaster anymore

 

Oh God, what now?

 

Suffice it to say the built engine has low compression.

 

I haz many sads for PGH and his sweet ride.

 

Spontaneous engine de-building? That sucks! Damn K24s..

 

Yall beat me to the punch as normal
This car man... I swear...




So yeah, this Gridlife weekend at Pitt was gonna be hyyype. Last major event at Pitt, my first time there, looooong 13hr tow from GA to PA, "big" field of 8 cars in unlimited... I was pretty excited for it. Weather in the mornings was cold enough to leave frost, the forecast for Sunday all but guaranteed rain, I was anticipating a podium finish and some airtime on the livestream.




First session Friday morning was nothing special from me- I went out on my DE spec RC-1's and just tried to focus on learning the track. I got lucky and was gridded right behind an ecoboost swapped ND that I knew had a good driver in it, so I left the car on low boost and just focused on chasing. Got 4 good flyer laps behind before he waved me on by and I was on my own- I kicked the car into high boost mode but everything was hot and kicked the EGT and coolant alarms almost instantly. I bought it in with a time I knew was wayyyy off what the car was capable of, but was enough to put me top 2 in class. I wasn't super worried, I had 6 sessions still to go to learn the track and set something more representative.

I didn't get a chance to look the car over thoroughly after session 1- the radiator cap had done some funny stuff and dumped coolant all over the bay. We used the time in-between session 1 and 2 to pop to a local autozone and grab a new cap- I normally have one on hand, but I think I loaned it out to BRZ Seth way back at Norton during his headgasket issues and forgot to replace it. I started the car 15min or so before session 2 to warm it and it just sounded... odd. Like there was extra air being moved around, or something was loose.... And that's when the weekend really started to nose dive.


Yup, that is a cracked TURBINE HOUSING. Not the previously cracked and welded manifold, but the turbine housing itself had cracked though 70% of the flange and was holding on for dear life. I was literally stunned as this was a failure mode so unforseen I couldn't have come up with it in a thousand years.
I scoured the paddock for a welder, but it seems this was the weekend EVERYONE said "nah" and left the welders at home. Not even the drifters had brought anything. I pulled the manifold and turbo off the car and popped "fab shop" into google. As luck would have it, the one place you can count on to have lots of local welding shops is industrialized Pennsylvania, as there was a metal shop just 10min away. The welder I talked to was reluctant at first, as we didn't have a way to preheat the housing, and only had MIG on hand when this was really a TIG job. I promised I was not looking for a long term fix and eventually convinced him to lay a bead of weld on it.
That vband clamp was now 100% just there for show, as the manifold and turbo were now completely made one.


I got the turbo back on with time to spare, a quick bleed after having the turbo coolant lines opened and a few minutes at idle to make sure it didn't immediately fall off and she was ready. I had missed session 2 during this whole incident, so I was eager to get back out and turn some laps. I left the endro RC-1's on, saving the nice A7's for when it mattered, but kicked the car onto high boost from the get go. The pace from the two cars ahead of me was... not amazing, but it ended up not mattering at all, as less then half a lap in an extra noise started with some additional vibration as well. I honestly thought this was the welds on the repaired turbine failing and the turbo was now vibrating against the manifold, but said **** it, I'll finish the lap at least to solidify my spot in the top 5 and give myself a full day to repair the car.

It didn't make it through the lap.
(ignore the camera rattle at the start... you will know the real rattle when you hear it).

I found a nice spot to park and chill with the safety crew. I couldn't find a hole in the block, no fluid were dumping, but I could hear an empty cylinder when cranking it over. I knew something bad had happened and suspected the motor was dead, but didn't know for sure. After the session I was flatbedded back to paddock. Pulled the plugs... no mechanical regapping. Pulled the valve cover... found the rockers for #4 intake valves had 1/4" of lash in them, so definitely some malice in the combustion palace. Stuck the dipstick down the spark plug hole and manually turned the motor over... no movement. #4 piston was stuck at the top of the bore, now sporting a disconnecting rod.

Weekend over.



I pulled the ECU data from that session and it confirmed that I hadn't imagined the extra vibration. You can see the normal noise levels during the warmup/start of the lap(highlighted in white), then a steady increase in noise until everything goes quiet. Motor let go at 5700RPM, 230KPA, 38PSI of oil pressure, and 206* coolant temp.



I got back home early afternoon Sunday and by nightfall had the motor out of the car for the autopsy.


My first clue that this would not be a case of "pop a new rod and piston in and fire it back up" was an exit attempt in the passenger side of the block just aft of the motor mount, small but enough that a 6" puddle of oil had accumulated on the trailer during the drive home.



The rest of the teardown pretty much confirmed my suspicions. I'll let photos do the talking.







Leading theory is the rod bolts let go. I have video of me torquing them so I know they weren't loose upon install, and they lasted 3 track events and 3 hillclimbs, plus a few hours of street driving so improperly tightened rod bolts is all but ruled out.
ARP rod bolts failing is also unlikely but that's what I think happened here. While the remaining bearings aren't exactly what I would call perfect, they don't look anything approaching rodknock territory. 3, 2, 1, pictured, I found #4 hanging out in the pan and oil filter in the form of flakes and glitter. The rapid nature of the failure tells me the bolts loosened/failed enough for play in the bearing, the bearing was beat to snot in a few corners, and finally the rod itself exited after beating the crank directly.



So now's when I would post some photos of my extra spare spare block getting delivered to the machine shop, some space-age titanium rods waiting for install with ARP-giga-ultra-supreme-times-1,000,000 fasteners, all while signing up for an even two weeks out to add the pressure but honestly... I'm beat. 85% of this year has been akin to franticly stopping a lunatic from jumping off a bridge to their death. Where the lunatic is my motor. That turbine housing cracking in half was really a final straw for me even before the motor emptied its guts. Bolts I can drill and safety wire. Lines I can wrap and heatshield. Exhausts I can brace and support. Suspension items I can locktite. But how on earth do I prevent a solid, cast stainless steel turbine from snapping in half?

I know this was said in(partial) joke at the start of the year, but now I've arrived at that reality. If I were to stick with the K24 I'd be starting from essentially scratch. New head, would need guides, seals, and 2 replacement intake valves. A new block would have to be resleeved, all new hardware and crossed fingers whatever happened to this motor doesn't happen again. I cannot bring myself to do this all over again, mentally or financially.


I don't know what motor will go in this car next, but it will not be another K24. I finally reached my limit and I'm done with them.












I'll hit a few highlights because I know they will come up immediately.

"why not go K20?"
K20 is the obvious switch. K20's do not suffer from the same vibrations the K24 does and are very smooth, high revving engines. Would use all the same adaptor parts, manifolds, and supporting mods. But the loss of the the .4 liters is even worse then going from a BP 1.8 to a 1.6. Spool suffers, the same sized turbo comes online later, and you have to rev out to 9-10K RPM to have an acceptable powerband. This would not work at all for me in hillclimbs where I need low end torque, and a 10,000RPM boosted screamer is a ticking time bomb by every metric. Additionally, the lower block height means the turbo manifold, already tight to the NA miata frame rails, would now occupy the same space as the passenger frame rail, and would need extensive cutting, boxing, and welding to make work. Doable, yes, troublesome, also yes, sub-optimal, absolutely.

"Time for an LS swap"
LS is the easy button. Its tried, true, is easy power and there's a known, tested formula for reliable power. Junkyard aluminum 6.2L motors are reasonable prices and will make a solid 550/500whp with the right combo of heads/cam/exhaust. With a drysump or accusump system the oiling isn't a concern.
It's ******* boring and doesn't excite me whatsoever(sorry Padlock, nothing personal). Everyone and their mom has an LS of some form and benchmarks for performance. A normal run of the mill LS swap isn't challenging, isn't groundbreaking, and frankly doesn't excite me at all.

"1.6 swap it" **** off

"LFX/J35/Jag V6 for lightweight power!"
LFX is a legendary engine. Its my honest to god most favorite motor for a fun Miata(Hi Rob). But the performance out of the box isn't competitive for what I need, and adding FI to a limited aftermarket, direct injection engine is its own headache.
J35 is alright but the performance is still less then the LFX and the kit's(unless things have changed) method of mounting is... ehhh....
The Jag V6 is a terrible motor and that's all that really needs said.

 

Ouch, I feel you man, this must be gut-wrenching, so sad for you.

This is what I'm really here to shoot the **** about... I'm with you on all of these, except maybe the LFX. For my needs, it seems about right, though I'd probably just detune a LS because reasons. My other concern with both of these swaps is the reliance on another sole-source vendor with shall we say, inconsistent quality control.

There's always the Ecotec swap, but honestly at your power levels that's going to be another 4 cylinder asked to do an 8 cylinder's job.

There seems to be a missing evolutionary step in V6 engines where they're modern enough to make decent power, compact enough to fit inside the Miata engine bay, and don't rely on DI. That space seems to have been taken over by boosted 4-cylinders. Oh, and everything longitudinal these days seems to have a front sump, just to really screw us.

I'd have to guess Cyclone or Ecoboost, though seeing as you ran with a ND Ecoboost, you probably know more about that solution than I do...

 

I'm gonna be "that guy" and offer up the Dorito suggestion. Just because you obviously need a LESS reliable engine and I want to see a crazy miata with spinnythings .

But there's also coyote (doubt that such a wide/tall engine fits your bill)

Or go way out of the groove and put some angry pixies and magnets in there (electric)