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Good progress brother and Impressive as always. Scary moment with that turbo going out like that but seems like you might be in the clear .
Cool stuff with that Mazda built turbo NC! Would have love some more pics of the interior and the wiring work on it. And hell yeah for Miata bros swapping parts, and 12:1 comp NC! Gotta go watch that build
Dudes, the built NC was super sick and I completely failed by taking only one picture of it. Fully gutted/caged, MK60 ABS, racedash, full custom wiring harness, etc etc. The top was a single piece of molded dry carbon fiber made by one of his buddies and weighed only six pounds. No rear window so it's got a rear view camera screen where the center mirror would be. Thing's a beast.
Minor hiccup on installing the blue azz wheels. The 17x9 RPF1's don't fit my front brakes even with 5mm spacers! Maybe next weekend I'll remove my rear 5mm spacers and double up the fronts just so I can install em for sh*ts and giggles. I'll get a pic with better lighting this week, but I honestly really like how the rears look on the car haha.
How's that noco battery treating you? Was it the Noco NLP20? Currently battery shopping for my FD and considering one. If it runs your miata it should run my FD no problem.
Yeah, I'm running the NLP20. It's been working just as good as my old Antigrav for about three months now. Don't have any worthy long-term data on it but it hasn't had any issues starting my car on colder mornings or anything. I'm keeping the car on a tender now so we'll see how long it lasts.
Since I'm making a post anyways: I tore down the $50 secondary backup engine today.
Everything looked good, except the cylinder 1 rod bearing and journal. One half of the bearing has a notch in it, along with some damage that catches a fingernail. #1 rod journal has a matching score that catches a fingernail. #4 rod bearing also has some wear but not as bad as #1.
#1 rod bearing. A lot of that ugliness near the top catches a fingernail.
Radial score mark on the corresponding journal catches a nail.
All four of the rods/rod caps seem to indicate the bearings were walking around as well. I don't remember seeing wear like this on my other Duratec that I fully tore down.
Main and thrust bearings look good tho.
The damage on the bearing and journal are bad enough that I'm not going to just hone and slap this engine back together. After buying a set of rod bearings, getting the crank turned, head gasket and new one time use hardware, putting this engine back together will cost more than just buying another used one. That being said, it's an absolute perfect candidate to throw a 2.3L EcoBoost crank in (destroking it to 2365cc) and build into a full forged motor. I'm gonna leave it torn down and keep it for that purpose, some day way off in the future.
Turbo showed up Christmas Eve around noon. It was raining out and I had nothing going on until the evening, so I got it installed, fired the car up for a minute, then did another (third) oil change to try and get rid of any metal shavings that might still be sitting in the oil pan. Didn't find much of anything when I drained the oil filter onto a paper plate, but haven't gone deeper than that. I'll be cutting the filters open this week to see if any shavings are ending up in them.
Spoolius Caesar back from vacation in Florida. Now with 10,000% more ceramic coating.
The rain subsided for a bit on Christmas, so I took the car to our family get-togethers. As usual, it was a crowd pleaser among all of the extended family haha.
Friday, I took the car to work and did a couple quick health checks on the engine. Compression test, borescoped the cylinders, and checked the plugs for any signs of detonation.
Drumroll for the compression test numbers... 85psi on cylinder 1, 90psi on all others! Warm, dry. Valve overlap with big cams is a b*tch haha. I knew the numbers would be low due to the cams, and was very happy to see even numbers on all cylinders.
Borescope findings were promising too. Cylinder walls all look nearly mint with good crosshatching. Piston crowns all had some weird texturing to them that at first glance I thought might be detonation, but I compared them to the OG 2.5L's pistons and they look exactly the same, so I'm not worried.
Sample piston crown. I thought this looked alarming until looking at my other engine. All four pistons in both engines look like this and you can see it's carbon buildup if you look through the spark plug bores with a flashlight.
Cylinder walls. This is the worst score mark I found in any cylinder.
Then I checked the spark plugs again, which all came out looking good. Of course I ended up knocking one off my workbench and cracking the insulator, though. Needed to drive the car home so I referenced NGK's website and found that the plugs from 2.0/2.3/2.7/3.0L EcoBoost engines are a heat range 6 (one range colder than the stock 2.5L plugs) and share the same dimensions. I've got a ton of those plugs laying around so I gapped four down to .034" and sent it. Car runs great on said plugs so far. I'll pull them next week to see if they're fouling or showing any signs of preignition. I assume they'll be fine. Part number for these plugs is CYFS-12Y-RT3, if anyone out there reading this is in a pinch.
This is just a spare I threw in my bag. More worn than the ones I threw in but should still work fine in a pinch.
Upon pulling the OG 2.5L apart last week, I found the valve cover ventilation baffle was loose and about to fall off, so I decided to check the baffle on my current motor as well. The aftermarket aluminum covers use rivets to hold the baffle plate in place and they'd loosened up on the OG motor, allowing the baffle to rattle around. I popped the baffle on that VC off pretty easily with a panel popper and will be drilling and tapping the mounts for M5 bolts instead, and installing with lots and lots of red loctite, or maybe even hi-temp JB weld.
Chopped the rivet heads off the OG valve cover, just need to drill and tap now.
I pulled the current motor's VC yesterday and luckily the rivets holding the baffle plate on were still very tight. Cams look good too, almost zero signs of wear. There are a couple voids in one or two of the lobes, but I remember those being there when I first got them. Not sure if that's a sign that these were manufactured sloppily but it doesn't seem to be causing any problems at the moment.
Went and hit the mountains today with a buddy and put another ~160 miles on the car. Oil pressure's spot on where it's always been at all temperatures and RPM's, and she's running smooth as she ever has. Gonna take an oil sample and cut open the filter tomorrow for another inspection. Hopefully I got all of those metal shavings out of the oil and there aren't any new ones lol. If all's well enough, I'll likely sign up for a track day at Chuck next weekend and see about getting this car on the dyno soon. If not, the motor's getting swapped next weekend.
The LKQ an hour from me has a handful of these motors for sale at under $300 currently. Might pick up another spare if they're open on NYE as well...
Last edited by Z_WAAAAAZ; Dec 29, 2025 at 12:38 AM.
Glad I at least contributed one thing with that turbo name this week
Ahh yeah, those machining marks (can you even call them that?) are because the cams are regrinds. Looks like Fab9 welds on additional material for their cams. The other Esslinger cams in the OG motor are a little different. They grind the lobes down to a smaller diameter and broader shape and then use 3mm lash caps under the buckets to take up the extra space.
I have no idea why the side of the lobes look like that though. That's above my pay grade. The stock cams definitely don't look like that.
Checked clearance in the rear with the 255's today. After carving the canyons and hitting numerous hard compressions on the freeway yesterday, it looks like the tires are only making contact on the outer edge of the fender tubs and the inside of the rear bumper, which I was not expecting.
Tub rub.
Lil rub on the inner bumper liner. Easy fix.
Also I forgot that in order to sign up for a track day, there have to be spots open. Went to sign up for the track day at Chuck on Sunday and forgot that these things sell out. I messaged the organizers to see if there's any chance in heck I can get a spot if someone backs out. Rookie move on my part haha.
No track this weekend so I booked a dyno slot for tomorrow morning. Swapped my rear wheels back tonight in preparation.
My loose plan is to see what she makes on the current tune at 7psi, optimize spark and VVT, then up the boost depending on results. I'll pull the plug at ~320whp, and am gonna shoot for 285-295whp for track use. I'm currently running 18-19* of ignition advance at 8psi, and haven't messed much with VVT (set to 25* until 5k rpm tapering to 10* above 6k.) With the current setup, I think I've got a lot of headroom as far as ignition advance goes, but I guess we'll find out more tomorrow.
Dyno day done and dusted and the numbers did not disappoint! A small bummer, when I showed up to the dyno, the car spat out some oil smoke getting on throttle after idling for an extended period of time. I have reason to believe the turbo oil seal is to blame for this but that's a problem for next week Zak. F*ck that guy.
Otherwise, this morning went about as smoothly as I could've expected, and we were done in exactly an hour!
After I installed the turbo, I did some spitball math using the MAF sensor readings and figured it was making about 260whp at 6.5-7psi. Then I realized I made an error and my revised estimate ended up being closer to 280whp. We strapped the car to the dyno for a 7psi baseline pull this morning and it made 282whp on the first shot. Super sick, already pretty close to my target.
With the first pull done, I told Toby that I wanted to mess with ignition and VVT before upping the boost. I started with VVT. Toby's advice was to start with exactly what the engine liked when it was N/A. I copied my atmospheric rows into the boost rows, going from 25* to 33* in the midrange, and adding 10* of advance above 5,500rpm, for 20* at redline like I was running when the car was N/A. We did another pull and it made basically no difference aside from losing a tiny bit of power up top. I reverted to my previous settings and moved onto spark next.
Log of the first two pulls showed 18-19* of ignition advance across the board, so I set timing to 21-22* for the next pull and sent it. No change in power aside from a marginal (8ft/lb?) increase in torque from 4.1-5.5k rpm. I figured we were probably getting into the area of diminishing returns, so I pulled the timing out and we moved onto boost.
First three pulls. Red is the baseline, blue with modified VVT, green with additional spark advance.
Next was upping the boost, which was quick and easy using the MBT instead of having to reflash the entire tune between pulls. I upped my overboost protection from 9.5psi to 12 and we started turning the magic ****. First pull at ~7.5-8psi made 291whp/265wtq. Bumped that up to a 9 and then 9.5psi and made 303 and 306whp respectively. At that point I almost called it, but ended up playing the fool and gave the MBC **** one more turn, resulting in 10.5psi for the final pull. 320whp on the money! Yep, that's enough. I pulled the plug after that pull haha.
Haha, thanks all! Yeah, the powerband is perfect. Kinda lazy to build boost before 3.5k rpm, but after that the power just keeps coming. It looks like it'd still make a touch more power after redline, but I'm sticking to the 6,800 rev limiter to be "nice" to the motor.
Sim, I also don't want to start tearing through transmissions. I allowed myself some pulls at 320whp on the way home but then turned the boost controller down once I got back. Gonna run it at 290 for all scenarios unless I'm just off the podium at a race and need to give 'er the "kill tune". My WHP limit for the car's race class this year is 334 but based on last year's class times, the car should still be proper competitive at just under 300whp.
The turbo seal remark was a knee-jerk reaction on my part. We get lots of vehicles in at my work that exhibit this same concern. Bring the car to a stop and let it idle. No smoke from the tailpipe. Let the car/truck idle for an extended period of time (sometimes up to five or ten minutes). No smoke. Blip the throttle or put the engine under a bit of a load, big smoke poof out the back then no smoke till you rinse and repeat. Blown turbo seals almost every single time.
Could totally still be valve stem seals, I just expected to see more consistent smoke out the tailpipe at idle and decel if they were the culprit. Cylinders were dry when I scoped them last week, but I'll borescope the intake valves on Monday.
Can confirm. I blew up my NA's 6 speed on a Saturday as well.
There's less of a general consensus than on the NA/NB boxes, but it seems like the 5 speeds are good up till about 300whp, and the 6 speeds are good for 350whp, or maybe a bit above. NC2/3 6 speeds also have a couple beefier components than the NC1's, namely the 3/4 shift fork which apparently likes to break on the NC1. Luckily Mazda Motorsports sells individual parts so if I blow a shift fork, I can pop in an NC2/3 part and be on my way. I also have my 5 speed sitting in the garage as a backup, but will have to get a clutch disc to run it with my SuperMiata clutch (the NC 5 and 6 speeds have different input and output shaft spline counts).
Dove deeper into diagnosing the smoking issue this week, and did some routine engine health checks along the way. I started out by pulling the injectors and borescoping the intake ports. By some stroke of misfortune, all four of my injector o-rings broke when I pulled the fuel rail, which has never happened to me before. The Injector Dynamix o-rings where the adapters meet the cylinder head are super thin compared to standard sized o-rings, though, so maybe I should've seen this coming. Luckily I had some similarly-sized o-rings sitting around at work and was able to use those. Threw a bunch of extras in a bag and tossed them in the glove box in case I need 'em in the future.
So I found some oily buildup in the intake ports, which I thought was a smoking gun at first.
Luckily, I had the OG 2.5 sitting six feet away and was able to use that as a comparison. Exact same deposits on the intake ports of that motor, and it wasn't smoking back when I pulled it out. I mean maybe the valve stem seals on my current motor are bad, but I think those deposits are from fuel/combustion gases getting blown back into the intake ports at idle due to valve overlap. I'm running both of my crankcase breathers VTA, so no other vapors should be entering the intake ports.
(OG 2.5 intake ports)
To follow up on this, I pulled the spark plugs and found a whole lot of nothing on the plug tips. I'd expect to see some deposits on the side electrode and center electrode insulator, but nothing. I've only had these plugs in for two weeks and a few hundred miles, though, so maybe they haven't had enough time to "absorb" any notable oil vapor yet.
Looks like there's a handful of white dots on the side electrode but that's a product of the lighting/reflection.
Not entirely related to the smoking issue, but since I was already doing various engine checkups, I figured I'd do a leakdown test as well. All four cylinders showed 20% leakage at 90psi, same as the day I finished putting the motor together, so nice win there. I didn't suspect rings to be an issue, as I couldn't feel any excessive crankcase pressure buildup or fuel odor in the oil. However, it's nice to know the engine's still sealing as well as it did on day one.
Somewhere in the midst of all these tests, my ADD took over and I decided to change gears. Busted out the fender roller and pulled the front fenders a bit to ensure there's clearance for the 255's when they go on.
Then I made a little gurney flap for the wing out of some 1/2" aluminum angle I had laying around. It's got about 3/8" of protrusion above the trailing edge of the wing. Figured it might come in handy while I'm figuring out aero balance with the new 6" splitter.
Decoupled the downpipe and stuck a borescope in the turbine housing to try and see any oil residue. No joy, but I did this after getting home from work and letting the car cool all the way down, so maybe any oil that was in there burned off by the time I checked. I'll have to retry this test when the engine's colder, it might be a bit of a PITA since the car doesn't smoke on cold starts.
Smoking aside, though, I'm super happy to report that I took another couple oil samples today and found zero metal particles in either. I'm actually happier about that than I'm bummed on the smoking issue, so this week has been a net win so far. I'll cut the filter open soon and take a look in there, but for now my nerves regarding the metal particles I found last month are at ease (even though it was most likely shavings from the decomposing turbo bearing the whole time).
Next up: replacing the turbo oil drain tube with some clear tubing so I can see what's going on in there, and borescoping the exhuast housing again. Oh, and signing up for some more track days, I gotta see if I absolutely need to respring this car with the 255's before NASA Chuckwalla on Feb 21-22...
I assume the clear oil drain tube is temporary just to make sure things are flowing like you want? If there was some type of clear nylon tube that would hold up in that environment it would actually be pretty neat to leave that on the car full time.
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