Awesome! I look forward to seeing it!

 

Update Time!

After the new crank sensor and new trigger wheel, she fired right up!! I only ran it for about 7 seconds because it was too cold to take her out. I gapped the sensor to the wheel down to .012" per Curly's recommendation. The problem with trying 3 things at once is you don't know which part/technique actually solved the issue but I'm happy with the end result regardless.

If you take a look at the Fab9 trigger wheel, you can see the teeth are smaller in stature and the holes never lined up when I got the piece last year so I had to drill them wider. The Flyin Miata piece is just so much better in every way and fit was perfect. I've had some issues with the aforementioned company and will not be using them for any further purchases. Flyin Miata is just by far and away the best miata company out there. Of course theres others for OEM replacement parts that are great too, no disrespect there! FM just puts a lot of effort into R&D and engineering and it shows.






She finally saw the sun this weekend as I took her out on Friday and Saturday. Friday I drove about 1/4mi over to a side street and just went up and down about 10 times for about 3ish miles just doing light load pulls and staying in gear for heavy vacuum. Then yesterday, I went around on town on some more main roads doing heavier pulls, staying in gear longer, varying RPM. Got about 15 miles in so far, no obvious leaks and things look really promising. Pulling 20psi in vacuum according to my gauge.




I have the internal wastegate physically wired open to not generate an ounce of boost on accident until I get a couple hundred miles in. I noticed I was running pretty lean using the same tune as I was before. If my knowledge of engine theory is correct, that would mean my volumetric efficiency is already better as I've had to increase the number in the table, aka more fuel. So I think the rings are seating better already. I pulled the first oil filter off and the oil looked good. Unfortunately, its a brute of a filter so I can't cut it open without getting metal shards all over and then I wouldn't know if it was from the engine or not (I tried lol). Got a cheaper one on there now and will pull it around 100 miles and cut it open.

I was also reflecting on what went wrong the first build and had another thought. I had the Fab9 heads studs on there torqued somewhere around the 85-90ft lb range. I believe this may have distorted the bore and changed the P2W clearance, causing the bad seating and blowby. Just another small piece to the puzzle and only a hunch. This time around, running ARP at 65ftlbs.

Looking forward to my next weekend where I can set base timing, burp the cooling system (she was a lil hot after my drive) and just start getting miles on her! Thanks for reading

 

Glad to hear you're up and running Matt.... congrats. After my own build experience, I'm now leery of Fab9, and prefer other vendors like FM, for better quality, service and delivery. For your fueling changes, I'm wondering if you also upped your displacement (1.884L?) to account for the overbore, which slightly changes the fueling equation and adds some fuel. There is also that change in compression ratio with the new pistons.

 

Thanks Mark! Hope once I re-introduce boost it stays this good. I'm currently logging and diagnosing why it likes to die when coming to a stop or when you free rev it and the revs come down too fast. I'm thinking of trying turning on engine states after reading a Braineack post.

All I did was a new hone, its the same displacement as it was the first time around (84mm). I'm going to go to the Castle Rock meet Sunday morning, hope to see you there!

 

I would have loved to come on here with good news or talk about the nice new shelves I built in the garage, the 240v outlet I wired up with a self-designed and printed outlet. Or my first couple welding projects for the car. Or the countless hours I spent tuning it to run and idle well. Unfortunately, none of it matters.

700 miles on the engine. Did the break in oil change at 500 miles, oil looked fantastic, as did the filters. Bought a borescope and decided to look at it before I plug the turbo back in and start boost tuning. As I feared, the bores look like ****. Same issue as before with tons of scratches all over the thrust and anti thrust side in all cylinders. Haven't done a leakdown test but doesn't matter, the walls are absolutely awful. (date isn't accurate in photos)







It probably needs a new block, I don't think the bores are round and I am blaming the first machine shop for that. But it doesn't matter. I don't have the heart to build this engine for the third time and throw another $2k and 200 hours into it. If anyone wants to make me an offer on the car, shoot me a message. I'll list it locally but will likely just part it out and sell it as a shell to try and get some money back.

GG's Minny

 

They are most likely just wipe marks. It doesn’t look that bad. You might be a bit low on the PTW clearance. Do a compression test.

 

Reading your thread makes my heart hurt for you ... but, I agree with the last comment. Don't give up quite yet, as vertical marks like that can look worse than they are. Compression and leak down needs to be done first, and it may be fine. It seems unlikely the machine shop would have made an oval bore, but I guess its possible.

If compression is even and its not actually doing anything funny, just send it.

Btw, it's pretty simple to check bore roundness. I have a little set of gauges I bought way back for like $25, and they have been nice to have a few times now.

 

Good morning! The emotions have subsided and I'm not going to throw in the towel just yet. Thanks for the support y'all, it really means a lot.
I will absolutely do a leakdown and compression test before making any further decisions, probably next weekend.

P2W was .004" per the shop that honed the bores the second time around, which I think is actually on the high side? I have also had the thought of just sending it but these marks were there for the first build and it was causing a crap load of blow by and pressurizing the crankcase. I have also thought saying screw it and just driving it like that and treating it like a rotary by adding oil every tank lol.

akaryrye, I don't suppose theres any way to measure roundness without pulling the head off? I'm just at an absolute loss for what these marks are being caused by if its not out of round.

Other thoughts are scrounge what I can out of this by selling it and getting an s2000. Or maybe K swapping this chassis and leaving it N/A for a season so I can actually drive and enjoy it. Or just LS the thing since its probably the price of a K swap and I'd rather put the money towards that before building the B series again. Forced Induction is fun but the simplicity of N/A from a maintenance and tuning perspective sounds so nice right now haha.

Will update next weekend, thanks again guys!

 

They are not deep score marks. There is still remnants of cross hatch across many of them. I have seen these on many engines including many very good running units. Even my current engine has some. Check your tuning and use good oil. If it runs well keep using it. Good luck.

 

Hey Leo, that does make me feel better. I've had a hard time researching these score marks and their origin or effect on the motor. Where those N/A or forced induction motors? When you say check the tuning, do you have an idea of what would cause that? Only thing I can think would be timing or way too rich but I've gotten it to idle 14.3-15.0 and the auto tune has been doing a bang-up job getting it close to 14.7 under partial throttle and close to WOT. I'm worried the second I plug the wastegate actuator in and hit even 5psi I'm going to see the same problems I saw before.

 

Both NA & FI. When you run boost make sure you’re safe with the timing and AFR. I doubt over fueling is the root cause. Could be cold seizing. The piston heats up/expands much faster than the coolant filled cast iron block.

 

Compression test results were...not great, but I expected that. Drove the car to operating temp, dry test, wet test and then leakdown so there was oil in the cylinders during the leakdown, which I'm sure helped.

Guess its decision time now. Sell or rebuild with a new block and probably new pistons just in case. My biggest fear with rebuild is that I tear it down, measure and find out the bore was perfectly round and then I'm totally stumped. Or I sell it for about 30% of what I got into it and move to a different platform like an s2000 or something. That is appealing since the entire drivetrain is incredible but the F20c is also not an easy engine to rebuild when it comes time. I'm going to take a few weeks to ponder but I am totally open to input on here as well.

 

I don’t believe those are accurate leak down numbers. Why would cylinders 2&3 be so much higher than 1&2. It also doesn’t coincide with the comp test. What is your c/r?

 

Yeah I'm really not sure but I think they might be up to mid 30s even since I'm using a crappy Amazon gauge and the set level drops well below 0 during hookup.

9:1. I realized I didn't hold open the throttle during my comp tests, would that make a big difference? It just seems those comp numbers are really low and 23% leakdown isn't horrible but I was expecting <10% on a fresh build.

For those that can't se the pic or my handwriting is bad...
1: 110dry / 120wet / 5%leak
2 :115 / 130 / 23%
3: 110 / 130 / 23%
4: 110 / 125 / 6%

 

Yes it'll make a difference, not sure how "big". I would redo the test, also doesn't hurt to put a charger on the battery while you're doing the test. I have a medium sized charger where you can switch charging amperage, a trickle charger won't help.

 

The biggest affect on a compression test is the cranking speed, cranking time followed by the throttle being open. If you use a long cranking time it will minimize the affect of the throttle not being open. Some will crank until the pressure stops increasing. I use a count. If possible I prefer to have a battery charger connected before and sometimes during the test. The test is obviously affected by the scavenging which is speed and airflow sensitive.

The std leak down tester uses a .040” orfice which is fine for the original application which was a 1000ci engine. Obviously we are working with much less displacement and should be comparing the leak rate to a smaller orfice. I’m not sure if I have ever seen any vids or instruction of someone using one correctly. With that said since there are several variables it is a test that should be used as a relative measurement. Comparing one cylinder to another or an engine with use to when it was new. Pressurizing the cylinder can be a good diagnostic tool just by itself. I used to custom build them for road racing bikes. Mainly to keep tabs on how the engine was degrading in use. It is not a good tool to do what you’re doing because there is nothing to comparing it to.

There is a possibility that the vertical lines are from contamination. I would check the oil and filter.

 

Hey guys, thanks for the input. I already unplugged a bunch of stuff but I'll plug it back in and re-test with open throttle and a battery charger hooked up just in case. Cranking RPM is set to 350 for what its worth. And I did about 6-8 compression cycles per cylinder. With the battery charger I'll go to 10 or so this time.
I know running these tests is somewhat relative and with no baseline, its tough to decipher the results. A stock miata engine should be 180-200psi from what I've gathered so I still think mine is super low. I'll try and find another set of tools to verify the accuracy of the results.

As you can probably guess, I'm keeping the car. I can't quit now, no way. Since I'm already hooking it back up to test again, I think I'll just hook the turbo up as well and run wastegate pressure (12psi I think, will double check) to see if I have any blow-by symptoms. If its pissing oil again, rebuild with new block or bore this one and get the wiseco 8.5:1 84.5mm pistons. Probably the same cost either way.

Who knows, maybe it will be totally fine and these marks are superficial, that would be super nice haha.
Going out of town, next update in two weeks. Til then miata fam :salute:

 

Godspeed man! Prayin' for ya and looking forward to the next update.

FWIW, my buddy's built BP6D (which is currently running great and making 400whp with minimal blowby) ran 120psi in all 4 cylinders during a cold compression test. Forged pistons are obviously gonna have more P2W clearance and thus a larger disparity between hot and cold compression numbers, but just thought I'd throw that out there.

 

That is a great point Z, higher P2W clearance would mean lower compression just with the higher tolerances of the ring gaps. Good input!

So I plugged everything in, hooked up the turbo running wastegate pressure on a 7psi spring and slowly started letting auto tune work at the VE table. I figured who cares what the tests say right now, the only thing I really wanted to know is if the crankcase is getting pressurized and causing oil to leak again. Well, I've done about 200 miles and have been driving in boost a lot and so far its looking perfectly fine! I'm hesitant to get my hopes up but I'm certainly enjoying being able to drive it in our gorgeous weather right now.

I fixed a coolant leak on the AN fitting going to the turbo feed and played whack a mole with a couple rattles that are much better now. I'm going to drive it at this boost level another 3-500 miles then re-test and chuck the camera in the bores again and see whats what. As long as it all looks the same, I'll throw a 10psi spring in there and turn on boost control and keep on tuning.

Currently researching how to wire up this 15" spal fan I bought a while ago. I have my fan set to come on at 205 but I don't like that it takes a while to go back to 195. I will also work on some very minor ducting to hopefully keep those temps in check as we approach summer and 90*F days.

 

Great to hear that Matt. Sounds like you're on the right path and got some better luck now. I'm about 400 miles into my motor/trans rebuild and all good so far too. Pueblo open lapping is very tempting next Friday to see how some stress testing turns out. I also got FMs Stage 3 fans last year in the Black Friday sale. Gotta say, those are pretty amazing so far. I'm set up now to plumb in an oil cooler but want to see my temps first without to make sure its necessary. Keep us posted on your progress. I look forward to the updates.