Pretty Sure My Engine A-Splode. Please Help.
 

EDIT: I did research, didnt find a situation like this, prepare yourself, if you are an impatient person skip to the all caps.

A long long time ago, in a galaxy far far away...

I bought this "rebuilt" motor from a guy who said the dude (third party) who rebuilt it was fairly reputable (rebuilds a lot of spec miata motors), but never rebuilds turbo motors. Long story short, it sounded like the rebuilder was a bit inpatient with the person I bought the motor from, since he knew he was rebuilding a turbo motor. I thought this was an important detail, but idk I have had a couple beers (5).

This rebuilt motor aparently had forged rods and low compression pistons from a 94 miata other wise bolted up to a 99 motor.

So after getting this motor and marrying it to a FMII turbo kit that was previously use by yours truely on a stock 99 motor for several track events at 10 to 15 psi happily, I buttoned the new car all up and ran 7 psi on the street for roughly 1000 miles.

After this, i thought it was time to turn it up to all the horsepowerz. So i strapped on the boost controller and cranked it to 14 psi (since you know, it had forged rods, itll be fine right?). well when i was tuning, during the 5th pull or so on the way to my boyfriends house, i clutched in after a 9000hp pull to hyper space and the engine died and i noticed some smoke coming from the tail pipe and hood. so I pulled off and popped the bonnet and noticed that i had no light because it was night time. so i pulled my phone out and turned the light on and noticed that there was oilz alll over my hoodz. (ive had 6 beers now).

Once my boyfriend showed up, we discovered our love, and then that i blew my....dipstick.....all over my hood. ........ ... ...... so after that we popped the dip stick back in and cranked it over. ran like garbage but long story short, got it back to my garage (not under its own power). towed mostly.

OK so after pulling my car and much kissing later, i discovered with my boyfriends that it was piston 1 that was not having any affecting the idle after pulling all of the plug wires. Spark was confirmed. Fuel was confirmed.

Ran and coerced the autozone tenant with many sexual favors for a compression tester......and coolant pressure tester.

SO HERE IS THE IMPORTANT PART

Coolant pressure holds 25 PSI no problem.............after we skeeted coolant all over a shitload of facial components and tightened multiple hoses and clamps.

Cylinders provide the following compression results, cold:

Cylidner 4: 160
Cylinder 3:160
Cylindre 2: 160.5
Cylinder 1: ZERROOOOOOOO.....ok maybe 2 or 3

for real though. nothing on cylinder 1. I do not have a borescope to figure out if there is any cracks or bullshit happening.

MY QUESTION IS:

Who wants to do this to my butthole: :vash2: ????

HAHAHA OKOK im sorry. at this point i realize that no one is reading this. but for the hope that someone is:

I get the feeling that my piston rings are fucked, or pistons,

but what are the chances of blowing the head gasket ONLY to an oil galley to over pressurize the crank case and NOT affect the coolant system AT ALL?

Seems extremely unlikely to me, but i thought i would ask the internets.

If you have made it to this point. you win all the thiings. On beer 7

You ran it up to 14psi without checking for detonation or lean AFRs, presumably. Just assumed that your tune from your last setup would be fine, and now you have a hole in the #1 piston. It's not your head gasket. If you're lucky, the rod and block survived. If you aren't, start shopping for a longblock.

What engine management were you using and what wideband?

impatient inpatient

Yeah, you probably have a hole in a piston, although I'm not sure how that gets oil all over the hood -- open cam breather, maybe? The next step is to pull the head off to confirm the carnage.

When you say "FMII" is it an actual complete FM kit, or just an FM manifold? Which electronics? Link, piggyback Link, or Hydra?

FMII means full hardware. Ran MSPNPII with exact timing map as old higher compression 99 motor, but when i "blew this motor" i was tuning for new injectors on the lower compression motor. It is POSSIBLE that i leaned out, but it would have only been VERY temporarily. I was running the TunerStudio auto tuner for the fuel map and I want to say I burned the fuel (to the megasquirt) after a couple of pulls before the blow.

I actually somewhat agree, i suspect that it's the bottom end. The biggest question I would like to know is that is it very likely for the BP to blow the head gasket, but just for an oil galley? otherwise i would suspect its bottom end. Unless it's something stupid.

Would going lean for literally one pull blow a piston ring or crack a piston?

Yes......it literally could.

A hole melted in the piston, would let all of the boost into the crank case, pushing out the dipstick and blowing oil all over the hood.

I can melt a hole through a piston with my welder, in about three seconds. So can your engine in lean conditions .

Ah, I missed the dipstick bit the first time I read the post.

Head gasket failure as the sole cause is very unlikely. Still, the next step for HG failure is the same as the next step for hole-in-piston -- pull the head off to confirm.

As for why, perhaps new head flows better than old one, causing leanness. Perhaps block and head were decked too much, giving significantly higher compression than you would normally calculate. Did you log the pull where it died? Do you have logs of it at 7 psi? Maybe it was lean the whole time.

The precise mechanism for destroying it doesn't really matter all that much at this point, except as an expensive lesson in why you need to approach tuning carefully and methodically, approaching your target through incremental steps and double-checking everything all the time.

--Ian

Piston had a bad day, probably in pieces or has a hole in it. Welcome to the club!

What wideband and what AFRs were you tuning to?

I would guess something went wrong in cylinder 1. Maybe a clogged fuel injector or detonation in that cylinder only? Maybe the mystery builder did headwork that caused 1 to flow more air and run lean? One cylinder leanness might not show on the wideband if you're running rich on the other cylinders and lean on one. I wouldn't expect cylinder 1 to run hot normally since it's usually the best cooled cylinder, stock or reroute.

This is one reason it's usually wise to start your tuning off mild and keep an eye on old fashioned stuff like spark plug appearance.

Did you run a timing light to verify base timing when you put on the new head?

Are you running 93 octane?

I'm guessing you weren't logging at the time?


You will log while tuning from now on.

At this point I have accepted that my engine is probably doneskies. I need to take a peak with a borescope. I won't pull the head just to check the piston. I plan to pull the whole motor and get it rebuilt. Probably with forged pistons this time. Next time i will tune the car 1 psi at a time. To be honest, I was more focusing on the boost not spiking. I was somewhat paying attention to the AFR gauge but not as much as boost. And it never went crazy lean from what I can remember, but saying that doesn't carry much weight. But the AFRs i was tuning to was 12 I believe.

I don't suppose anyone on this site is from around Nashville. ? I am wondering if there is someone who rebuilds Miata motors around here.

Probably everyone here has blown up at least one engine. It's how you learn to be careful.

I'm not even certain it was necessarily a tuning issue. Only way to know for sure is to pull the engine and read the entrails. Even the most educated guess is bulllshit until you take it apart and confirm suspicions.

I haven't. In fact, one of my goals is to never need to open the engine. Instead, I've tried to learn from Other People's Mistakes. Of course, only time will tell if I succeed or not. To me, that is part of the value of this forum: good advice as to where the limits tend to be, and how not to cross them.

Btw to answer a couple other questions on here I am running an AEM UEGO 34-4100...or whatever the number is. Something like that. And I was running 93 octane pump gas when the engine blew. And unfortunately I was not logging at the time. Another mistake that I will definitely note for the future.

There is overboost protection. Enable it, never worry about spikes again. Also note that it will scare the piss out of you when you hit it.

L2t.

In for carnage pics of #1 piston

Confuckinggratulations. You've never blown a motor because you push less air through your motor than some nat asp builds. You've succeded at not blowing your motor but you've failed at being a man. Then again you're probably one of those rogue target miata demographic 60+ year olds that dead ended here in a journey of unfortunate serendipity.

Also not explode motor is not that hard. Afr above 10.5 and below 12. closed loop knock trim cus ur map prob sux. nonsuicidal timing. Boost cutoff. Done.

For fucks sake. Is it really that hard? Next steps for you


Insert :eggplant: into sitz bath. Internalize.

Race a stock 4cyl mustang. Lose. :vash2:

do a 1 wheel burnout, break ur 5spd at 7000rpm clutch sidestep, ,

part out, buy a cr-z :

give up on dream of finding a 40 year old mistress.

: die.

Ur oldest son gets the cr-z.

Sells it.

Buys a 4cyk mustang, keeps it stock. :vash2:

Now now. This is a place for love. We are mostly dudes probably that all drive or have driven miatas. No need to wreck the joy. I was just boozin after I checked the compressions with my boy toy so I wanted to document my impatience so that maybe someone reading would avoid this in the future.

My motor was totally my fault. Like the first or second post said, I got impatient. I just wanted to go to hyperspace too quickly. There were a couple of things I should have done prior to all of boosties that I even thought of at one point or another, but in the moment it just didn't happen. There is a SMALL chance that the build could have something to do with it, since I have had my reservations since the beginning about the motor since I did not oversee the process. But probably not.

I will definitely post up some pics of the piston when I get around to tearing the motor down or if the borescope can capture the carnage.

The big debate in my head now is: WHAT DO!?!? I am seriously considering just finding a long block that has low miles and throwing it in. That will make 3 miata engines in my garage, but damn, forged internals are a-spensive!!! I could also find some Stock NA 9:1 pistons that arent totally destroyed and try and piece together an engine with what I got. How much does a set of pistons run? Also, one thing that the last dude said about the pistons that I put a hole in is that the builder blended some of the sharp edges as to avoid hot spots, further avoiding the likelihood of knock. Is that a thing? It makes sense, but I just havent ever heard of it.

Okie doke. The head has been removed. I am at a total loss. I have no idea what the issue is. The piston looks fine to me, granted I have never checked anything like this out before. Anyway. Here are pictars. I tried to get the best I could of the gaps between the sidewalls and pistons. I honestly suspect that the head is screwed. Like it got warped or something.
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My point exactly.

Rest of your post I don't understand your points or motivation.

piston looks melted.

We need pics of more than one piston. All four please, and pictures of the cylinder bores of all 4 as well. Pictures of all four cylinder head combustion chambers. We can't diagnose your sickness, with a picture of 1/8th of your turd. We aren't Dr's god dammmit.

Notice how clean #1 is compared to #2 -- that often indicates that the head gasket has been leaking coolant into that cylinder. Look at the head gasket between the coolant passages and the cylinder, see if you can see a failure.

--Ian

Yup. #1 piston is destroyed. You can see the top ring clearly even from a slightly oblique angle. Cylinder head shows signs of severe prolonged detonation too. IOW, motor is trashed and needs a full teardown+rebuild.

Being able to see the top ring is a bad thing.

I'm curious how #1 detonation happened.

More carnage pics since some wanted to see the whole motor. In order:

Cylinder 2
Cylinder 3
Cylinder 4
All Cylinders
Cylinder 1 and 2
Cylinder 3 and 4
Cylinder 1 Again
Whole Head
Valves 2
Valves 3
Valves 4
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Also, the whole decking and head machining and head gasket all look like total garbage. Nothing can be concluded from the gasket. It just looks like total trash. I have some pretty serious doubts about the last rebuild. I don't think the head gasket was leaking coolant though because I ran a pressure test on it and it held strong. I feel like everything on the long block is fine except for the pistons. (meaning I am hoping the rods, block, head, etc can be reused but not pistons) But I need to finish tearing it down.

Ya, that # 1 took a beating.

Pistons/rings will obviously need replaced.


The big thing to check is that the damaged piston did not cause damage to the bore. You may be able to just hone, there's a chance not. The head itself looks to have some physical damage. That will need blended out.



FWIW: I'd be replacing the delicate stock rods if you still have them, and making sure the rods did not deform if you have.





Full valve job (checking the valve while they're out), smooth the chambers out. Machinist should inspect/measure all the bores. Pistons and a hone at minimum.


EDIT: How many miles/hours were on the motor, post rebuild until failure?

There was about 1000 miles on the rebuild.

Probably the same way it happened in #2, #3, and #4

You're clearly looking for someone other than yourself to blame, which is pretty disheartening, since a failure to learn from this will just result in you blowing up the next engine you get your hands on too. You don't "see" anything regarding the quality of a decking/surfacing operation on a cylinder head after 1000 miles. You measure that quality with a machinist's straightedge and feeler gauge, and I doubt you've done that.

You blew up this engine. Any engine builder will look at the pistons and head surface and laugh you out of the shop if you expect to convince them that this was anything other than your own fault.

Since this is the internet, it is going to sound like I am getting offended and defensive, but you are just going to trust that's not the case.

I have mentioned several times on this thread that everything that has happened has been my fault. To say that I will not learn from this experience is simply false. Will this ever happen again? Maybe. But there is a whole slew of things I will be doing on the next go-round in order to avoid this outcome.

I thought it was relatively clear from the very start that I am not disgruntled. I am not on a search to point fingers. I am just on this forum sharing my situation largely for fun. I like talking about engines and cars and I like working on them. This is my toy. It broke, and I will enjoy fixing it.

It is clear that the piston is toast, which was my doing. My whole thing about the machining and gasket was just information that I observed. I mean shit, I don't even know the guy who built this motor. So it's not like I am even trying to ruin anyone's name.

Correct me if I am wrong but I have always been under the impression that if you blow a head gasket, when you remove it, it is pretty obvious where the failure occurred. What I was saying about the machining and gasket was just that 1) You cannot denote a failure point and 2) The whole gasket and mating surface generally look terrible. I was also under the impression that a head gasket and head after 1000 miles and a fresh rebuild would generally still look pretty clean, which it clearly does not.

Anyway. I am appreciating everyone's responses. I don't mean to waste anyone's time, I am just enjoying the hobby.

What was the timing running at? can you post you last MSQ? and did you confirm the timing was in sync?

Might not be strictly relevant, but any idea what sort of foreign object was rattling around inside cyl 4?

Yeah, you might want to take a look at your throttle body and see if it's still got both of its screws. :)

The photos of the deck & head surface look pretty much like what I'd expect. I think the black coating on the MLS gasket starts coming apart the first time you get it nice and hot, so 1K miles isn't going to look all that different from 50K.

How badly was it running before you shut it down? Was it running-on-3-cylinders bad? If so, then perhaps the unburnt gasoline acted as a solvent to clean up #1? I dunno.

--Ian

I will have to post up the MSQ file on Friday for everyone to laugh at. I'm out of town for work and my tuning computer is at home. The car was timed. Unless it "fell out" of timing for some weird reason, it should have been calibrated correctly.

The car actually drove 30 or so miles on 7psi doing just fine before I turned the boost up. I turned AE off to tune the fuel map for the higher boost. I think that's the only thing that was changed.

I will look when I get home, but I don't think there was anything in cylinder 4. A friend of mine and me looked through the cylinders very thoroughly. Cylinder 1 is definitely the worst in person. I will have to check the throttle body. That would suck if a screw went through my motor. That makes little sense to me though.

The car ran actually pretty good on 3 cylinders actually. I mean, the idle sucked, but other than that it ran OK. I didnt rev it up at all though after this all happened.

I'm not saying that #1 isn't fucked up, but something metal was definitely bouncing around inside #4:


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Might have happened a long time ago, and whatever it was finally found its way to the inlet side of the catalytic converter, but it definitely bears looking into.

Any damage to the leading edges of the turbine blades?

I will definitely be checking the turbo. I hope to GOD that it's good. Also, what's a catalytic converter? teehee

Number 3 has a little FOD also, just not as bad as 4.

Did you drag the head on the concrete with the mating surface down after you took it off the car? Those scratches are no bueno.

It looks like you scraped the gasket off with a file.

My guess would be chunks of molted piston exhaled through the intake valves during overlap, pushed up the #1 intake runner, cooled down and forced to the back of the IM by incoming air, then forced into cylinders #3 (a bit) and #4 (more than a bit) and re-ingested.

:likecat:

With organic head gaskets, you can typically see the gasket blown away, but your head gasket is multi-layer steel which won't exhibit similar symptoms. By the time you get a steel head gasket hot enough to actually blow out like that, you've typically blown big holes in the block and head surface above/below the gasket too. You may not see clear signs of a blown HG with an MLS gasket. (Having said that, I'm not convinced your HG was blown - all the oil you were burning in cylinder #1 has a lot of detergents in it, which can have the same effect in a short period of time.)

Your impression re: head surfaces after 1000 miles being clean is incorrect. Your head/block surfaces look about like how I would expect a healthy surface to look after that many miles. Even after a short period of time, you'll have to do some R&R to those surfaces to safely re-install a new gasket.

What signs point you towards prolonged detonation when looking at the head? Not doubting, just tryna learn a thing or two.

The erosion on the squish area is a dead giveaway.

PJnB - Thanks for posting all of this... very informative thread based on the failure analysis!

Savington - I believe PJnB's comments about suspected lack of quality work during the last rebuild is at least partially due to all of the scratches on the surface of the head, not just the black/brown residue. Those scratches don't look like the types of machining marks one should have on a cylinder head for use with a MLS headgasket... Looks like someone took a gasket scrapper to the head at some point and went to town! The block surface has a few scratches as well, but not near as many as the head.

The head and block should have a very smooth (low RA) surface for a MLS type head gasket, correct?

Thanks for the props noname! Regardless about the build quality, what happened happened. My biggest goal for the thread is to learn about what could have gone wrong, what DEFINITELY went wrong, and what I can do to prevent it in the future. As is my goal for any reader to learn.

Now for some more data. Here is the MSQ. Let 'er rip. For the experienced tuners, this is probably going to warrant a double facepalm aimed at me.

This was the tune right AFTER the blown dipstick.

Timing is too aggressive for CA91, but you might have better gas. Fuel map is clearly untuned north of 10psi. You're commanding more fuel at 10psi than you are at 14psi or 17psi. Fuel map blew the motor up.

Running 93 in TN. But still im surprised you say it's aggressive. Since I ran that timing on 9.5:1 compression ratio on a stock 99 motor for 3 or 4 track events.

the timing map seems fine to me. you're pulling about 7-8° of timing at 10psi. I sent the map at ~18.5° at 175kPa.

The fuel map looks completely untuned.

The 40usec of timing latency also worries me. That seems high for a CAS. I feel like it may have been advancing timing in higher rpms.

turning on dual map sensors, when you only have one also could completely fubar fueling. Do you have a recent datalog?

Unfortunately I do not have a recent data long, yet another detail I will know for the future. Ok so it sounds like there are a couple settings I need to change in my MSQ that aren't just fuel. BTW this is not the megasquirt that I bought from you, Brain. This is an off the shelf MSPNP2 for a 90-93 with the stock base map loaded onto it and then adjusted for the 1000cc injectors and tuned to 7 psi.

NOW PREPARE FOR THE CARNAGE!!!!!!!!!!!!!!!!!!!!!!!!!!

Boys and girls, this is how you crush hopes and dreams.


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AND NOW FOR THE FINALE!


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Extra bonus points for anyone who can identify those rods. Pretty damn sure they are ebay rods, but they sure as hell look beefier than stock. I plan to reuse then, as they look like they are in perfect condition. I think there are a couple more stamps on them but I will have to get pictures at the end of the week.

looks like what happened to my pistons's ringlands when I first boosted.

they lasted the test run.

87 octane, stock timing, 6psi. :)

They are 5.230 rods.

1 bonus kitty point awarded to Joe Perez.


This is what I thought of because of your response.