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:


https://www.miataturbo.net/attachmen...ine=1453153719


https://www.miataturbo.net/attachmen...ine=1453153719


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.


https://www.miataturbo.net/attachmen...ine=1453825143


https://www.miataturbo.net/attachmen...ine=1453825143


https://www.miataturbo.net/attachmen...ine=1453825143


AND NOW FOR THE FINALE!


https://www.miataturbo.net/attachmen...ine=1453825143


https://www.miataturbo.net/attachmen...ine=1453825143


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.