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: ????

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 **** out of you when you hit it.

 

L2t.

 

In for carnage pics of #1 piston