That'll buff out.

Nice Pictures!
and this is why I am learning to tune before turboz.
cut open oil filter?, pics of bearings?
I am curious as to how the rest of the engine looks after this type of failure.
best of luck

I'm sure they're all fine. This failure is directly attributable to acute detonation under high load, not to chronic wear such as would be found from under-oiling, over-temperature, etc. There might be a few tiny bits of piston skirt in the oil filter, but most of them (what little there were) were probably stopped at the pickup tube inlet screen.


It looks like a block mounted to an engine stand, and a bunch of parts strewn out over a workbench.

I don't really expect any sort of damage, but am curious about the bearing wear as the bearings have seen high loads from detonation, not that I expect much, It being a street engine.

This is correct. Bearings look perfect actually. I can post pictures of everything at the end of the week. I will also try and get some cylinder wall pics. I would say the walls have the highest likelihood of damage, but it's not that extensive.


Spot on.

Someone correct me if I am wrong, but I was under the impression that in a situation of catastrophic failure during detonation, there is't very much overloading on the bearings. Also, I know I leaned out due to boosting past my fuel map's thresholds, but does that automatically mean that there was detonation? I thought that the failure was due to inadequate cooling of the pistons (due to no gas) and extremely hot combustion temperatures from a really lean AFR (due to no gas).

This may all be a moot point, since the bottom line is that the AFRs should be around 12, which mine clearly were not.

Bearings are harder than the pistons / rods, so I'd expect those to fail first unless I'm completely off here.

Thanks for the pics, always nice to have a teardown and examination of things.

Bearings are softer, actually. Quite a lot softer. That's why you never hear about one breaking.

Main and rod bearings are alloyed from materials such as copper, lead, tin, and antimony. In a holistic sense, they're designed to be sacrificial (relative to the crank journals), as they're much cheaper and easier to replace than crankshafts. Their soft surface design, in fact, permits small particles of hard material such as silica to become embedded into the surface to such an extent that they essentially disappear.

But it's not a fair comparison. The compressive forces exerted on a piston and rod simply don't translate directly to stress applied to a bearing, in part due to the geometry of the parts involved, but mostly because oil is a thing that exists. Even wrist pins are pretty damned hard to break, mostly because they're a lot stronger than pistons, and partly because cylindrical pieces of metal are a bitch.

In fact, materials which are "hard" are, by definition, also brittle. This is why pistons crack. They have to be hardened to the point where they aren't ablated by contact with the iron / steel cylinder liner, and this has the unfortunate effect of decreasing their resistance to fracturing when exposed to abnormally high loads.

Alright. I'm bringing this crapshoot back to life. Please allow me to fill everyone in with pictures.


https://www.miataturbo.net/attachmen...ine=1458011700


https://www.miataturbo.net/attachmen...ine=1458011700


https://www.miataturbo.net/attachmen...ine=1458011700


https://www.miataturbo.net/attachmen...ine=1458011700


https://www.miataturbo.net/attachmen...ine=1458011700




Ok so now that we are all back up to speed, some deets. The new motor is a stock 95 motor with around 130k miles on the clock. Ok that's about it. I have uploaded the old tune, set it to 14 psi, and wailed on it.......and for some reason it blew my dipstick again.........








.........just kidding. Watch, that will happen to me now. :party:





But as for what I have actually done so far as far as tuning, very little. I put it back at 7psi which was what the other motor was running pretty decent for about 1000 miles. My friends and I had to fiddle around with the fuel rail on the older style intake maifold to get the fuel injectors to stop leaking and here we are. It runs and drives OK on 7psi but I've barely driven 10 miles on it because I'm scared shitless of blowing something up.

And here is where I start to beg. I have attached the current tune and a data log (drove around for maybe 5-7 minutes). Please rain all of the insults and knowledge on me that you can. I will admit that I am a total idiot with tuning and MSs. I apologize. The tune that's attached is me trying my best to figure out what the internet says to do.

Referencing back a few comments to where Brain asked if I had a decent data log. I think you reference in there that this may be one of your DIYPNPs. It isn't. It's a different unit from MS. It's the MSPNP2 for the 90-93. It has the base startup map for a stock 1.6 from DIYAutoTune and it has my old spark map from my 99 that I ran with Brain's DIYPNP. The fuel injectors are Injector Dynamics 1000cc injectors and I think I have the tune adjusted correctly for those.....but maybe not.

Please help me not explode this motor.

It sucks to be getting good at changing engines.

Nice job.

Anybody got any advice on that tune/data log? Pretty please?