No, it looks like a little wheel from a tool or something...

Car is at the garage - hopefully I will know more soon.

 

O.K. first news about my engine - the mechanic just told me its a damage on cylinders 2 and 4. (I don't know the english word for Kolbenkipper - piston is moving to much to the sides and damaging the sides of the cylinder walls)

Engine is going to the rebuilder on Monday to give me some numbers about overbore.

 

O.K. now for some pics...

all valves - a little black because of the cold starts verifying the nasty noise:


cylinder 1


cylinder 2


cylinder 3


cylinder 4


No worries about the valves.

First glimpse inside cylinder Nr. 4 - scratchmarks


piston bearing of cylinder 4 - just like new


piston Nr. 2 - small scratches


Nr. 2 again


piston Nr. 4 - oh oh!


Nr. 4 again


and again Nr. 4


inside cylinder 4 - walls are scratched


again inside Nr. 4


and again inside Nr. 4


indside of Nr. 2 compared with the inside of Nr. 1 looking just like new...



Conclusion?
Damages on Nr. 4 should be a reason for a coolant reroute
But why are the damages on Nr. 2?

Nr. 1&3 are just like new.

Rods are in perfect shape.

Any thoughts and comments would help me a lot!

 

Its not what you would call normal wear. What are your AFRs like? Could that be caused by excessive bore wash from weeping injectors?

 

Hi,

the AFRs were within reasonable values. Espacially when this happend (~6k RPM, 5th gear full boost ~10-11PSI) there were ~12.0 AFR nearly flat.

Edit:
That is a screenshot of when I believe that happened. I had some slight bogging just up top. I suppose this was when the piston hit the wall.

https://www.miataturbo.net/forum/att...1&d=1240839123

Greets

 

Looking at the data log it looks like you were under a lot of load for at least 30 seconds. Being a noob I don't know what the factory piston to wall clearance is, but I would venture to guess the excess heat by such long high load runs caused the piston to expand into the cylinder walls. #2 must have had less tolerance than 1 and 3, and we all know that #4 gets hot anyways. This being the case I would suggest having the block bored ever so slightly larger than the factory tolerances to alleviate this problem in the future.

And that bog would have been the pistons digging into the cylinder walls.

 

Thats what I am thinking... BUT being on the German Autobahn this isn't an awful long time. So I will have a word with the engine shop, once my ingrediences are in...

Greets

 

Today I might have found a hint, why the engine was damaged.

I was wrong with my inital thought it couldn't have come from the MS - because indeed we have a batch injection of Nr. 1&3 and Nr. 2&4

Today a Release Candidate for the new NS2extra firmware came out with a correction of two bugs from the last beta versions:

*
2) Fixed a problem with the "Incorporate AFR" feature that could cause the second injector channel to not get the AFR incorporated into the equation, causing pw1 and pw2 to be different. (Jean found and fixed this in the 3.0 alphas, I backported it).
*

I got 2 screenshot of logs old (version 2.0.1) vs. last beta (version 2.1.0)

old: PW is nearly identical to PW2


new: PW is mostly ~0.2 sometimes a up to 2.0 higher than PW2


I get the feeling this could have caused a overheating of Nr. 2&4.

What do you think?

Greets