Piston damage!

Hi guys. This is a 4b11t engine from a Ralliart lancer.

i purchased this used “built” engine from a wrecker with relatively low hopes! (I just needed the transfer case that came with it)

it was in the previous car for over 40,000km and I have no idea on the clearances!

I did 10,000km @ 440hp e85 only

and 2000km @600whp before it ultimately suffered oil surge and later bearing failure at the track.

however when disassembled I noticed excessive scoring on the pistons.

i would just like someone to confirm what the route cause was?

was it potentially detonation, maybe pistons to wall clearance too tight?

thanks guys!

That's definitely caused by piston overheating. In its turn piston overheating can be caused by too much boost or knock (too much of ignition timing or low fuel octane rating).

As Shota said, it's probably that, but it may also be in part due to a 'dirty build' where the engine has either breathed in debris, or wasn't thoroughly clean on assembly.

I say that because I've seen similar piston damage on even relatively low powered NA engines that weren't looked after.

I also thought about it but the reason I ruled it out is big milage. With that level of power dirty oil would show up very quickly

I was thinking initial assembly and/or breathing unfiltered air?

It would help if the chap posted some pic's of the piston tops, as you're certainly MUCH more experienced and knowledgable where forced induction is concerned, and reading the piston tops! :-)

Do you think the bore prep'n could also have been a problem? I don't know how that could affect the pistons under the higher mechanical and thermal stresses of high boost?

Oh, what about bore wash? The E85 may have compromised the bore oil film, especially if running rich and/or less than frequent oil changes?

I doubt that it could be the bore wash as I used E85 on my engine for almost 7000 km with 500-700+ hp all the time. I disassembled the short block, refreshed hone and assembled it again for 900hp. Didn't see any signs of bore wash.

I'm attaching the picture of my own piston that definitely suffered from severe knock.

This is the only pic I have of the pistons crown at the moment!

Two more pictures