Guys, I opened my engine due to a blown HG and decided to freshen up the block with new rings, rod bearings and cylinder head overhaul. The engine ran fine till the end but was consuming a bit of water and after each use the car was difficult to start when hot so I decided to open her up and see what was going on. Sure to find the HG had the black coating stripped from between the cylinders and to one area of the water jacket. So took out the pistons and after clean up they look strange on the intake valve reliefs and top of the piston rings. They seem to have a ruff surface on the top and edge on the intake side and I don't know if this is part of the original piston forging or is a deformation of the piston. I bought the car second hand and had a comptech SC on it with 10psi but the last owner didnt know anything about cars so the engine might had been subjected to untuned abuse beforehand. After bought I got it tuned (very reputable shop PR) SC and turbo at 11psi both with water/meth and 11.5-8 AF.

So anyways these are the pics of the pistons. Let me know if this is normal forged casting or are FukdUp!

All of them looked the same. The thing is the exh side which is the hotter looks smoother.

 

Looks like detonation to me, looks like it was very minor, maybee done over a long period of time. Usually if you detonate severely your rings will shatter, ask me how I know, lol.

 

So, are they salvageable? Compression was 230,225,220,240 on dry test and blown HG. So I bought new rings before I cleaned them up.

 

detonation for sure

 

The pistons don't look great, but if you blend out any peaks from the detonation you could probably run them again. I would be concerned about whether the cylinder walls are scored though. That happens relatively easily in the S2000, especially in #4.

Tim

 

Thank guys..the cylinder walls look ok. They are not scored,only stained on the top by the combustion. Well, I will polish any piston imperfection and put them back with new rings to see how more I can push them. If they fail later on my only option will be to sleeve the block and get new pistons/rods. Mahles dont make much sense for me right now as they dont offer stock compression pistons. Either way the rings are the one that are going to do the sealing.

 

Don't forget to fix the cause as well.

 

High concentrations of methanol can deteriorate Aluminum over time, since that was mentioned and looking at the pistons with he damage just on the intake side, that to me would coincide with this kind of damage rather then detonation. If it was detonation it should not be isolated to just the intake side, but it would make sense for the pistons seeing something injected into the intake stream. Are you still running the injection kit? What % of water to meth are you running?

 

Yes..I thought of that too. Detonation on intake side of piston only, raised a flag for me but didnt think the water meth would affect much or erode the piston. Well I use AEM kit with the largest jet supposed to be 500cc "BUT" I bought the failsafe gauge and with the new 200psi pump it pushes a measured 800cc of fluid. I use M1 50% + 50% distilled water and dialed back the full psi to a measured 400cc at 11psi of boost.

 

50/50 should be ok. The total amount injected might be in question as well as how well its atomizing, 11psi isnt much to warrant that injection level typically. (the 800cc I mean) If it isnt atomizing fully, it could theoretically be a factor exploring. How many miles have you been injecting?

I wonder myself if the OEM pistons vs Forged with iron sleeve can hold up to the corrosive properties of meth as well over the long haul.