Dave W.

I see pitting on the edges of the pistons. It looks like some debris was smashed in the quench zone. Did the plugs break apart? I'd also check the entire intake tract for signs of dirt that may have gotten sucked in.

Eric_Oz_S2

That kind of damage can happen from running lean or coolant leaking into the bores. The pistons look oily - were the breathers and vacuum hoses correctly routed? When my supercharged s2 motor went it had one cylinder that looked like that - it ran lean due to sucking in oil then sucked in water then hydrolock and cracked cylinder. What were the afr's during tuning? If the tuner started with a lean tune, that type of damage can occur in a few seconds under full load on a dyno.

I would check to see if there is a lot of oil in the intake / on throttle body as a start.

KSira

The pistons are Wössner alusil compatible from Lindsey Racing. The oil was 10-60 Millers nano tech racing oil. The pitting looks like ignition knock. I am leaning against overheat or some error during mapping, wrong gaping of the rings, ore the bore not being to spec. All pistons have made contact with the cylinder, so if there where debris in the intake, it must have been a lot of it.

Edit: The scratches are only on the intake and exhaust side of the cylinder wals. The exhaust side seems to be the worst.

KSira

Since I am completely out of money after this disaster, please contact me if you have pistons, block, or anything else I can use, for sale. Thanks!

EDIT: Not sure if my PM works, send me an email.

Voith

Are the pistons oversize? Is it possible that this could be because alusil silica exposure procedure was not done right?

Sorry for your loss. I hope pistons are in salvageable state..

KSira

They are oversize and where supposedly honed with special stones to expose silica. I doubt the piston can be reused. Looks like there is a deposit from the pistons in some of the cylinders.

Chris White

The cylinder damage looks like two possibilities - either incorrect ring gap or detonation. Most likely you will find broken rings when the engine gets torn down.
The damage to the top of the pistons is fairly consistent to what you would see from detonation damage, the odd thing is that there is no marks in the combustion chamber, piston bowl or spark plug electrode. If you get detonation bad enough to break the piston rings its pretty hard to miss while tuning.
Do you know what the piston to wall clearance was? Piston alloy?

too bad about the mess, that really sucks.

Voith

Hm, all the info that I read on the topic, suggest that it needs to be done with AN-30 Sunnen paste and felt brushes after the honing.

KSira

Thanks for chiming in. Not sure about the piston wall clerance yet. Will measure this when I pull the engine next week. The car missfired badly because of trigger problems. Pistons are from lindsey racing. Is there anything I can look for to determin the cause, when I pull the engine apart?

blade7

Perhaps if the rings are broken it will suggest they weren't gapped correctly ?

Dave W.

" The car missfired badly because of trigger problems. "

How bad was it misfiring? Was it misfiring all the time? Full throttle only?

refresh951

Sorry to see this. Were you monitoring knock?

KSira

I where not doing the tuning myself, but they where using equipment to hear the engine knocking

blown 944

Sorry to hear.

Might consider sleeving the block and using appropriate pistons for the least expensive repair. Might also recommend flanged ductile iron sleeves.

Quite s mess for such a short time. Hard to determine whether the piston material may have caused the oil detonation or detonation caused the broken ring possibility.

I havnt heard that many aftermarket pistons working with alusil bores. I would personally want the exact specs of pistons used and the clearances as well.

Again very sorry to read this.

333pg333

Where the tuners the same people that put the engine together? What are they saying at this stage? Are they taking any responsibility?