Scooby horror show

Ouch! Any idea what caused the probs with #4 piston? It seems to be part-melted on the lands below the rings ...

It might be oil starvation, certainly looks like a hot spot, don't know if its been causing det/knock with the fuelling either so its hard to say. No other piston showed any sign of damage. Off to engine machine shop later to see what they reckon.

Possible sequence of events ?? >>>>>> Damaged turbo runs inefficiently >>>>>> increased exhaust gas backpressure is required to achieve target boost >>>>>> the resulting higher cylinder pressures promote det >>>>>> this cracks the top ring land >>>>>> which increases oil use and crankcase backpressure >>>>>> this creates even more det (oil is very low octane) >>>>>> which cracks the 2nd ring land allowing excessive blowby >>>>>> hot blowby gasses melt side of piston.

I would also check carefully the big end bearings as the det may have overloaded them, it would be good insurance to replace them regardless of appearance.

I have spare pistons from my WRX if you need one.

Andy

PS The cam timing being that far out wouldn't have helped either :eek:

Thanks for the reply Andy, the bent blade on the turbo shown on the site was infact my old one from last year. Car has ran for 12 months with the replacement with no apparent damage or lack of performance. As for the timing being out, we were very shocked to see this as when the WRX was imported into the UK, one of the 1st jobs was book car into garage to have timing belt changed. Trust was put on the garage to do this work but next time the covers were off was last week on the strip down. I'll wait for JEM to tell me what the damage is going to require then if I need a piston from you then I'll let you know. I did cater for replacing the big ends after all I'm in this far. Thanks for the advise m8.

caz,

who did you cam belt then? mail off line if you prefer,

cheers robinh20

Derek

What are you doing over here :)

Hey I could ask you the same question Mr S ;)

No chance of catching me on this one

Seems a fine mess mate, good luck with the rebuild!!!
Just got my engine back in, will 'plumb' it in tomorrow evening, so fingers crossed??

Ive

Good Luck Ive


As for you Mr S - Been on the muppet area ;)

Never