[Mk2] [Turbo] over fueling

[GTS GAV]

these are my old standard pistons there flat with valves cut




im pritty sure if the secound lot are dished they are a lower compresion set

and raising the boost to 1bar on oem pistons imo there not going to last long beofre ringland failure again from deternation, unless you retard the timing wich inturn heats the pistons valves etc etc.

if the oem sets have gone up that much i would invest in a set of forged items there not alot more.

[sawicki]

im deffently going for forged this time

[GTS GAV]

iv just had a though toyota lowerd the c/r on the rev3 compaired to the rev1/2

rev1/2 are 8:8:1
rev3 are 8:5:1

i wonder if they fitted the wrong revision set ie rev2 instead or rev3 wich wouls raise the c/r wich would cause the seveare ringland failure

the flat set taken out my engine were from a rev2 block flat
iv seen rev3 are slightly dished

[sawicki]

that sounds like it could be the case as the standard ones were slightly dished dident know the rev 1 and 2 were different to rev 3

[GTS GAV]

the only way to make sure is to see if toyota have diffrent part numbers for pistons the change happend just after 1992 i.e 8:8:1 c/r after 1992 the lowerd the c/r to 8:5:1 and raised the standard boost, i bet your bottom doller it that mate yours is a rev3 isnt it, as soon as you would of drove it would of started detting because of the hightend c/r and more boost, i reckon thats it matey

[ashley]

Closer inspection of my rev3 pistons shows that they are indeed slightly dished- something I hadn't noticed before- apologies for claiming they were flat



Sounds like you've found the problem with your rebuild...the only question is what caused the damage on your original engine that did have dished pistons...

[sawicki]

thanks for everyones help think we might have cracked it i will check with toyota and yes it is a rev 3 1995

[sawicki]

original engine did have dished pistons yes im hopeing the first time was just age as they had done 90k

[Jim Galbally]

those are clearly detonation marks

[ashley]

Glad I didn't sell them then- wouldn't want someone to suffer the results of any damage!

In the bin they go...