Broken piston on 6 bolt engine

[DarkstarTsi]

Need a little advice here on a problem, the piston on the 1st cilinder broke on my friends 90 talon tsi. The car has a fully built engine, ross pistons, eagle beams, cometic head gasket, cams, valves, springs, etc. 660cc inyectors, 255lph fuel pump, T4 turbo, Maft, etc. The thing is that the car is only boosting 17psi, oil pressure is ok, spark plugs are ok, even in the 1st cilinder where the piston broke and we are trying to figure out the possible reasons for the broken piston. Just for the record, the other three pistons are in perfect condition.
Any ideas on what to look for or the possible reasons for the broken piston only in the 1st cilinder???
Thanx

 

[Mike1992]

Define broken piston

 

[DarkstarTsi]

It looks more like it melted, here are the pics....

 

[1fast97gsx]

I'm assuming a bad / clogged injector on that cylinder?

 

[Mike1992]

Thats what happens when you up the boost without fuel control. Take it as a lesson learned the hard way.

 

[eclipse98gs-t]

Hello.
That is my motor.
1st of all, i was running 17psi on pump with 650cc injectors and 255 walbro...
I think that is not enough to broke a piston...
Normally i was run 14.5psi and 17psi to tune SAFCII just one day...
Here we are nuts about this!
Oil pressure was fine because i built motor with a new oil pump.
What are correct gap for RINGS who came included in Ross piston kit?
The motor was 0.30 overbore.
Now i think to buy Piston kit 0.60 overbore... maybe to grow displacement... what do you think?
Please somebody tell me WTF is going on!
Thanks for your help.

 

[Mike1992]

Bad tuning, clogged injector so many variables. Cylinder 3 looks a little out of place too. Maybe its just the picture, but there looks to be alot of piston to wall clearence. .030" over is already pretty drastic, I think you can only bore over .040" total. I think you need to look for a new block. All in my opinion, but I garantee others will agree with me.

 

[project_tsi]

Id agree, find a new 6 bolt block and go from there. Get link to tune w/ and be carefull.

 

[j.d.roost]

My .30 over ross pistons have the part number stamped into the top of them. I don't see that in your pics.
What was the piston to wall clearance set to? I had my pistons set to .005 piston to wall and .017 top ring gap .018 2nd ring gap.

 

[eclipse98gs-t]

We dis injector flow test today.
Injectors are working perfect.
I still wondering about wtf happened to 1st piston?
I gonna order Wiseco piston kit today at 0.040 overbore.
Maybe i gonna run only 14.7 psi now.
Im very disapointed at this time.
Thanks for coments

 

[Mike1992]

Have the block checked before you go ordering pistons. What if that melted piston scored or made that cylinder out of round and a .040" overbore cant make it true. Catch what Im saying?

 

[eclipse98gs-t]

You are right.
Thanks for advice.

 

[Waredtalontsi]

Just an idea, but aren't 660 injectors to small for a full T4 turbo.