During a trackday  @ Vålerbanen June 7. my 2.0 suffered a piston failure on cylinder #4.
Not sure what caused the damage based on the data and the resulting damage.
I had two abrupt engine cut outs of 1-2 sec  during the first session.
Logs shows IAT sensor (integrated in the MAP sensor) jumping all over the place from -37 C to 90 C...


Not visible on the pic but AFR was enriched to sub 10:1 during the session to compensate for the spikes to -37 C . No knock registered though.
I checked the wiring from end to end without finding any problems and went out again keeping a close eye on the IAT.

One lap in and it happens again during boost. This time with blue smoke so straight back to the pits.
Not my first rodeo so I suspected collapsed ring land --> pinched top ring  --> Sad Panda Face etc.
This was ~ 170 Km from home so I had the most nerve-wracking 3 hour trip home burning off 3 l of oil. I'm actually getting too old for this s#&"!

Plugs after. Not relevant for what happened on the track though since I limped it home:

The piston have seen better days.

Some observations.
- Ring land is broken.
- Top ring pinched in grove
- Oil ring center spacer disintegrated.
- Middel and top ring broke or wore off
- Skirt has sign of high heat and zero lubrication

Much of the carnage probably happened on the way home.
The piston is what looks like a very cheap aftermarket part with an unusual oil ring design.
Also the low friction coating seems to be a total joke. Like painted on.
I was kind of aware of this since the short block was £450 on ebay.co.uk and came in a crate from Saudi Arabia LoL.  
That said, this engine has delivered the performance I needed and then some. Dipped below 1:40 on the first outing and has ensured sub 1:40 laps on all trackdays since.
But 7500 rpm at 10-12 psi on sub par internals is obviously not the best recepie for a trackday engine.
I counted 7 trackdays since fall 2018 + a trip to the Nürburgring with this engine.  For the cost + my own labor it's worth it. Maybe it would last longer if the IAT sensor didn't fail.
I'll def add a fail safe or max min value on the new sensor.