Stefan Dieters said:

Check if your head is getting enough oil. If he rebuild the block without knowing what he was doing, he might placed the gasket the other way around, realised it to late, damaged that one lobe to low oil feed, replaced the gasket the proper way.

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That's very interesting! If this is true, do you have any idea which valve and which cylinder will start complaining?

My problem is located at the valve ( I can't remember if it's intake or exhaust) of the third cylinder.

Today I noticed something new.
The car operates fine under half throttle all the way up to the red line

The car pops and bangs under full throttle. I hear no metalic noises. It's like something is holding the car back. And when the tacho reaches the middle area the bing bang show starts:bang:.

Also when bangs starts, it's overboosting like crazy. I saw peak boost of 1,57 bar.

All this happens with full throttle only. Half throttle everything is fine.

I have reseted my boost controller (Blitz sbc i-colour) and program it again with lower values but nothing has changed except peak values of boost.

target boost is at 0.8 bar
gain is at 20
scramble boost is off
limiter is off

Please share your experiences cause my patience is running out.:bang:

I haven't had the pleasure of working with a boosted engine, but my first instinct is to check the dumpvalve. If it peaks, it might be a sign of your dumpvalve not opening properly when needed. And since it works fine under half throttle, you dont give the engine a chance to build presure before the rutbo

Looks to me like you need a complete top-end job, head off, camshaft replaced, springs checked for length and replaced if short, new valve seals, valves checked and refaced if they will stand it, careful reassembly with clearances properly set up with new shims, new [good] gaskets, proper refrigerant and a new radiator cap.

That may be just for starters but I've never heard of one of these little engines giving either big end or main bearing trouble so I'd make that a last resort.

Stefan Dieters said:

I haven't had the pleasure of working with a boosted engine, but my first instinct is to check the dumpvalve. If it peaks, it might be a sign of your dumpvalve not opening properly when needed. And since it works fine under half throttle, you dont give the engine a chance to build presure before the rutbo

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Dear Stefan I would like to thank you for your reply.
Blow off valve works fine. It's synapse blow off valve not the oem one. I removed it from the car and check it with pressured air and a pressure meter and it works as it should be.

rolandbrindley said:

Looks to me like you need a complete top-end job, head off, camshaft replaced, springs checked for length and replaced if short, new valve seals, valves checked and refaced if they will stand it, careful reassembly with clearances properly set up with new shims, new [good] gaskets, proper refrigerant and a new radiator cap.

That may be just for starters but I've never heard of one of these little engines giving either big end or main bearing trouble so I'd make that a last resort.

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Dear Roland thank you for your reply.
Your point of view makes sense. I wonder if all electronics work as they should be, and to tell you the truth, I have doughts for the air flow meter.
I think the car had very rough times and a garage that didn't know what they were doing brought the car at this level.
And that is 100% sure cause I can't imagine a mechanic doing an overhaul and leaving the oil pan screws loose...and all the rest i described...

I will get a quotation for a proper head job...

Im talking about the dumpvalve, not the blow of valve

Stefan Dieters said:

Im talking about the dumpvalve, not the blow of valve

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If there was a hole at the diaphragm of the dumpvalve then it would not built up boost. That is the most common problem. Turbo and the equipment surrounding it seems to work fine.

In any way if there was a trouble at the hot side of the turbo then the car wouldn't build boost. I face the exact oposite. I had some conversation today with a fiat expert. He said pops and bangs come from "damage" to the colars of the turbo, or a faulty air flow meter. I have to check every collar extensively...

im also not saying there is a hole on the dumpvalve, only to check if it works. If the dumpvalve doesnt open under WOT, it will overboost, and there is a chance that the ECU is not able to handle all that boost, resulting in pops and bangs.