Big story with this car with the alot of mecanical failure but I will skip this part.

My brother buy a Cobalt LNF from a Garage with already a ZZP turbo kit (S256ET turbo, piping, intercooler, external wastegate, ZZP tune)

the car NEVER pass around 140kpa of boost without popping.
pops from around 6k to 7500k with no knock and no misfire.
WAIT before saying injectors seals
The timing chain broke up and we put a new one with a ZZP ported head with stage 2 comp cams and upgraded fuel lob and a new ZZP tune for the cams.
Since the new cams, the engine runs not really nice at 2K rpm and I first thinking that was normal because of big cams.. but pretty sure now this is a tune problem.

We change the S256ET for a S257SXE because of to much bearing shaft play..
and go big or go home so we change the injectors for the Opel kit because we want push it to 200kpa at least and because of the bad popping sound at 6k..

but again with the new injectors we have the same problem...

I tried to adjuste Injection timing because the ZZP tune is changed from GM stage 1...

so I tried GM stage 1 injection timing table value (because I see alot cobalt LNF running 180kpa on stock turbo without touching injection timing......I think it a bit better but.. is it the weather today or the tune or anything else??

when the engine pops at high rpm I'm loosing power and its hard to it the rev limiter.. but again no knock and no misfire.7

Am I the only one to experience this problem? I'm not the only one with this ZZP stage kit and all this stuff.

I tried to inject Meth in the intake with a Meth kit and some times its popping like other test and some times i'm able to hold a nice 200kpa of boost without any popping sound and lost of power to the redline 7.5K

HELP ME!!! haha 4 years of problem with this bad car and alot of money.

I have hptuner by the way and never had this problem with other LNF even with K04 ou ZFR at high boost..

 

Whats your spark plug gap?

 

Whats your injector ms? Fuel pressure vs commanded?

 

This is brand new ACdelco and I did not touch the gap for this one and its not running well.

Last year on a previous kit of NGK iridium, i tested so many gap sizing from really close to the tip or any recommendation but nothing stop it from cuts like this.
The NGK can cause problems to people in forums so this is why I put ACdelco this month on it.

It backfiring in the exaust like hell (in external dump pipe and exhaust downpipe) but no missfire in hptuners

 

With stock injectors, commended was 2600 and actual 2600 or so
with opel, commended up to 2600 but actual not exceed 2200 so I expecting low pressure intank pump but the backfiring problem was there before the opel swap so I did not watch the hpfp for the moment.

the ms is between 6 and 5.3ms

 

 

Spark plugs tested anywhere from 0.034 to 0.022 and nothing helped

 

Does your coolant get above 178*F? I generally don't start logging until the car has been at 185*F for 5-10mins. Also what is the commanded lambda vs the actual? I see the actual at 0.86 at your screen grab.

For that turbo I would say try a plug gap around 0.030" or 0.028", also lower your desired fuel pressure to what you're seeing. I'm sure the ECU doesn't like the 400psi delta, and I don't recall what mode it can kick it into if there is a huge delta there, but it's best to remove it.

 

The coolant is 186 at idle but every times we going on the road it go down to 176-178-180max

for the pressure delta I can test to drop desired but as I explaned, with original injectors I had the backfiring problem even with 0 of delta between commended and actual

 

commended lambda is 86-87

 

I know you said it was doing it before, but it's best to get everything squared away so you don't have multiple issues causing problems.

I would try driving for 5-10mins and see if you can get it above 180*, I find that pretty unusual for an LNF to not get above 180* while driving in mid 70* weather, I can get my LNF to 185F driving in 30* weather.

 

You know what?
With the AC Delco gaped to 0.026 correct my problem at 26psi boost but need to be a bit closer at 30psi cause the engine cuts a bit a 7200rpm to 7500

Last years we already try at 0.028 0.026 0.024 and 0.022 and it didnt solve the problem but it can be a NGK problem

 

Try copper plugs