Help Me Find A Needle In The Haystack!

[SGT StudMuffiin]

Hey guys, I would love some help and feedback on an issue I’ve been chasing for months without success, and a lot of time and money wasted. Every time I get under boost, starting as low as 3000rpm, I get a horrible misfire and knock. 2 mechanics, 2 tuners, and my engine builder cannot seem to figure out the issue. We messed around with a lot of the tuning in TunerStudio and lots of the hardware. I changed my whole ignition setup, changed the spark plugs 3 times with lots of different gaps, and have tested common sensors such as my CPS. I’ve also done a leak-down test, compression test, engine oil inspection, and basically just a lot of tinkering around. My tuner tried to add timing to get rid of the misfire and it goes away but starts knocking like crazy. He also tried to take some timing away and we got even more misfire. No matter what he did on the dyno, he and 2 of his colleagues could not figure it out. To verify if it’s the engine, we unbolted to the BOV and did a pull to replicate N/A somewhat, and the motor did not knock or misfire, so it seems that the engine is fine.

Any help of suggestions would be greatly appreciated. The car was turbo’d back in June of 2016 and in that time, we haven’t had the car on the road a single time with a proper boostable state. (I have terrible luck)

Engine setup:
-M20B28
-M52 crankshaft
-CP 9.0:1 Forged pistons
-Eagle Forged rods
-ARP hardware + ARP head studs

Turbo setup:
-Precision 6262 T3 .82
-Blunttech manifold
-Precision 46mm wastegate (recirculated)
-Greddy BOV
-Fully straight piped 3” exhaust

Fuel setup:
-Walboro 255LPH
-Siemens Deka 80lb injectors (should I test these??)
-Pump gas

ECU setup:
-Megasquirt 2 PNP E30
-Wasted spark using Megasquirt ignition coil and spark driver
-Stock Engine harness mostly



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[chikinhed]

I have a few possible ideas.

1) Ring out the wiring harness.
2) Verify your timing is what you think it is.
3) Check the location of the MAF, if using one. MAF readings can be affected by clock position in the pipe a significant amount.
4) Is your fuel still good?
5) Verify your fuel pressure is rising with boost and that you have the correct base fuel pressure.
6) Test for an exhaust restriction causing high back pressure.
7) Datalog AFR, rpm, psi, TP, timing and %load. Post the datalog.
8) What were the compression test numbers? Are they consistant with a 9.0:1 engine?

[Substance D]

I had a miss under boost only, tightened up spark plug gap, cleared it up, as I raised the boost level, I would need to tighten up the gap, I think .018 is what I was running last.

Oh wait, your m20, sorry, your on your own haha