Member
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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Member
The first thing I would check is the dwell settings in TunerStudio. I'm running an M73 with MS3Pro, and it took me several tries before I could get the engine to run under load without misfiring. Be VERY careful about adding timing under boost. Usually you would retard timing above 100KPA. Ultimately, I ended up running MSD as well, but you shouldn't have to do that with wasted spark.
Member
Also, you might check the fuel pressure under boost. Trying to feed 80lb injectors with a 255LPH fuel pump doesn't seem like it would be enough. Just a thought....
Member
We messed around with the dwell too without luck.Originally Posted by C3Ferrari
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Member
The 80lb injectors, is just more of an overkill thing, the duty cycle is very low at the moment.
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Lurker
I dont think your problem is fuel related....I run those same injectors no problem....Do you have a log file you can send me, Ill dig through it and see if I see anything?
Member
Hey that would be awesome. My investors have been sent out for testing and cleaning but when they come back I’ll go for a quick drive and take a datalog. Hopefully you see something we’ve been missing.
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Member
Update: I double checked my wastegate lines and they were reversed. In a datalog it showed the car creeping/spiking to 20psi with a 12.5 psi spring. I have now correctly installed the vacuum lines and the boost stays steady. I’m pretty sure the knock issue has gone away now that it holds boost steadily, but the misfire is still there.
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Member
Recheck spark plugs and AF then. You may have hurt something
Member
Spark plugs are fine. The AFR is pig rich because we were trying all sorts of things o. The dyno to get rid of the misfire and knock. Now that I think the knock aspect has been taken care of, I’ll get it retuned as a normal car without knock to try to get rid of the misfire.
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