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rocklizzard91

Misfire issues?

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Hey everyone! I'm having some issues with what I think is my Link G4+ tune. I am getting an odd occurrence at about 3500rpm and about 15MAP. It almost feels like a misfire and makes a pop that sounds like a backfire through the intake. I have checked plug gap to be .028, no boost leaks, when I installed the cams and redid the timing belt I did verify timing was correct but as I am writing this I guess it could have jumped? I will check that tomorrow. I have played with ignition timing, fueling, AVCS and dwell with no luck. The problem stays on e85 as well as 91oct and 93oct. Sometimes it pops really bad and sometimes it is more mild, but it seems like a tune issue because after 4000rpm it drives completely normal. Any ideas?
 
Build info:
V9 EJ207, 266/268 Brian Crower cams, Borg Warner S200SXE (7670) IAT in the manifold plenum, Link G4+ PNP ECU, factory fuel rails, ID1300 injectors, Factory FPR, Walbro 255, Hybrid MBC/EBCS boost control, GM ethanol content sensor. That should be all the pertinent info. This map is tweaked off the factory V9 Link basemap to get me by; it definitely needs work but I wanted to figure out this issue before I got too far with everything else.
 
Thanks for any help! I included a log/map for you all, let me know if you need anything else.

flat 2.llg

91oct1.6dwell.pclr

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I am going to say it has something to do with the fuel table values differing so much in that one area. Someone correct me though, I am still learning. 
You can see the INJ PW jumping around because of this.

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it is pretty rough there, but if you zoom in to look at the actual events on the MAP line you can see the PWs look pretty consistent. I dont think its really a fuel issue because I have ran it richer and leaner with no help in the occurrence.

 

image.thumb.png.7b549c8370dfa695ce77f1635cfb91c8.png 

even across a few events like this you can see the PWs look pretty smooth. the spikes are there, but i think those are from the mysterious events that cause the MAP jump  which makes it want to dump fuel as if it was really seeing that MAPimage.thumb.png.8c0f085b30819239b448078caa41a777.png

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I think it it might be mechanical - as in something non-ecu related makes the engine misfire. Looks to me like the first thing that happens during each of these events is that MAP rises by 10-15kpa, which would line up with either the turbo spooling a bit quicker or from a backfire up the intake. All the other changes we see (VVT target, fuel numbers, etc) come after this and are simply because the engine is operating a few kpa higher and therefore getting different values out of the tables. 

Have you checked that the plugs all look ok? leak down test maybe? Its entirely possible to have mechanical/electrical issues that only hit at a certain RPM due to resonant frequencies, the right amount of pressure on various components.

Is your dyno capable of holding that same RPM but under more load? i'd be interested to see if the issue is still at the same rpm if you add in say 3psi more boost. 

The other thing in your log that is a bit weird is you have the knock level gains set quite differently for each cylinder, and with the gains you have set, cylinder 3 is showing as very noisy. Has all of this been tuned intentionally or is it just left over from a base map/testing things?

 

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Im running the factory STI fuel pulse dampers and it has the factory length vac hose. I haven't touched them.

 

So I decided to remove and replace the timing belt just to be safe and i made sure the Link was sync'd with the crank correctly. All is good mechanically, but I still plan to do a compression and leakdown test.

Unfortunately the car is only street tuned and I wont have time to go rent a dyno until the car is closer to "done"

 

Here is something interesting though. I found a guy with a similar setup and the same turbo and got ROM from him for my factory ecu. I loaded that up and aside from the AFR's (likely due to cams) it seems to not suffer from the odd miss. The car seems to spool the turbo noticeable faster (probably because its not missing) but the top end seems a little slower. 

I decided to pull the ignition and AVCS table over into my Link ecu and the miss still remains. However, even with the same ignition and AVCS values the top end feels more powerful. I'm not sure what this means really, but i feel like it is likely a setting in my Link map that is causing my issues.

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I didnt see this post earlier.  To me it looks a bit lean in general, can you try just changing the 100 & 130kpa rows in the lambda target table to 0.9 to see if that makes any difference.

mNzsav7.png

 

Also dwell time might be a bit heavy if you still have stock coils, can you try dropping that back to about 2.5ms in the normal running area and see if that makes any difference.

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On 11/22/2018 at 1:56 AM, Adamw said:

I didnt see this post earlier.  To me it looks a bit lean in general, can you try just changing the 100 & 130kpa rows in the lambda target table to 0.9 to see if that makes any difference.

mNzsav7.png

 

Also dwell time might be a bit heavy if you still have stock coils, can you try dropping that back to about 2.5ms in the normal running area and see if that makes any difference.

I will try to richen up the map and see how that affects the popping. 

 

I was a little curious on the dwell, the Link values were a bit lower versus my factory ecu values so I changed them (only in the 12-14v areas if I remember correctly)

Are my factory dwell times too long? Should I stick with the Link values?

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7 hours ago, rocklizzard91 said:

I was a little curious on the dwell, the Link values were a bit lower versus my factory ecu values so I changed them (only in the 12-14v areas if I remember correctly)

Are my factory dwell times too long? Should I stick with the Link values?

I have little experience with this particular model but just as a general comment your dwell times look significantly higher than typical for a small COP coil.  So with little other clues to go I think it is worth a try to drop them back to something more typical.  

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Just wanted to check in, I did resolve the problem! Switching the 1.0 lambda target down to 0.9 lambda solved it!

I could have sworn I heard you can run near stoich for 0-2 or 3psi. I am pretty sure I did on the factory cams and turbo. I'm thinking maybe the bigger cams are causing some overlap which give a false stoich reading? 

 

But regardless the new target fixed my hiccup and it runs great now!

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