427 with a big cam popping

[triple4x4]

Trying to tune a 427 in a 2013 Camaro, its an LQ4 block with LS3 heads and intake, and a big cam .600+ big, 2" long tube headers. No VVT or DOD, what I cant get around is a popping noise and some back fires around 2000-3000 after shifts and lugging it before passing gear. I have tried everything I can think of from shuting down VVT tables and Oil pressure enable disables, timing give it more or take it away, have though about messing with the DFCO, the MAF curve tuning helped the car in the fuel trims but not with the popping. Out of ideas. Any help will be greatly appreciated.
I will load a log file and tune file shortly.
Holden

[GHuggins]

Have you tried injection timing? Problem is you have raw fuel going into the exhaust... From stock injection timing values start adding right around 5 at a time to your injection boundary until your problem goes away then "fine tune" in your settings. See if that doesn't help you out.

[triple4x4]

sounds like that's whats going on. Didn't know where to adjust it I will try that tomorrow. I've been told that with those heads and the big cam the exhaust valve might be opening while the combustion is still going on and that's where the popping is coming from. I would post the tune and log but I'm not sure how to.

[mowton]

To monitor how you are doing, log your Lambda/afr during idle and note the value. Move the timing as Greg said above and re check, if doing right, the value should begin to become a bit richer. Keep going until there is no change and back it back to the subsequent setting.

As a general note, the direction you should be going is predicated on the cold to hot delta change. Depending on which year, the injection timing can be in ms, reference periods or even degrees. if cold to hot is increasing than add the 5% to the entire table, if decreasing than reduce by the 5%.

Ed M

[triple4x4]

Update: Car runs great in auto mode, once you switch over to manual mode and lug the car it starts popping again. Same symptoms and rpm range as before. Any help would be appreciated.
Holden
Run 9.hpl
427 Camaro Tune.hpt

[Higgs Boson]

decel spark will also affect this. if the car is going into dfco and cutting spark to 5-10 degrees it will crackle on decel. old ecms used to allow you to change dfco spark to 40 and it would smooth out. new ecms are torque based and I haven't seen how to control spark during dfco without disabling it.

if you are getting popping when you are lugging it, that sounds like knock to me.

[triple4x4]

Ya, I noticed in the scanner when it was popping really bad it was also knocking off the chat. So if I go in and change the Main Spark table where the knock was the worst will that effect the Automatic mode at all? In theory it shouldn't, should it?

[Higgs Boson]

how much knock are you getting? pull a corresponding amount of timing from that part of the map.

[triple4x4]

pull that amount out of the map or the main spark table? I have been pulling timing out of the main spark as the knocks hit in the same table range, but it seems like Im chasing my tail.