Overly rich Decel and Sporadic Ignition Timing

looking for a little help understanding something I see on my car from time to time (like every other time I drive it)

sometimes on deceleration, typically on the way to a stoplight, i'll notice the wideband go from full lean/no fuel, to something around .7-.8 lambda. it'll last about 20 seconds or until I blip the throttle or start accelerating. I have my cat warmup disabled on an older version of the software, the car is plenty warm at this point. The commanded EQ shows 1.0 during this time (9:14 into the log). Any ideas what's going on here?

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I know these torque managed cars are a bit different, but i'm not used to seeing sporadic timing this bad. Just curious if what is shown at 19:50 is considered "normal" or acceptable. Full throttle follows the base timing map well. the part throttle stuff is all over the place though

My truck did the same rich idle thing. Notice the STFT goes to 34% both banks, I don't know why it does this. It went away when I disabled LTFT and Idle LTFT. Since then I have turned all LTFT back on and it still does it but only rarely.

I don't know for sure about the spark issue. It looks like you are still running stock VVE and at 19:52 the MAF and VE are pretty different, I don't think the computer likes this and it throws off the torque calc.
I think one main difference with torque based tunes is that you can't ever go MAF only, the compute needs the VVE for the torque calc. Even a rough VVE tune would be a lot better than what you have.

really appreciate the insight.

So what confuses me on the second part, is multiple people have said the vve tune i have is trash (and I don't disagree lol, I dont know why it looks the way it does). that said, its what came on the car, and is almost identical to the 14' and 15' c7 z51 tunes i pulled from the repository as far as the jumps and spikes go. I've done some vve logging, thats actually what this log was intended to be, but the gmve adjustment table i'm getting is a bit all over the place even with the standard filters so I've been hesitant to start making adjustments.

btw, car is a 14 C7 M7 Z51 that is stock other than headers and an exhaust.

You currently have the cam locked at 5 degrees. You need to lock it at 0 to do any main VVE table editing as it will always idle at 0 pretty much no matter how you set the other tables.

You can then lock it at 5 or whatever to adjust your VVE intake cam multipliers for the different zones.

That VVE table is stock, but if you've installed a cam or something it should be tuned in...

You can use this math to calculate the VVE table while dialing in your MAF - just make sure to use some common sense for the decel zones and hand shape the outliars that it'll come up with during sudden throttle changes. It needs good easy slow pedal focused movements to be accurate.

(([50041.223]*(273.15+[50011.241]) * (1000/[50030.91]))

EDIT - just saw where car only had headers and exhaust - you need to fix some O2 settings for this - otherwise don't bother with the VVE.

You're welcome to try these O2 settings since yours is still NA with headers. May or may not work depending on the length to sensors.

thanks!

I'm using the GMVE calc from smokeshows thread and with those settings you sent it really seemed to smooth out the error corrections I was getting. What parameters do you use to dial those settings in? I had only seen topics regarding the idle PID loop, makes sense it's needed for non idle closed loop control.


I went to add (([50041.223]*(273.15+[50011.241]) * (1000/[50030.91])). I'm a little confused on the units, I've got (g * ?K / Pa) . I think I'm missing something, or looking at it the wrong way

Units should be correct - this formula uses airmass and temps to calculate the table out. Just noticed the one temp should be Celsius. I know it gets the MAF and VVE almost identical after a couple of passes depending on how the throttle inputs are carried out.

I guess my head has been in the sand. I don't know how I've missed this method. thanks for sharing.

ok to use manifold air temp (2126) instead?

Yes sir. Anything to make it more accurate is better. I typically use manifold temp on boosted setups as not every NA platform has one, so I keep my own set up more universal if you will....