Why is my stock commanded AFR so rich? 14.1 and 11.9 (PE)

[cp-the-nerd]

Engine is the port injected 3.6L VVT (DOHC). I was driving around scanning with TorquePro and noticed my car runs unnecessarily rich, I was getting a commanded 14.1 AFR while cruising and 11.9 during power enrichment. Shouldn't those numbers be closer to 15 for fuel economy and mid 12s for power?

Is there a simple way to bump up the commanded AFR and see if there's improvement? Right now I'm getting around 18 cty/29 hwy and if I could bump that up an mpg or two (especially on the highway) that would be awesome. Also open to DFCO suggestions.

cp-the-nerd_09-Malibu-LY7_v3.2.hpt

[5FDP]

Log alcohol content in the table display, I can bet money that you run a fuel that has atleast 5-10% ethanol content in it.

Your vehicles flex fuel option is figuring out how much ethanol is in your gas and adjusting the stoich on the fly.

[cp-the-nerd]

Yes, the BP station I go to lists Ethanol content as ~10%. Is that the cause?

I'll run a scan as soon as I can. Thanks. Any comment on DFCO? I'm having trouble learning the parameters. Seems like every new version of the ECU uses different terminology so it's hard to research past threads.

[jtrosky]

I've been struggling with DFCO as well. I found that it was the cause of some strange RPM fluctutation when coasting off the the highway on an exit ramp, for example (when fuel gets turned back on). I raised the "enable" limit to 1500 and it seems to still come on sometimes, even with the RPMs are way under 1500 - don't quite understand why. Its certainly "less intrustive" now, but still kicks in when it shouldn't be (unless I just don't understand all fo the reasons why it kicks in). I've also disabled DFCO from kicking in when in gears 1-3.

[cp-the-nerd]

My DFCO changes also seemed to have less effect than I expected. I've set it up so it doesn't activate in lower gears or until I'm going 30 mph, because the drivetrain lash can be obnoxious when coasting between traffic lights. But I also lowered my enabled RPM so higher gears like 5th and 6th would use it more readily. However, it also takes several seconds to kick in, and that's annoying me.

Can I cut the "Blend Crank Refs" and "Delay Crank Refs" in half to get faster DFCO entry? Should I raise entry spark at low revs to 15 or 20?

[jtrosky]

The available DFCO parameters between your LY7 and my LFX are very differernt. Only the enable and disable RPM parameters are common between our engines. It's amazing how much different the LFX is tuned compared to the LY7 - even besides the direct-injection-related differences, I mean...

Sorry - can't hep with any of your questions! I started another thread about my DFCO issues - feel free to post your questions there if anyone responds. May also want to try your DFCO-related questions in the V8 threads - seem to get much more exposure there!

[ScarabEpic22]

Stoich on pure gas is 14.7:1, on E10 is 14.1:1 so I bet you're running E10. Heck my Sonic doesnt even have stoich at 14.7:1, GM put 14.1:1 in the 0-12.5% ethanol part of the stoich AFR table.

For DFCO, you could try making those changes and seeing what happens (put the scanner on it too and datalog!), should at least make DFCO exit faster. I found on my TBSS with the converter locked, that the DFCO exit was harsh as GM didnt expect the converter to stay locked with 0% TPS.

[jtrosky]

@cp-the-nerd - in case you weren't aware, there is actually a DFCO status bit that you can log. At least there is on my LFX engine.

[cp-the-nerd]

Stoich on pure gas is 14.7:1, on E10 is 14.1:1 so I bet you're running E10. Heck my Sonic doesnt even have stoich at 14.7:1, GM put 14.1:1 in the 0-12.5% ethanol part of the stoich AFR table.

For DFCO, you could try making those changes and seeing what happens (put the scanner on it too and datalog!), should at least make DFCO exit faster. I found on my TBSS with the converter locked, that the DFCO exit was harsh as GM didnt expect the converter to stay locked with 0% TPS.

Thanks!! I feel like my DFCO exit is harsh as well, I wonder if that's the culprit. I'll play around with it, just needed to make sure I wasn't about to do something idiotic.

How do you like your Sonic RS? I think those are super cool and really considered trading when I got the new car bug a while back, but the crazy aggressive gearing put me off. I can't drive a car that runs 3500+ rpm on the highway, gives me a migraine. They feel great from the driver's seat though.

[cp-the-nerd]

Are there risks to playing with AFR?

I'm tempted to bump up stoich by .3 or .4 across the board and see how the car responds. It might sacrifice a bit of power, but I'll compensate with more responsive PE settings when calling for moderate to strong acceleration.