LS3 has trouble returning to idle w/ AC On - tried most suggested recommendations

[jclayc]

Hi everyone, I'm very much a newbie at tuning and have had someone working on my tune up until this point. I have a 2005 CTS-V that came with a LS6 but I've now put a 416ci LS3 into it. Other than being a bit lean in bank 2 at idle, the only issue I seem to have is that, when the AC is on and I'm out of the gas coming to a stop, the RPMs dip twice to like 300rpm and recover.

More details:
11.7:1 compression
245/250 114+2 cam
Mamo 235 heads
ported FAST 102
LS2 TB
stock LS6 MAF & MAP
Deka 60 lb injectors
return style fueling w/ a walboro 255 through FAST rails and an aeromotive FPR (connected to the intake)
TR6 plugs

I've gone through the forums and seen people suggest increasing AC Offset Max/InGear from 0.40 g/s to 3.40 g/s. That's the "_v1" HPT and HPL files I've attached - where I start w/ no AC drive up to a stop sign in the first few seconds and turn it on then drive more. No difference.

I've also seen people suggest modifying the AC Torque vs. AC Pressure settings. I left AC Offset Max/InGear at 3.40 g/s & set AC Torque vs. AC Pressure to x2 & no difference. That's the "_v2" HPT and HPL files I've attached - where I start w/ no AC drive up to a stop sign in the first few seconds and turn it on then drive more.

I've seen people suggest turning off all stall saver functions and suggest setting AC Torque Max Retard to all 0s... those didn't seem to help.

Can anyone give me an opinion on what's next? I think it may have to do with fine tuning of the spark but that's waaay beyond my level.

72416_1.hpl

72416_1.hpt

72416_2.hpl

72416_2.hpt

[2007V]

Hey Clay,

I tried to open the files tonight but its on an updated version of hptuners that I haven't done yet. I do have it installed on another computer so I'll try on it tomorrow.

Here is what I would do:

1) Put all your fuel injector flow vs pressure at the 58 psi values. So that means if the hp tuners table column is 40 psi, the values you put in here should be the 58 psi values from your injector flow spreadsheet. This is because the computer is expecting a different delta fuel pressure than what you are giving it with the regulated return system.
2) Copy the throttle body area/airflow values from a 06-07 CTS-V stock file from the HPtuners tune repository. Also copy anything related to AC and airmass from the 06-07 file.
3)That cam seems to have a fairly good duration and will have some reversion. You will likely need to change the End Of Injection timing. Research which way it needs moved. I think it needs to move later in the cycle after the exhaust valve closes. This keeps the fuel from short circuiting out the exhaust and a false reading on your wide band.

I don't know what else is changed from your stock file. Is this a first tune on the stroker or has it been running like this for a while?

These should be a good start to look into.

[Area47]

torque management > engine > ac vs pressure. increase this table.

[jclayc]

thanks for the replies... I'll tweak some things and report back.

[jclayc]

Following up on this: I'm continuing to diagnose. Watching my latest log (around 6:38) the A/C is on, I bring the RPMs up and then let off. The MAP goes up to 90+ kPAs, bank 2 LTFT goes lean (odd), RPMs drop and it struggles to return to idle. My thought is that since the Torque Management > Engine > Max Retard only goes up to 80 kPAs, perhaps I've run into the need to scale the tune??? I tried doing things like increasing torque management > engine > ac vs pressure but it didn't seem to make a difference.

FYI - bank 2 LTFT shows lean early in the log because it was learning out a vac leak I had.

080316.hpl

[schpenxel]

Add throttle to the log--not pedal, but throttle blade. It's probably opening for the MAP to go that high IMO

Also add idle adapt advance and anything else idle wise you can find

Those are some huge differences in fuel trims between banks. Something isn't right IMO. Either sensor or leak

[jclayc]

When it comes to adding throttle (blade)... I see throttle position (SAE) [ratio], throttle position [ratio], throttle position sensor [electric potential] and throttle desired position [ratio]. Are you talking about the throttle position sensor?

Regarding the fuel trims between banks: as I say, I had an intake manifold leak that I fixed before startup and believe you can see the STFTs and LTFTs even out about 1/2 way through the file. Yes, bank 2 was way lean but only appears to go lean now when the AC is on and at idle which, as I say, is odd. Thoughts on that?

[schpenxel]

They aren't even close to evened out at the end of the log. They're apart by 15-20% even at the very end and O2 sensors are switching normally, so it's not a matter of the new trims being learned or not.. that is what they are.

There is something else wrong to have a 20% difference bank to bank. I would try to figure out that first.