I’m probably like many of u and avoid using the AC in the ZR. As a result I do very little to no “tuning” under conditions that involve the AC. Well, if I want my gf on a trip, I need to use the AC. The last several weeks were spent installing a non-leaking condenser, accumulator, tensioner, and a low mile compressor.
So, I imagine I need to provide a bump in idle speed for clutch engagement. What else to avoid the typical seesaw idle on modded motors when using AC?
IAC steps added?, Deadband? timing?

 

I used to hate running the a/c on my 86 with a hotcam. When the compressor was running the whole car would shake at idle. I finally fixed it by increasing the idle o2 window terms to decrease idle AFR. My car idles good at 750, 850 with a/c on.

 

Don't know what mask you're using, but GMs generally handle everything. I know AUJP automatically handles A/C-on adjustments (slight RPM bump in P/N, IAC anticipation adjustments & learn, IAC adjustments if idle below a deadband threshold RPM, one-time BPW increase of approx. 2ms when A/C 1st turned on, proper ECM fan control, HPCO, high MPH A/C clutch disengage, etc.) Bottom line, the code address everything that affects idle speed with logic for A/C on or off, even startup. Nothing really needed once in gear other than MPH based clutch cutoff.

Like Larry, I had compressor chattering at idle, so just changed idle speed at temp table to correct. Granted idle is also higher with A/C off but OK. May also have to adjust max idle in gear RPM upward if the idle table change exceeds the max threshold. Optionally to promote increase in idle speed, if mask allows, can consider changing the IAC learn min and max steps to be added with A/C-on.

 

Elky,

Already done a number of the things u point out. The Mask ID I am using is the
$D0A for the 92 LT-5. I will look into the BPW bump because its clear when at idle and the fans kick, it sends the motor into a lazy oscillation.

 

Nope, don't see anything dealing with BPW for AC ON parameter in $D0A or the $8EA masks. Both LT5.

 

Are you looking at XDF files or code hacks? It may be in the code but not editable via the XDF. RBob may know.

While it happens very quickly (only one time in 12.5ms) and may not be detectable in a log, could try and see if get BPW bump with A/C on. AUJP and others add 1.95ms which is a lot, and it's added irrespective of idle or otherwise.

 

No just the .xdf. Don't have the hacks for this. Maybe RBob does. I will check the log and see if there are a bump w AC turn ON.

 

I don't believe that there is a fuel bump.

RBob.

 

Thanks RBob. I have found that ECM will learn as far as keeping motor idling. Its even avoided the seesaw when u come to a stop. I think one issue that may be contributing is the underdrive pulley on the alternator. I was running around on a pretty hot day this weekend in stop and go when I noticed the alternator gauge showing a slight discharging situation. LT-5 alternators, along w AC compressors, are notoriously small. "Adequate" would be a word too kind for those components. However, cruising it appears to be sufficient. I am sure the fans and blower are pulling the amps.
Would u make any changes to the stock settings on IAC when it comes to a "cammed" motor? I may need to bump idle a touch more.

 

There is an idle speed adder for when the A/C is active. I do an idle speed bump using this parameter.

RBob.

 

RBob,

I have bumped that 100rpm. May add another 25-50rpm.

 

RBob - For clarification, no fuel bump for $D0, or generally across the board. Looks like AUJP does provide it (1.95ms).