Hello everyone,

I am needing some experienced opinions on my closed loop idle. I have my closed loop idle 100% where i want it with the A/C off, however, i am having an issue with stalling with the A/C on. My setup is:

• MS2extra 3.4.2 firmware, No A/C IDLE UP INPUT/OUTPUT (ran out of extra inputs/outputs for now)
• bp4w motor 9.5:1 compression
• exhintake mod
• custom intake manifold plenum
• 1000cc bosch ev14 injector dynamics, etc.

I have tuned idle in this order and have been very meticulous. Idle target is 950 rpm:

1. idle valve disconnected/plugged closed, set base idle with idle screw to 800 rpm
2. Plugged in idle valve. Ran idle valve test, got linear PWM values from 43.9% to 72%. IAC is from a FWD BP05 protege/escort, 153hz?
3. Tuned open loop idle, stable AFRs (13.7-14.0, batch), flat timing 10 BTDC
4. Enabled Idle advance timing, adaptive, separately from closed loop idle, ramping up to approx 28 degrees of timing, possibly past MBT
5. Tested with A/C on (open loop + idle advance), in the garage, no driving. No stalls under load.
6. Enabled Closed loop, tuned settings and initial values table based on datalogs, PWM voltage compensation, etc. Everything is working as it should and Closed loop is enabling.
7. Tested with A/C, lights on, etc (closed loop + idle advance), drove around, about 85% good EXCEPT during sudden stop and go traffic, doing a 3 point turn or going from reverse to 1st gear, it stalled.

I am trying to figure out this last piece of the puzzle so i can avoid stalling at all costs. Please take a look at the logs/MSQ and let me know what settings i should tweak?

Thanks in advance for your help.

Jon

 

Didn't open tune, but did you tune the voltage compensation, and/or are you running an NA alternator? Check Vbatt in your log when this happens.

28 deg is too much.

tune afr for lowest manifold vac, focus dead time tuning on idle, not high VE regions

MS2 is tough to get good idle everywhere.

edit: why the heck are you running 1000cc injectors?

 

Without the a/c idle up it will be difficult to catch it, especially if you are just above idle (say 1700-2200rpm) with a small TPS percentage, and suddenly release the throttle.

 

Ted- All the things you mentioned have been done. GT3076r at 20+lbs requires alot of fuel, forgot to mention i was boosted lol.

Reverant - I understand the A/C idle up is important, but that's a relatively new added feature, so what did everyone do before it?

So i messed with it again last night and what really helped alot was adding time to the "PID delay" from 2 seconds to 4 seconds.

Also creating a valley of timing in the idle advance settings, helped a ton, which was SURPRISING cuz i expected the timing to be linear, but thats not the case. Linear timing caused oscillation, this hits a timing wall, then stabilizes it. lowest dip in idle ive seen is 700 rpm at full load (lights on, a/c, etc). Looks something like this:


timing- 18 16 14 20 0
rpm delta- (-600) (-400) (-275) (0) (+400)


I'll mess with it more this weekend to fine tune it, but for now its the best its ever been with the A/C on. It makes me wonder if idling lower than 950rpm be more difficult or easier, opinions? Trying to get as close to OEM idle (750-850 rpm-ish) as possible.

I'll update the thread so hopefully it helps other ppl in the future.

Thanks again,
Jonathan

 

A/C idle-up has been in the code since 2013 I think. Before that, I had the Enhanced MS2s which added the idle-up through hardware.