Dixit

iTrader: (1)

Let me explain the problem first, If I leave the AC off, drive around town, it drives fine, can take the RPM upto 4000, press the clutch, it drops to 900 and holds there with no issue, drives like a normal car. Turn the AC on and drive around town, its a nightmare because if I press the clutch in at anywhere above 2000rpm and it has to drop to idle, it goes past 900 to 300-400 and sometimes just dies, sometimes the VCM kicks it back up to about 1500 and then it just starts hunting till it finds 900. Sometimes I can actually assist by when it drops to idle to give it every so little gas so it keeps it from dropping below 900. Once its there I can be at a light and it idles fine, its just when its coming down from say 2000rpm that it doesnt seem to lock on 900, it drops below it and the VCM fights to keep it alive.

Ive been dicking with this for a few weeks now and simply cant get this right. At first I thought maybe my Cracker/Follower was too low and it was not letting it back to idle gracefully and that really did nothing.

Ive checked my RAF and its definetely dead on, my LTIT is like -0.25g/sec (well within limits) and my STIT doesnt move over +/- 1.00g/sec on the normal drives. Ive left most of the idle values stock like Fan1, Fan2 load, AC on load, etc.

I have a Fast90/Ls2 90mm Ported TB, 228/232 .600 112lsa CAM, AFR205cc heads, SVO30s if you need to know what Im running to better assist.

Dixit

jimmyblue

iTrader: (11)

I recently saw some folk talking about raising the
AC max airflow limit to a higher g/sec value, this
value caps off the allowed bump for the drag torque
to less than what it takes to run the pump unless
you give it some more room to move (big cam
making less torque per airflow down low than
stock, following the VE drop pretty much, so more
air bump is needed for accessory loads. May want
to do the same for the other accessory load fields
like fans etc. while you're at it.

Dixit

iTrader: (1)

Yea I saw the same thread you are talking about then, about raising the AC Offset Max in Gear to say 3.00.

Dixit

SSpdDmon

iTrader: (10)

I don't know what it is in HPT, but I'd try messing with the B4515 table to help with the huge swings. In EFI Live, it's called the "Direct Airflow Correction" table. It has 6 different airflow correctors that account for when the RPMs are either overshooting or undershooting the desired idle speed during various transmission and A/C conditions (ie In Gear, A/C On, Idle Too High OR In P/N, A/C Off, Idle Too Low). My stock '02 table shows it won't even begin to start correcting things until you're about 70 RPM's too high or too low. In order to help my friends' cam'd cars keep from surging, I took about 25% out of this table. But, every car is different...so yours might like something else.

Phil99vette

iTrader: (11)

Make sure:
1) your idle desired and MAF are = when logged
2) Bump AC Max from 1.0 to 3.0
3) Multiply AC torque by 125%
4) Do a cold start learn with the AC on.

Dixit

iTrader: (1)

Phil, My Idle desired and MAF are identical, I played with the scaler till I got it on point. My AC Min/Max was -0.40/0.50 and going to try -2.00/2.00.

Which AC torque table do i increase? The Inertia Torque? or the vs AC Pressure or vs IAT, Im thiking you mean Inertia Torque. Thanks for the help.

Dixit

Phil99vette

iTrader: (11)

Change:
VS AC pressure * 125%
AC Max and Min to 3.00 and -3.00
Cold idle learn

ZL1Killa

iTrader: (17)

are you running OL or CL?

Dixit

iTrader: (1)

Im running closed loop.

Phil, how does one do a cold idle learn? Im familiar with the RAF, but not that, maybe its terminology.

Dixit

Phil99vette

iTrader: (11)

Start the car up and as soon as you start it up turn the AC on and let it idle until it gets to operating temps, if you have a low temp thermostat remember to change your adaptive idle learn temp down to 160.

Dixit

iTrader: (1)

Got it, you the man. I already had the Min ECT on the Adaptive Idle RPM set to 154F. That cold idle learn isnt that just really the LTIT setting in?