Idle surge when hot with a/c on

[86mcss]

Just started happening. I have an idle surge when its hot outside(reads 100* + on outside temp monitor) with the a/c on. It does not do it severely bad and usually a tap on the gas will fix the problem but I would like to stop it from happening all together.

What tables should I modify?

Idle air flow> AC offset tabs?

How much g/sec should I add/Take away?



mods: Comp Cam XR265HR 212/218, .522/.529, 114LSA, Pacesetter LT's & ORY, Intake, Gibson catback, 35" tires, 4.10 gears, stock 1800 stall

thanks in advance.

[jimmyblue]

My impression is, that the problem really lies with the airflow /
torque model which is something we can't see. There is a model
for A/C drag vs IAT and A/C pressure and this seems to be a
relatively realistic thing. But a modded car just does not make
the same low-end torque for the same airflow as a stocker and
when you demand said torque (A/C on) it asks for less air via
that route than you really need. Conversely you can sometimes
see A/C produce "cruise control effect" if you have excess air
commanded through the base running airflow.

Ideally you would tweak something like A/C offset until you see
no significant RPM excursion across A/C clutch apply/de-apply.
Look at A/C clutch events and whether the initial response is
RPM up subtract A/C air) or down (add). Rule of thumb, however
much (RPMoff/RPMon) it deflects, use that ratio to scale the A/C
delivered airflow (meaning you may have to change the adder
by more). Ignore all the pitching and yawing after, just look for
the "first valley" or "first peak" after the clutch event.