NEWBIE and need help with A/C idle
Thread Starter
Teching In
Joined: Nov 2018
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From: las vegas, nv
NEWBIE and need help with A/C idle Hello all,
I am new to the site and need some help with an issue I have regarding the A/C and idle. I recently put a LS3 gm525 with 4L65E into a 72 chevelle. I have E38 and T42 controllers and a PSI harness. The problem is when the A/C is turned on the idle drops and almost stalls. What causes this? and What can I do to prevent this from happening? Do I need a larger alternator? The heater works fine with no changes in RPM at idle.
I am new to the site and need some help with an issue I have regarding the A/C and idle. I recently put a LS3 gm525 with 4L65E into a 72 chevelle. I have E38 and T42 controllers and a PSI harness. The problem is when the A/C is turned on the idle drops and almost stalls. What causes this? and What can I do to prevent this from happening? Do I need a larger alternator? The heater works fine with no changes in RPM at idle.
Thread Starter
Teching In
Joined: Nov 2018
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From: las vegas, nv
i also have hptuners and have went through all the tables and see nothing related to a/c. My a/c is vintage air and is not connected to the ecu. Do you know what particular tables in the tune that accounts for the extra load?
If you don't have the ECU controlling the A/C, you can't account for the torque loss. I usually use EFI Live instead of HPT and there are a host of AC tables to account for the torque loss.
Thread Starter
Teching In
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From: las vegas, nv
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They would be ECU controlled so the ECU knows when to add additional idle air due to added engine load. Not sure why this is a tough topic to understand. A compressor takes horsepower to turn and the computer needs to know when this added load is going to be pulled on the engine so it can compensate.
Thread Starter
Teching In
Joined: Nov 2018
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From: las vegas, nv
They would be ECU controlled so the ECU knows when to add additional idle air due to added engine load. Not sure why this is a tough topic to understand. A compressor takes horsepower to turn and the computer needs to know when this added load is going to be pulled on the engine so it can compensate.
That is a failure of the swap harness maker and has nothing to do with the ECU. You could always add a pin.
Thread Starter
Teching In
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From: las vegas, nv
so i spoke with a local tuner as well as the harness maker today. I guess for several year vehicles that use an E38 there is also an BCM (body control module) that controls the idle when the a/c is on. And in many ls swap cases, modern engine into 72 chevelle without an BCM the fix is to simply raise the base/park/gear/ target idle speed 50-100 rpm and tune it from there.
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HPT tuners>Engine>Idle>Base Idle RPM>Idle Target speed,
In Gear AC off 850 850 850 825 775 700 700 700 650 559.9609375 550 550 550 550 550 550
In Gear AC on 850 850 850 825 775 700 700 700 650 559.9609375 550 550 550 550 550 550
P/N AC off 900 900 900 875 875 875 875 725 675 650 650 650 650 650 650 650
P/N AC on 900 900 900 875 875 875 875 725 675 650 650 650 650 650 650 650
Here is the table to try and adjust your target idle speed for Ac in gear on and park/neutral idle speed.AC on.
In Gear AC off 850 850 850 825 775 700 700 700 650 559.9609375 550 550 550 550 550 550
In Gear AC on 850 850 850 825 775 700 700 700 650 559.9609375 550 550 550 550 550 550
P/N AC off 900 900 900 875 875 875 875 725 675 650 650 650 650 650 650 650
P/N AC on 900 900 900 875 875 875 875 725 675 650 650 650 650 650 650 650
Here is the table to try and adjust your target idle speed for Ac in gear on and park/neutral idle speed.AC on.
Thread Starter
Teching In
Joined: Nov 2018
Posts: 12
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From: las vegas, nv
HPT tuners>Engine>Idle>Base Idle RPM>Idle Target speed,
In Gear AC off 850 850 850 825 775 700 700 700 650 559.9609375 550 550 550 550 550 550
In Gear AC on 850 850 850 825 775 700 700 700 650 559.9609375 550 550 550 550 550 550
P/N AC off 900 900 900 875 875 875 875 725 675 650 650 650 650 650 650 650
P/N AC on 900 900 900 875 875 875 875 725 675 650 650 650 650 650 650 650
Here is the table to try and adjust your target idle speed for Ac in gear on and park/neutral idle speed.AC on.
In Gear AC off 850 850 850 825 775 700 700 700 650 559.9609375 550 550 550 550 550 550
In Gear AC on 850 850 850 825 775 700 700 700 650 559.9609375 550 550 550 550 550 550
P/N AC off 900 900 900 875 875 875 875 725 675 650 650 650 650 650 650 650
P/N AC on 900 900 900 875 875 875 875 725 675 650 650 650 650 650 650 650
Here is the table to try and adjust your target idle speed for Ac in gear on and park/neutral idle speed.AC on.