Really Stupid or Really Creative?

[MaroonMonsterLS1]

Ok, First I'd like to ask if anyone has ever done this (I doubt it...but we will see)

Second...Will it even work?

I was looking at the idle tables and recognized that they have different target idle speeds for A/C on vs A/C off. And the table maxxes out at 8k RPM!!

My Foxbody LS swap doesn't have AC...so could I wire in a switch to tell the ecu that the A/C is on and set that part of the table to a higher rpm to use a a poor man's way to make launching more consistent. For example if I want to launch at exactly 3000 rpm every time, could I set that idle table to 3k when the AC is on? then I would just pull to the line, stage, flip my "launch control" switch and hold the brakes. Then have the ECU do the hard work of keeping the car right at 3000rpm for me to launch.Hp Tuners Idle Table.PNG

[5FDP]

Try it first without hooking up the switch to see if the computer will even allow you idle it that high.

[nobox351y]

That would be a really interesting thing to do. If it works, I would be interested to see how quickly it would go from 1000 to 3000 rpms. Personally I would want it to ramp in slowly. Would be awesome to change starting line rpms between rds as well.

While I wont be racing an efi car any time soon this is pretty neat.

Let us know what you find out.

[Ben C]

Give it a go, but I can't see it happening if the car is an auto

[GHuggins]

Interested in this as well, but I think it limits it to around 2000ish? Could be wrong...

[cobaltssoverbooster]

although you can set the idle rpm to just about any rpm (up to 8000?); i think the limit is defined by the amount of airflow range the iac is allowed to use in the positive direction when used in AC mode along with max mechanical iac flow. There is a setting for max step i believe its called AC Offset Max/InGear. its an airflow setting for the adaptive settings. i haven't tried it but adjusting that to give more headroom to go above could net you some higher results. unfortunately the iac rpm increase will be limited by the amount of airflow it can pass at wide open iac. This max iac airflow may not be enough to hold a loaded converter at say 3000 because as the rpm goes up so does the required converter input trq as it starts to stall. This will demand an increase in airflow on an exponential increase as you drive the rpm higher into the converter and push it closer to the stall limit.

i mentioned the table in another thread but never heard back if that was a limiting factor to allow the idle to increase over 1300 rpm on a stock yukon. My 408 is still not operational so i cant test it myself. Curious if that helps drive desired rpm higher.

[MaroonMonsterLS1]

So from another forum I have read about using a 5 pin relay in the VSS circuit and utilizing the "Bad VSS cutoff" section rev limit. Has anyone heard of something similar or maybe done it yourself.

[MaroonMonsterLS1]

Update on this. The RPM limit IDLE table did not work. The IAC steps maxed and it would only idle up to about 2400 rpm and it took quite a while to get there.

Will test the Bad VSS cutoff when I get the car back out in the spring, but if anyone has some insight or experience with using that table, I'm all ears.

[KFXGUY]

All you have to do is put max negative spark in your in drive spark table past 3000rpm. When you let off the brake and the car starts rolling it will revert to the main spark table. Kinda like a poor mans two step. Works a little different than what your wanting but helps launch at the correct rpm. I haven’t tried it but I read somewhere it works.