88 350 tbi. AC signal to ecu?

[mrgto]

I have a custom project I've been working on. I installed a new engine wire harness and eliminated all electrical/ wiring that is not associated with the operation of the motor.

One of the things I'm looking to accomplish is a way to increase the idle on the fly. Reason for this is I'm running two high output alternators that need to the motor to be at a minimum 950rpm idle for maximum output.

One option would be the ac signal to the ecu. It's my understandunf that when the ac is engaged it signals the ecm to bump up the idle. I could run that wire to a toggle switch and flip it when increased idle is needed.

Is it a 12v hot to the wire that alerts the ecu to bump the idle?

Were the computers for these trucks programmed for each individual model and features? My truck did not come with AC. I would assume that it wouldn't matter, if a signal was sent it would it still bump the idle?

How much of an idle increase can I expect once the switch is activated?

Thanks guys.

 

[bucket]

How about just a simple adjustable PTO throttle cable? You can easily set it to whatever idle speed you want.

I don't think the idle increase for AC would be enough for your needs.

 

[mrgto]

I've thought of this, but not sure how it would hook up on a tbi system

 

[yevgenievich]

12v on green wire to ecm will tell it to bump idle, but probably not enough as was mentioned above

 

[bucket]

I've thought of this, but not sure how it would hook up on a tbi system

Basically the same as a carb. Different type cables will hook up in a different manner, usually involving some minor modifications.

 

[1987 GMC Jimmy]

I agree. The idle increase that the A/C signal warrants is too close to negligibility for what you’re looking to do.