hey guys... i did a search but couldn't find an exact answer on how important this was. I have an aftermarket 58mm throttle body and I had to drill the hole in the IAC port to get the thing to idel right and get my IAC counts down. Now many of you know that the iac tunnel isnt completely blocked off to have the air enter into that small port in the front of the intake mani. It has cutouts on both sides for air to bleed into the main plenum. My question is iv seen guys block those holes that lead into the main plenum off so that all that IAC air goes into that small port in the mani (much like the factory one does) my question is what the purpose of this and how important is it to the functionality and tune of the car. I should be going for a dyno tune on wed and wanted to know if I should do this or if it wont really matter. Car is a N/A 383 lt1 m6... nothing really to crazy decent cam size. thanks for any help on the subject.

 

Idle quality is the biggest impact it will have.

 

great! thanks... car idles fine so i guess im ok then... just didnt want this thing going lean or something on full throttle because of this...

 

I did the IAC circuit mod to mine. Before the mod I had nasty split cell 16 BLMs and they would raise and lower at random.

After the mod. The split BLMs are gone and now my cell 16 BLMs are 128/128 90% of the time. Sometimes they move but never more than 2+/- or so.

Like Cap said, it smooths out the idle and the PCM does not have to work nearly as hard to maintain stoic. I have not datalogged recently to see if it had any effect on other BLMs but I dont see how it really could.

Worth doing on a aftermarket TB IMHO. Also the car does not seem nearly as smelly when running at idle.

 

What size hole did you drill?

 

Closest I could find to the size hole in the OEM TB IAC passage. Dont recall the actual size.

 

I think it is 11/64th. Regardless, I need to get my iac counts down to the 20-30 area.