IAC position vs effective area
IAC position vs effective area Well I modified my IAC position vs effective area table last weekend and sure enough I was able to get my desired airflow to match my dynamic airflow at idle. It was off by about 10% before and now it's dead on. My overall goal in this is to have my actual airflow=desired airflow=airflow tables without relying on the IAC. That way i don't have to worry about stalling even if i unplug my battery, I will have no cruise control side effects, and it will make me feel all warm inside to have my all the numbers match.
When I adjusted my idle set screw to get my IAC counts down, i was increasing the effective area but the pcm didn't know it. If you look at the table in question, you'll see how the first several cells are 0's. On the stock tune the cells are 0 from 0-12, meaning there is about 12mm^2 of area for the air to pass through with the IAC completely closed. When you adjust your set screw or drill the tb hole you increase this area so it would make sense to move the table to the right so the pcm knows you already have more area. I ended up moving the table 8 cells to the right after some trial and error so the zeros go 0-26.
Next i'm going to try getting my IAC counts down to 10 and use this method to eliminate any cruise control side effects. I would have done it already but i was hitting the tps voltage limit with the set screw method so i'll have to either drill the tb hole or the tps mounting holes so i can turn it.
When I adjusted my idle set screw to get my IAC counts down, i was increasing the effective area but the pcm didn't know it. If you look at the table in question, you'll see how the first several cells are 0's. On the stock tune the cells are 0 from 0-12, meaning there is about 12mm^2 of area for the air to pass through with the IAC completely closed. When you adjust your set screw or drill the tb hole you increase this area so it would make sense to move the table to the right so the pcm knows you already have more area. I ended up moving the table 8 cells to the right after some trial and error so the zeros go 0-26.
Next i'm going to try getting my IAC counts down to 10 and use this method to eliminate any cruise control side effects. I would have done it already but i was hitting the tps voltage limit with the set screw method so i'll have to either drill the tb hole or the tps mounting holes so i can turn it.
Well it depends more on the size of your cam and what you get your iac counts to more than the size of the tb. I tried to calculate how much the table should change by how much my iac counts changed when i adjusted it, but that didn't work, i just had to go with trial and error.
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TECH Fanatic
Joined: Mar 2003
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From: La Porte, TX
hmmm My IAC's are hovering right around 95 when at hot idle...which are way too high. However I have the RAF set low enough to compensate. If I shift my cells in the Effec Area table to the right, will that lower the IAC's? Also did you see any direct correlation to how much the IAC's change vs how much you shift the table? I'm sure one I do this, I will have to re-work the RAF table, but that is not a big deal. I've just about got RAF down to an art. LOL
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can someone explain this and the reasons for me? i saw it depends on cam size and im gonna be doing a cam and i dont really know about these tables and what they help and what they do and how to change it. so any more explaination woudl be great
The only way to change your IAC counts is to get more air to your engine, by drilling or adjusting the set screw. If you do this before lowering your IAC counts your car will probably try to stall on you. So this will not change your IAC counts but it's a good idea to do it after you do change them.
Ws6FirebirdTA00, the single most important thing you'll have to do to get your car to idle with a bigger cam is to let the engine get more air by adjusting the set screw or drilling the hole bigger. Once you do that you may notice your rpms will hang when coming to a stop, and that's what this is intended to fix.
Ws6FirebirdTA00, the single most important thing you'll have to do to get your car to idle with a bigger cam is to let the engine get more air by adjusting the set screw or drilling the hole bigger. Once you do that you may notice your rpms will hang when coming to a stop, and that's what this is intended to fix.
TECH Fanatic
Joined: Mar 2003
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From: La Porte, TX
Ok, gotcha...Basically I need to adjust the screw little more. Once I get the IAC down to 50ish then I need to log IAC pid and Desired IAC pid is that correct? Then shift until the two fall in line with each other?????
Actually, log dynamic airflow and desired airflow. That's another thing I found out, IAC and desired IAC are almost always the same, the only difference is the response time of the IAC motor.
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Joined: Feb 2004
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Originally Posted by P Mack
Actually, log dynamic airflow and desired airflow. That's another thing I found out, IAC and desired IAC are almost always the same, the only difference is the response time of the IAC motor.
. He has a 00 I made an idle config with all the normal stuff plus dynamic airflow, desired idle airflow, iac position, and fuel trim cell. TPS voltage would probably be good too. I had to get rid of my o2 voltage and pulsewidth to make room.
so when i look at these numbers, waht are the key things im looking for, like on fuel trims u want them near 0, what will i do for this? i havent found many posts on this
For this, look for the difference between desired idle airflow and dynamic airflow. If desired idle airflow is smaller, the table needs to shift to the right. For fuel trims you'd want to do some sd tuning, but that belongs in a different post.
I was intrigued after reading this post and decided to go log my dynamic and desired idle airflow. Sure enough, they weren't even close to each other. My car is stock cammed, but has a ported throttle body, so I'm guessing that's what accounted for it. I shifted the cells over 5 to the right, and what do you know? They are almost identical now...revved it up a bit, and the idle fell directly back to my desired 800 RPMs, no stopping at 1000-1100 RPMs like it does from time to time.
Thanks for posting this up! It ended up being a help to me, and made perfect sense once I started looking at it. We'll see how it works on my daily driver...
Thanks for posting this up! It ended up being a help to me, and made perfect sense once I started looking at it. We'll see how it works on my daily driver...