Results: Tuning IAC effective area and Idle Airflow
05-30-2005, 08:35 PM
#1
Results: Tuning IAC effective area and Idle Airflow well i just about have this all wrapped up and i see lots of guys posting up on here about idle issues. so i figured i would let you guys know what has worked for me. also kinda put things together from other threads, ive been getting pms about what i have been doing. lots of people are doing this but now you guys that want to and have no idea can do it lol
first off the logging configuration, btw this was all in hp tuners. i logged:
-IAC Position
-Desired Idle Airflow (g/sec)
-Dynamic Airflow (g/sec)
-STIT
-LTIT Gear, AC off
i logged from a cold start in the morning so i could get coolant and intake air temps as low as possible. i then let the car reach operating temp at IDLE, no gas what-so-ever.
after this i went into the graph in the scanner after i saved the log and had it show only 2 sections, one was the desired and dynamic airflow and the other section was the IAC position. you want the airflow lines to pretty much overlap each other. on the high side IAC counts (125-290) i was getting less air than desired and on the other end i was getting too much. normally for a variance of 1-2 g/sec i used 5-10 IAC steps, 3-4 g/sec 10-15 steps, 4-6 g/sec 15-20 steps, and 8+ g/sec i used 20+. this will really vary on your TB and whats been done with it. mine is a ported jantzer tb with epoxy filling.
that will take some playing with to find out what will work, what i did was make small changes until i saw the lines get close. once they got really close i would make small changes, about 2-3 IAC steps until the lines overlaped.
here is an example. say at IAC step you have more air desired than the dynamic airflow is reading. you will want to increase the IAC number in this area. what you are doing is telling your car that the effective open area is smaller than it thinks, so this will make it open the IAC motor more to let in more air because where it was just wasnt cutting it.
now if the dynamic is higher than the desired you want to lower the number. usually if they are off like this there is a point at which the iac step is set right. remember whta the number is where they switch if this is whats happening to you, you dont want to change that number because its pretty good. and then branch out from there. completing this step doesnt matter if your VE table is set right or anything. this simply "recalibrates" the IAC steps/effective opening area. once this all falls in line you can now recalibrate the idle airflow.
to fix the idle airflow you will have to make sure the IAC effective area is all set right AND that your VE table is set where you want it and you have the fuel trims you desire, at idle. now you want to see what the idle trims are off by. ive just started this step and whatever g/sec it says its off by at each ECT i will change it by about 75% of what i see. so far its been working pretty good. if its negative u want to decrease and if positive, increase it.
now my car will idle very well, my idle speed is set at 800 at operating temps and this is with the f13 cam (230ish duration and .590ish lift on a 112) when i tap the gas the rpms go up and the idle recovers nicely with no over or undershooting. comming to a stop the car will not dip down in rpm or anything.
hopefully this will help some of you guys out tuning for a better idle. if anything is unclear let me know and i will try to clear it up. but so far this has worked out perfectly for me. it takes some time since the car has to be cold. i have made about 10 tunes and counting to get this right, although most was trial and error becuase i didnt understand too much others were doing before.
here are my numbers i have for my iac steps, maybe help some of you all with similar TB for a starting point.
starting at 16 the IAC steps go:
2 5 7 11 16 23 32 42 54 71 87 105 122 140 163 179 199 221 244 261 276 287 298 307 313 315---->this is my highest number and goes from #68 all the way up to 120, that was my max before so i left it. and questions or something i have wrong let me know.
hope this helps guys
first off the logging configuration, btw this was all in hp tuners. i logged:
-IAC Position
-Desired Idle Airflow (g/sec)
-Dynamic Airflow (g/sec)
-STIT
-LTIT Gear, AC off
i logged from a cold start in the morning so i could get coolant and intake air temps as low as possible. i then let the car reach operating temp at IDLE, no gas what-so-ever.
after this i went into the graph in the scanner after i saved the log and had it show only 2 sections, one was the desired and dynamic airflow and the other section was the IAC position. you want the airflow lines to pretty much overlap each other. on the high side IAC counts (125-290) i was getting less air than desired and on the other end i was getting too much. normally for a variance of 1-2 g/sec i used 5-10 IAC steps, 3-4 g/sec 10-15 steps, 4-6 g/sec 15-20 steps, and 8+ g/sec i used 20+. this will really vary on your TB and whats been done with it. mine is a ported jantzer tb with epoxy filling.
that will take some playing with to find out what will work, what i did was make small changes until i saw the lines get close. once they got really close i would make small changes, about 2-3 IAC steps until the lines overlaped.
here is an example. say at IAC step you have more air desired than the dynamic airflow is reading. you will want to increase the IAC number in this area. what you are doing is telling your car that the effective open area is smaller than it thinks, so this will make it open the IAC motor more to let in more air because where it was just wasnt cutting it.
now if the dynamic is higher than the desired you want to lower the number. usually if they are off like this there is a point at which the iac step is set right. remember whta the number is where they switch if this is whats happening to you, you dont want to change that number because its pretty good. and then branch out from there. completing this step doesnt matter if your VE table is set right or anything. this simply "recalibrates" the IAC steps/effective opening area. once this all falls in line you can now recalibrate the idle airflow.
to fix the idle airflow you will have to make sure the IAC effective area is all set right AND that your VE table is set where you want it and you have the fuel trims you desire, at idle. now you want to see what the idle trims are off by. ive just started this step and whatever g/sec it says its off by at each ECT i will change it by about 75% of what i see. so far its been working pretty good. if its negative u want to decrease and if positive, increase it.
now my car will idle very well, my idle speed is set at 800 at operating temps and this is with the f13 cam (230ish duration and .590ish lift on a 112) when i tap the gas the rpms go up and the idle recovers nicely with no over or undershooting. comming to a stop the car will not dip down in rpm or anything.
hopefully this will help some of you guys out tuning for a better idle. if anything is unclear let me know and i will try to clear it up. but so far this has worked out perfectly for me. it takes some time since the car has to be cold. i have made about 10 tunes and counting to get this right, although most was trial and error becuase i didnt understand too much others were doing before.
here are my numbers i have for my iac steps, maybe help some of you all with similar TB for a starting point.
starting at 16 the IAC steps go:
2 5 7 11 16 23 32 42 54 71 87 105 122 140 163 179 199 221 244 261 276 287 298 307 313 315---->this is my highest number and goes from #68 all the way up to 120, that was my max before so i left it. and questions or something i have wrong let me know.
hope this helps guys
05-30-2005, 09:52 PM
#3
i am not really sure about it, i am assuming the drive by wire uses different throttle position for idle airflow so i dont know how the tables are for this, i could be wrong though. maybe someone else can chime in here and give some insight
05-30-2005, 10:56 PM
#4
Originally Posted by WS6FirebirdTA00
i am not really sure about it, i am assuming the drive by wire uses different throttle position for idle airflow so i dont know how the tables are for this, i could be wrong though. maybe someone else can chime in here and give some insight
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05-31-2005, 07:52 PM
#9
ok when i pull that up it shows the effective area the same as mine, so i would assume it would work, only one way to find out, give it a shot. if u need any help just send me your log file
let me know if you see this table as well or not
let me know if you see this table as well or not
