Iac steps vs effective area table
08-06-2018, 12:33 PM
#1
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Iac steps vs effective area table How do I correct this table so the iac will work correctly. Car is heads cam Ls1 with fast 102 and nick Williams 102. Sd tune running in open loop.
Been reading up on it some but not exactly sure what to do. Do I log dynamic airflow, desired idle airflow and iac steps. Take that specific iac step cell and change low or higher so that the desired idle airflow and dynamic airflow gets close to matching? Do that for as much as I can on the table.
The main problem I have with the setup is blipping the throttle and the engine dying. Have messed with idle over speed and under speed, tried adjusting the proportional table, changed some fueling which helped the most.
It just flat out drops to nothing and will occasionally catch back up.
Im thinking part of my issue maybe where I have the throttle blade adjusted. Car won’t idle correctly at a set timing. Only idles right with over speed and under speed catching it. TPS voltage is .69 and the hot iac counts seem to stay from 80 to 110.
Car cranks and idles good but as soon as I blip throttle it’s over.
Been reading up on it some but not exactly sure what to do. Do I log dynamic airflow, desired idle airflow and iac steps. Take that specific iac step cell and change low or higher so that the desired idle airflow and dynamic airflow gets close to matching? Do that for as much as I can on the table.
The main problem I have with the setup is blipping the throttle and the engine dying. Have messed with idle over speed and under speed, tried adjusting the proportional table, changed some fueling which helped the most.
It just flat out drops to nothing and will occasionally catch back up.
Im thinking part of my issue maybe where I have the throttle blade adjusted. Car won’t idle correctly at a set timing. Only idles right with over speed and under speed catching it. TPS voltage is .69 and the hot iac counts seem to stay from 80 to 110.
Car cranks and idles good but as soon as I blip throttle it’s over.
08-06-2018, 06:25 PM
#2
Have you tried adjusting your Throttle Follower table for that?
Edit: Responded to soon without reading your whole post. I would open the throttle blade to get those counts down to 50-60 then do a TPS reset and see how it acts. You may need to lower your TPS voltage also. Read through my thread titled "Idle Airflow config?". Theres a lot of good sugestions in there.
Edit: Responded to soon without reading your whole post. I would open the throttle blade to get those counts down to 50-60 then do a TPS reset and see how it acts. You may need to lower your TPS voltage also. Read through my thread titled "Idle Airflow config?". Theres a lot of good sugestions in there.
Last edited by Monte4ever; 08-06-2018 at 06:38 PM.
08-06-2018, 07:01 PM
#3
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Have you tried adjusting your Throttle Follower table for that?
Edit: Responded to soon without reading your whole post. I would open the throttle blade to get those counts down to 50-60 then do a TPS reset and see how it acts. You may need to lower your TPS voltage also. Read through my thread titled "Idle Airflow config?". Theres a lot of good sugestions in there.
Edit: Responded to soon without reading your whole post. I would open the throttle blade to get those counts down to 50-60 then do a TPS reset and see how it acts. You may need to lower your TPS voltage also. Read through my thread titled "Idle Airflow config?". Theres a lot of good sugestions in there.
The main reason I came to that conclusion was when we switched from an ls6 intake and stock throttle body to fast 102 and nick Williams 102 tb on my dads heads and cam car. I didn’t have to really do anything but tune the ve on his with the stock tb. After the change to the 102 intake and tb it didn’t wanna run very well but I half assed it and made it work a little better.
08-13-2018, 06:15 AM
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It is difficult to describe how to do this. First get your warm idle counts down to about 30. With a NW 102, this may involve drilling if you get past .67 volts. What makes it tricky is you can not log effective area, so this has to be done indirectly.
Log desired idle air vs iac counts
Log dynamic air vs iac counts. Same log, just a different histogram.
Copy both into excel
Copy your effective area table into excel
Then, for a specific effective area, look up the counts, find the dynamic air that matches those counts. Then, use the desired air that matches the dynamic air and find the counts for the desired air and key that into the effective area.
Confused yet?
Example: 44 sq mm area IAC is 100. When IAC is 100, desired air is 12, dynamic air is 16 g/sec. when dynamic air is 12, iac is 36. Key 36 into the 44 sq mm cell.
Rinse and repeat. A lot. After 1-3 logs it should be close enough to help with stability. Typically after the first log there is a notable improvement.
Hope that makes sense. And helps.
Log desired idle air vs iac counts
Log dynamic air vs iac counts. Same log, just a different histogram.
Copy both into excel
Copy your effective area table into excel
Then, for a specific effective area, look up the counts, find the dynamic air that matches those counts. Then, use the desired air that matches the dynamic air and find the counts for the desired air and key that into the effective area.
Confused yet?
Example: 44 sq mm area IAC is 100. When IAC is 100, desired air is 12, dynamic air is 16 g/sec. when dynamic air is 12, iac is 36. Key 36 into the 44 sq mm cell.
Rinse and repeat. A lot. After 1-3 logs it should be close enough to help with stability. Typically after the first log there is a notable improvement.
Hope that makes sense. And helps.
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08-13-2018, 06:44 PM
#5
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Thread Starter
It is difficult to describe how to do this. First get your warm idle counts down to about 30. With a NW 102, this may involve drilling if you get past .67 volts. What makes it tricky is you can not log effective area, so this has to be done indirectly.
Log desired idle air vs iac counts
Log dynamic air vs iac counts. Same log, just a different histogram.
Copy both into excel
Copy your effective area table into excel
Then, for a specific effective area, look up the counts, find the dynamic air that matches those counts. Then, use the desired air that matches the dynamic air and find the counts for the desired air and key that into the effective area.
Confused yet?
Example: 44 sq mm area IAC is 100. When IAC is 100, desired air is 12, dynamic air is 16 g/sec. when dynamic air is 12, iac is 36. Key 36 into the 44 sq mm cell.
Rinse and repeat. A lot. After 1-3 logs it should be close enough to help with stability. Typically after the first log there is a notable improvement.
Hope that makes sense. And helps.
Log desired idle air vs iac counts
Log dynamic air vs iac counts. Same log, just a different histogram.
Copy both into excel
Copy your effective area table into excel
Then, for a specific effective area, look up the counts, find the dynamic air that matches those counts. Then, use the desired air that matches the dynamic air and find the counts for the desired air and key that into the effective area.
Confused yet?
Example: 44 sq mm area IAC is 100. When IAC is 100, desired air is 12, dynamic air is 16 g/sec. when dynamic air is 12, iac is 36. Key 36 into the 44 sq mm cell.
Rinse and repeat. A lot. After 1-3 logs it should be close enough to help with stability. Typically after the first log there is a notable improvement.
Hope that makes sense. And helps.
08-13-2018, 08:57 PM
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11-26-2019, 03:54 PM
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It is difficult to describe how to do this. First get your warm idle counts down to about 30. With a NW 102, this may involve drilling if you get past .67 volts. What makes it tricky is you can not log effective area, so this has to be done indirectly.
Log desired idle air vs iac counts
Log dynamic air vs iac counts. Same log, just a different histogram.
Copy both into excel
Copy your effective area table into excel
Then, for a specific effective area, look up the counts, find the dynamic air that matches those counts. Then, use the desired air that matches the dynamic air and find the counts for the desired air and key that into the effective area.
Confused yet?
Example: 44 sq mm area IAC is 100. When IAC is 100, desired air is 12, dynamic air is 16 g/sec. when dynamic air is 12, iac is 36. Key 36 into the 44 sq mm cell.
Rinse and repeat. A lot. After 1-3 logs it should be close enough to help with stability. Typically after the first log there is a notable improvement.
Hope that makes sense. And helps.
Log desired idle air vs iac counts
Log dynamic air vs iac counts. Same log, just a different histogram.
Copy both into excel
Copy your effective area table into excel
Then, for a specific effective area, look up the counts, find the dynamic air that matches those counts. Then, use the desired air that matches the dynamic air and find the counts for the desired air and key that into the effective area.
Confused yet?
Example: 44 sq mm area IAC is 100. When IAC is 100, desired air is 12, dynamic air is 16 g/sec. when dynamic air is 12, iac is 36. Key 36 into the 44 sq mm cell.
Rinse and repeat. A lot. After 1-3 logs it should be close enough to help with stability. Typically after the first log there is a notable improvement.
Hope that makes sense. And helps.
Is the above quote in regard to gen 3 or 4? I have a gen 3 and I am trying to understand what you have written. I am confused about the effective area table part of your explanation. The table I am looking at has the row labeled as IAC steps and then the columns are labeled from 0 to 120. Thank you in advance!
11-26-2019, 08:25 PM
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Originally Posted by shinyrust
I know this thread is a little old but I'm new to this and I have a similar issue. I think if I get this parameter inline it will make the tuning process a little easier.
Is the above quote in regard to gen 3 or 4? I have a gen 3 and I am trying to understand what you have written. I am confused about the effective area table part of your explanation. The table I am looking at has the row labeled as IAC steps and then the columns are labeled from 0 to 120. Thank you in advance!
Is the above quote in regard to gen 3 or 4? I have a gen 3 and I am trying to understand what you have written. I am confused about the effective area table part of your explanation. The table I am looking at has the row labeled as IAC steps and then the columns are labeled from 0 to 120. Thank you in advance!
It is the most confusing table in the tune. The columns are throttle effective area in sq-mm. The data points are IAC steps. Or how far open the IAC is. 310 is wide open. Zero is closed.
The problem is that throttle effective area is not a channel available in the tune. But it corresponds to a certain desired idle airflow.
The trick is to adjust the IAC steps so that the desired air and dynamic air match reasonably well enough to help avoid over/under shooting idle rpm.
But it will not help until your fueling and spark are correct first.
For argument sake, say you still a hole in the blade. You just increased effective idle area. But the ECU does not know this. So when it needs to command say 16 g/sec idle air, it opens the IAC to where it thinks it should and rpm goes too high. Then it cuts way back. You have to find the effective area that corresponds to 16 g/sec and reduce IAC steps until it is actually getting the 16 g/sec the ECU commands.
It is a way effed up way of doing it but it is how the gen 3 ECU works.
12-01-2019, 05:52 PM
#11
If you have a NW 102, just move everything in your IAC effective area over to start at 20 "transfer function cell heading." Meaning everything before is now zeroed out. Just copy the table and paste the old zero step at 20 and let it keep the same curve (it's pretty unchanged vs stock since the NW has a similar IAC port passage). But it allows more bypass airflow... hence the need to move the transfer table to the right. That will allow the stepper motor to engage and affect idle airflow in a way you expect.
If you drill a hole... you have to keep going. Mine doesn't start until 38. Everything up to that point is bypass air. Once the PCM knows that, it can control the IAC properly for the airflow values you provide.
And you can log it by looking at dynamic flow, IAC steps, and idle air. You set up the channel to record steps for both dynamic and idle air. Then you compare. If dynamic air is off 2g or more from idle air, I'd fix it. If it's 1g or less, don't worry about it. And what you're see if that each step allows a certain amount of airflow. I think it's around every 25 or so steps is about 1g of air IIRC. So you just have to adjust by however far you're off. And with the NW 102, you'll probably be 5g off. So at least 125 steps off... when you look at the transfer table, 125 steps is around 20 or 22 in the table. So that's where you'd start to bring the actual airflow and the idle airflow in line.
If you drill a hole... you have to keep going. Mine doesn't start until 38. Everything up to that point is bypass air. Once the PCM knows that, it can control the IAC properly for the airflow values you provide.
And you can log it by looking at dynamic flow, IAC steps, and idle air. You set up the channel to record steps for both dynamic and idle air. Then you compare. If dynamic air is off 2g or more from idle air, I'd fix it. If it's 1g or less, don't worry about it. And what you're see if that each step allows a certain amount of airflow. I think it's around every 25 or so steps is about 1g of air IIRC. So you just have to adjust by however far you're off. And with the NW 102, you'll probably be 5g off. So at least 125 steps off... when you look at the transfer table, 125 steps is around 20 or 22 in the table. So that's where you'd start to bring the actual airflow and the idle airflow in line.
12-02-2019, 10:42 AM
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If you have a NW 102, just move everything in your IAC effective area over to start at 20 "transfer function cell heading." Meaning everything before is now zeroed out. Just copy the table and paste the old zero step at 20 and let it keep the same curve (it's pretty unchanged vs stock since the NW has a similar IAC port passage). But it allows more bypass airflow... hence the need to move the transfer table to the right. That will allow the stepper motor to engage and affect idle airflow in a way you expect.
If you drill a hole... you have to keep going. Mine doesn't start until 38. Everything up to that point is bypass air. Once the PCM knows that, it can control the IAC properly for the airflow values you provide.
And you can log it by looking at dynamic flow, IAC steps, and idle air. You set up the channel to record steps for both dynamic and idle air. Then you compare. If dynamic air is off 2g or more from idle air, I'd fix it. If it's 1g or less, don't worry about it.
And what you're see if that each step allows a certain amount of airflow. I think it's around every 25 or so steps is about 1g of air IIRC. So you just have to adjust by however far you're off. And with the NW 102, you'll probably be 5g off. So at least 125 steps off... when you look at the transfer table, 125 steps is around 20 or 22 in the table. So that's where you'd start to bring the actual airflow and the idle airflow in line.
Usually, i'll start by moving the curve over ten cells. Then log and see what I have. Cold start is best with no throttle touches. You pretty much see the entire IAC curve on a cold start with full warm up.