Author Topic: PV IAC steps  (Read 1262 times)

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Offline Sunny Jim

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PV IAC steps
« on: November 03, 2020, 04:39:17 AM »
Excuse my ignorance , but I am attempting to get my head around the IAC steps.
On the PV you can display the IAC steps and log them, along with multiple other parameters.
My question is
If you are recording the IAC step data , where is it reflected
In your map?
Eg. If you record 59
Steps @ 115 deg f .
Is it IAC steps vs temp, or IAC warm up?
Is it supposed to match the target on your
Map?

Offline rbabos

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Re: PV IAC steps
« Reply #1 on: November 03, 2020, 07:58:26 AM »
I believe IAC warmup steps. What you log is actually what the ECM is determining for steps and they won't be what's in the cal, from what I've seen. At least for me, the two are quite different. Ions ago, Cole mentioned taking the logged IAC temp steps from the ECM and changing the cal table to reflect the same for a more refined cal. Like I say, this was a long time ago so memory memory might be flawed.
Ron

Offline ben31

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Re: PV IAC steps
« Reply #2 on: November 26, 2020, 05:00:04 AM »
IAC is the result of a calculation according to engine's phase (cranking, starting, running).
ECM uses three IAC tables (Crank Steps, Crank to Run, Warmup Steps) and an internal constant to set IAC.

Phase 1: when you trigger start button and when RPM is still under a certain value (around 750)
IAC = constant + IAC Crank Steps (at Engine Temp)
With this you should be able to know the constant

Phase 2: above the RPM limit
At this point, IAC is set to:
IAC = constant + IAC Crank to Run(current temp) + IAC Warmup Steps(current temp)
Then IAC decreases during few seconds (10 s ? don't remember)

Phase 3: engin is running and warming up
IAC = constant + IAC Warmup Steps(current temp)

ECM is constantly changing IAC according to its sensors.
After calculating the constant, you should adjust Warmup Steps table to make it match effective IAC during warmup.

Then you can adjust Crank to Run and Crank Steps to have a nice cranking without high revs or any issue, and a nice transition between phase 2 and warming.


FLSTNSE 14, 117ci, T-Man 625 PS2, Fastlane Heads, Target Tune

Offline Pirsch Fire Wagon

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Re: PV IAC steps
« Reply #3 on: November 26, 2020, 08:49:31 AM »
 :agree:

Most Software does not have a Data PID for the "Start-UP-Fuel". Although most CPU based software does.

Depending on the Scale, you should be able to get an accurate capture (recording) at a capture rate of 20-50ms. 

But I am not familiar with the PV. Just the CPU based softwares. The PV may not even have such a function as this.
Tom

Offline Sunny Jim

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Re: PV IAC steps
« Reply #4 on: December 01, 2020, 03:56:19 AM »
IAC is the result of a calculation according to engine's phase (cranking, starting, running).
ECM uses three IAC tables (Crank Steps, Crank to Run, Warmup Steps) and an internal constant to set IAC.

Phase 1: when you trigger start button and when RPM is still under a certain value (around 750)
IAC = constant + IAC Crank Steps (at Engine Temp)
With this you should be able to know the constant

Phase 2: above the RPM limit
At this point, IAC is set to:
IAC = constant + IAC Crank to Run(current temp) + IAC Warmup Steps(current temp)
Then IAC decreases during few seconds (10 s ? don't remember)

Phase 3: engin is running and warming up
IAC = constant + IAC Warmup Steps(current temp)

ECM is constantly changing IAC according to its sensors.
After calculating the constant, you should adjust Warmup Steps table to make it match effective IAC during warmup.

Then you can adjust Crank to Run and Crank Steps to have a nice cranking without high revs or any issue, and a nice transition between phase 2 and warming.



Ben, thanks for giving some shape to my question.
Are there steps in the power vision that I can use,as a DIY guy, to calculate the constant? I am somewhat lost as to finding a starting point in adjusting the idle quality and cold start effects in my tune. After several VE adjustments and Autotunes, I still have difficulty in nullifying the stumble at idle, 7-10 seconds after start up.

Offline ben31

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Re: PV IAC steps
« Reply #5 on: December 01, 2020, 05:00:34 AM »
Jim, it's easy to get the constant:
before cranking, display IAC value and Engine Temp on your PV (or log the whole cranking, from ignition on to engine warming up).

Then in your PV tune, read (or interpolate) the IAC Crank Steps vs Temp value at the recorded engine temp. The difference is the constant.
FLSTNSE 14, 117ci, T-Man 625 PS2, Fastlane Heads, Target Tune

Offline ben31

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Re: PV IAC steps
« Reply #6 on: December 01, 2020, 05:22:30 AM »
Maybe it will be clearer with a little picture...

  [ You are not allowed to view attachments ]  
FLSTNSE 14, 117ci, T-Man 625 PS2, Fastlane Heads, Target Tune

Offline Sunny Jim

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Re: PV IAC steps
« Reply #7 on: December 01, 2020, 05:29:35 AM »
I will attempt
This , one day this week and get back to you.

Offline rbabos

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Re: PV IAC steps
« Reply #8 on: December 01, 2020, 10:12:11 AM »
IAC is the result of a calculation according to engine's phase (cranking, starting, running).
ECM uses three IAC tables (Crank Steps, Crank to Run, Warmup Steps) and an internal constant to set IAC.

Phase 1: when you trigger start button and when RPM is still under a certain value (around 750)
IAC = constant + IAC Crank Steps (at Engine Temp)
With this you should be able to know the constant

Phase 2: above the RPM limit
At this point, IAC is set to:
IAC = constant + IAC Crank to Run(current temp) + IAC Warmup Steps(current temp)
Then IAC decreases during few seconds (10 s ? don't remember)

Phase 3: engin is running and warming up
IAC = constant + IAC Warmup Steps(current temp)

ECM is constantly changing IAC according to its sensors.
After calculating the constant, you should adjust Warmup Steps table to make it match effective IAC during warmup.

Then you can adjust Crank to Run and Crank Steps to have a nice cranking without high revs or any issue, and a nice transition between phase 2 and warming.



Ben, thanks for giving some shape to my question.
Are there steps in the power vision that I can use,as a DIY guy, to calculate the constant? I am somewhat lost as to finding a starting point in adjusting the idle quality and cold start effects in my tune. After several VE adjustments and Autotunes, I still have difficulty in nullifying the stumble at idle, 7-10 seconds after start up.
That sounds more like the warmup table for fuel, in regards to stumble.
Ron

Offline Sunny Jim

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Re: PV IAC steps
« Reply #9 on: February 18, 2021, 01:12:17 AM »
IAC is the result of a calculation according to engine's phase (cranking, starting, running).
ECM uses three IAC tables (Crank Steps, Crank to Run, Warmup Steps) and an internal constant to set IAC.

Phase 1: when you trigger start button and when RPM is still under a certain value (around 750)
IAC = constant + IAC Crank Steps (at Engine Temp)
With this you should be able to know the constant

Phase 2: above the RPM limit
At this point, IAC is set to:
IAC = constant + IAC Crank to Run(current temp) + IAC Warmup Steps(current temp)
Then IAC decreases during few seconds (10 s ? don't remember)

Phase 3: engin is running and warming up
IAC = constant + IAC Warmup Steps(current temp)

ECM is constantly changing IAC according to its sensors.
After calculating the constant, you should adjust Warmup Steps table to make it match effective IAC during warmup.

Then you can adjust Crank to Run and Crank Steps to have a nice cranking without high revs or any issue, and a nice transition between phase 2 and warming.



Ben, thanks for giving some shape to my question.
Are there steps in the power vision that I can use,as a DIY guy, to calculate the constant? I am somewhat lost as to finding a starting point in adjusting the idle quality and cold start effects in my tune. After several VE adjustments and Autotunes, I still have difficulty in nullifying the stumble at idle, 7-10 seconds after start up.
That sounds more like the warmup table for fuel, in regards to stumble.
Ron

Thanks Ben.
I sat back and digested your info. I have consequently reset my IAC tables with success!!!
The secret
Is that constant!!! The math was simple.
Bike idles
Way better.

Cheers!

Offline Matty_d

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Re: PV IAC steps
« Reply #10 on: May 03, 2021, 03:45:59 PM »
I am currently trying to get my warm-up dialed in. How does one go about finding the "constant"?

Offline ben31

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Re: PV IAC steps
« Reply #11 on: May 03, 2021, 03:50:23 PM »
See Phase 1 above.

Before engine starts IAC is XXX (read the logs), check Crank Steps in calibration, substract, here you are.
FLSTNSE 14, 117ci, T-Man 625 PS2, Fastlane Heads, Target Tune