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PV IAC steps

Started by Sunny Jim, November 03, 2020, 04:39:17 AM

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Sunny Jim

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?

rbabos

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

ben31

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, Fastlane Heads, 58TB, 5.3 Inj, 32t sprocket, TTune

Pirsch Fire Wagon

 :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

Sunny Jim

Quote from: ben31 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.



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.

ben31

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, Fastlane Heads, 58TB, 5.3 Inj, 32t sprocket, TTune

ben31

Maybe it will be clearer with a little picture...

[attach=0]
FLSTNSE 14, 117ci, T-Man 625, Fastlane Heads, 58TB, 5.3 Inj, 32t sprocket, TTune

Sunny Jim

I will attempt
This , one day this week and get back to you.

rbabos

Quote from: Sunny Jim on December 01, 2020, 03:56:19 AM
Quote from: ben31 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.



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

Sunny Jim

Quote from: rbabos on December 01, 2020, 10:12:11 AM
Quote from: Sunny Jim on December 01, 2020, 03:56:19 AM
Quote from: ben31 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.



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!

Matty_d

I am currently trying to get my warm-up dialed in. How does one go about finding the "constant"?

ben31

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, Fastlane Heads, 58TB, 5.3 Inj, 32t sprocket, TTune

Sunny Jim

Ben, Could you demistify the Phase 2 in you explaination please? I just want to be clear on that precise step. Ate these 2 steps added together?

ben31

Hello Jim, what could see, is that as soon as the engine revs more than ~700 (difficult to be sure), IAC takes a new value, which is the sum of three values: the constant, IAC Crank to Run (value at current temp, read from calibration), IAC Warmup Steps (also from calibration).
Then the IAC value decreases during some seconds.

After this, the engine enters in its warmup phase.
FLSTNSE 14, 117ci, T-Man 625, Fastlane Heads, 58TB, 5.3 Inj, 32t sprocket, TTune

Sunny Jim

Cool! I was on the right track all the time.
What a positive difference it makes when you get this sorted.
Interesting point - when I collect data and reveal it on HD MLV
- and demonstrate the IAC on the histogram graph , my IAC sit
Predominantly on 46 steps at running temp.
Constant and constant!!!
Again-
Thanks for your help with this Ben.

Gordon61

May 18, 2021, 10:03:43 AM #15 Last Edit: May 18, 2021, 03:46:23 PM by Gordon61
Is this the same for the M8?

I get the stage 1 ...that gives me a constant of 40
I get the warm up ...although once up to 118 or higher the IAC is down to about 42 ...and out riding and stop to idle it can be down as low as 35  :scratch:

What I don't see is any step around the 750 rpm just before it starts  :scratch: best I might guess is stage 2 is...
IAC = CONST + Crank2Run   (even Crank2Run + WUp without the CONST, would be waaay higher than shows)

cheers

ben31

Sorry Gordon, I don't know the startup sequence of the M8...
FLSTNSE 14, 117ci, T-Man 625, Fastlane Heads, 58TB, 5.3 Inj, 32t sprocket, TTune

Gordon61


Sunny Jim

May 19, 2021, 04:55:37 AM #18 Last Edit: May 19, 2021, 05:11:10 AM by Sunny Jim
Gordon , I am using this info on mine, and other  M8s. My constant according to the PV IAC steps vs temp pre start , is 45-46. I do a data log from cold to full engine temp and translate that data on HD MLV. You can compare the IAC steps vs temp at any given temp , and the compare that info to the IAC warm table in your calibration. I then correct the calibration. It works.
I might add, I connect the PV to an external power
Supply so I can record the initial start up data - first 2 minutes.

Gordon61

May 20, 2021, 11:44:11 AM #19 Last Edit: May 20, 2021, 12:07:53 PM by Gordon61
Here's a pic of my cold start (with external power supply to capture it all  :up:) ...I couldn't see where the Crank2Run number came in? 

I'm already running at 1200 or so rpm before the IAC starts to drop and those steps are only one sample wide (0.1 second) and are at 114, 98, 88, 82, 80 and 77

...I think just a coincidence that the 3rd step of 88 is C2R+Const or C2R+WarmUp (const being 35 this time), I have another startup at 112 degrees and there is only one of those 1 sample wide steps and nothing correlates that would hint at a calculation for C2R

ben31

I do think that until you reach the conditions for the second step, the IAC value remains as it was calculated for the first step.
Therefore, the first different value after first step should be your Cst + CtR + WUpSt.

Of course depending on recording rate and MLV graph rendering ability.
FLSTNSE 14, 117ci, T-Man 625, Fastlane Heads, 58TB, 5.3 Inj, 32t sprocket, TTune

Sunny Jim

My constant pretty much remains the same right through the
Temp range. Constant is what it is.
That first
12 seconds is where the maths comes
Into play regarding stage 1 and stage 2.

Gordon61

May 21, 2021, 03:10:39 AM #22 Last Edit: May 21, 2021, 08:10:58 AM by Gordon61
the constant stays constant right across the temperature range ...and I think, for that whole power on session, if not beyond.
My constant changed from 40 to 35 when I updated the WUp steps table and refreshed the map.

12 seconds... naw, not seeing that on mine...  here is the same recording as before showing 30 seconds worth, the rest is just a smooth continuation of the lines.  All the transitional stuff seems to be over by that 6.6 seconds?

The second pic is a hot start @ 113 degrees ...exactly the same trend (within the sampling frequency), exactly the same 6.6 seconds to end of transition??


EDIT: the hot start shows a bit too much overshoot to me, ...so either the Steps or the Cr2Run needs to be reduced a bit, and I suppose which one was what I was trying to work, out but don't quite see the maths.

EDIT: reattached proper Coldstart pic

Harley Pilot

So what are you calling "effective" iac steps? Would this be the same as the constant? 
Here are my steps at same temp upon start up
Key on before starting =122
Immediately after start up =65
Crank step vs temp =80
Crank to run=38
Warm up step = 22

Please help a dirt farmer understand. :scratch:

Sunny Jim

Quote from: Harley Pilot on May 29, 2021, 08:35:47 PM
So what are you calling "effective" iac steps? Would this be the same as the constant? 
Here are my steps at same temp upon start up
Key on before starting =122
Immediately after start up =65
Crank step vs temp =80
Crank to run=38
Warm up step = 22

Please help a dirt farmer understand. :scratch:


So key on before starting is 122 steps at what ambient / engine temp?