Dynamic Airflow and MAF Airflow

[printmanjackson]

Should these match when tuned correctly?
And do they correlate to one another?

[jimmyblue]

They won't match well on transient airflow conditions
(MAF is slow). At steady throttle & RPM, they ought
to agree.

[printmanjackson]

that's what I'm seeing

[LSxpwrdZ]

Dynamic airflow on the PID you datalog is the final calculated airflow that is matched with fuel. So it will be affected by VE and MAF depending on the conditions. Usually steady state is 95% MAF so the dynamic airflow will be filtered MAF in that condition. Blip the throttle a couple of times really quick and take a look at the MAF vs Dynamic on the graph screen and you'll see that the MAF is delayed, not much but it is.

[printmanjackson]

Dynamic airflow on the PID you datalog is the final calculated airflow that is matched with fuel. So it will be affected by VE and MAF depending on the conditions. Usually steady state is 95% MAF so the dynamic airflow will be filtered MAF in that condition. Blip the throttle a couple of times really quick and take a look at the MAF vs Dynamic on the graph screen and you'll see that the MAF is delayed, not much but it is.

are you saying as a final tune I need to log dynamic airflow and paste that into the MAF table?

[LSxpwrdZ]

No that will give a good starting point on MAF tuning though if you are in SD logging dynamic airflow into the MAF table. It will give you a close starting point on the MAF.

[mowton]

My question is as to why Idle Desired Air is always so far away from the MAF and DYN AIR PID's? It seems the only way to get Idle Desired down is to "fudge" the ETC Scalar which goes against my Engineering mindset....

It has to be in how I tune big cam setups, because the stock setups seem like RAF and MAF are about equal at idle!

Inquiring minds want to know

Ed M

[LSxpwrdZ]

Don't confuse idle airflow with actual airflow. They are two completely separate routines and have little in common other than using airflow measurement as a basis of adjustment. Like you though I like to try to have idle desired airflow match dynamic but then I realize the model isn't truly fullproof. The IAC on cable TB cars only calculates the airflow through the valve, the PCV and hole in the TB also supply airflow that is not calculated in the idle routine. So basically on those type setups I want the desired to be slightly less than dynamic because dynamic should be the sum of the uncalculated airflow (PCV and hole in TB) + the calculated airflow (IACV/cracked blade on ETC).

I've not seen a "right way" of calibrating all that but this is just how I do mine as it seems the most logical to me.

[printmanjackson]

why would you want desired air and dynamic air to match? Mine never has, the desired is always higher. My dynamic and MAF are almost a match.

[mowton]

why would you want desired air and dynamic air to match? Mine never has, the desired is always higher. My dynamic and MAF are almost a match.

I don't, I set ETC scalar to the mathmatical equivalent value and let the car tell me what the desired AF should be. Desired always higher than a matching MAF/Dyn Air as an end result

Ed M

[JoshBoody]

Thread revival.
So dyn air is dependent on MAF (if enabled)... basically the final air mass used combining SD and MAF.
If in SD only, then MAF is not factored.

Edit: but wait why do they deviate slightly in upper rpm when SD is not factored? Here's the thread that got me thinking with a highly modded MAF but stockish VE in upper MAP.
http://ls1tech.com/forums/pcm-diagno...e-tuneing.html

EDIT2: I found the answer... dyn air is final air mass used to calc fuel. Unfortunately seems VE Airflow is not a useable channel anymore. Why?