Dialing in MAF tables anyone????
Wow Jim, didn't know you knew Chinese! 
Originally Posted by JimMueller
Stock MAF table appears to be a perfect fit with a 3rd order poly, and looks pretty good for the custom table as well. To clarify an earlier statement, once the trendline is added to the large dataset chart, things get REAL sluggish. Looks like we need an array formula using the LINEST function to convert it to a table.
My modified MAF table regression formula (from trendline):
y=3E-10x^3-8E-07x^2+0.0039x-2.9051
My stock MAF table regression formula (from trendline):
y=4E-10x^3-1E-06x^2+0.0058x-6.1464
Now to see if I can get that array formula working...
My modified MAF table regression formula (from trendline):
y=3E-10x^3-8E-07x^2+0.0039x-2.9051
My stock MAF table regression formula (from trendline):
y=4E-10x^3-1E-06x^2+0.0058x-6.1464
Now to see if I can get that array formula working...
I can't get the formula result to match the stock MAF curve.
The raw values are:
The formula I'm using to calculate Y is:
=L2*(I2^3)-M2*(I2^2)+0.0058*I2-6.1464
and the (rounded) raw formula is:
y=4E-10x^3-1E-06x^2+0.0058x-6.1464
Maybe it's just late. To me the formula appears right, but the y value comes out to 24.x at 2687 RPM, whereas the stock g/sec is 8.x
The raw values are:
Code:
I J L M N O Hz Maf g/sec 2687 8.08 0.00000000035453 -0.00000114936437 0.00577445218620 24.61452983
=L2*(I2^3)-M2*(I2^2)+0.0058*I2-6.1464
and the (rounded) raw formula is:
y=4E-10x^3-1E-06x^2+0.0058x-6.1464
Maybe it's just late. To me the formula appears right, but the y value comes out to 24.x at 2687 RPM, whereas the stock g/sec is 8.x
i think you are missing something to the effect of after a cetain amount of air speed enters the maf the electronics in it cause an airflow turbulance and it has a weird pattern of air to it, kinda like lift on an airplane, so they have to make up for that??? so pretty much no matter what mathamatical equasion you come up with it will be not accurate unless you had an air machine hooked up to the inlet of your airbox and the outlet of your maf and measured the hz output of the maf thru the hole band and then input your readings into the computer...
even with a ported maf, you have that flat section in the center that creates a void in the airflow at high air speed, and the faster the volosity of the air traveling thru the bigger the center void gets.
This test could be better done with Flashscan as it lets you make custom maps that can be plotted against ANY pid the progrma offers. If any of you have efilive V6 can you log the same dynair pid and maf frequency and send it to me. I will see what the averages come back with using a map instead of fooling around to much with Excel (unless you are cool with it)
It seems the variance between the stock calibration of the MAF and what you have at this point is way too large... But bear with me here, how does it compare to the data of the dynamic airflow? I'm under the thought that we are trying to create a MAF table that should line up closely to the dynamic airflow curve/function right? Is this wrong?
But bear with me here, how does it compare to the data of the dynamic airflow? I'm under the thought that we are trying to create a MAF table that should line up closely to the dynamic airflow curve/function right? Is this wrong? LS1 Tech Stories
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Verdad Gallardo The theory here is that IF your ve table is dialed in the PCM uses dynamic airflow to still be able to tell the pcm of air flow in the case of a maf failure. If you log raw frequency and the dynamic airflow (which you feel confident is spot on) then you can backward calculate a maf table. The ve table is the airmas table and if this is dialed in and accurate you can compensate for an inaccurate maf.
THe difference between the the stock maf and the new maf table could be all the inaccuracies showing up from a lid, cam and other modifications that you a have made to the intake tract.
When you are finsihed plotting out your new MAF table and you flash the PCM the AFR's should stay the same....
THe difference between the the stock maf and the new maf table could be all the inaccuracies showing up from a lid, cam and other modifications that you a have made to the intake tract.
When you are finsihed plotting out your new MAF table and you flash the PCM the AFR's should stay the same....
Originally Posted by HumpinSS
The theory here is that IF your ve table is dialed in the PCM uses dynamic airflow to still be able to tell the pcm of air flow in the case of a maf failure. If you log raw frequency and the dynamic airflow (which you feel confident is spot on) then you can backward calculate a maf table. The ve table is the airmas table and if this is dialed in and accurate you can compensate for an inaccurate maf.
THe difference between the the stock maf and the new maf table could be all the inaccuracies showing up from a lid, cam and other modifications that you a have made to the intake tract.
When you are finsihed plotting out your new MAF table and you flash the PCM the AFR's should stay the same....
THe difference between the the stock maf and the new maf table could be all the inaccuracies showing up from a lid, cam and other modifications that you a have made to the intake tract.
When you are finsihed plotting out your new MAF table and you flash the PCM the AFR's should stay the same....
I haven't tried any of this yet, just trying to lock down some concepts here but Mass AF is logged vs Frequencies right? and what is Dynamic Airflow logged against? RPMs? Ok so for example, let's say that at 2000 rpm raw MAF data reads 20 g/sec and the Dynamic airflow 15 g/sec, what would you do with this data, and how do we relate the data in terms in frequency? A newbie like me would just take the 15 g/sec and replace the 20 g/sec at whatever frequency it was set. This seems just way too easy so I'm pretty sure I'm wrong...
Originally Posted by txhorns281
OK so I guess what I took from this is that the MAF could be reporting more or less airflow than what the VE table is actually using correct? (Well, that's obvious since that's why we correct the VE anyway via SD) So we want to calibrate the MAF to be reporting similar data as the VE that way the two are not in conflict, thus not confusing fuel trims right?
I haven't tried any of this yet, just trying to lock down some concepts here but Mass AF is logged vs Frequencies right?
and what is Dynamic Airflow logged against? RPMs? Ok so for example, let's say that at 2000 rpm raw MAF data reads 20 g/sec and the Dynamic airflow 15 g/sec, what would you do with this data, and how do we relate the data in terms in frequency? A newbie like me would just take the 15 g/sec and replace the 20 g/sec at whatever frequency it was set. This seems just way too easy so I'm pretty sure I'm wrong...
Average the dynamic airflow against the frequency (freq table is not dependant on rpm so we dont need it) so if you have an average of 20 for freqs 0-1500 hz i would put 20 g/sec in that colum
Originally Posted by HumpinSS
Correct
Not quite right if we are trying to correct maf airflow we need to log dynamic(ve derived) against raw frequency then average the data for those frequency ranges and plug them back inot the maf freq table
Average the dynamic airflow against the frequency (freq table is not dependant on rpm so we dont need it) so if you have an average of 20 for freqs 0-1500 hz i would put 20 g/sec in that colum
Not quite right if we are trying to correct maf airflow we need to log dynamic(ve derived) against raw frequency then average the data for those frequency ranges and plug them back inot the maf freq table
Average the dynamic airflow against the frequency (freq table is not dependant on rpm so we dont need it) so if you have an average of 20 for freqs 0-1500 hz i would put 20 g/sec in that colum
BTW, thanks to everyone for their input! This thread is becoming very very interesting and very very useful too! You guys rock!
Originally Posted by txhorns281
RocknRoll Humpin! Glad someone's willing to put up with the education of this guy! So we average the Mass AF and the Dyn AF and at whatever MAF frequency these two data were logged, that's what we input to build the new table right?
So here's my next question, when we average Mass AF and Dyn AF, depending on the swing, we could end up getting a table that's either reports a little more or a little less flow than what the VE derives right???
Either way it's still closer than raw MAF readings, but wouldn't it still not be directly on VE derived dyn AF??? Is there any reason why we would not want to be pretty much ON the dyn AF curve/function as opposed to slightly offset?
Ok, so I'm thinking bout hitting up the MAF today.... my VE looks pretty good, when i plug it back in I have to set the fail frequency to zero right??? And when I'm logging Mass AF vs Dynamic AF, where do I get the frequency from??? When I export the data does it show the MAF frequency? Thanks!
Originally Posted by txhorns281
Ok, so I'm thinking bout hitting up the MAF today.... my VE looks pretty good, when i plug it back in I have to set the fail frequency to zero right??? And when I'm logging Mass AF vs Dynamic AF, where do I get the frequency from??? When I export the data does it show the MAF frequency? Thanks!
Forget about mass airflow
. You love that pid, dont you? All you need is maf frequency and dynamic airflow....