txhorns281

iTrader: (12)

Wow Jim, didn't know you knew Chinese!

JimMueller

iTrader: (9)

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

wait4me

iTrader: (10)

divide the 24 by 3 and poof, back to 8 lol

JimMueller

iTrader: (9)

Sure, 3 is the factor between those sample values.

But if I change the Hz to 10528, the result remains the same as if it the Hz was 2678.

wait4me

iTrader: (10)

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...

wait4me

iTrader: (10)

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.

HumpinSS

iTrader: (1)

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)

txhorns281

iTrader: (12)

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?

HumpinSS

iTrader: (1)

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....

txhorns281

iTrader: (12)

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...

HumpinSS

iTrader: (1)

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

Bink

txhorns281

iTrader: (12)

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?

BTW, thanks to everyone for their input! This thread is becoming very very interesting and very very useful too! You guys rock!

HumpinSS

iTrader: (1)

Forget about the Maf for the time being we only need the frequency from it. the Dynamic air and the frequency is what is needed for the re-building the table.

Yes this is true this is why it is important your ve table be spot on. Dynaminc airflow is the ve table. If you check the ve table cracked thread at the top of the fourm gameover spells out how the computer calculates dynamic airflow from the ve table, the map sensor and the IAT sensor....

When i say raw maf data is a referring to raw frequency in HZ. The only thing we need the maf for is the frequency at this stage of the game. This coupled with an accurate ve table will give you a dynamic air value thus you should be able to back calculate good G/sec values for a new maf table. Then after it is flashed back and you have verified your AFR's havent changed you can log both to see how much they differ.

txhorns281

iTrader: (12)

You da man Humpin... headed to Houston to do a H/C setup right now... I'll post later if my brain starts churning (it rarely does... lol)

txhorns281

iTrader: (12)

Hey JimMueller, did you have any luck figuring out your formulas???

JimMueller

iTrader: (9)

No luck. I gave the 'excel experts' a piece of my mind on another forum, so I'll probably have to switch forums

txhorns281

iTrader: (12)

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!

JimMueller

iTrader: (9)

I think setting the MAF Fail Frequesncy is an alternative method to force the PCM into SD mode, with or without the MAF plugged in.

You need to log MAF Frequncy as well.

HumpinSS

iTrader: (1)

Forget about mass airflow . You love that pid, dont you? All you need is maf frequency and dynamic airflow....