300g/s at 140kpa 6800rpm

[solidsnake11]

C

[Kodename47]

The problem with this is that by changing the MAF scale you can get completely different readings, or where the MAF is located can have a big impact. Unless it's on an identical setup running the same tune, the MAF output is pretty much irrelevant.

[tomm.brz]

there are many variables and tolerances in each sensors and actuators (injectors for example) so that every single car is different and as kodename said you cannot compare this

[tomm.brz]

you would need two identical cars tuned the same way (di/pi, lambda scaling, other sensors scaling, corrections ecc) and even then you see differences
even lambda position for different headers matters

[tomm.brz]

Don t really getting what you are talking about. you scale the maf on your specific car to make the afr reflect the target, and SD is the same. if you change pipe diameter the air sample will have different characteristics than before so you change it to make the voltage measure adeguate grams of air, that then provide adeguate fuel to have afr similar to target
Identical cars with same exact mods and configs, will always bave differences, mostly because of the sensors and injectors that have tolerances
can be similar, but never the exact same

[tomm.brz]

of course is an extimated value of airflow, but there are so many variables and ways that tuners can tune this car that you can't take it as an exactly measurement of how much air is entering

[solidsnake11]

I just figured if subaru said it flowed let's say 30g/s at 1 v, that 30gs would be flowing thru the maf, then we put in a bigger housing and scaled it correctly we should be able to know when 30gs is flowing by our new calibration. At least pretty close, well at least closer than + -50% accuracy.

[tomm.brz]

You really can't estabilish mathematically how the scaling woud be if you change X things, or, better, you maybe could but then you just rely heavily on the fuel trims to adjust things
and stock logic doesn t even fix trims really good during open loop

the maf just samples a tiny portion of all the air that is entering, and you never know what REALLY happen inside the intake/charge tube, you can t know how much turbulence there is
Hell, even a differenr panel filter induces different flow
For good maf scaling forget the math and do good logs and fix things from them

[Kodename47]

Originally Posted by solidsnake11

So why do we scale the maf when changing pipe size? I thought it was to read the correct g/s. If you change injectors and screw with maf scaling your lying to your ecu. On speed density do you also change scaling of the map to tune. How about changing the scaling on the intake air tempature to add more fuel, timing or raise your idle.

You only change the MAP sensor scaling if you change the MAP sensor, but that's more simple as it's linear. People can change the MAF scaling to correct fuelling or even to just get it where they want. Some might argue that the 1st is better, but so long as it works, does it matter? Plus where is your AFR reference to scale the MAF? Stock O2 that is sort of accurate if you scale that correctly. How many cylinders is that reading from? Is there any offset in the fuelling in those etc etc etc. And a good point you mention, with all the other compensations (IAT/Engine Load) you can really make the MAF read what you want. The twin injector sets can also make MAF scales less accurate. I could go on, but you get the picture.

It will give you a ballpark idea if many of the parameters haven't been played with too much and on the same setup.

[steve99]

Air flow vs pressure and velocity is not simple