What MAF scaling says about your intake
 

Some may be aware that I recently rescaled my intake and was getting a corrected scale with lower massflow per volt than the stock intake. Instead of 315 mass flow @ 5v, my intake calibrated to 260 @5v... The same trend continued from 3v and up, which is really all I was scaling for with 3rd gear pulls.(meaning the whole scale is probably going to be lower vs stock)

Does this mean that I am getting less air through my aftermarket intake, therefore I would be better off switching back to stock? Is this a correct assumption, or is there more to it than that? Any help is appreciated, thank you.

It means the MAF sensor is getting a different amount of air. It does not mean the intake overall is capable of flowing less or more air.

Think: you can have two intakes with the exact same airflow, but the one which focuses the airflow onto the sensor will read more volts.

It possible the new intake may flow better than the stock intake, however the maf sensor only samples the flow past it so its reading is very sensitive to its positioning in the intake and how the air flows past the maf sensor.

most of the recalibration required is to account for the different positioning of the sensor reliative to the position in the stock intake. the stock intake also has an air straightner to smooth the flow past the sensor many aftermarket intakes do not have a similar device.

if you put stock intake bak on you will need to use the stock scaling in the oft tune whick is much better that thge factory scaling or re do maf scaling on stock intake.

Good explanations, thank you. I am flabbergasted as to how a device used for measuring can have variables and still be used for measuring, but I may soon come to an epiphany. haha

I think I have a fundamental misunderstanding of the tables that is causing this struggle... haha I see max load at 1.4 on the Open Loop Fueling and Advance tables... Where is the 1.4 coming from?

The ecu calculated this load value using some weird mathmatical algorythm that i dont understand, one of the main inputs to this load calculation is the maf sensor volts, i would also imagine throttle position possibly manifold pressure may also be used to calculate load and maybe other sensor inputs

The load calculation is very important to ecu calculations as its used for fuel and timing ect

google " badnoodle tuning guide"

Okay, so just for the sake of further understanding... We believe the MAF Voltage plays a big part in the equation to come up with the Engine Load, so let's pretend the MAF V IS the Engine Load...

-Let's assume that the new intake flows the same as the stock intake at any given amount of throttle or RPM, but just directs more air over the MAF sensor.
This means we would then have a higher Engine Load at all RPMS and therefore a commanded AFR that was richer.(at least in OFT roms, the AFR is richer from left to right) The injectors are then putting in too much fuel and ECU corrects with a negative(leaner) fuel trim.

-Let's assume that another intake flows greater than the stock intake, but directs the same amount of air over the MAF sensor at any given amount of throttle or RPM.
This means that we would be at the same engine load as the stock intake, but have more air coming in. This results in a AFR that is leaner than commanded, so the ECU corrects this with a positive fuel trim.

-Let's assume we have a third intake. This intake flows worse than the stock intake, but has a greater flow over the MAF sensor at any given amount of throttle or RPM.
This means that we would have a commanded AFR that was richer than the stock intake, but it flows less... So we get an extremely rich AFR and a large negative fuel trim.

Okay, so that's it for fueling. Pretty easy to understand and correct now that I think of it...

So let's talk about timing...
-Let's go back to the first intake. Same airflow, more air over MAF sensor. Our advance table isn't very linear, so it's more difficult to describe, but clearly a MAF sensor that is getting more airflow than stock is going to cause timing to be different and sometimes radically different. How is this corrected by MAF scaling? I may have to sleep on this.

Load calc is likely quite complex

but by scaling maf againt the 02 sensor your hopefully correcting the air flow reading into the engine that the ecu uses as an input to the load calculation. In this case we are assuming the O2 sensor is correct and adjusting the maf scaling to correct the afr seen by the o2 sensor to it matches the targets in the OL fuel table.

So hopefully you have now corrected the maf reading which corrected the afr and corrects the load calc.

The load calculated has an impact on the timing as timing tables are rpm vs load.

Thats why you car feels so much better now the maf has been corrected for the intake your using

Afr is now following the OL fuel table
ltft is low so again ecu hits it fueling targets better in ol/cl
load calc is now better resulting in you running the correct timing advance for the calculated load.
valve timing is also load dependant
drive by wire throttle is load dependant

a large percentage of what the ecu does is dependant on the load calc which is dependant on maf input so if its way off like your was it has a significant effect when it corrected.

Load on this engine = grams of air per revolution. That's why the MAF plays such an important part. Then obviously compensation/corrections are added but the basis is, if you increase the MAF scale, you'll end up with higher loads.

So calibrating the MAF Sensor using just fuel trims corrects both timing and AFR at the same time, meaning I should have done it a laaawng time ago! Ho-leeee, crap! It all makes a little more sense to me now.

Hey just wanted to take this chance to say thank you to Steve99, Kodename47, and you Bublake! I learned a lot from the road tuning thread and recently tried out my first new scale...just like you said I should've done it a long time ago haha I'll probably still need to take some logs to correct the scaling even more but wow what a difference!

@ray7792 If you running same intake a @BuBlake get him to send you his maf scale it will save you lots of time :-)

Does anyone have a maf scale for a perrin inlet tube with stock intake box and dryflow filter?
Is maf scale the same for all 2.x fuel tunes (91,85, etc)


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MAF scale not generally needed if your using stock intake and maf positioning, intake tubes and filters don't effect maf scaling .

just check you LTFT if is over 5% in places probably worth scaling maf.

All V2 oft petrol tunes using new maf scale the E85 tunes are unchanged V1.5 to V2 so they have old maf scale.

I created a spreadsheet to track the updates to the off the shelf scaling.

2.06 has 3 different MAF scales for stock intake!

I'm going to try the 2.06 Stg 1 scale on E85 because it seems to be the latest revision.

https://docs.google.com/spreadsheet/...18&output=html