DBW load and maf calculations...
01-18-2008, 05:39 AM
#1
DBW load and maf calculations...
ever wonder what % load is on a vag-com log? its basically the parameter that drives all the maps in the ECU, and the tuning.
There was an unconfirmed suspicion that the load and maf values were connected. An equation posted <a href="http://www.passatworld.com/forums/showthread.php?t=190324">passwatworld</a> which sort of confirmed this. I threw an old vag-com log of mine into the equation and the PW calculated load correlated with the logged load:
<img src="http://www.modifieda4.com/images/ecu-logs/PW_load_calc.png">
the PW calc is sort of cryptic...how does it work?
a further suspicion was that load % is the ratio of boosted cylinder fill to unboosted cylinder fill. using this and some base data from a bosch ME7 software paper, I calculated from the ground up boosted cylinder fill / nominal cylinder fill. The two graphs are nearly identical.
<img src="http://www.modifieda4.com/images/ecu-logs/m4_load_calc.png">
So basically at WOT, load % reported is driven by the maf. what does this mean?
-you dont have to log maf...you can back those values out of load with reasonable accuracy
-for people with non-stock mafs and/or tweaked programming you can back out real "maf" values
-insights into BT programs can be made
There are correction factors that get applied to load percentages, and the programming is much more complicated than this, but this is a very basic look inside the ECU...and helpful to me at least
There was an unconfirmed suspicion that the load and maf values were connected. An equation posted <a href="http://www.passatworld.com/forums/showthread.php?t=190324">passwatworld</a> which sort of confirmed this. I threw an old vag-com log of mine into the equation and the PW calculated load correlated with the logged load:
<img src="http://www.modifieda4.com/images/ecu-logs/PW_load_calc.png">
the PW calc is sort of cryptic...how does it work?
a further suspicion was that load % is the ratio of boosted cylinder fill to unboosted cylinder fill. using this and some base data from a bosch ME7 software paper, I calculated from the ground up boosted cylinder fill / nominal cylinder fill. The two graphs are nearly identical.
<img src="http://www.modifieda4.com/images/ecu-logs/m4_load_calc.png">
So basically at WOT, load % reported is driven by the maf. what does this mean?
-you dont have to log maf...you can back those values out of load with reasonable accuracy
-for people with non-stock mafs and/or tweaked programming you can back out real "maf" values
-insights into BT programs can be made
There are correction factors that get applied to load percentages, and the programming is much more complicated than this, but this is a very basic look inside the ECU...and helpful to me at least
01-18-2008, 05:54 AM
#3
Yes, the load is calculated purely of the MAF readings
that's why those with bad MAFs of bad MAF wiring can sometimes see load calc error codes. I can actually force these errors codes to appear if I set my piggy-back to change the MAF values in too steep increments across the RPMs or across the boost range.
01-18-2008, 11:20 AM
#7
wait, how can you miss this post?
<a href="https://forums.audiworld.com/a4/msgs/134280.phtml">
</a>
One thing I have noted over time is that spec load for basically any ME7 system I logged peaks at 190 (stock or modified ECU). I haven't seen a log past 190 on actual load even for boost pressures about 1 bar, so there might be an upper limit on the calculation.
One thing for sure, spec load and load correction means adjusted load, and that affects actual load (i.e n75 and/or spark control).
</a>One thing I have noted over time is that spec load for basically any ME7 system I logged peaks at 190 (stock or modified ECU). I haven't seen a log past 190 on actual load even for boost pressures about 1 bar, so there might be an upper limit on the calculation.
One thing for sure, spec load and load correction means adjusted load, and that affects actual load (i.e n75 and/or spark control).