With properly scaled MAF and injectors the values should be >90% dead-on, except when fueltrim modulations are in action (e.g. acceleration enrichment). 100% Load should be equivalent with "boost = atmospheric pressure", otherwise many corrections and modulations aren't triggered correctly and also calculations on injector timings aren't correct.

I had to adjust both (MAF/inj.) from scratch as i'm using E7/8 ECU with E9 injectors and E4 MAF on a slightly modified Galant VR4 engine. For scaling I disabled as much modulations as possible and later just had to fine-tune temperature compensation over the year.
Now my wideband-o2 readings are ~95% equal to the fuel map values (+/- 0.1) - except for acceleration/deceleration and sometimes on idle which i think is related to idle rpm stabilisation.

Tuning gets A WHOLE LOT easier when your map values correspond to the actual AFR.

Especially functions like lean-spool rely on this, as the clipping values are taken from your fuelmap! E.g. if you are a lot leaner than map, lean spool could lean out the mixture way too much. If you are running a lot richer, acc. enrichment could make the mixture too rich, eventually causing misfiring and also boost built-up is negatively affected (12.5 is perfect).


If your o2 readings are way off, check the exhaust system for leaks! You have to be 100% sure the wideband sensor is reading the actual o2 values from the exhaust gas, not from any additional fresh air being sucked in on a damaged gasket or flexpipe! Also check for air leaks behind the MAF (injectors!!). Everything from the MAF up to your o2 sensor has to be gas-tight!

 

I'm also interested in doing this. Is there a MAF formula/stock injectors?

 

any update on this? im still learning how to fully understand SD, i tuned my car with SD but the tables dont fully match.

everything you read online seems a little complicated.....there gotta be a easier way to get it working somewhat properly.

 

r4pt has the right idea, the AFR is supposed to match the map, and can generally be made to do so with some MAF table tweaking. The injector scaling has to be correct though.