MAF scaling or Load scaling/comp

Hi,

Note: this is theoretical questions for educative purpose only.

How would you address a car that is completely stock but have 5-7% fuel trims (STFT + LTFT) and why ?

1. Leave it alone.

Implies that OL fueling will most likely be off.

2. Scale the MAF.

In pretty much every example given by Andre he always seems to address fuel trims (of course that exclude new injectors) with the MAF scaling even when the intake track is completely stock. Knowing that most MAF based ECU use the MAF readings for load calculation and hence are very impactful on the system as whole why would you scale the MAF to address fuels trims if no change were made there ?

3. Address in the load scaling/compensation table.

Note: This point deserve a bit of explaining as it might be platform specific, eg: an 2.0L N/A 2009 NC MX5. We have a table that's called "Load scaling - VE corrections" and basically it is to correct the difference between Air mass calculated from MAF/RPM vs. the real Air mass inside the cylinder hence VE. Make sens ? So by correcting that table I get all my trims very closed to 0.

In this specific case, would it make more sens to address the issue in the load scaling table described above ? Somehow it would make sens to change this table if the engine VE is somewhat changed, eg: new headers, perphap cams, etc.

Charles D.

Hi,

You may want to add fuel composition to your example.

Additional ethanol content in the fuel can cause this, assuming no flexfuel sensor.

Cheers,

Brady

Very valid point! Thanks for bringing that up!