MAF and predetermined values

[dr_jekyll]

When the airmass sensor registers a fault (fboSLMM=1), there is a default airmass map inside the ECU which determines the value used as the current airmass per cylinder stroke (for anyone reading along at home - armM_List) and thus used in the smoke limiter axis. IME it depends on the software version as to the values in this map - 206 is different to 306 and iirc I've seen differing values between 306 variants. The maps axes for the default airmass maps (in the case of the HDi90...) are Engine Speed in RPM (Y Axis - along the top) and Atmospheric Pressure in millibar (X Axis - up the side) and outputting the mass of air in each cylinder stroke (mg/str).



So in answer to your question - as standard, the "default" airmass values used will allow full fuel up to the maximum torque limiter value, hence why unplugging it will cause the management to provide full fuel, even if there are boost leaks or even if the turbo isn't spooled, it has no idea. The MAF sensor can fail in so many ways, positive or negative - usually negative however. There are many, many things that can set an airmass sensor fault - if you want to see what values are being derived, unplug your MAF and watch on PP2k - it will show you the default airmass value being used at present, however from PP2k it's often difficult to notice when the default airmass map is in use or it's actually using the airmass sensor - only thing that will tell you is whether there's a fault code set for the MAF sensor.

Essay over.

Sorry just read this thread (mildly late)

With a healthy maf will the ecu potential fuel higher then with the maf unplugged or just give a much more efficent atomisation?
Just wondering as notice a huge difference with mine unplugged but alway wondered if a new maf sensor would exceed the feel of the car over when i unplug the maf?

If that makes sense. Cheers

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