Severe MAF fluctuation at WOT high RPM?
 

Getting the tune lined out for the solid roller cam and I've noticed that despite my efforts to correct it I'm having an issue where at WOT my MAF lb/min reading is fluctuating by 10-12 lbs/min.

It's always had a little fluctuation but this seems excessive to me.

Old setup was filter on the maf which was directly on the 90* turn. Since then I've added a long straight piece of aluminum pipe after the MAF.

So the new setup for intake tract is a large filter with a velocity ring built inside of it mounted to the MAF which is attached to a straight section with a 90* at the TB. The MAF has a Saxon airflow straightener screen in it.

I'm just trying to determine if the MAF could be damaged or if it's a sign there is a mechanical problem somewhere else.

This is an 85mm truck MAF with the stock screen replaced by the straightener. I'm also getting really close to maxing it out. In fact, the fluctuations are hitting peak. So that could be the issue...I've never read about what happens when a MAF maxes out but I do recall some posts from Frost about these hitting the limit somewhat easily.

Also wanted to note that even though this is happening the car runs great and pulls hard. Wideband readings stay consistent so it doesn't actually seem to be hurting the fueling which makes me more confused.

Why not run speed density? It would be more consistent in turbulent air. I switched to Hptuners 1 bar OS and didn't notice any loss of driveabilty.

Check whether this is noise, or perhaps some bistable
mode (like, service manuals say MAF signal can have
EMI issues - is this notchy and flickering between two
values (or bunches of values) at some particular range
of RPM, where (say) 4X for spark happens to land on
MAF frequency?). The diagnostic there says to debundle
the MAF wires from the harness and see if anything
changes.

There can be fueling based longer term oscillations in
airflow, burn quality affects subsequent evacuation /
filling to some degree and this can make a "subharmonic
oscillation" where the mixture error never settles in to
one spot but bumps forward and back indefinitely. I see
this some, when VE table's MAP-axis slope is not right.
A little wow-wow-wow. Is anything on the SD side showing
a similar wandering / yo-yo behavior or is this all and only
about MAF stability?

And there could well be intake tract resonances though
I'd call that a pretty weak possibility.

Hmm, well one other thing that's changed is the cam sensor harness now runs under the portion of harness with the MAF wiring. It's been like that since the LS2 swap but maybe during the recent cam swap they became closer together and it's picking up interference?

The PCM filters out (smooths out) those fluctuations...

but, yes, try to separate the CMP subharness to see if ut makes a difference.


( BTW: in scantool chart display chose the MAF pid with units g/s, it's easier to understand )