[Biginboca]

I finally got around to measuring the MAF area of the stock airbox and the AFE intake around the MAF area.

Stock ID at the MAF is 3.0”
AFE ID at the MAF ~ 3.125”

No wonder my fuel trims have pretty much cut in half since I swapped back to stock airbox.

From research I have done this week on airflow it seems that a 3” pipe approx 1 foot in length at 1atm will flow over 500cfm with less than a 5% pressure drop.

Our motor at 7500rpms would need ~400cfm and 450cfm would allow it to hit a theoretical 300bhp.

So a stock 3” maf housing diameter would seem to be sufficient depending on how much the actual maf sensor obstructs the airflow. (From what I’ve read an unobstructed 3” diameter pipe 12” long should be sufficient for up to like 330 N/A HP)

Also since K&N specs their stock drop in filter for our airbox at 518cfm using a stock airbox with a k&n drop in should provide all the airflow our motor needs even with every available mod we can do in place.

My conclusion is on my car running a MAF I should stick with the stock airbox and MAF section and then do flow mods like the Dinan style RAM, a drop in filter, charcoal delete, and REV silicone.

If you have Alpha N tuning and an increased redline then screw all that and run the AFE intake... or go even bigger and make a smooth and unobstructed 3.25-3.5” intake tract.

One question I have is this...

Did AFE open the MAF area 1/8” larger than stock figuring the increased airflow would cause a lean condition but it’s slight enough that the motor could still address with more fuel and it would be below the threshold to throw codes.

And I wonder if on my motor I’m flowing so much more air with the mods I’ve done that it’s above that “no lean code threshold”. Like some of the mods I’ve done are outside AFE’s calculations. (Big bore TB, n54 intake, MILVs, Headers, No Cats, etc)