[Grabber523]

Originally Posted by Jim Allen

Pretty coo1!

I'm new here and hesitate to start in such a way, but at the risk of being labeled a "Negative Nelly" after my first post.... is there any proof these mods actually increase airflow? The reason I ask goes back many years to my days as a Land Rover tech.

Late '80s and early '90s EFI Range Rovers had a "trumpet" on the end of of the air cleaner, similar to the part that was replaced in these examples. It necked down to a diameter many people were sure was restrictive, so they lobbed off the trumpet thinking it helped airflow.

I thought it would too, but then I took a bunch of air filters to the late, great Earl Davis for flowbench tests back when he was running the test lab at K&N. I had both a standard Range Rover filter with the trumpet and one modified similar to the way this Ford one is done. No significant difference in airflow. In fact, the trumpet actually flowed slightly more. Earl postulated that the trumpet design actually had something to do with that, smoothing and consolidating air flow, much like velocity tubes will do on carbs. I later backed that airflow test up with a dyno test.. no difference in power the chassis dyno could pick up (admittedly, chassis dynos are "numb" to small changes). Operationally, you couldn't tell a difference, except that the modified horn was noisier.

I won't say definitively that the Ford mod will flow more, or less, than the stock setup because I haven't tested it, but previous experience leads me to ask the question at least.

I have limited access to a flow bench, so in theory, I could test the various permutations of this filter. I have a stock filter from my '05 5.4 F-150 (I am running an AEM CAI). If we wanted to do a test, I could probably make that happen. Bill can vouch for me. I hope!!?

I have to agree with your statements here. It's kinda been a nagging question in my head but I'm new here so I didn't want to seem like the naysayer...I guess in my head the "velocity stack" on the intake is there to improve airflow into the intake tube by compressing and accelerating the air as it flows into the tube. Because of the inverse relationship between pressure and velocity, as the diameter of the tube increases behind the inlet and the velocity decreases, the pressure increases (I guess really it's decreasing the vacuum) in the tube. I guess if my theory's not too far off, that "trumpet" inlet tube serves to increase the density of the air charge before the throttle body...does that make sense? It would improve low-end torque and throttle response but cause slight restriction at high rpm.