Vertical Induction FAB Differences

[Sparky]

I will have a vertical induction Airflow Performance fuel injection system on my RV-7, so I ordered the "FAB-360/540 AP" filtered airbox from VAN's. I was hoping the documentation would clarify the difference from the standard "FAB-360/540" FAB, but it doesn't. Anyone know the difference?

[JordanGrant]

I just bought another one to replace the broken one I found during annual. I'm 99% sure that the "non-AP" version is for an engine with standard carburetor. The Airflow Performance setup does not attach to the engine the same way, so the top plate of the FAB is different.

TIP: I just replaced the top plate on mine at about 350 hrs after it broke in two from vibration. One way to forestall that problem is to upgrade the top plate to 0.090" thick plate, instead of .063 that is standard from Van's. Airflow Performance might actually have them pre-cut for you, or you can always get some plate and make your own.

The other way to forestall is to make sure your clearance from the FAB inlet to the cowl is sufficient (i.e. some say a full 1"). Reference following thread for more discussion.

[osxuser]

Building a couple of angle support for the front and back edges that screws to the sump where the metering unit attaches (between the metering unit and the nut that holds it on) also helps forestall the cracking issue.