This is probably guna sound stupid, but I've noticed several Hondas around with ovals cut out of the rear bumper. Im curious as to what the benefit is, I assumed it was for airflow? Thanks

 

Unless you're talking about aftermarket bumper fascia's (a part of a body kit), I don't have a clue as to what you're talking about.

Exhaust outlet cut-outs?
A picture would help

P

 

It's what idiot ricers do to keep themselves occupied when they have too much free time on their hands. Ruining perfectly good parts is a favorite ricer pastime, especially items that cost several hundred dollars to replace when they realize how dumb it was to mess with it in the first place.

But yes, the general theory is that when running without bumper reinforcement beams and splash guards, the bumper cover acts as a parachute and increases drag. Modifying the bumper to allow the air to flow through instead of being trapped will theoretically improve aerodynamics. Drilling several large round holes in the bumper with a holesaw is the most half-assed cheapskate way to do it, and probably does more harm than good by increasing turbulence. It also looks trash.

If you really want to improve aerodynamics, use smooth undertrays and fabricate a diffuser for the rear end instead of hacking up the bumper.

 

The use of a chin spoiler or air dam will accomplish the same by diverting air from going under the car and directing it either into the engine compartment or over the top.
This reduces parasitic drag and improves downforce.

P

 

so that's what they're for! lol never knew, thanks!

 

while we're on the subject of the rear bumper.. there seems to be some kind of flap on the driver's inside side, and idk why it's here.. i'm guessing something for the gas tank? just curious

 

More than likely the passenger compartment air circulation vent.
Ever wonder where all that air that your heater / AC pulls into the car goes?
Now you do.

P

 

that would make sense lol thanks