Why do people with Honda Civics drill holes on the rear bumper?
 

Is it to save weight?
I don't even...

I think it's to "decrease drag" (it probably does nothing at all, no harm no gain).

^Yep, air pressure 'behind/inside' the rear bumper. Ive never looked into the facts either.

http://www.d-series.org/forums/1666178-post1.html

Rather than making a diffuser they just cut holes in the bumper to try and get the airflow under the car to cleanly escape the rear rather than creating turbulence by catching on the rear bumper.

I've heard it makes a difference, and some hard core Honda drag guys swear by it, others hit 9's w/o them at all, so not really sure what they are worth.

yup, they are called 'speed holes' they release pressure from the high pressure area created by the open area in the bumper

We put them in our race cars bumper as a joke. We also put LEDs behind it to make others laugh during overnight races.

Does it do anything, well the bumper no longer flexes and bends around, so maybe. I haven't noticed any difference from that though so probably not. We were bored. :shrug:

There typically isn't a "high pressure" area behind the bumper because not enough airflow makes it under the car and to the rear.

If it were so easy to reduce drag, don't you think manufacturers would just put the bumper 2 inches higher, maybe save some material costs in the process?

JDM, yo! lol

On our honda drag cars we have this, we pick up mph on the top end due to drag release, seeing how our car runs in the 160-170mph trap you could understand why this would be helpful.

The first step is admitting the problem Dave! :thumbup:

Cheers man

it's a super low-budget diffuser

some people cut out the center section entirely

I would say it but I cant. See avatar.

They then go on to claim that their "modification" somehow allowed their engines to churn out 5-10 more HP. :bs:

LOL dude we rice out the chump car all the time for s&g. Also it annoys our BMW guy, which entertains the rest of us. And you'd think the bright ass LEDs would make the car more visible.. last sebring race we still got rear ended though.