what does these plastic removable vents do in the front arch - Z4MC

[NLW73]

had the wheels off to paint up the brake calipers in some black and noticed these removable plastic parts

top one must be easier access to parts so no need for bumper off?

is the bottom one to help with brake cooling in the summer or on a track day?

thanks

 

[bigwinn]

allow you access to change your bulbs in headlights and foglight

 

[Argenta]

Indeed brake cooling ducts. I know they look misguided for aiming mostly at the tire.. But then again aerodynamic works in mysterious ways & Bmw usually knows what they’re doing in this regard.
Why theyre partly covered from factory I don’t know. I do know covering front inlets generally lowers drag.

 

[DevonPaul]

I tried getting the bottom one out the other day to investigate the washer fluid leak - they are part of the air duct, which is wider than the hole and seems to clip inside the bumper as well, so I couldn't work out how to get mine out.

 

[Argenta]

Why d’you wanna take it out? To change bulb etc its the bigger lid above it

 

[buzyg]

I believe it is indeed there to aid brake cooling on track days. I don't have it, so removed before I bought the car 11+ years ago. We need a track guy to post and confirm, I'm not such a person these days .

 

[srhutch]

Brake ducts. There are two versions. Some cars came half covered up, others came fully open. No rhyme or reason though that I recall.

 

[Vanne]

they are there to pressurize the wheel well, does it aid with cooling? not sure, or is it to keep your shiny rims cleaner? who knows.

 

[Argenta]

Wheel wells are generally too pressurized anyway (not good for drag) so I doubt thats the reason tho

 

[grannyknot]

On the top of the brake ducts there are vents and the half opening at the back, I'm thinking if the duct was sealed off at the back and on top so no air could move through it it would result in less drag.
The air inside would pressurize slightly and would become a pillow air that the oncoming air would slide off, does that make sense?

Something I just thought of, those vents on the top of the duct being used to cool the xenon bulbs other wise there would be no air movement behind the headlights.

 

[Argenta]

I think the "vents" are there for the horns

 

[grannyknot]

I think the "vents" are there for the horns

The vents in the top of the brake ducts may also let some sound out but keeping the xenons cool is more of a priority I would think, the lighting wiring harness already has a reputation for drying of a cracking down to bare wire.

 

[Argenta]

Mine

 

[MrPT]

On the top of the brake ducts there are vents and the half opening at the back, I'm thinking if the duct was sealed off at the back and on top so no air could move through it it would result in less drag.
The air inside would pressurize slightly and would become a pillow air that the oncoming air would slide off, does that make sense?

This makes sense to me. I bet the plate was added to stop the vent catching water/crap slung forwards off the tyre.

Ideally you'd route/duct the air to somewhere useful - e.g. to cool the brakes or to direct air cleanly around the outside of the wheel well - or blank them off, flush with the face of the bumper (but that would look a bit odd).

 

[Mikey_Boy]

Top ones in the arch liner are to access bulbs - still a pig of a job with them out...!

I removed the bottom ones on my car trying to improve brake cooling on the standard brakes - made absolutely naff all difference!

They're still removed with the AP brakes fitted, but these of course are *much* better!