Will Ng

I just removed the center and right dash vents and their open/close damper flaps. The center opening is actually a small 1/2" slit formed by molded plastic!
It looks like Audi did this on purpose to limit the airflow out of the center vents. Personally, I always found the type44's HVAC to be annoyingly loud compared to other cars. Now I know why. That slit is causing a lot of turbulent back pressure.

I'm going to see if a heat gun can soften the plastic and pry it back some.

rooster 2

however, opening it up may reduce air flow from vents elsewhere. Something to think about Wil.

Will Ng

<center><img src="http://pictureposter.audiworld.com/38606/img_2289.jpg"></center><p>
So that all vents get somewhat equal flow.
But the background noise it creates is driving me nuts. Even on LO fan, there's enough ambient noise.
I guess I'm just **** about it.
;-)

CARSNPLANES

Center vents are for A/C only, therefore the other vents are closed by design. The small restriction will increase the resultant outflow for better cooling effect . When air is compressed , by sort of restricting the volume of air coming up to the outlet vents, as it exits that area, it adds cooling to the resultant air as it's realeased, but also increases the pressure of that air. Hold your finger over the garden hose and what do you get, a stronger water flow as it exits. The air would just trickle out if it didn't have that design. It might be compensating for a weak fan by design too. The downfall is the noise, though.
Is there suppode to be some insulation around that ducting maybe?

Will Ng

In this case, I don't believe it's the goal of increasing the air velocity. The center vents' proximity to the squirrel cage fan means most of the flow would exit there (point of least resistance). The side and rear vents would get reduced airflow compared to the center vents.
But the noise is not worth the equalized flow IMHO.
A fellow forum member is creating a center vent mount for a boost gauge, for me. That should provide more than enough restriction.
;-)

Will Ng

I softened the plastic with a heatgun and pryed open the slit. It's about twice the size as before. No big change in noise or flow to the side vents.
Oh well. Noise must be coming from the fan itself.