Bryce

I didn't read all the posts so I may have missed something.. 2.8s do not have the flap. Only the 1.8 and the 2.7, because of the turbo. Mmmm heat. The flap closes while at slow speed or stopped so that the fans can pull/push air across the engine bay. It blocks exit out the top, same with the seal accross the back of the hood near the windshield. It's okay to have it missing at high speeds for cooling, but then you have to contend with noise and when you stop the underhood flows will not be correct. While at higher speeds the flap will open helping cooling flow over the engine. Still exiting out the bottom past the turbos. I'm not saying this is a wonderful design, but like you said, they have a wind tunnel and I'm sure it was tested thoroughly.

I would be interested in what Corey and Sharon are seeing with their vented hood, since at slow speeds the flows are definitely strange.

donp

Interesting. Is this on good authority? I wondered about the seal at the rear. Interesting indeed.

NASA racer

very interesting!

Bryce

Sorry no authority, I should have stated this is my hypothesis of the situation.

Andy Hedin

My 1997 A4 1.8T did not have that "flap", probably added later.