Originally Posted by JAJ
The string was flapping in the breeze up to and beyond 100MPH - there was clearly a strong blast OUT of the opening. Until I went full throttle I was convinced the opening was an outlet not an inlet. At wide-open throttle the string would suck down onto the grill on the opening and stay there. It didn't seem to matter how fast I was going, at least up to about 120MPH. I watched it do this all day.
My conclusion is that at full throttle the opening provides extra air for the engine, and at part throttle it keeps cool air coming in and warm air blowing out to prevent heat soak. You could put a flap on it, but then on a hot day in traffic it would cut power because the intake air would be super hot.
At this point, your conclusion makes good sense.
As for the flap and a hot day in traffic...well, I wouldn't be beating on it in traffic...I usually save my "fun" for the track or roads I know well and only when they are quite empty. It usually only takes a short time for the movement of warm air to be replaced by cooler air. My thought was that the flapper may help with higher pressure intake air at high speed on the track, but based on your experience with the string...the flapper would not seal= no benefit of positive pressure.
I'm going to Limerock on Nov1st...I'll do the string thing as well and should be able to get it on video as well.