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Theory behind hood vent    

Why vent through the hood

The standard solution for a 911 center-mount cooler is to vent beneath the car.   This works very well and cools effectively.  But on this project we wanted to experiment with a hood-vent, on the theory that less airflow under the car can only be good.

Plus, the lineage to the 917 was compelling and in keeping with the Gulf livery.  Hood vents are cool!

But cool only gets you so far, let's see some science.  Following are some computer models of airflow with different hood-vent configurations.

Models indicate a hood-vent should reduce lift at the front.  Further, that moving the air exit vent to mid-hood should create a pressure differential to force air through the cooler.   At least that's what the model says.

Click any image to see a larger view.   <Prev | Next>

	Stock 911 SC.  High pressure zone in red pushes on under side of bumper and valence, causing lift.
	Cooler vent near front of hood.  High pressure zone is now pushing down on hood and intake, at least equalizing upward pressure.  But exit vent is in red/yellow pressure reducing flow.
	Cooler vents to mid-hood.   Exit vent has moved to low pressure zone, maximizing pressure differential and flow.  High pressure now appears to be creating net down-force.
	If it's good enough for the 917.....   Yet another reason to do it.

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