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RedDevil · 09-26-2015, 05:25 PM

As Aerohead mentioned vent holes often behave contradictory to what you'd expect.

One stunning example is the bonnet scoop on the 2000 Subaru Impreza Turbo. That scoop allows air to flow through the intercooler.
One Impreza owner set out to measure the air flow and found that the scoop actually released air instead of taking it in.

The reason for that is simple; the high pressure area ahead of the big grill makes sure a lot of air flows into the engine bay, and it has to go somewhere.
The bonnet is slightly curved and creates negative pressure overhead.

One of my friends did own a couple of Subarus and noticed that at 250 kph on the Autobahn the bonnet was ballooning upwards, so much so that he thought he damaged it permanently. When he dropped the speed the bonnet sank back into position; apparently it could cope with the flexing.

But who would have expected the air flows out of that front facing bonnet scoop instead it into it?

09-26-2015, 05:25 PM	#6 (permalink)
RedDevil Master EcoWalker Join Date: Dec 2012 Location: Nieuwegein, the Netherlands Posts: 3,999 Red Devil - '11 Honda Insight Elegance Team Honda 90 day: 54.9 mpg (US) Thanks: 1,714 Thanked 2,247 Times in 1,455 Posts	As Aerohead mentioned vent holes often behave contradictory to what you'd expect. One stunning example is the bonnet scoop on the 2000 Subaru Impreza Turbo. That scoop allows air to flow through the intercooler. One Impreza owner set out to measure the air flow and found that the scoop actually released air instead of taking it in. The reason for that is simple; the high pressure area ahead of the big grill makes sure a lot of air flows into the engine bay, and it has to go somewhere. The bonnet is slightly curved and creates negative pressure overhead. One of my friends did own a couple of Subarus and noticed that at 250 kph on the Autobahn the bonnet was ballooning upwards, so much so that he thought he damaged it permanently. When he dropped the speed the bonnet sank back into position; apparently it could cope with the flexing. But who would have expected the air flows out of that front facing bonnet scoop instead it into it? __________________ 2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut. lifetime FE over 0.2 Gigameter or 0.13 Megamile. For confirmation go to people just like you. For education go to people unlike yourself.