Bonnet Vent Design

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here are a large number of alternative bonnet vent designs, some are more discrete than others. Some put functionality in front of design, whereas others put the design in front of functionality. With some, it’s difficult to tell quite what the owner had in mind!

The first example illustrates Ford Fiesta RS Turbo style, on a Ka.

This has the advantage of keeping the vents in the family.

The second example shows Mynheer Rover 200 vents, these being flush fitted within the bonnet.

You will note that these vents are situated a few inches further forward of the RS Turbo vents, shown above.

More to the point, as Charlie so eloquently put it, “ew, those look like nostrils, or blow holes.”

I suspect that just one of those vents in the middle of Kermit’s bonnet would certainly look like a blow hole; a pity he isn’t a whale, then!

The third example illustrates louvers. This car has a total of twenty four louvers pressed into the bonnet. It’s simple, it’s possibly quite elegant, and it’s even relatively subtle. But they are also functional!

This unusual shot shows Stunty’s Ka wearing Escort Cosworth style vents.

This Escort demonstrates one style of vent that I am considering: very flush with the bonnet, and with a mesh under it. The downside of this particular style is that there are no aerodynamic refinements to promote low pressure immediately above the vent – in other words, depending on the aerodynamics of the front of the car, air may be forced into those vents, rather than out.

The Mitsubishi Evo rally car has two large bonnet vents, which point back towards the driver, in a moulding which is designed to reduce the air pressure above the vent and thus drawing air out of the engine bay.

This shot shows the Subaru Impreza bonnet setup: a scoop, for the intercooler, and four small vents. These vents are subtle even with the black plastic mesh grill under: they would look even more subtle with body coloured mesh.

The Astra GTE may be an older car, but these vents are nicely subtle.

Indeed, the Astra GTE vents are currently my favourite style . . . so watch this space!