Why Do Some Cars Have Hood Scoops? Here's What They're For

Hood scoops have been a perennial staple of powerful sports cars and muscle cars with wild hoods for decades. And from the early post-war era right up to today, they all served a similar purpose: allowing more air to enter the engine bay. Most of these scoops provided fresh air for the car's intake, such as ram-air ducts, cowl induction, and shaker hoods. Others redirected air to assist with a car's forced-induction system, like a NACA duct leading to a turbocharger, or a cutout for the intercooler. We'll discuss the purpose and fundamental principles behind each of these types, but ultimately, most of them serve the same basic function as a cold-air intake. That is, rather than receiving hot air from an engine bay, a scoop instead draws in high-pressure, cooler air for the intake to use. They're distinctly different from a blower sticking out of the hood in that they channel the air using the hood's geometry, rather than simply cutting a hole for the engine to fit through.

Of course, all this relies on the scoop itself being functional. It's not uncommon to see cosmetic scoops on some cars' hoods, along with similar additions like nonfunctional side vents and so on. Hood scoops can enhance a car's performance image more so than actually providing fresh air to an engine, so this article will only discuss functional hood scoops and other elements present on a car's hood that serve similar purposes. 

The "scoop" element of a hood scoop means that there's a raised portion above the car's natural hood line. Sometimes these scoops lead directly to an engine's intake system, meaning if you look inside it, you'll see the top of the carburetor and its filter. Others have special ducting on the hood's underside to retain captured air and feed it into the system. In either case, these both serve the same function of drawing in cool, fresh air. This is why the hood scoop is, practically speaking, a cold-air intake. And since cooler air is denser than the hot air in the engine bay, it provides more available air molecules to burn, hence why true cold-air intakes provide minor horsepower benefits.

These hood scoops come in a variety of flavors, depending on the car. More specialized variants include: ram-air intakes, which are designed to alter the airflow pressure; shaker hoods, which aren't actually true "hood scoops" but rather are mounted directly to the engine like a blower (hence why they shake), and cowl induction. A hood with cowl induction appears to have a reverse scoop, with the intake facing towards the windshield. While this may seem counterintuitive, a true cowl induction scoop uses a cowl vent to draw in air from the high-pressure current at the base of the windshield. This vent can either be static or operate on a hinge that opens when the throttle is depressed a certain amount. Unlike traditional scoops, the "reverse" setup allows for a more aerodynamic and cleaner design while still providing adequate clearance in the engine bay.

This is where we'll get into forced-induction. Some cars, like the Z31 Nissan 300ZX, feature a functional hood scoop on turbocharged models. It's actually a separate piece, mounted to a hood with a cutout section, feeding cool air to the turbo. Other similar cars feature functional hood scoops in their designs, such as the Subaru Impreza, Fox-platform Mustang SVO, and many others. Generally, these serve specific functions related to cooling air for the turbo or supercharger, such as redirecting air to a top-mounted intercooler.

Others, like the vents found on the NISMO R-Tune hood for the R34 Skyline GT-R, feature prominent raised rearward-facing vents, much like cowl induction. These vents may still contribute to cooling the engine, but the differences are largely minor. These aren't true hood scoops in either form or function; they draw hot air out versus pull cool air in. So even though they're often raised like a hood scoop, they in fact serve a different purpose (though generally towards the same goal of making the engine bay cooler).

Similar systems to hood scoops utilize depressions in the hood instead. Notably, they're mounted perfectly flush with the hood line, so while they're sometimes called "scoops," these are more accurately vents. But unlike vents, these serve the purpose of redirecting cooler exterior air where it's needed -– the same as a hood scoop. These vents are called "NACA ducts," named after the National Advisory Committee for Aeronautics (NACA). They essentially act like more aerodynamic hood scoops, and are especially useful on vehicles with mid or rear-mounted engines.