Media post: How Hood Scoops Work

Hood scoops are those bumps you see on performance cars that let air feed into the engine compartment. They are frequently on the hoods of cars, especially on the muscle cars of the 1960 but you may see them on other locations too.

Have you ever wondered if these things contribute to performance of the vehicle or are they just there to look good? We wondered too and posed the question to our friends at Waldorf Dodge of Waldorf, MD, an authorized Chrysler, Dodge, Jeep, Ram dealer.

Hood scoops 101

It’s pretty easy to understand the basic principles behind hood scoops. Let’s start with a car’s engine. An internal combustion engine needs oxygen from the outside air to burn during the combustion cycle. Cool air is denser than hot air and has more oxygen in it. So when cool air burns, it produces more power. Since the air in the engine compartment is usually hotter than the outside air (50 degree F difference!), you don’t want to pull engine compartment air into the engine. What you want to do is pull in nice fresh air from outside. This is where hood scoops come into play. Not only are they sticking out into cooler air, they have a ram effect where the air is slightly pressurized and is driven into the engine’s intake.

Different types of hood scoops

Raised Scoops – These are the scoops that stick up off a car’s body. Most hood scoops are just an inch or so tall but you will see some cars with tall scoops that rise far above the car’s surface. While this may look like the styling department is showing off a little, there’s really a lot more to it. When a scoop is up in the air, it escapes the slower “boundary layer” level air near the hood surface. This allows the scoop to not only funnel cooler air down into the engine but enjoy a ram-effect where air is actually pushed into the engine.

Duct Scoops – You’ve probably seen these on race cars. Duct scoops are reversed scoops buried below the surface of a car’s body. They are roughly delta-shaped with gently sloped ramps and curved walls. I the race car world, these are often called “NACA ducts” (at least in the US). This is because the NACA was a federal agency developed them in 1940s for the aviation industry. NACA ducts are common on road race cars. They typically don’t grab a lot of air but produce much less drag than protruding scoops do.

Cowl-induction Scoops – Many scoops face forward in the direction of the oncoming air, but every so often you’ll see a scoop facing backwards. These are called reversed scoops or cowl-induction scoops. Here’s how they work. Consider first that at the base of car’s windshield is a high-pressure zone. If a reversed scoop is mounted close enough to the windshield, that high pressure will force cool air into the scoop. It won’t be quite as much as a forward-facing scoop will grab but it will be significant enough to use.

Scoops – why don’t all cars have them?

Well, Scoops have disadvantages too. First, functional scoops often don’t appeal to the design guys because they disturb the flowing lines of many car designs. Plus, there are times you don’t want a scoop operating, such as during rainstorms and heavy snow. Bottom line: Hood scoops are popular on cars of the past but aren’t a feature that Detroit values today. You will still see them on performance cars because the allow the engine to produce a little more horsepower and that could mean the difference between winning and losing a race.