What Are Hood Scoops?
At their core, hood scoops are simply openings that allow additional airflow for an engine.
Theoretically, this should always provide a power boost. Cooler, denser air is better for engine performance than the hot air that’s under your hood. Many hood scoops don’t provide a power boost though, either because they’re designed strictly for appearance, or because they’re poorly designed and the drag associated with them is greater than the power boost they’re capable of creating.
Hood scoops are a muscle car staple. As common as spoilers and wings, hood scoops give a vehicle a fierce look and are associated with performance boosts. Whether you just like the aesthetics or you’re interested in how it works to boost engine performance, there are a variety of hood scoop options.
Technically, the types of hood scoops are only limited by your imagination, from the truly wild “Air Grabber” that looks like a tiny Pac-Man trying to capture air to the sleek look of Shelby’s hood scoops. Any opening in a car’s hood can be considered a hood scoop, but some types are defined more by function than by form. Because these types of hood scoops are used so frequently and across so many different car manufacturers their results are easier to quantify.
It’s a little misleading to call a shaker system a “hood scoop.” Unlike other hood scoops, Shaker systems are mounted directly to the engine and they protrude through a hole in the hood. They’re sometimes labeled as “shaker hoods” and “shaker systems.”
Chrysler tried to market shaker hoods as the “Incredible Quivering Exposed Cold Air Grabber.” It’s a very descriptive name, but thankfully it didn’t stick.
Because the scoop is mounted directly to the engine, it vibrates along with the engine. The nickname “shaker” stuck. And because shakers tend to be installed on V8s, they shake a lot.
Shaker hoods work by capturing cool dense air, pressurized by the velocity of the car, and funneling it directly to the air filter of the engine. Unfortunately, shaker hoods tend to be loud, and they may violate localities “nuisance” laws.
Ram Air Intake
Like other hood scoops, the Ram Air’s easiest to explain gain comes simply from providing cooler air to the engine. The Ram Air functions as a cold air intake, but then it provides additional benefits by altering the pressure of the air being admitted to the engine.
A ram-scoop tends to start small and then widen as it gets closer to the engine. This forces the air to enter quickly but then slow down. Slow air gradually surrounds the engine, with fast air continuing to come down the scoop, increasing the pressure. The high-pressure air acts like a supercharger would.
If you’re wondering how a Ram Air system would work with a carburetor, you’re not alone. Unfortunately, the short answer is that it won’t. Carburetors rely on a pressure drop to draw fuel. Ram Air changes the pressure equation, and that creates problems.
Ram Air systems work best in a vehicle with a fuel injection system, or with a carburetor designed to work within a pressurized system.
Ram Air scoops only really provide benefits at high speeds, and subsequently aren’t usually installed on non-racing Mustangs.
These scoops are usually part of a supercharger system and are there to provide cooler air to your intercooler.
The major difference in an intercooler scoop (or turbo scoop as it is sometimes called) is that it doesn’t offer any performance boosts on its own. The turbocharger offers the additional power boost and the intercooler and accompanying scoop simply exist in an attempt to keep the engine cool enough that it doesn’t detonate or incur any substantial damage related to the increased temperatures that can exist inside of a turbocharged engine.
One of the major downsides of a supercharger system is that it creates additional heat. Thankfully the intercooler can alleviate some of that additional heat. Most intercoolers are air to air, which means that they use the outside air to cool down the air of the engine. An intercooler scoop provides an additional point of ventilation that’s near the intercooler. Obviously, the scoops are only functional if the intercooler is top mounted.
Cowl induction hood scoops sometimes get mislabeled as non-functional because people don’t see the opening. While as almost all hood scoops open at the front of a car’s hood, the cowl induction hood opens facing the windshield of a car.
The windshield’s base is another area of the car that’s high pressure. As air hits the windshield, it is propelled down and into the opening of the hood scoop. Even on cars without cowl induction hood scoops you may see vents in this area of your car.
This hood scoop brings cooler highly pressurized air into the car, benefitting it similarly to a cold air intake, but unlike other hood scoops it isn’t as susceptible to rock damage as its forward facing brethren.
Downsides of Hood Scoops
Hood scoops are an opening into the hood of your car. The major downside of installing them is that it provides an additional point of access to your engine. Thankfully there are rock screens available, so you can avoid that catastrophe, but there’s no way of keeping out additional dirt and debris.
Cars with hood scoops should be cleaned out more regularly to account for this and will need replacement air filters at a greater frequency.
Even though their owners might intend for them to be functional hood scoops, a poorly designed hood scoop won’t provide any additional performance boost and may even be detrimental since they contribute to drag.
It’s also important to consider the other underhood components of your car and how the pressure and turbulence of a hood scoop may affect them. In some cases, the effect will be neutral. For example, if your airbox has a clamp-down cover on it, then any hood scoop you install is going to be useless since there is no way for the additional flow of cooler air to reach the air inlet.
In other cases, installing a hood scoop can be a serious problem for your engine. If you have a carburetor, then a Ram Air hood scoop could cause serious harm to the inner workings of your car if you don’t take the proper precautions.
The Scoop on Hood Scoops
Though sometimes added purely for aesthetic appeal, hood scoops can be functional as well. By increasing air flow to the engine, hood scoops can boost performance. But there are a few things to keep in mind if you’re interested in functionality rather than just an appearance boost.
Functional hood scoops are situated in a high-pressure area of the hood. At higher rates of speed, more air will enter the hood scoop, and it will be moving at a higher velocity as it does. This cooler, denser air is responsible for the performance boost associated with hood scoops. In order to “catch” this air, the hood scoop needs to have an opening that’s high enough to clear the boundary layer around your car.
Engines rely on fuel and air to propel your car. Fuel is easy to increase, but it’s harder to increase the air intake or to get more power from each combustion. Hood scoops are an easy way to increase the air intake and also to ensure that the air being used is a desirable temperature or pressure for optimal combustion. In short, hood scoops function much the same way as cold air intakes, but they can be combined with cold air intakes for even greater power gains.
Sources: An Explanation of Hood Scoops, Ate Up with Motor | The Straight Scoop: Exploring the Science Behind Hood Scoop Design, On All Cylinders | The Chevy Silverado's New Hood Scoop Looks Hungry, Jalopnik | The 17 Coolest Factory Hood Scoops, Road and Track |