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What's Air Dam?

in Ownership
Car grille

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If you want to get better performance out of your car, one of the easiest ways to improve it is with aerodynamics. One simple car part that can help significantly improve your airflow is an air dam.

It is a vertical piece of metal, carbon fiber, plastic, etc., that sits below the grill and extends the front fascia of your car closer to the road to divert air that would normally flow underneath the car to the top of the car.

All production cars will come with some sort of air dam attached; on trucks and SUVs it is typically a black strip of plastic sitting below the front bumper that you barely even notice, while on sedans and hatchbacks, it is usually just a part of the front bumper.

But gear-heads who want the best performance they can get out of their cars will often install aftermarket air dams to provide even better aerodynamics. If you are considering modifying your current car by adding a larger, performance-oriented air dam or purchasing a car that already has one, you should know about some of the advantages and disadvantages of air dams and some other options to improve your car’s aerodynamics.

Advantages

By lowering the front end of the car, less airflow goes under the car, and it ends up flowing up and to the side. This makes the air pressure underneath the car lower while making the air pressure above the car higher.

That pressure differential produces downforce on your car, pushing it down towards the ground, which increases the grip that the tires can achieve. Normally, to increase the traction between your tires and the pavement, you need to add weight to the vehicle, but that comes with the downside of added mass for the engine to propel forward. Downforce keeps the mass low and the grip high.

This allows for better acceleration when you need straight-line speed and better handling when you need to hug the turns. In addition to increasing the downforce, an air dam can also improve the performance of the engine.

Much of the air diverted by the air dam goes right over the car, but a lot of it ends up going to the grille, through the air intakes, and into the engine bay. This forces more cool air to flow through the radiator, so the cooling system is better able to dissipate the heat coming off of the engine.

This might not seem hugely important, but an overheated engine that runs less efficiently and at very high temperatures might even cause damage to your engine’s components.


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Disadvantages

As great as performance air dams can be, there are a few reasons why car manufacturers like Toyota don’t put the same one on your Camry as they put on their NASCAR Camrys.

While low ground clearance is great for aerodynamics on a smooth, perfectly maintained racetrack, the real world is a little bit messier. If you have an air dam that sits only an inch or two off the ground, your aerodynamics will be incredible, but the second you hit a minor pothole, or even most street intersections with some slope for rain drainage, that thing is going to get scraped up pretty bad.

Even in a normal car with a standard air dam, this may have already been an issue for you. Pulling into a parking space with a parking block can already be treacherous with production air dams, and there is no feeling worse than trying to pull all the way into your spot only to hear the scraping of plastic on concrete, then knowing that you will soon have to hear that noise again when you back out.

The risk of damage leads to one important challenge with air dams: the aerodynamics of your car were designed with the stock air dam in mind. If the manufacturer really anticipated a lot of air being pushed into the air intake instead of flowing under the car, it may have been designed with a smaller grille to cut down on drag.

But if you put a dent in that air dam from a pothole or a curb, now all of a sudden, the airflow is far different from what was expected, which can not only decrease the downforce and reduce the car’s stability during cornering, but the engine won’t take in as much air as intended which could lead to overheating or inefficient fuel consumption.

So, if you do want to install a larger air dam or buy a car that already has one, consider all the places you normally drive and how much ground clearance you need.


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Other Options

If you want to improve the aerodynamics of your car, there are a few other options, each with their own advantages and disadvantages. In addition to an air dam, most cars have what is known as a splitter. This is another piece of the car’s body that sits horizontally below the air dam, running parallel to the street below.

This produces even more downforce on the front end of the car, but like the air dam, lowers the front end and decreases the effective ground clearance. Another option that increases the downforce and the cool factor of your car is a wing.

This is a horizontal piece of bodywork that sits above the back end of the car and redirects air upward, pushing the car down. This is particularly effective for rear-wheel or all-wheel drive cars as this pushes the back of the car down even more.

Another similar yet distinct option is a spoiler. Spoilers don’t produce more downforce, but they do divert air away from the area of low pressure that forms behind the car.


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This reduces the turbulence that holds your car back and reduces top speeds and fuel efficiency. Both of these are great options to improve the performance of your car, and they have much less risk of being damaged under normal driving conditions, but unlike an air dam, they do nothing for the cooling and air intake.

If you are interested in installing any of these options to improve the aerodynamics of your car, you will want to discuss this with a trusted mechanic who can help you form a plan specific to your vehicle and your taste.



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