Can You Leave Car Air Filter Cover Off?

By November 21, 2020July 19th, 2021Air Filter

You should not leave your air filter cover off. Without the cover, you risk sucking hotter air from the engine bay – resulting in reduced performance and also risk the air filter popping out of place – which causes unfiltered debris, dust and insects to enter the engine.

Now with the summary out of the way, let’s dive into more details. Starting with why do we even need air filters and its covers and what’s the pros and cons for removing them. 

This article focuses on the air filter cover (not the air filter itself). If you want to know what happens with driving without an air filter, then wait a bit! That’s coming soon. In the meantime, let’s understand the importance of its cover.

What’s The Use Of Air Filter?

If you don’t already know, a car needs to use air and fuel to generate power and move. Fuel is supplied from the fuel tank, whereas air is sucked from the surrounding – this is the job of the intake system.

When sucking air, your car needs to make sure only air comes through. We don’t want any dust, debris and insects in our engine, do we? This is where the air filter comes in – they are fitted right in the middle of the intake system.

Audi-A3-8P-Arma-Carbon-Intake
Air intake. Air is sucked from here.
Air filter is enclosed inside this air box.

Any incoming air must first pass through the air filter and get “cleaned”. Sounds pretty good right? Yeah, except the fact that thick air filters can restrict air flow. They do a good job in filtering dirt but they also make it hard for air to reach our engine. 

This is why car enthusiasts install performance air filters. They work a little differently to make sure dirt is filtered but air flow is not restricted. 

I have an article here where I discuss more about performance air filters. Check it out if you want to learn more. What Does Performance Air Filter Do?

What’s The Function Of Air Filter Cover?

Now that you know the gist of air filters, let’s talk about the highlight of this article – the cover.  Air filter cover encloses an air filter inside the air box. You could open and close the cover when you replace your air filter.

image of stock air intake
The air filter cover

Aside from seemingly being simple, there are 3 important functions to an air filter cover:

  • Keeps hot air from entering. I mentioned that car engines need air to generate power. Truth is, car engines need Oxygen in the air (not the air itself). Hot air is less dense and can hold less oxygen – which means hot air cannot generate as much power. This is why we don’t ever want to suck hot air to our engine.
  • Acts as silencer. Manufacturers purposely engineer the air box / cover to silence air intake sound. Although the added noise is great for us, the majority of drivers are not car heads and they prefer less noise. 
  • Keeps the air filter in place. If you don’t already notice, air filters do not have clamps or drills to keep it locked. They just pop into the air box – which is why we need the cover to lock the air filter in place. 

What’s The Function Of Air Filter Cover?

Removing air filter cover is not all good or bad. Although I don’t recommend it here’s a list of pros and cons. 

The Pros

  1. Louder engine sound. This is probably what got you searching in the first place. Keeping the cover off will definitely give you more sound – especially the sound of air rushing into the engine (a very satisfying sound). It won’t increase the sound greatly but it’s noticeable.
  2. More air flow. Theoretically, there will be more air rushing into the engine. However this will not really improve performance because they are all hot air from the engine bay (more on this in the cons).

The Cons

  1. Potential engine damage. Without a cover in place, it’s only a matter of time before your air filter is jolted out of place (a speed bump could be enough). Once the air filter is not in place, dirt, debris and insects will end up in the engine. Causing wear and tear damages at best and engine failure at worst.
  2. Reduced performance. Hot air with less oxygen can now flow directly into the air filter because it’s no longer closed. This means your engine cannot generate as much power. Though, you probably won’t have this problem if your car is moving (engine bay is not as hot then).

Potential Alternatives

As you can see, the cons of removing the air filter cover are quite significant. I don’t recommend you to do this at all. But if you still insist, there are a few alternatives or workarounds you can do.

1. Clamp Air Filter In Place And Use Heat Shield

The biggest problem with removing air filter cover is the air filter not locked into place and hot air going in. So let’s address those problems.

You could use clamps to ensure the air filter is locked into place despite missing cover and then install a heat shield around the air box to ensure hot air does not enter. This means you need to spend extra money to buy and install them.

I would say this is not worth the hassle. Instead, you could drill holes on the airbox and leave the cover in place. Let’s talk about this next.

Here’s the heat shield from Amazon that I have personally used.

Air filter heat shield
Example of a heat shield around air filter. The air filter in image is cone air filter (not stock).

2. Drill Holes In AirBox (Swiss Cheese Mod)

Drilling holes in the airbox is also known as the swiss cheese mod – because of how the holes will look in the end.

Drilling holes in the airbox will give you a louder intake sound and more air flow without risking the air filter popping out of place or sucking hot air in. 

Make sure the holes are below the airbox or on the sides. This way the additional air is cooler air, instead of hot air from the engine bay.

Here’s a YouTube video showing you exactly how and where you should drill the holes.

3. Replace With Cone Air Filter

If you want to go the proper route, then I suggest you look into aftermarket air filters – specifically the cone shaped ones. 

Cone air filters are large and completely exposed – they are not confined inside the airbox. In fact, when you install a cone air filter, you need to replace the stock air filter and air box. 

This means you will get much more air flow and intake sound when you step on the throttle. Here’s a before and after video comparing the sound between stock and cone air filter.

Here’s a cone air filter from Amazon that I have personally used in my car. It’s by K&N and it worked pretty great.

Better Ways To Improve Car Sound

If all you want is an improved engine sound, then I recommend you check out my other article. 5 Ways To Make Your Car Louder For Cheap. 

Find a method that provides you with the sound you want and your budget. I am sure there are many alternatives for you 🙂

Ifandi S.

Ifandi S.

Passionate about everything mechanical. Ifandi has been involved with motorcycles and cars since the old days - in his family's auto parts shop. Want to keep in touch? Scream "STRAIGHT PIPEEEEE" at the top of your lungs and Ifandi will show up.

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