How to Tell if Swirl Flaps Have Been Removed

Swirl flaps help improve airflow in the engine, but they also come with many problems. Here’s how to tell if swirl flaps have been removed in your car.

There are many reasons for which you can ask your mechanic to remove the swirl flaps of your car. You need to remove the swirl flaps if the engine’s efficiency or performance is going down or its upkeep is digging a hole in your pocket. 

To confirm the modification, there are a few signs that can indicate whether or not swirl flaps have been removed from a car. Read this post to get all the information regarding swirl flaps and the advantages of removing them. 

What Are Swirl Flaps?

Swirl flaps are valves used to regulate an engine’s airflow. The flap is opened and closed by a cam controlled by the engine’s computer. The computer controls the cam when the engine is running, so the flap opens and closes in sync with the engine’s cycle. This allows the engine to breathe correctly and produce power efficiently.

If your vehicle has a swirl flap system, it must be inspected regularly to ensure it works properly. Swirl flaps can become clogged with carbon deposits over time, which can cause performance issues. 

In some cases, the flap may not open or close properly, which can restrict airflow and cause the engine to run less efficiently. You can find the swirl flaps inside the inlet manifold.

How to Tell if Swirl Flaps Have Been Removed

How Do Swirl Flaps Work?

The main advantages of swirl flaps are that they are designed to improve engine performance and fuel efficiency by swirl-charging the engine’s air. The flaps redirect the airflow in a way that creates a swirl effect, which increases the amount of oxygen available for combustion. This allows the engine to run more efficiently and produce fewer emissions.

Swirl flaps can be found in gasoline and diesel engines and are often used in turbocharged engines. They are typically located in the intake manifold before the cylinder head. An actuator controls swirl flaps, usually operated by vacuum pressure or an electrical signal from the engine control unit (ECU).

While swirl flaps can improve engine performance but also cause problems if they fail, if the actuator fails, it can cause the flaps to become stuck in the open or closed position. This can cause an engine to misfire, increase emissions, and reduce fuel efficiency.

Disadvantages of Swirl Flaps

Swirl flaps help to improve engine performance and fuel efficiency. It improves torque when the engine is moving at a low speed. However, they can also cause several problems, including:

  1. Reduced engine performance – The swirl flaps can restrict airflow to the engine, reducing its power and efficiency.
  2. Excessive engine noise – The swirl flaps can cause a “flapping” noise as they open and close. This can be not very pleasant for drivers and passengers alike.
  3. Higher emissions – Due to the reduced airflow, engines with swirl flaps tend to produce more emissions than those without them. This is terrible news for the environment and your wallet!
  4. Increased wear and tear – The constant opening and closing of the swirl flaps can cause wear and tear on the engine, leading to premature failure.

Benefits of Removing Swirl Flaps

1. Swirl flaps can cause engine damage

If swirl flaps are not functioning correctly, they can cause engine damage. This is because the flap can become stuck in the open position, which will cause a loss of compression and eventually lead to engine failure.

2. Swirl flaps can reduce fuel economy

Another downside of swirl flaps is that they can reduce fuel economy. This is because the flap creates turbulence in the intake airflow, which causes the engine to work harder and use more fuel.

3. Swirl flaps can increase emissions

Yet another problem with swirl flaps is that they can increase emissions. This is because the flap can cause the engine to run richer, which will lead to more emissions.


4. Swirl flaps can cause knock

Another issue is that swirl flaps can cause knock. This is when the air/fuel mixture in the cylinders detonates prematurely, which can cause engine damage.

5. Swirl flaps can create excessive noise

Finally, swirl flaps can also create excessive noise. This is because the flap creates turbulence in the intake airflow, which can be pretty loud.

As you can see, there are several downsides to swirl flaps. Therefore, it is generally best to remove them when possible.


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How to Remove Swirl Flaps and Fit Blanks in a BMW?

If you own a BMW with the M47 or M57 engine, then it’s likely that your car is fitted with swirl flaps. Swirl flaps are designed to help improve engine performance and efficiency, but over time they can become clogged up with oil and debris, which can restrict airflow and cause performance issues.

Fortunately, removing and replacing your swirl flaps is relatively easy, and we’ll show you how in this guide. We’ll also provide tips on fitting replacement blanks to help prevent future problems.

So let’s get started!

  1. Firstly, you’ll need to locate the swirl flaps on your engine. On the M47 engine, they’re located just behind the air filter box, while on the M57 engine, they’re located further back, behind the intercooler.
  2. Once you’ve found the swirl flaps, you’ll need to disconnect the vacuum hose. This will prevent oil or debris from entering the engine when removing the flaps. Remove the screws gently to disconnect the vacuum hose.
  3. Next, use a screwdriver or similar tool to pry the swirl flaps out of their housings. There’s no need to be gentle here – ensure you don’t damage the housing itself.
  4. With the swirl flaps removed, look at the condition of both them and their housings. If they’re heavily clogged up with oil and debris, then it’s likely that they’ll need to be replaced.
  5. If you fit replacement swirl flaps, lightly lubricate the O-rings with oil. This will make it easier to insert them into the housings.
  6. Insert the swirl flaps into their respective housings, ensuring they’re fully seated.
  7. Finally, reconnect the vacuum hose and check for any leaks. If everything is secure, then you’re all done!


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Signs of a Swirl Flap Removal or How To Check For Swirl Flap Delete

If you’re lucky enough to have a swirl flaps-free engine, there are a few ways to tell. Here are some signs that your engine is free of swirl flaps:

  1. There’s no flapping noise inside the combustion chamber– If you start up your engine and there’s no strange flap noise, the chances are that your engine doesn’t have swirl flaps.
  2. The exhaust sounds smooth – Another way to tell if your engine doesn’t have swirl flaps is by listening to the exhaust. If it sounds smooth and quiet, your engine is likely flap-free.
  3. There’s no check engine light – One of the most reliable indicators that your engine doesn’t have swirl flaps is if there’s no check engine light on the dash. If the light is off, the engine isn’t triggering any error codes related to swirl flaps.
  4. The engine starts without any delay – If your car starts immediately after inserting the keys and there is no delay, then it’s a sign that the swirl flaps are missing.
  5. Powerful drives – when you are driving on uneven terrains or hilly region and you car is running at a steady speed then its a sign that your car no longer has a swirl flap. Swirl flaps cause a bit of power loss.
  6. Low smoke emission – when earlier you were driving your car and it was producing excess smoke then it can be due to swirl flaps. But if after the modifications the smoke emission is almost nil then its a sign that swirl flaps are gone.  

Suppose you have any of these signs; congratulations! You have a flap-free engine. Swirl flaps can cause all sorts of problems, so it’s good to know that your engine doesn’t have them. Keep up the excellent work, and enjoy your flap-free ride! Another sign to notice is that if there are no swirl flaps, you would see blanking plates inside the manifold.

Frequently Asked Questions

What happens when you remove swirl flaps?

When you remove swirl flaps from an engine, the airflow around the cylinders is no longer controlled. This can lead to increased exhaust gas temperatures and potentially cause engine damage. Additionally, without swirl flaps, engines may produce more noise and vibration.

How do I know if I have swirl flaps?

If you’re not sure whether your car has swirl flaps, there are a few things you can check. First, look for a metal plate with several small holes in it on the intake side of your engine. This is where the swirl flaps are present. 

If you can’t see this plate, your car may not have swirl flaps. You can also try starting your engine and listening for a rattling noise. 

If you hear this noise, your car likely has swirl flaps. Finally, you can consult your owner’s manual or ask a mechanic to look at your engine to determine if it has swirl flaps.

When did BMW stop putting swirl flaps in their engines?

BMW stopped them in 2006. Swirl flaps help improve engine performance and efficiency but can cause problems if they fail. 

If the flaps fail, they can cause engine damage and may lead to a fire. BMW has recalled some vehicles equipped with swirl flaps and has offered to repair them for free.


Swirl flaps have many disadvantages; in some situations, removing them from the car’s engine is essential. If you asked your mechanic to remove the flaps and want to be sure about them, we hope the above signs will help you identify them. If you have any questions, please comment below or contact us directly. We would be happy to help!

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Sean Mendez

Hi, I am Sean, a self-confessed petrolhead. I live in Boise, Idaho with a busy family of four and our energetic Labrador retriever. Thank you for visiting my website. You can find my email on the contact page.

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