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Swirl flaps / intake manifold flaps: Identify and fix defects!

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Recently updated on October 20, 2023 at 02:20 am

Swirl flaps / intake manifold flaps: Identify and fix defects!

[Update: 20.09.2023] This post was updatedto take more recent information into account. An internal combustion engine needs air to burn the fuel. So that the air filling in the combustion chamber is optimized, so-called Swirl flaps installed in the intake tract of diesel engines (also called intake manifold flap or swirl flap). There is a similar procedure in gasoline engines and this is called a tumble flap. By opening and closing the flaps in a targeted manner - depending on the load and engine speed - better fuel combustion can be achieved. Exhaust emissions are reduced and consumption drops.

Signs / Symptoms

However, due to age-related wear or errors in the design, it can happen that the swirl flaps are no longer controlled properly or break or malfunction. Then, insofar as you don't rely on one Swirl Removal Kit can/would like to fall back on a Repair

Swirl flaps / intake manifold flaps: Identify and fix defects!

  • Reduced engine power
  • engine judder
  • RPM fluctuations at idle
  • slow drop in speed after releasing the gas
  • possibly the mixing ratio of fuel and air in the cylinders is no longer correct
  • Check engine light comes on
  • Faulty memory entry such as: "Function of the variable intake manifold incorrect", "Intake manifold flap air flow control bank 1 is stuck"

Since it is a mechanical component, a diagnosis can usually only be made via a visual inspection. The following problems would have to be ruled out:

  • Servomotor or actuator linkage is loose or stuck.
  • The vacuum hose on the actuator is leaking or it is not seated correctly.

What can you confuse defective suction flaps with?

If the diagnosis is poor, defects in the suction flaps can be mistaken for a defect in the throttle valve, for example. Since the engine system does not always recognize the mechanical fault as the cause, there are also some wrong error memory entries. For example, such a may misleadingly suggest that the diesel particulate Filter is full, although the problem is not with the filter but with the suction flaps. A correct diagnosis is therefore important so that parts that are still working correctly are not replaced unnecessarily.

Swirl flaps / intake manifold flaps: Identify and fix defects!

Continue driving with defective suction flaps?

If the problem is known, the defect in the suction flaps must be repaired quickly. A defect in the flaps increases exhaust emissions and fuel consumption. The environment and wallet are unnecessarily burdened. If a flap breaks, small parts can also get into the extraction tract and cause expensive damage to the engine. In the event of malfunctions in the suction flaps, the diesel particles also become clogged over time. This can also end up being expensive. And you should also consider that if the check engine light comes on because of a defective intake flap, the main inspection will not be passed. And that also applies if the exhaust emissions are too high because of the defect.

Replace or repair defective suction flaps.

In the event of a defect, all suction flaps should be together with the control be replaced. Replacing individual flaps or installing used spare parts is not recommended. On the contrary, we even recommend an improved one Swirl flap repair kit. Improved variants are made, for example, from high-quality aluminum 6060-T66. In order to exchange the suction flaps, the suction pipe be dismantled. Depending on vehicle type, other parts and hoses may need to be removed first to gain access. And after the exchange, one usually has to be Basic setting be made.

Costs of changing: Swirl flaps / intake manifold flaps

The material costs of new suction flaps depend on the problem and vehicle type. For some vehicles there are only complete packages with original parts from the manufacturer, for other models there are special sets that can be used. Well-known manufacturers include Bosch, Pierburg and Febi Bielstein. The total material costs are between 80 and 650 EUR. Depending on the vehicle type, there is also the amount of work involved. The effort can take one to six hours. And if there are two banks of cylinders, the effort required to change them increases even more. And even more extra work is added when deposits in the intake tract caused by the exhaust gas recirculation have to be removed first. The pure labor costs should also be taken into account.

Swirl flaps in diesel vehicles:

  • Function: Optimum mixing of the fuel-air mixture at low speeds.
  • Positioning: Two channels in the intake manifold supply air to the cylinders.
  • Procedure: One of the swirl flaps can close a channel, causing fresh air to swirl.
  • Result: Better mixing of fuel and air.
  • Function at higher speeds: Swirl flap opens for higher filling level.
  • Starting the engine: Swirl flaps are open.
  • Additional feature: Regulation of exhaust gas recirculation on some models.

Symptoms of a defective swirl flap system:

  • power loss
  • Heavy contamination
  • Significantly reduced performance
  • Increased fuel consumption
  • Soot formation due to unhindered exhaust gas entry into the combustion chamber.
  • Possibility of the swirl flaps breaking off with potential engine damage.

Possible actions if the swirl flap system is defective:

  1. Replacing the defective swirl flap: Useful if all swirl flaps are replaced during an action.
  2. Using a removal kit: Cheaper than individual exchanges. Custom-fitting closures are installed in intake manifold openings.
  3. Consideration: Removal of swirl flaps could prevent benefits such as emissions reductions and increased performance.

Swirl flaps vs. intake manifold flaps:

  • Partial load range: Both contribute to the optimal mixing of air and fuel through the swirl effect.
  • Some models use them for Regulation of EGR (exhaust gas recirculation) rate.

Symptoms of a defective throttle body:

  • Irregular idle speed
  • Poor response to accelerator pedal movements
  • Motor may stutter or even stall.

The following note is essential: For safety reasons, tuningblog recommends all repair, inspection and maintenance work exclusively to be carried out in a specialist workshop! Although our information is summarized to the best of our knowledge and belief, we cannot assume any liability for the content. All information is therefore "without guarantee".

Of course, that wasn't the end of it!

In this tuning blog category there are guides and instructions on common defects/repairs on the vehicle as well as on installing accessories/tuning parts. Our articles explain common defects and the corresponding repairs in a simple manner, and they also explain how the first signs of a defect become apparent.

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Swirl flaps / intake manifold flaps: Identify and fix defects!

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About Thomas Wachsmuth

Thomas Wachsmuth - He has been an integral part of tuningblog.eu since 2013. His passion for cars is so intense that he invests every available penny in them. While he dreams of a BMW E31 850CSI and a Hennessey 6x6 Ford F-150, he currently drives a rather inconspicuous BMW 540i (G31/LCI). His collection of books, magazines and brochures on the subject of car tuning has now reached such proportions that he himself has become a walking reference work for the tuning scene.  More about Thomas

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