The 4-cylinder M47, M57, M47TU, and 6-cylinder M57TU were among the M series engines to incorporate swirl flaps as a first for a BMW. Any BMW manufactured between 2000 and 2008 is likely to have swirl flaps installed as standard because BMW phased out the usage of swirl flaps in their engines in late 2008.
Fortunately, BMW was able to learn from their mistakes, and starting in 2014, the B series of BMW engines won’t have swirl flaps. Even though swirl flap failure is a significant issue for older BMW vehicles, many of them have already had the faulty flaps removed.
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One of BMW’s major design errors is swirl flaps.
This results in thousands of owners worldwide having to pay for highly expensive repairs or possibly having their cars written off.
The flaps are found in the inlet manifold of the BMW diesel engines M47TU and M57TU (either 4 or 6 flaps depending on the amount of cylinders).
These numbers are intended to produce a swirl (thus the name) in the inlet manifold, which helps to improve combustion when the engine is not under heavy load. To maximize volumetric efficiency and power output under higher load circumstances, the flaps are completely open. This approach really performs worse in practice than it does on paper.
A typical BMW swirl flap has been removed in the image above to make room for an inlet manifold.
Unfortunately, swirl flaps are poorly designed and prone to malfunction. As you can see in the image below of a used swirl flap that was taken from a car with 80,000 miles on it, the shaft has been shattered (where the closest bolt meets the base).
When a swirl flap malfunctions, the debris falls into the engine and either sticks in the valve port and forces it open, pushing the piston into the valve, or it falls into the cylinder, damaging the piston, valves, and head.
The other problem we frequently encounter with these swirl flaps is that the tiny screws anchoring the flap to the shaft come loose and end up in the combustion chamber, where they cause significant harm. When they go through the turbo and CAT on their way out of the engine, they do more harm.
In the image below, a brand-new piston and swirl flap are shown next to a damaged piston and swirl flap (on the right). At 3000 rpm, when a component strikes a piston, you can see the extent of the damage.
Right side was taken from an engine with swirl flap damage; the left side is brand-new.
BMW attempted to address this issue by introducing a redesigned inlet manifold (still equipped with swirl flaps), which has a thicker and stronger valve spindle but is tragically still prone to failure. In late 2008, BMW eventually gave up on swirl flaps.
BMW only provides one solution if you are unfortunate enough to have swirl flap failure with your car. a new motor (circa PS8,500 to PS13.500 fitted).
At Grosvenor, engines with swirl flap damage can be repaired for about PS2,750 (depending on the extent of the damage).
My vehicle is a 2011-registered E92 335D. (“61” Plate)
On the internet, I’ve seen a number of articles claiming that BMW STOPPED utilizing swirl flaps in 2008. However, I’ve also heard that the engines mentioned above have swirl flaps installed that can be removed and blocked off.
Is it possible to quickly determine whether the car’s engine has swirl flaps without removing the inlet manifold?
Yes, it will have received them from the manufacturer, but they might have already been blanked.
If you remove the engine cover from the M57 and examine the area under the inlet manifold with a torch and a mirror, you can find out.
I initially believed that this engine had flaps, but then I keep seeing that BMW stopped employing swirl flaps after 2008, so I assume they are referring to later model engines from that year.
Even more recent engines still have swirl flaps, however they are of a completely different design. My 2010 330d has the later N57 engine.
Do the BMW f30’s swirl flaps work?
Unquestionably, the F3X 30d/35d units have swirl flaps. They do have carbon build-up, which can be removed, but all they need is a thorough cleaning, along with the inlet manifold.
How do BMW swirl flaps function?
How do swirl flaps work? On contemporary diesel engines, swirl flaps are tiny butterfly valves found on the inlet manifold. They are intended to enhance emissions at low engine speeds and assist in regulating the fuel to air ratio. The flaps close while the engine is running lightly, which causes the air to swirl into the combustion chamber. The spinning effect promotes leaner air to fuel ratios and aids in combustion. The flaps typically activate to a completely open position after 2000 rpm and have relatively little impact on engine output and emissions.
The swirl flaps installed on early BMWs were very prone to failure; with time, they were brittle and susceptible to breaking. In addition, the tiny screws securing the metal flap to the spindle are prone to breaking off and coming free. Any flap or screw that separates from its resting place within the input manifold is likely to enter the combustion chamber. This frequently causes severe engine damage, including cylinder head, valve, turbo, cylinder head, injector, and piston damage.
BMW upgraded the flaps’ design in 2004 by enlarging the spindle and screws’ diameters, but failure still happened. On later editions, the design underwent another alteration that involved the use of plastic flaps rather than screws. When removing the manifold for inspection, we have occasionally observed loose or missing flaps even though failure on the plastic variety is less prevalent.
In addition to catastrophic engine damage, swirl flaps can also have a negative impact on performance and MPG during normal operation. Regardless of their design, all flaps eventually acquire a thick layer of carbon and oil buildup from the EGR and breather systems. Due to the internal size of the inlet manifold being reduced as a result of the increased flap size, performance and efficiency are lost.
Depending on the design, there are many ways to remove the flaps, but in most cases, the manifold is unbolted from the cylinder head, the flaps and connection rods are taken out, and then specially made blanking plates are installed in their place. The ECU is reprogrammed and the actuator function is turned off if the car has an electronic swirl flap actuator.
We also advise performing a Custom ECU Remap concurrently with this modification. The remap is intended to counteract the slight loss of low-end torque that may result from removal.
Very little, in our opinion. The loss of efficiency and performance at low engine speeds is very imperceptible and would only be significant in the absence of carbon buildup. The removal of the flaps is expected to lead to an increase in performance and economy because carbon buildup starts as soon as the vehicle leaves the factory. BMW ceased installing swirl flaps on the majority of its vehicles after 2010, which implies that even the manufacturers are now aware that swirl flaps have more drawbacks than advantages.
Are swirl flaps included in the BMW N57 engine?
The 4 cylinder M47 and N47 diesel BMW engines are vulnerable to this. The 6-cylinder M57 and N57 engines will follow. When we removed the metal swirl flaps from the early M engines and installed blank plates in their place, the restriction and potential flap failure were eliminated.
While the manifold is being removed, we manually clean the manifold of unwanted carbon buildup.
You’d think BMW would have learned from their earlier M engine blunder with the subsequent N engines. They have used a big rod with plastic swirl flaps and fully reworked the intake manifold and swirl flaps. Unfortunately, with time, engine vibration and movement cause the plastic flaps to wear out and become loose. To avoid constriction and potential flap failure, we remove the metal bar and plastic flaps. While the manifold is being removed, we manually clean the manifold of unwanted carbon buildup.
The more recent B Diesel engines (made in 2014 and after) do not currently appear to experience the same problem. We believe that these will eventually need to be removed when they age. They resemble the earlier N engines in terms of design. At Burch Motor Works, the blank plugs are already prepared for installation.
All contain fresh inlet manifold gaskets as well as the necessary swirl flap blanks or bungs. Please be aware that possible ECU map tweaks may be needed for the later B series engines to enable swirl flap removal and prevent engine light illumination when in limp mode. A Remap of the DDE-ECU software is an additional PS199.00 inc. VAT if this is necessary.
Do m57n2 swirl flaps exist?
This kit gets rid of the troublesome swirl flaps, which are known to deteriorate and eventually fall apart. This ultimately gets sucked into the engine, often with disastrous results.
If you’re not sure what size swirl flaps you need, take a measurement using the example in the image above as a guide.
Do the swirl flaps on the B47 engine exist?
BMW 4 cylinder B47 and BMW 3 cylinder B37 diesel engines Darkside Swirl Flap Delete Kit
With the help of this package, you may get rid of the troublesome swirl flaps, which are known to deteriorate and eventually fall apart.
This ultimately gets sucked into the engine, often with disastrous results.
Our kit is intended to fill the gap left in the inlet manifold by removing the swirl flaps. The hole needs to be tapped to fit the provided bolt.
Do the swirl flaps on the N47 engine exist?
What year is the vehicle? There is no need to be concerned because the N47 engine’s swirl flaps were changed to a single flap in the manifold.
Impact of swirl flaps on emissions?
On contemporary diesel and gasoline engines, the inlet manifold houses swirl flaps, which are tiny butterfly valves. They are intended to enhance pollution control, fuel to air ratio regulation, and torque production at low engine speeds. The flaps close while the engine is running lightly, which causes the air to swirl into the combustion chamber.
The whirling effect improves combustion, lowers pollutants, and increases torque. The flaps typically activate to a completely open position after 2000 rpm and have relatively little impact on engine output and emissions.
What purpose do swirl flaps serve?
A swirl is created alongside the cylinder axle thanks to swirl flaps. In diesel automobiles, they are used to enhance the fuel-air mixture mixing at low engine speeds. For this reason, each cylinder receives air through two different channels in the intake manifold. With a swirl flap, one of the two channels may be closed. This causes the fresh air to swirl. Better mixing lowers fuel use and emissions of pollutants. To provide a greater filling level, the swirl flap is opened at higher engine speeds and torques. The swirl flaps are also opened when the engine starts and when it is overrun.
Another name for swirl flaps is “inlet duct cutoffs”. The swirl flap of the Opel Twinport engine lowers the throttle losses when operating at part-load.