| Diesel technology, engine technology, vehicle diagnostics, repair & maintenance. |
Lots of show, little substance: sports air filters (Articles) |
|
|
| 🔗 ⭐ 🖨 |
| Lots of show, little substance: sports air filters | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
dieselschrauber  23-05-2003, 14:31 |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
![[Luftfilter im Test]](/localfiles/Lufis.jpg) Why this comparison?
In order for an engine to deliver the highest possible power output (i.e., to burn the largest possible amount of fuel cleanly per power stroke), air with the highest possible density must enter the cylinders, therefore... -> Keep it as cool as possible. -> with the highest possible pressure. Since any air leak in the intake system reduces air density, the entire intake path, including the filter, should have the lowest possible flow resistance. This is the only way to get air into the engine with the lowest (but fundamentally unavoidable) pressure losses. In reality, the pressure already exists in the air filter housing, below the atmospheric pressure, and this is particularly noticeable at high airflow rates, such as when the engine is running at full throttle and high RPM = Pmax. The resulting pressure loss in the intake air is, in most passenger cars, almost exclusively caused by the intake manifold , whose inlet often represents the narrowest point of the intake passages through which all the air must flow. For example, in TDIs, pressure sensors with a range of up to approximately 50 mbar are often located behind the intake manifold, which means before the actual air filter, and this is a common size range. A pressure loss of 50 mbar compared to the outside pressure can reduce the potential power output of a naturally aspirated gasoline engine by approximately 5%; in turbocharged engines (including... In TDIs (Turbocharged Direct Injection engines), this loss is practically completely compensated for by the turbocharger. Standard paper filter elements cause very little additional pressure loss - at least as long as they are reasonably clean. For example, if a paper air filter causes an additional 10 mbar of vacuum pressure after several thousand kilometers of use, and a new or different (performance) filter only causes a 4 mbar pressure drop, then replacing the filter would reduce the pressure loss caused by the filter by 6 mbar. This pressure gain of 6 mbar would, in the case of naturally aspirated engines, correspond to a power increase of as much as approximately 0.6%, while a "normal" intake manifold still results in a loss of potential power of about 5%. The balance sheet could be even better for current paper wick filters with mutually sealed filter channels. This type of filter offers a very large surface area in a compact design. According to experiences from the forum (thank you, Julian  ), filters can sometimes become so clogged even within the normal maintenance interval that it results in a noticeable loss of performance and increased fuel consumption.
The optimal time to replace a paper filter can be estimated by its light permeability; hold it up to the sun. In a new filter, light shines through the folds of the paper very clearly, and the fins also allow some light to pass through. If a used filter allows very little or no light to pass through, it should be replaced. If there is a lot of coarse dust in the filter, you may be able to improve its permeability somewhat by tapping it (carefully tapping the element with the airflow side facing down on a smooth surface). However, the filter is usually so clogged with fine particles that even after tapping, light will no longer pass through -> replace it. As long as a paper filter is regularly checked or replaced according to the operating conditions (dust levels, etc.), it will not cause a noticeable loss of performance or increased consumption. Of course, this doesn't stop manufacturers of sports air filters from advertising their products. 1. Plate elements (also known as cartridge filters) . By using phrases like "40% more airflow, better acceleration, higher top speed..." to create completely unrealistic expectations among potential customers regarding performance gains, which are only conceivable under specific circumstances, such as replacing a paper filter that has been unused for over 200,000 km with a new one. Where a paper filter, for the reasons mentioned above, would provide the same performance gain as a sports filter... Rainers comparative measurements using two standard filters and a sports filter confirm that sports replacement filters do not provide any significant improvements to the engine's air supply, at least in the case of TDIs.
The statement regarding a higher air mass flow should be verified here. To do this, the air mass was measured using a diagnostic tool (VAG-COM, now VCDS diagnostic system, or KOBD2Check) on an Audi A3 TDI with engine code AHF, at two different, defined load conditions (measuring block 3 in the engine control unit). In addition, three acceleration measurements were taken from 1800min-1 to 4100min-1 in 3rd gear, and the air mass values were also recorded during these measurements. To exclude the influence of the exhaust gas recirculation system, it was temporarily deactivated for the measurement. Similarly, the air conditioning was turned off during the measurements. The fabric air filter was lightly sprayed with 15W40 oil after cleaning, at a distance of 6,000 km. Measurement conditions {MAThe test candidates Measurements at 924 min-1 / 1197 min-1 Measurement at 924 min Measurement at 1197 min Measurements at full load 1800min {-1} to 4100min{-1} ![[Volle Beschleunigung, Papierfilter mit 12.000km]](/localfiles/Lufi_full_dreck.jpg) Surprising result: The ![[Volle Beschleunigung, Papierfilter neu]](/localfiles/Lufi_full_neu.jpg) oldpaper air filter shows the best result, both with the engine unloaded and at full acceleration! The reason for this can only be speculated upon, as the two paper air filters come from different manufacturers. It is possible that driving in the rain can also cause a change in the filter's surface, resulting in an improvement in airflow compared to its initial state. The measured Ulf times are all within a narrow range of approximately 5.7 seconds, and no variation in the required turbocharger power output was observed. Since the measured values are all within a narrow range, it can be said with confidence that it doesn't matter which type of filter cartridge is chosen. ![[Volle Beschleunigung, Gewebefilter mit 6.000km]](/localfiles/Lufi_full_bmc.jpg) My decision was in favor of paper filters because, during trips in heavy rain, the air filter box of my A3 became very wet inside, and the fabric filter was completely washed out. A paper air filter here shows only a -like behavior. Measurement data for download... Zip file containing VCDS measurement data Therefore, the performance-enhancing effect of increasing the pressure in open filters In the mid and low RPM ranges, and under partial load conditions, virtually no pressure loss occurs behind (clean) standard filters in almost any vehicle. Therefore, an open filter cannot provide any improvement in this case (it's impossible to have fewer losses than zero), but the hot air issue is a significant problem, leading to torque losses, poorer responsiveness, etc. In the higher RPM range, the overall balance of pressure gain and temperature increase in the intake air, which is specific to each vehicle, determines whether installing an open filter will increase or decrease engine power. The best performance for open filters is achieved at high engine speeds and with the coolest possible air in the engine compartment, i.e., when the engine is cold. In other words: Open filters provide the greatest performance gain when the engine is immediately revved to its maximum RPM after a cold start . In tuned TDIs with significantly increased boost pressure, reducing the intake manifold vacuum can be beneficial to relieve the turbocharger from extremely high RPMs - but the higher intake temperatures further increase the already significant thermal loads on the engine and turbocharger . For unmodified TDIs, the primary mechanical effect of open filters in the hot air intake system will be to reduce performance, rather than increase it, as described. In particular, in the low-rpm range, the torque will be reduced compared to the standard configuration due to the reduced fuel injection amount (soot reduction). If the turbocharger engages (delayed) when the accelerator is fully pressed, and if it overrides the soot reduction system with the torque limitation, the increase in torque will logically be more measurable than in the standard configuration. Since a devout sports filter driver tends to only perceive positive things, the poorer throttle response in the vacuum range is simply ignored, and only the more noticeable turbo boost is noticed -> Wow! To address the issue of hot air, filter manufacturers typically offer two solutions: 1. Shielding plates between the engine block and the filter. Imagine a filter researcher working in a well-heated room in winter, standing near a radiator (which represents the warm motor), and using a vacuum cleaner to suck in air. Suddenly, the man says that the air being drawn in is actually too warm (which is quite surprising, considering it was originally drawing in cold air from outside), and he presents a piece of sheet metal that he has attached between the heater and the vacuum cleaner hose as a solution to the problem. Subsequently, the filter researcher continues to draw air from the heated room, but now claims that the intake temperature has been significantly reduced, thus solving the warm air problem. Whoever believes will be blessed... 
2. Through hoses to supply the filter with cold air:evil:. The engine should draw in air that is richer in oxygen. The hoses should be installed so that one end is positioned next to the filter. Apparently, filter manufacturers assume that their products possess a kind of intelligence that recognizes the adjacent hose opening and subsequently only draws air in that direction. Or they hope that at least their customers will imagine something like that... In reality, the warm air accumulates above, under the hood, around the filter, due to the natural temperature stratification. So, the engine will continue to draw in hot air instead of pulling cold air "uphill" through the hose. If the inlet opening of the hose is directed forward, the airflow can initiate the desired cold air flow to the filter. However, the amount of cold air that can be achieved depends on factors such as engine displacement, RPM, speed, hose diameter, and engine load. The turbocharger only releases a fraction of the engine's air intake, and in addition, depending on the orientation of the hose, a portion of the carefully supplied cold air will bypass the filter. But even for that, the filter specialists have a solution: You simply reshape (figuratively speaking) the engine-side end of the cold air duct into a ball that surrounds the sports filter, thus preventing the intake of warm air. Now, only cold outside air is being drawn in - and the discerning reader will recognize that here, the well-known principle of the series filter has simply been reinvented  .
In order to distinguish these products from mass-produced items (and to sell them with high profit margins as groundbreaking developments from motorsports), they are given new names and designs that promise performance, high-tech features, and dynamism. We will refer to them here as...  3. Sport filter boxes. 
The air filter housing is often significantly smaller compared to the standard version and is only visible from the outside as a thickened section of the intake path. In addition, they usually feature generously sized intake hoses or pipes, and can therefore actually achieve a performance gain of several % in the higher RPM range, especially when the standard intake paths are too narrow (see above). You can, of course, achieve the same effect for a fraction of the cost with the standard filter by removing the restrictions in the intake passages -> Part 1 in  .
One possible modification, depending on the design of the filter box, is to extend the continuous column of airflow compared to the standard intake paths by using a sports filter box. This allows for the creation, amplification, or modification of resonance charging effects, which often also changes the perceived performance characteristics of the engine. That means that in certain speed ranges, more torque is available, while in other speed ranges, less torque is available. Convinced users of sports filter boxes will only notice the welcome changes -> see item No. 2. It is generally conceivable that, in TDIs, shifted resonances can improve cylinder filling in the lowest speed range. Then it is possible to increase the injection amount due to the increasing soot limit, which, in the absence of boost pressure, improves torque and shifts the turbocharger's spool-up towards lower speeds. In the best-case scenario, the engine's responsiveness at low RPMs will be noticeably improved. Wind charging during travel? To protect the engine and mass airflow sensor from water being drawn in during rainy conditions, most standard intake air ducts have drain openings for water, water-deflecting surfaces in front of the intake openings, or the intake openings are angled relative to the airflow, so that most of the water droplets flow past the intake opening. When installing sports air filter housings or modifying the intake system to remove restrictions, it may seem appealing to route the intake hoses in a way that the air intake opening is directly exposed to the airflow. Depending on the engine displacement, RPM, speed, cross-section of the intake opening, and engine load or boost pressure, this can create a pressure buildup that improves cylinder filling in naturally aspirated engines, and in favorable cases, can increase power by a few percent. In turbo engines, the effect is limited to a slight reduction in the load on the turbocharger. However, this only works if the entire path between the intake opening and the engine is completely sealed, so that the painstakingly generated back pressure is not lost. Sealed intake passages also mean that any water that is drawn in (e.g., from the spray of the vehicle in front during heavy rain) cannot drain away before reaching the engine, and therefore enters the engine as soon as the filter, the insides of the intake passages, and possibly the intercooler are saturated with the accumulated water. Many LMM are known to be allergic to water in the flowing air, which, under such operating conditions, leads to their expected premature failure. Of course, an engine failure is even more expensive than replacing a faulty mass airflow sensor. If water enters the intake opening, there is a risk of hydraulic shock when the volume fraction of liquid water in the cylinder exceeds the inverse of the engine's compression ratio. "In a gasoline engine with a compression ratio of 1:11, the air is compressed to 1/11 = 9% of the intake volume. If the volume of water entering the cylinders exceeds 9%, the volume of water becomes larger than the combustion chamber, meaning that the piston will hit the wall of incompressible water on its way to top dead center during the compression stroke." Common failure: One or more connecting rods and/or the crankshaft bend, and the engine is only worth scrap metal. In a naturally aspirated diesel engine, even a water content of just 5% in the cylinder charge is enough to cause a "water hammer" due to the higher compression. For engines with pre-turbochargers (turbochargers, superchargers, etc.), the situation is even more critical. Let's take an example of a turbocharged diesel engine with a compression ratio of 1:20, 1 bar of boost pressure, and a 3% water content in the intake air. The water already occupies 6% of the volume of the boosted air after the turbocharger, because the water droplets cannot be compressed. Since the combustion chamber volume is only 5% of the total filling volume, the water hammer effect is predictable. However, the sudden rush of water usually doesn't occur with the very first sip. Initially, a certain amount of water can accumulate in the filter, on the inner walls of the suction pipes, and possibly in the coolant system, which effectively provides a grace period for the engine. Only when these areas filled with isolated water are "saturated" will the next, sufficiently strong surge of water damage the engine. In this case, high-flow sport filters can allow water to pass through too quickly, potentially causing the engine to stall in extreme situations, while an original paper filter would provide sufficient time to slow the water flow and save the engine. Side effects Sport filters are manufactured by companies such as... Hopa has been investigated in connection with LMM issues, but unfortunately, the document is no longer available online. Here's a summary of the key points (the water issues at LMM were already mentioned above): A. Aftermarket air filters, regardless of their design, often have a less effective filtration performance (due to larger pores) compared to the original filters, and therefore allow more dirt into the engine. A common solution is to soak the filter elements with oil, which can then be carried away as a mist by the airflow. If filter oil deposits on the measuring membrane of a hot-film air mass sensor, its measured values decrease, which eventually leads to a loss of power due to a reduction in the injection quantity, and possibly to jolting and/or other malfunctions. B. Furthermore, the installation of an open filter or a sports filter box can alter the airflow profile in the mass airflow sensor, causing it to report too little or too much air intake, which in turn disrupts the engine management. Possible consequences include: loss of power, hesitation, or (in diesel engines) increased soot production. C. Since Hopa only deals with diesel tuning, the following topic is missing from the link: Many gasoline engines have an intake air temperature control system (which mixes warm air drawn from above the exhaust manifold with cold air, depending on the engine's operating conditions) designed to optimize engine smoothness and/or emissions. When installing an open filter or a sports filter box, this device must inevitably be removed, with the corresponding consequences. 4. Conclusion From a technical perspective, open and panel-type sports filters generally offer almost no advantages compared to standard intake systems. By expanding the often somewhat narrow intake manifold on series air filters, the engine (even after tuning) always receives enough air, which is also optimally verschandeln and cold - meaning more than most sports air filters can offer. The actual benefit of open and panel-type sports filters mainly lies in show effects, such as the louder intake noise in gasoline engines and the different appearance in the engine compartment, and in the profit for manufacturers and distributors. Significant performance gains can be achieved simply by switching to sports filters, as is regularly advertised with. -> "Hocus pocus" features like overly complex air intakes in the filter (every swirl, vortex, or "internal" air acceleration in the intake path costs energy, which ultimately results in a reduced air density, which in turn reduces engine power!). -> misleading descriptions. -> empty phrases like dynamic, powerful, optimized, etc. The suggested modifications are practically impossible unless the standard air filter system is a complete design flaw with excessively narrow flow passages and/or unnecessarily convoluted air ducts. Only with sports air filter boxes does the situation look a little different: With a well-designed construction (i.e., without internal air accelerators or other gimmicks), they can, depending on the interaction with the engine, actually provide slight, localized performance gains, in addition to the visual effect. When considering the cost-effectiveness (cleaning and reusing a sports filter multiple times instead of discarding many paper filters), not only the prices of sports filters and paper filters should be taken into account, but also, in the case of sports filters, the costs of the filter oil, the cleaning fluid, and potentially the disposal of the used cleaning fluid. Ultimately, one must also consider whether one is willing to take on the "dirty work" of cleaning the filter. Authors: Ulf & Rainer Translated on 03-07-2026, 15:19. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Ratings - Lots of show, little substance: sports air filters | |
Average rating: 5.00 - worst rating: 5 - best rating: 5 - number of ratings: 11 - View ratings |
|
|
| 🔗 ⭐ 🖨 |
|
You cannot post new topics in this forum. |
|
|
Foren- und Portal-Software: V7.4 © 2003 - 2026 Kaufmann Automotive GmbH, Embedded Softwareentwicklung & Shop für VCDS und OBD-Diagnosegeräte. Parse time: 0.076s
 |
Bookmarks
Links
Garage
FAQ, Legal Notice & Privacy
RSS Feed
Register
Login
![[Papierluftfilter, 12.000km]](/localfiles/Lufi_dreck.jpg)
![[Papierluftfilter, neu]](/localfiles/Lufi_neu.jpg)
![[Gewebeluftfilter, 6.000km]](/localfiles/Lufi_BMC.jpg)
