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Perhaps the manufacturers of Rainers-Sport air filters didn't care about airflow resistance because they know that it doesn't make a difference with ATL anyway. Then its only advantage is the ability to be washed and the placebo effect .
It would be surprising if this air filter fits not only in the A3 TDI but also in a naturally aspirated engine (which I doubt).

while single-point injection systems are not affected by this (a good example are the 1.6i 75HP engines) and run noticeably better with open filters or inserts, multi-point injection systems often experience DRASTIC performance losses. Inserts usually only result in marginal changes, as the original air intake and the air filter housing often act as limiting factors. OPEN filters (which are often used for the sound) often result in long faces.
Why? With multi-point injection, you can position the intake manifold however you want, allowing you to utilize resonance effects. And that's exactly what's done, and quite extensively. In my old Opel Ascona with a 2.0i engine, simply removing the pipe from the air filter box resulted in a significant loss of power. With an open air filter box, Fiat Pandas were able to overtake me...
Although the filter flow rate is better, the cylinder receives a much poorer fuel-air mixture because the resonances designed by the manufacturer are no longer present, and the valve timing no longer matches the intake manifold.
This resonance issue, incidentally, also applies to Diesels to a limited extent. Variants with a throttle body intake manifold may suffer from this (DTI).

Therefore, this also addresses the 'secrets' of resonance charging (or whatever it may be called).
It is clear that this effect depends on the design of the intake manifold. Consequently, open filters, which inevitably have a shorter overall intake pipe length, can completely disrupt the overall tuning, which can potentially significantly increase performance.

However, in my opinion, this aspect of the filter question should not be discussed further here, as the overall effect is based on the sum of two completely different phenomena (namely resonance and flow resistance), and one could argue endlessly about which effect contributes which specific part of the overall result.



Okay, the filters definitely change the frequencies (revolutions per minute) at which this charging occurs. And there's only one RPM at which the effect takes place, unless a variable intake manifold is installed. It's possible that the engine control unit (ECU) even expects a certain resonance at a specific RPM, and if that resonance is shifted due to the filter, it could have performance-reducing consequences.

In principle, the entire intake system, including the filter's flow resistance, is optimized for the engine and the airflow within the intake passages. It's difficult to say to what extent economists might interfere or whether financial considerations play a role, and whether this would allow for further improvements.

A different fuel mixture can therefore definitely produce positive effects in some RPM ranges, while having negative effects in others.

As everywhere, it can have not only advantages. A piece of wisdom that proves itself time and again!!

The objection that diesel engines have a larger excess of air is justified. I would like to reiterate my statement that, in TDI and similar engines, the cylinder filling is largely determined by the turbocharger and its pressure.

Perhaps the manufacturers of Rainers-Sport air filters didn't care about airflow resistance because they know that it doesn't make a difference with ATL anyway. Then its only advantage is the washability and the placebo effect.
It would be surprising if this air filter not only fits in the A3 TDI but also in a naturally aspirated engine (which I doubt). }

In the Golf III, with a few exceptions (round filters in older 60 and 75 horsepower gasoline engines), all plate filters are the same, ranging from the newer 60 horsepower gasoline engine to the 90 and 110 horsepower TDI models and the VR6.

So far, so good, but I suggest replacing the term 'air flow' (which also depends on environmental conditions such as engine displacement, RPM, etc.!) with 'flow resistance,' because that is a purely filter-specific parameter.

okay


However, this aspect of the filter question should not be discussed further here, as the overall effect is based on the sum of two completely different phenomena (namely resonance and flow resistance), and one could argue endlessly about which effect contributes which specific part of the overall effect.

ACK.


'Free airflow access' would likely again be the open filter with a completely redesigned intake geometry?

Actually, yes. Replacing the filter inside the airbox won't make much difference, because the limiting factor isn't the filter itself, but rather the air intake on the airbox and its airflow design.



for me: any part that is advertised as having a performance improvement compared to the original filters, or where such an impression is created, --> 'more air for your engine...'

Well... that just leaves open filters. } That also aligns with my experiences. } Aftermarket filters offer almost no to no advantage. } It largely depends on the air filter housing. } For older motorcycles, it can be beneficial because no one considered airflow when designing them. } They had maximum opening cross-sections (whatever they could fit). } That's where K&N inserts can make a difference... } but only in those cases. } I wanted to try it on my old-timer bike, but the transmission failed four weeks before the structural integrity of the housing was compromised. }

CU Gremlin.

Hi.

Quote:

An aftermarket filter in the airbox won't make much difference, because the limiting factor here isn't the filter itself, but rather the air intake on the airbox and its airflow design...

That may very well be the case... When I look at the "leading" intake opening, or air snorkel, on my car, I can almost feel the engine's, or the turbocharger's, struggle for air at higher RPMs.

That would mean that "noticeable effects" from sports air filters are likely (almost) always due to the change from the original filter housing to an open filter?
And that comparable results can also be achieved without expensive "sports" parts, for example, by expanding the cross-section of the intake manifold using DIY methods .

Okay, so here's the question again for those "enthusiastic" sports filter users: Do you use replacement filters in the original filter box, or do you use open filters or have you modified the air intake system in any other way?

Hello,

I haven't read all the posts in detail (it's possible that this has already been posted), but I just wanted to mention that...
Resonance in the intake and exhaust manifolds of a turbocharged engine does not play a significant role because the turbocharger's compressor is constantly operating.

To provide accurate information about the performance of the sports air filter (at least in terms of calculations), it would be necessary to have the characteristic curves of both filters.
In other words, to examine the flow resistance at different flow rates.
In my opinion, the difference is likely negligible.
Greetings.
Jean.

Hello Ulf,

I wouldn't have thought it was possible to analyze the topic of air filters so comprehensively, but it's definitely interesting.

I mentioned the example with my brother because, if we're being honest, we always tend to hope for something good when it comes to new things.
I replaced the dirty paper filter with a new one, and the car ran better.
Three days later, I replaced the brand new paper filter with the K&N filter, and the car ran even better.
Of course, I could have also convinced myself of that, but my brother noticed this difference without knowing about the further change.
Please don't mention things like temperature differences, different fuel types, vehicle weight, or anything else.
I have the experimental setup for my test subject - no, wait, I can keep the test drivers roughly the same.

My Golf I GTD, with its aftermarket long-life coolant, had approximately 95 horsepower and could reach speeds of up to 185 km/h according to the speedometer (the paper air filter was relatively clean before I changed it).
With the K&N replacement filter, it once reached 190 km/h, which it didn't achieve before. Of course, not for a long time, as it's a diesel and not a rocket.
I could have had a favorable wind earlier as well.

It is often demonstrated on display stands using a test setup, where two identical filters (one with oiled cotton and one with an original paper filter) are placed in a Plexiglas container and air is forced through them, supposedly to show that these sports air filters have a lower air flow resistance.
In two glass tubes attached above the filters, it can be observed that a ball placed inside can be lifted significantly higher above the sports air filter.

I think it's much more difficult to clearly distinguish differences in modern vehicles.
There are so many ways to influence the combustion process in these engines.
You're definitely stuck without measuring instruments or diagnostic equipment, aren't you?

Regards,
Michael.

Hello.

Does anyone know a manufacturer's name for original or replacement paper filters?

I couldn't find anything on the K&N website, so I'll call them tomorrow and ask for a performance curve or diagram. Hopefully, the data they provide will be accurate. We'll probably have to trust the manufacturers' honesty in this case.

For comparison, we also need the characteristic curve of a paper filter. However, I need at least one manufacturer's name for that.


However, you would need the characteristic curves for the same vehicle model, i.e., the same car. Could someone please post the corresponding data? Or, you could just call them yourself!



A proper understanding will likely only come from comparing characteristic curves.


How could one perform a self-test? Would simply trying to blow air through the different filters work? That would probably only reveal larger differences.
Suggestions are welcome; I'll have some free time soon, as my vacation is coming up!

@Rainer: Could you please try this out and let us know if you notice any difference? (Of course, only if you have the time and the filters are still available.)
That would be nice. Was that a K&N?


Best regards,
Ingo

Hello Ingo,

Ingo wrote:

Hello, Does anyone know a manufacturer's name for original or replacement paper filters?

Yes, for example, "man".

Quote:

Gremlin: BUT: "This effect often reverses in engines with fuel injection systems, frequently leading to the exact opposite outcome. While single-point injection systems are often unaffected (a good example being the 1.6i 75HP engines), which still perform noticeably better with open filters or modifications, multi-point injection systems often experience DRASTIC power losses. Modifications usually result in only marginal improvements, as the original air intake and air filter housing often act as limiting factors. Open filters (which are often used for the sound) frequently result in disappointing performance."

I have already discussed in detail with Ulf in the previous post (/viewtopic.php?t=616&start=37 and following) the function and effectiveness of various injection systems. I can confirm these impressions (with Mono-Jet or -Motronic systems).

Quote:

Eike: Has anyone ever recorded and compared the boost pressure curves of the two air filters during a 1000-4000 RPM test? I think that should make the difference visible.

I think this is a great approach. Since the turbocharger-supercharger combination experiences less resistance (which we assume), and therefore the exhaust gases are less restricted, the pressure curve of the boost could be different. It's not necessarily true that this will drastically change the air mass measured by the mass airflow sensor.

Quote:

Ingo: What makes me suspicious is that when you blow through a standard filter, it gives the impression that all the air is... Air passes through the filter. With the standard filter, air is recirculated.

Der Unterschied vom Standartfilter zum Standartfilter??? Hier stimmt was nicht!! Sorry, Ingo.

Quote:

Ulf: Okay, so here's the question again for those "enthusiastic" sports filter users: Do you use replacement filters in the original filter box, or do you use open filters or other modified air intakes?

"I'm not exactly a 'passionate' K&N air filter user in my TDI; I'm just doing it to save money (regarding the washability, see another post)."

Replacement filters for air filter housings - All standard parts!!

Oops, sorry, I mixed something up there!


'This is how it should be translated correctly:'


What makes me suspicious is that when you blow air through a K&N filter, it gives the impression that all the air is...
Air passes through the filter. With the standard filter, air is recirculated.


Sorry again!





Okay, here's a question about the diagnostic tool:

Can you extract the boost pressure curve from this? Is that possible? Because if so, someone could figure it out.


Best regards,
Ingo

Michael B wrote:

I mentioned the example with my brother because, if we're being honest, we always tend to expect something from new things. I replaced the dirty paper filter with a new one, and the car ran better. Three days later, I replaced the brand new paper filter with the K&N filter, and the car ran even better. Of course, I could have also convinced myself of that, but my brother noticed this difference without knowing about the further change. Please don't mention things like temperature differences, different fuel types, vehicle weight, or anything else. I have the experimental setup for my test subject - no, wait, I can keep the test drivers roughly the same. My Golf I GTD, with its aftermarket long-life coolant, had approximately 95 horsepower and could reach speeds of up to 185 km/h according to the speedometer (the paper air filter was relatively clean before I changed it). With the K&N replacement filter, it once reached 190, which it didn't achieve before. Of course, not for a long time, as it's a diesel and not a rocket.

I could have had time for a tailwind before.

Hi.

Well, that's already heading in the direction of "pro sport filter". If differences in flow resistance were actually the cause, then they seem to have been hidden in Rainer's measurement

Quote:

.

It is often demonstrated on display stands using a test model that these sports air filters are supposed to have a lower flow resistance. This is done by showing two identical filters (one with oiled cotton and one with an original paper filter) in a Plexiglas container, through which air is flowing.
In two glass tubes attached above the filters, one can observe that a ball contained within them can be lifted significantly higher above the sports air filter.

Quote:

It would be interesting to see if someone could swap the supposedly original filter at a trade show stand with an identical one they brought themselves. Or just taking the filters out of the tubes. Do you think the balls would then be blown upwards the same distance? I'm sorry for the lack of trust, but I've already read, heard, or even experienced enough about attempted and successful scams.

I think that it is much more difficult to clearly distinguish differences in a modern vehicle.
There are so many ways to influence the combustion process in these engines.
Without measuring devices/diagnostic equipment, you're definitely } in a difficult situation, right?}

Mostly yes, but Rainer has approached the matter with the same equipment. His results are well-known...

Hmm, I have a question about something I don't quite understand.

Does the turbocharger in a TDI engine constantly provide more boost than is actually needed?
The turbo's rotational speed depends on the exhaust gas flow, but turbos produce higher pressure at higher rotational speeds. While the pressure is not directly proportional to the rotational speed, that's not relevant in this case.

So, if my assumption above is correct, then the turbo might compensate for the difference between a standard filter and a K&N filter.

is that correct?

Ingo wrote:

So, if my assumption above is correct, then the turbo might compensate for the difference between a standard filter and a K&N filter. is that correct like this?

Basically, yes, as long as he does a proper job. In other words, this has been described multiple times before.

Hi everyone,

'I once measured the vacuum pressure before the turbocharger. To do this, I connected a vacuum gauge to the intake manifold via a hose (approximately at the level of the engine ventilation). I ran this hose into the interior of the car and connected a (unfortunately, small) vacuum gauge (measurement range 0 to -1 bar) to it, and then I took it for a test drive. The engine was at operating temperature, and the intake system was in its original condition. The car has 25,000 km on the odometer with the original air filter.'
During the test drive, a measurable vacuum pressure only became apparent above 3000 RPM and with full throttle, with values ranging from approximately -50 to -70 mbar. Unfortunately, I don't have a textile filter to perform a comparative measurement. However, based on these low values, it's likely that the benefit is minimal.

So far...
Regards,

Eike.

eike wrote:

During the test drive, a readable vacuum pressure only appeared above 3000 RPM and with full throttle, showing values of approximately -50 to -70 mbar. Unfortunately, I don't have a textile filter to make a comparative measurement. However, based on these low values, it's likely that the benefit is only minimal.

Yep, although, in my opinion, the vacuum is mostly used to accelerate the air through the narrow opening in the intake snorkel.
The filter element likely contributes only a tiny fraction to "that small amount" of negative pressure.