Verhalten hier im Forum, Luftfilter, Liefergrad | Posts 16+

I wasn't the one who did the diesel filter!




Oh man, this is really not fun.

I don't doubt your efforts; if I did, I wouldn't have posted it, so don't worry.
Anyway, you haven't even looked at what I constantly post here!
The drag force did not have any influence in your experiment.
When investigating something, please consider all measurable parameters that can be influenced, including drag. This is and will remain different.


K&N filters have a 100% lower flow restriction compared to a standard filter.
This results in a marginal increase that is hardly noticeable.
However, it cannot be denied that the thermal efficiency increases as the suction work becomes slightly smaller. This is a necessary consequence. I can't do anything about it; that's just the way it is.


I have never claimed that a K&N filter allows more air to pass through, and it's not possible anyway, since no structural changes have been made to the engine or car.


That polishing the channels thing was just an example! Because most people don't know what it does. Anyway, it has the same effect as a K&N filter. This is not related to a diesel engine, as I mentioned, it was just an example!! I have written this several times.







It's your forum, and if you want to delete something, no one can stop you anyway.
But it's pointless to force people to adopt a certain opinion by changing the content through various measures.
I've never encouraged anyone to buy a K&N filter or any other brand, so there's no question of inciting anyone. This has nothing to do with advertising; it's simply a matter of thermodynamics! That's just a law of nature, and I didn't invent it.

I didn't want to start any arguments here. I'm sorry that I knew something that others didn't. I just wanted to help. I'm sorry.
If I have offended anyone in the heat of the moment, I would like to apologize for that. SORRY! When the post was simply blocked, I was absolutely furious!

PS: If everything I'm saying is wrong, as others claim, I would like to know why my car consumes 0.5 liters less fuel with a K&N filter compared to a standard filter.
During the testing process, when the system was returned to its original configuration, a fuel consumption increase of 0.5 liters was observed with the standard filter.

Why??

Best regards,
Ingo
Please provide the text you would like me to translate from German to English.

So, are you talking about the SDI now?

The amount of air per revolution is determined solely by the engine displacement.

Okay, let's say your fuel mixture is improving due to the filter, but your lambda sensor (LMM) isn't detecting any change. How would the engine control unit (ECU) know that the fuel mixture is better? In a gasoline engine, the engine loses power as it leans out. In a diesel engine, more air alone doesn't increase power without more fuel (I'm talking about power, not efficiency).

Ingo wrote:

The drag has not had any influence in your experiment. When investigating something, please consider all measurable parameters that can be influenced, including drag. This is and remains different.

Air mass per stroke, as well as a variation in performance, were determined through the pull test.
If the flow resistance of your K&N filter is lower than that of a paper filter, how do you explain the lower air mass per stroke?
The volumetric efficiency of an engine is determined by the ratio of the amount of fresh gas drawn in to the volume of the cylinder.
As the volume of air moved per rotation increases, the delivery rate inevitably rises.
If the delivery rate with K&N improves, then the mass of air per stroke must simultaneously increase!

-> The mass of air per stroke, and therefore the delivery rate, remains the same, and in fact, may even decrease slightly with a fabric air filter!

@Doctor: The amount (mass?) of air per revolution is not only determined by the displacement, but is linked to the delivery rate and therefore dependent on factors such as flow resistance in the intake manifold, valve timing, and, in the case of a TDI, also the turbocharger pressure, etc.

Best regards, Rainer.

Because the mass of air moved per stroke is not dependent on the flow resistance. The amount of air entering the engine is determined by the engine displacement, and in the case of turbocharged engines, also by the turbocharger.

Unfortunately, the actual fill level cannot be determined in this way. It's not defined by the amount or mass of air, either.

@Ingo. The thing about the diesel filter was just an example, and it wasn't directed at you.

@All

I'm not a TDI fanatic, but does the TDI try to maintain the idle speed?

If that's the case, he would need to inject more fuel to achieve the same RPM with higher airflow resistance, because the increased resistance would affect the engine's performance as it draws in air, requiring it to exert more force.

Assuming that the injection amount can be read, wouldn't it be possible to determine, based on that value, how much fuel the engine needs to inject in order to maintain the idle speed?

It was just one of my thought processes, so please correct me if I'm wrong about anything.

Doctor, close 2/3 of the intake opening of your air filter box snorkel and measure the air mass per stroke at idle (intake phase).
It will be lower than with an open intake manifold, and therefore significantly lower air flow resistance.
Reason: The increased flow resistance creates a higher pressure drop from the beginning of the "narrowing" to the cylinder.
Due to the now lower pressure at the end of the intake stroke in the cylinder, the density of the air in the cylinder decreases, and consequently, so does its mass.

'That would work if the mass airflow sensor (MAF) could detect the (different) fuel level. If the MAF doesn't detect this (which is evident from Rainer's readings), then no more fuel will be injected, and the engine will run with an (excessive) air-fuel ratio.' That doesn't change the performance.
K&N filters can cause gasoline engines to run leaner (which is noticeable at higher temperatures).

Okay, Christian.

Unfortunately, the amount of fuel injected per stroke is only estimated to be 0.1mg with a certain degree of accuracy by the engine control unit (based on the position of the control cam on the fuel injection pump), and in idle conditions, it is in the range of 2.2mg per stroke.
Assuming a sufficiently accurate method for measuring the distance traveled by the sliding carriage, your approach can be verified.

Measuring the transit time was simpler for me, as the available engine power for acceleration also needs to vary in this case, given a fixed (maximum) fuel injection rate.

Best regards, Rainer.

It's obviously annoying that the control unit is providing such inaccurate values. Maybe I'll get a TDI someday, then I would have known something like that.

The flow rates confirm that a sports air filter practically makes no difference. However, the flow rate measurements only cover the range between 2000 and 4000 RPM, but the turbocharger is already working at full capacity in that range. So, with a TDI engine, it practically won't make any difference.

It would be interesting to compare the flow rates of an SDI system using a paper filter versus a fabric filter.

I'm not very trusting of figures like '0.5 liters less per 100 km.' Mine consumes between 6 and 7.5 liters of fuel, and it really depends on how and where I've been driving. I don't think I could drive two full tanks of fuel in exactly the same way to be able to make such a comparison.

Docter wrote:

That would work if the mass airflow sensor (MAF) could detect the (different) fill level. If the MAF doesn't detect this (which is evident from Rainer's values), then no more fuel is injected, and the engine would run with (too much) excess air. That doesn't change the performance. Here's the translation: K&N filters can cause gasoline engines to run leaner, which is noticeable at higher temperatures

.

"Doctor, be careful, you must distinguish between air mass flow meters and air volume flow meters."
TDIs have a mass airflow sensor, meaning they can actually measure the number of gas molecules being drawn into the engine.
The air mass meter can determine a higher delivery rate (filling level) because the volume of gas drawn into the cylinder is related to the air mass, and this volume is measured under the same pressure (namely, the ambient pressure outside the engine, which is where it's drawn from).
A mass airflow sensor, on the other hand, only measures the volume of air being drawn in. The actual mass of air (i.e., the amount of gas molecules) still depends on air pressure and temperature.
At least in my engine, the amount of air being drawn in only has a limiting function; even with a higher volume of air, more fuel wouldn't be injected (although this shouldn't be the case with PD engines).
If an engine runs leaner when using a K&N filter, it can only be because the air-fuel ratio has been improved.
However, for that to be the case, the old filter element would have had to be too small in size or severely contaminated.
The original paper filter in the measuring device is clearly not undersized; the differences in the amount of air drawn in within the intake area are almost zero, and therefore the differences in flow resistance are not relevant.

Best regards, Rainer.

Stukov wrote:

It would be interesting to compare the flow rates of an SDI with a paper filter and a fabric filter.

Good idea, maybe Ingo will provide some measurements here.
Ingo -> Please perform a flow test with a new paper filter and a cleaned fabric air filter, under otherwise identical conditions (engine temperature, measurement location, wind, air temperature, etc.).
After that, you should have the courage to post your measurements here.
Please take at least three measurements on a level surface to eliminate the effects of wind or slope, and once in the opposite direction.
Then you should be able to see if it goes faster in one direction than the other.

Cost: One paper air filter (10 euros), a stopwatch, and 30 minutes of your time. So, let's get started! We're waiting!

Rainer K. wrote:

"Doctor, be careful, you must distinguish between air mass flow meters and air volume flow meters." TDIs have a mass airflow sensor, meaning it actually 'knows' the number of gas molecules being drawn into the engine.

Hello Rainer,

I need to slightly correct you! The mass airflow sensor can only measure the air mass if the cross-sectional area and flow conditions (flow resistance) are known. If you reduce the inlet cross-section, the air will flow faster past the measuring wire (because the volume remains the same), the wire will cool down more, and the mass airflow sensor (MAF) will report: "There's more air coming in" (which is not actually the case).

Unfortunately, that would also explain why you measured a higher air mass with the paper filter than with the textile filter.

Sorry, no offense intended!

Admittedly, the idea is really good.

The problem will be that my credibility will be questioned if the results turn out as I expect.
To be honest, if it were the other way around, I wouldn't believe in those values either!
Besides, I already have my own biases; I know what I want to see in these times. I doubt anyone will believe that.
Okay, I'll go find a stopwatch and try timing it this weekend. Although, it probably won't be very accurate since the tachometer is unreliable. I'll see if I can find some time. (I have exams in 2 weeks.)

Best regards,
Ingo


@ Stukov
What kind of car do they have with that SDI setup?

It seems like the fuel consumption is a bit high. Do you have a Polo or a Golf?

My Polo weighs 1020 kg according to the registration document and consumes between 4.2 and 5 liters of fuel. To achieve the former, however, one must sacrifice all driving pleasure.

Bertil wrote:

Rainer K. wrote: "Doctor, be careful, you must distinguish between air mass flow meters and air volume flow meters." TDIs have a mass airflow sensor, meaning it actually 'knows' the number of gas molecules being drawn into the engine. Hello Rainer, I need to slightly correct you! The mass airflow sensor can only measure the air mass if the cross-sectional area and flow conditions (flow resistance) are known. If you reduce the inlet cross-section, the air will flow faster past the measuring wire (because the volume remains the same), the wire will cool down more, and the mass airflow sensor (MAF) will report: "There's more air coming in" (which is not actually the case). Unfortunately, that would also explain why you measured a higher air mass with the paper filter than with the textile filter. Sorry, don't be mad!

Hi Bertil,

No, I am not bad to you .
When I said "cover 2/3", I didn't mean the intake snorkel in the upper part of the air filter housing, but the snorkel in the lower part.
Therefore, the air velocity at the wire or hot-film air mass sensor in the TDI engine does not increase; it only increases at the narrowest point.
If the snorkel is attached directly to the mass airflow sensor (MAF), the flow velocity at the measuring element will indeed be higher, but the conditions for a correct measurement will no longer be met (due to the airflow pattern).
The heating current supplied to a mass airflow sensor is a measure of the mass of air flowing through it. Due to the restriction at the beginning of the intake system, a higher vacuum is created in the intake manifold, which reduces the air density and, consequently, the measured air mass.
To compensate for the change in density, a larger volume would need to be drawn in, but the volume remains the same.

Best regards, Rainer.

Ingo wrote:

However, this doesn't really become very accurate, as it relies on the engine's RPM.

Hello, whether the tachometer is perfectly accurate is not a major concern for these measurements, as long as it consistently produces the same error with each measurement.
We don't want to determine the absolutely correct amount of the services, but only the difference between the theoretical amount and the actual amount.
Whether the power ratio is 59/60 hp or 61/62 hp doesn't really matter.

Best regards, Rainer.

Are you talking about a regulatory body like the DK?

This limits the amount of air that reaches the engine. However, the engine draws in the same amount of air, which creates the vacuum in the intake manifold. Of course, he's not getting the right amount of air.

I recall Ulf's calculations regarding the intake snorkel, where the narrowing accelerates the airflow.