Katatrappe beim AFN | Posts 32+

So, I should also think about that, because I, um, have approximately a 120% performance increase .

Do I really have to temporarily remove this part and test it out, and not test drive it in a way that violates traffic laws?

What aspects are monitored and regulated within the field of KAT?

Henrik wrote:

So, I should probably think about that too, since I, um, have approximately a 120% increase in performance .

Are we talking about 242 horsepower here?

It might actually be worthwhile to adapt the original exhaust system to the extremely harsh conditions it will now face.

However, in my case, a Kat would certainly have been too small (since it offers over 70% performance increase).


I just calculated it, and it's approximately 88% more performance .



Everything is being monitored and regulated.


This is nonsense . Absolutely nothing is monitored or regulated at the catalytic converter. The oxidation catalytic converter in the diesel engine operates purely passively. The boost pressure is regulated according to a map, as are the injection quantity and injection timing.

I would only remove Kat if he becomes a bottleneck – in situations with extreme performance increases.



So, I should probably also think about that, because I, um, have approximately a 120% increase in performance.

You still have a cat inside, and the stock exhaust .
Does it not cause any swelling?

Do I really have to take this part out for a test drive, and not test drive it in an area covered by traffic laws ...?

When you're doing renovations, the police won't be interested in a missing cat }.

'@Henrik and cksIT: This was also recently discussed in the Deppentuning.at forum. The thread was called 'empty exhaust,' but unfortunately, it mostly focused on sound (which is irrelevant for TDI engines anyway). However, everyone agreed that modifying the exhaust alone doesn't achieve much.'

'The 120% referred to my 90hp AHU engine, which I converted to an AFN and later refined it further, achieving approximately +/- 200 hp.'


Yes, it was about the sound. I also wanted to know if it offers any performance benefits.

I have a Remus exhaust system installed , and a catalytic converter, but I'm not being too cheeky about it }. It hasn't puffed out any smoke yet }, but the power is definitely lacking in the upper RPM range, so I suspect the catalytic converter is the bottleneck.

I didn't mean that the catalytic converter or its effectiveness is being monitored, but rather the boost pressure. Because without the catalytic converter, the engine can rev higher, but that's not beneficial, as the turbocharger will simply be down-tuned more aggressively.

but rather the boost pressure, because without a catalytic converter, it can rev higher, but this doesn't help, as the turbo is then down-regulated more strongly...

He can build pressure faster and exit boost mode sooner, but whether you'll actually notice it is another question!

However, it doesn't bring him any benefit, as the turbo is simply down-tuned more....

it already benefits him - namely, lower temperatures due to greater gas expansion .

cat or the filtering effect

'A catalyst is not a filter, but rather a porous, permeable material that is enriched with reaction accelerators (the actual substances that have a catalytic effect).'

'@Henrik: I would definitely remove that catalytic converter and replace it with a larger one - you have to imagine that a significantly larger amount of exhaust gas needs to pass through it than with the standard 66kW engine. The AFN engine also has a larger exhaust system...'

"It was meant in terms of performance," meaning that he has thermal advantages, which is clear, and that he spins up faster, which is also clear. But, as I said, at the standard power output, that doesn't benefit anyone.

'to bring him something' was meant in terms of performance, it's clear that he has thermal advantages, and it's also clear that he spins up a bit faster, but as I said: at the serial power level, that doesn't benefit anyone.

Okay - the performance gain from reducing the exhaust back pressure by a few mbar will be lost within the measurement tolerances.

Nebelwerfer_TDI wrote:

Quote: However, it doesn't bring him anything, because the turbo is simply down-tuned more.... it already benefits him - namely, lower temperatures due to greater gas expansion

.
"Hey, do you have any approximate data on what percentages of the exhaust backpressure upstream of the turbine at Pmax are attributable to..."

a) the turbine itself.
b) the cat
c) the silencer(s)?

In my opinion, it should add up like the partial voltages in a series circuit of electrical resistors...

@Henrik: I would definitely remove that cat and replace it with a larger one - you have to imagine that a significantly larger amount of exhaust gases needs to pass through it than with the standard 66kW engine. The AFN engine also has a thicker exhaust pipe...


I'm looking for a catalytic converter specifically designed for diesel engines (a metal catalytic converter), but I can't find one. Or can I use catalytic converters from gasoline engines instead?

This is my second question. Some people say the turbo exhaust flex pipe and catalytic converter are the same for all models, while others say the one from the AFN engine is larger... so which is it? Because if the AFN one is larger, I would take that part and use a larger catalytic converter, and then go for a Group A setup.

@ulf: kann man nur schätzen, da es ja bei jedem Motor anders ist, da abhängig von Laderwirkungsgrad, Aufladegrad, Dimensionierung der Abgasanlage incl. Kat.

However, in a heavily turbocharged diesel engine (i.e., with a boost pressure of over 1 bar at an engine speed of under 2000 rpm), there will already be several bar of pressure at the exhaust manifold (negative scavenging), with the majority of that pressure likely being attributable to the turbine, and in comparison, the catalytic converter alone does not have a significant impact.

The exhaust system, which is often quite complex in VW vehicles (with two mufflers and many tight bends), makes a significant difference in this regard.

Conclusion: If you want to remove the restrictions from your exhaust system, start by modifying the mufflers and using thinner, often curved, pipes, and as a last resort, remove the catalytic converter.

It should, in my opinion, add up like the partial voltages in a series circuit of electrical resistors.

Yes, but Kat and Auspuff could then be seen as the line resistance of the supply lines, and can be neglected if the turbine wheel represents the load resistance .

Or can you also use those from gasoline-powered vehicles?

I'm also interested in that. Basically, it does the same thing - it oxidizes HC and CO with oxygen or oxygen. I also have an oxygen catalyst lying around that I'd like to install in my diesel engine (Pöl/Schweröl 35i TD) to minimize or eliminate odor pollution at idle speed (e.g., when stopped at a red light).

Because if that were the case, I would take that part from the AFN and use a larger cat, and then group A...

My exhaust system for my 3B was a DIY project, and I would do it the same way again. I removed the middle muffler.

Nebelwerfer_TDI wrote:

The exhaust system, which is often complex in VW vehicles (with 2 mufflers and many tight bends), makes a significant difference in this case. Conclusion: Those who want to remove the restrictions from their exhaust system should start by modifying the mufflers and using thin, often curved pipes, and as a last resort, remove the catalytic converter.

Hmm, for example, for several years now, the ASZ (exhaust system manufacturer) has only offered a rear silencer in addition to the catalytic converter for the PQ24 platform (Polo/Ibi/Fabia).

The first Ibizas still had a center console, which was later removed.
At the same time, the rear silencer was given a different part number.

Therefore, can we assume that the old exhaust muffler...
-> has a lower flow resistance because there was still a central container in the way, which created its own "back pressure."
-> and thus be suitable as a subtle exhaust tuning part (with VAG number )?

Hm, for example, for several years, the ASZ (Abgasanlage System Zahnrad) in the PQ24 platform (Polo / Ibi / Fabia) has only had a single silencer in addition to the catalytic converter.


interesting - VW is finally learning to save money in meaningful places .

and thus potentially be suitable as a discreet exhaust tuning part (with VAG number ).




You can also modify a silencer, and weld a pipe to it. I've done that before for someone who absolutely wanted more noise - he didn't care about performance......well, to each their own .

ulf wrote:

... "Hey, do you have any approximate data on what percentages of the exhaust backpressure upstream of the turbine at Pmax are attributable to..." a) the turbine itself. b) the cat c) the silencer(s)? It should, in my opinion, add up like the partial voltages in a series circuit of electrical resistors...

a ... you can calculate this based on the power required for air compression and the amount of air. Don't forget the temperatures before and after the air-to-liquid heat exchanger, because the heat is a loss of power. Somewhere in this forum, there's a calculation for several kilowatts (I even think it's in the double digits).

b ... in its new condition, it's slightly less than what you'd expect from a muffler.

c ... Each silencer has approximately the same amount of "resistance" as a 90° bend in the exhaust system.
(Statements b and c are from a developer at Supersprint.)


My Jetta originally came with only two mufflers. Now it only has one + catalytic converter (complete).

Nebelwerfer_TDI wrote:

You can also modify a central pot and weld a pipe to it...

Sure, but that wasn't really what I was talking about.
If the systems with 1 and 2 mufflers for the same engine are designed for the same total back pressure, then, in principle, the end muffler of the older system should be suitable for reducing the back pressure, for example, after a chip tuning (of a newer car without a center muffler).
The question is, what order of magnitude would the pressure reduction (at Pmax) be in?

Bertil wrote:

a ... you can calculate this based on the power required for air compression and the amount of air. Don't forget the temperatures before and after the air-liquid heat exchanger, because the heat is a loss of power. Somewhere in this forum, there's a calculation about several kilowatts (I even think it's in the double digits).

Yes, the approximate power output of the drive system was in the range of about 15-20 kW, if I recall correctly.

The useful power output is determined by the product of the inlet volumetric flow rate and the pressure change.

Now, the hot exhaust gases, according to IMO, represent a higher volume flow than the cold intake air. Therefore, a relatively smaller pressure difference should be required on the turbine side to generate the power needed to drive the turbocharger... but by what factor is the exhaust gas volume flow greater than the intake air volume flow?
As long as you don't know that, you can't calculate the pressure requirements of the turbine .