Fachartikel über Auspuff-Tuning? | Posts 16+

dieselmartin wrote:

Quote: If I remember correctly, the resonance stories apply to naturally aspirated engines and don't play a role in turbocharged engines. I don't think so. Because the racing TDI engine for the 24-hour race had a resonance-tuned intake manifold, similar to the SDI, and of course, a turbocharger

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Regarding the fresh air side, you are probably right: it seems that a resonance charging might still have something to offer.
"However, even a tuner company that offers related products states that it mainly works in the low RPM range (or when there is no boost pressure yet, i.e., during the transition from acceleration to load)."

Here, we are talking about the emission side .
Does the book also provide specific facts (and not just information about, for example, a larger exhaust system with less back pressure)?

I had only read about the issue of back pressure with turbos, as I mentioned.

My old 1Z once unexpectedly failed the catalytic converter, ignition system, and emissions test because the pipe in front of the catalytic converter was damaged. During the approximately 80km journey to the workshop and the same distance back, we noticed that the car actually ran better with the new system than it had before. However, I didn't have VAGCom or LDA back then.

Exhaust side ???

Oops, I should have read everything more carefully. I was also wondering how you're achieving intake resonance.

Of course, it's also possible for it to resonate in the exhaust system.

Sorry.
m;

x world one wrote:

My old 1Z once unintentionally lacked both catalytic converter, oxygen sensor, and glow plug control, because the pipe in front of the oxygen sensor was damaged. During that approximately 80 km journey to the workshop and the same distance back, we noticed that the car ran better with the new system than before. However, I didn't have VAGCom or LDA back then.

You probably would have only been able to read the normal values anyway, even without the exhaust.

If the stock exhaust system actually increases performance on the given stock engines (with their original timing), it suggests a deliberate overall tuning – which is essentially how it should be.

Then, without an exhaust system, the overall efficiency would ultimately decrease (due to excessive scavenging losses, etc.), but without reducing the turbo boost pressure, fuel injection volume, etc., which are adjusted to normal values.

Please use your experience and Dieter's experience for the technical article .

Ah, another aspect that should be included in a technical article for the sake of completeness.
(hopefully Rainer won't mind this topic being discussed here):

In posing forums, it is generally lamented that TDIs, even with a sports exhaust, do not produce a "reasonable" sound.

What is the reason for that?
Does the loader completely eliminate the exhaust vibrations to the point where there's nothing left that could be used to create a "sporty" sound?
The fundamental vibrations (or, better, pulsations) are still present, as you can feel by placing your hand in front of the exhaust outlet...

Do gasoline turbo engines experience the same "problems" when trying to create a "sporty" exhaust sound?

You can probably only reproduce that "prollsound" with a TDI engine using the right CD and the appropriate external sound system. Although - that might actually be something special again; I have here the soundtrack from the BRM V16, year 1949...

But seriously, at first, it was surprisingly quiet. It only got quite loud when we added an emergency exhaust pipe (a 30cm arch angled downwards), because the sound reflected off the road. But it's not really suitable for sound tuning; it's mostly hissing and whistling from the turbo, with a slightly louder rumble in the background. Every pimped-out Golf is louder, and motorcycles are even louder.

Greetings.
dieter

Of course, resonance behavior also applies on the exhaust side, even though a diesel engine doesn't have a throttle valve.
I remember when designing the V12 engine for the Actros, that extremely high demands were placed on the exhaust side. Factors like the length of the exhaust system, noise levels, decibel reduction, fuel consumption optimization, and engine cooling all played a role. Even the timing chain components were designed for optimal flow. A lot of torque had to be generated even at low engine speeds, so the flow rate had to be right. The length of the exhaust system couldn't be too short, but also couldn't be too long.

On my old ALH, I also had an exhaust pipe (more for aesthetic reasons), and the nice thing was that you could hear the turbocharger's whine from the rear at idle, which was really cool. But otherwise, there were no measurable changes. Except that the rear was smokier, and VW/Audi know why the pipes should point downwards.
In terms of sound, I was able to extract something from the TDI, but it will never be able to match a high-displacement gasoline engine with an exhaust system. It sounded a bit grumbling and dull, you could hear the turbocharger more clearly from the outside when downshifting, but otherwise... no miracles!

dieter wrote:

But seriously, in my case, it was surprisingly quiet at first, only when we gave the turbo an emergency bypass pipe... mostly hissing and whistling from the turbo, with a slightly louder rumbling in the background.

Julian wrote:

On my old ALH, I also had a rear silencer installed (more for aesthetic reasons). The nice thing was that you could hear the turbocharger's whine from the rear at idle, which was really cool.

But otherwise, there were no measurable changes.

Hm, that seems to confirm my suspicion that the charger is acting as a sound absorber.

I didn't read everything, just wanted to share my brief experience with the Passat:

After the catalytic converter, no exhaust components (everything after that): no difference in performance.
No catalytic converter, but original exhaust: provides a slight performance gain (noticeably better acceleration).
No cat, no exhaust: same here.

Unfortunately, no readings were obtained...

DocSnydor wrote:

After the catalytic converter, no exhaust components (everything is removed): no difference in performance. No catalytic converter, but original exhaust: provides a slight performance gain (noticeably better acceleration). No cat, no exhaust: same here

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Hmm, so, was was your experience: did you find that "the less back pressure from the exhaust system, the more (perceived) power"?

That's going to mess up the nice, simple rules of thumb we've had so far .

And now what?
Is there any way to resolve this "contradiction"?

For example, does the Passat have a poorly designed exhaust system?

Or was it perhaps that your intake manifold was clogged with deposits due to the EGR system, causing the entire gas exchange process in your engine to become "abnormal," and therefore causing it to react "incorrectly" to changes in the exhaust system?

Or should we initially consider it only as an exception that confirms the rule ?

Or . . ..???

@everyone: Your ideas and comments are welcome.

Hm, that seems to confirm my suspicion that the charger is acting as a sound absorber...

Hi,

dabei bleibt dann noch die Frage, wieso die Schalldämpfer eines TDI immer noch so riesig und entsprechend teuer sind. Ich habe einen alten G3 1Z auch mal ohne Endschalldämpfer gefahren. Der war kaum lauter als mit. Wozu dann das Teil? FFor 3 dB less?
It doesn't seem like the Pareto principle is being applied here...
Greetings.

Eike.

Wozu dann das Teil? For 3 dB less?


Hehe, apparently you generally have bad hearing...

I once reversed my Alh and ended up hitting a gatepost with the catalytic converter, leaving a €2 hole in the body panel. The engine sound was incredibly loud.

Okay, regarding the topic of loaders as sound generators:
I once owned a Mazda 323 Turbo (gasoline engine) where the exhaust pipe detached after the catalytic converter. At low RPMs, it had a deep rumble, but when giving it full throttle and high RPMs, you could only hear a loud hissing sound from the turbo! So, the same 'problem' can also occur with a gasoline engine.

And because I've heard about flushing losses twice, my question is:
Can scavenging losses actually occur in a diesel engine?
Is it injected only after the valves are closed, or am I misunderstanding something?

Best regards, Daniel.

An exhaust system needs to be tuned for turbocharged engines. Then, a TDI can also produce a sporty sound. I recently heard one of these systems again (it sounded really good, rumbling but not tinny).

Best regards, WarLord.

DerBruzzler wrote:

And because I've heard twice about issues with pressure loss, my question is: Can scavenging losses actually occur in a diesel engine? Is it not injected until the valves are closed, or am I misunderstanding something?

You are right, diesel fundamentally cannot be lost.

But fresh air, which was painstakingly compressed by the turbocharger, could be wasted and escape to the exhaust during the overlap, which, in my opinion, ultimately reduces the overall efficiency.

Quote:

I once had a Mazda 323 Turbo (gasoline engine) where the exhaust pipe fell off after the catalytic converter. It would rumble deeply at low RPMs, but when giving it full throttle and high RPMs, you could only hear a loud hissing sound from the turbo! So, the same "problem" can also occur with a gasoline engine.

WarLord wrote:

An exhaust system needs to be tuned for turbocharged engines. Then, a sports sound can also come from a TDI. I recently heard one of those systems again (it sounded really good, rumbly, but not tinny).

Then the exhaust designer will likely use appropriately sized resonance chambers in the muffler to amplify any residual vibrations that the turbocharger hasn't already "absorbed."

Since sound absorption, as far as I know, generally affects the higher frequency range first, the remaining sound consists mostly of low-frequency components. If you amplify those, you're likely to end up with just a low-frequency hum.
It seems to be the same with turbochargers.

I think the "sound" aspect is sufficiently clarified (before Rainer puts the lock on the door here . . . ).

Hello Ulf!

After reading the thread, I also feel a little compelled to leave a comment .
I believe it is quite possible that the timing of the valve events in a TDI engine is designed in such a way that, with too low exhaust backpressure (no catalytic converter, no secondary air injection), increased scavenging losses can occur. However, this would necessarily require a certain degree of valve overlap (can anyone verify this?).
Regarding the turbocharger, it actually benefits in two ways from a reduced back pressure in the exhaust system: the power output on the turbine side increases, and the temperature level decreases.

Regards,
Alex.