Diesel Retrofit: Smell and Solutions

A few days ago, during a discussion on another topic, the issue of increased odor emissions came up: worn nozzles or a faulty catalytic converter.
https://community.dieselschrauber.org/en/viewtopic.php?t=1610&postdays=0&postorder=asc&start=100 or https://community.dieselschrauber.org/en/viewtopic.php?t=1610&start=125.
I've just installed a new catalytic converter in my car that makes it compliant with Euro2 standards, which will save me on taxes.
As a side effect, I can now say something more about the condition and effectiveness of the catalytic converter: The previously unusually strong odor has lessened, and in warm vehicles (which is currently rare), it has completely disappeared. The car now smells like a diesel engine when idling, but only faintly. However, the smell is more comparable to that of an old chamber diesel engine than to a current model.
Mechanically, the old Caterpillar was otherwise undamaged. Approximately 10% of the surface area is clogged with soot, which may also be due to the short-distance operation of the past few days.

Hi,

I've noticed that too!
I also had a EURO2 catalytic converter installed in my AAT (previously it was EURO1, which cost almost €580 in taxes ).
Since then, there has been hardly any more smell of diesel.
As a EURO1 engine, the smell was extremely strong; it seems that direct injection engines are particularly noticeable in this regard.
Our old 200D (also Euro1 compliant) smelled much less strongly.

Hi,

I can only confirm that! On my old car, I converted from a zero-catalyst system to a Euro I catalyst system, and the unpleasant smell completely disappeared.

Aromatic hydrocarbons (->smell) are also the only substances that a diesel catalytic converter removes through post-oxidation. Perhaps some soot as well. But the whole thing with the oxidation catalysts is mostly just politics! A particulate filter would be much more effective, especially since modern diesels emit very fine soot particles that are suspected of causing cancer due to their deep penetration into the bronchi. The large particles from older diesel tractors can easily be removed by the mucous membranes.

Exhaust gas recirculation is just as ridiculous -> like oil pumps, etc. There are already NOx catalysts, but urea needs to be added as a reducing agent for them to work. If you compare the NOx emissions of diesel passenger cars with those of trucks and buses, the proportion from passenger cars is quite small.

Best regards, Christian.

HI,
The catalyst also reduces the measured amount of soot. However, this is only because hydrocarbons adhere to the soot particles, which are weighed but then broken down in the catalyst.
As long as EGR systems eventually stop functioning correctly, the overall emissions could actually be higher due to increased smoke production, even compared to vehicles without EGR systems.

Hi there,

The particulate filter alone is not enough. French cars with FAP filters are not yet exempt from taxes to the same extent as Golf TDI PD models with 74 kW that do not have a particulate filter. Previously, sulfur in diesel was primarily responsible for soot emissions. Only when sulfur is largely removed from diesel will exhaust gases become significantly cleaner.
Soot in the exhaust always indicates a loss. If it were to burn completely, you would have more power or lower fuel consumption.
The only goal can be to optimize the combustion process in such a way that no soot is produced at all. Then there would be no need for particulate filters either.

Regards,

Eike.

haehnlein wrote:

.... The large particles from the old TD tractors can easily remove mucous membranes. ...

-On irony-
... does that mean we have to modify all our TDIs to the point where they become real "smoke belchers"?

Or did I misunderstand something...?
-End sarcasm-


The problem, however, lies elsewhere: The total amount (mass) of particles has also become significantly smaller, and not just because of the catalysts.

The total amount has decreased because the higher injection pressure resulted in smaller droplets.
The question is what happens when the pressure becomes even higher: Does the soot content then drop to zero, which would make filters unnecessary, or is it inevitable that every diesel droplet leaves behind a soot particle? Does the sulfur content play a role in this?

Hi Christian,

I want to modify your first sentence just a little bit.

The total amount has decreased because the higher injection pressure resulted in smaller droplets, and the sulfur content has been reduced.

--- Due to the improved atomization, the soot particles become smaller and fewer because the diesel fuel burns more completely.

The AXR PD engine has been modified in its injection process such that it meets the D4 emission standard without a particulate filter (and even achieves EU4 standards with emissions control via OBD).
Here's the translation:

"Volkswagen sees the advantage of the PD technology in this: higher injection pressure, better atomization, less soot, and fewer other emissions. This means no diesel particulate filter (DPF) is needed (Volkswagen opposes DPFs due to disposal issues)."
With the CR concept, a diesel particulate filter will definitely be necessary to comply with EU4 standards. Even the "cleanest" common rail diesel from Peugeot (HDI FAP), despite having a diesel particulate filter, is currently unable to meet the EU4 emission standard.

eike wrote:

The diesel particulate filter alone is not enough. French cars with FAP filters are

not yet as exempt from taxes as the Golf TDI PD 74kW without a diesel particulate filter. Previously, sulfur in diesel was primarily responsible for soot emissions. Only when sulfur is largely removed from diesel will exhaust gases become significantly cleaner.
Soot in the exhaust always indicates a loss. If it were to burn completely, you would have more power or lower fuel consumption.

Hi everyone,

The French person does not achieve the standard because taxation is purely political, so that VW can sell new cars . It is never possible to optimize combustion in such a way that (almost) no soot is produced, even with sulfur-free fuels, especially since more and more gasoline drivers and others who do not understand that diesel engines are not designed for speeds above 3500 rpm are switching to diesel .

Due to the high fuel prices and the demand for performance, it is automatically ensured that the engines are optimized; therefore, we should not take money from families who cannot afford a PD [presumably referring to a specific technology or feature] .

@Bertil:

The particle emissions have, of course, decreased for a specific speed range... but compare the emission test report of a well-tuned TD with a TDI -> the difference is not that significant .


If you calculate the emissions per kilometer, then no one can claim that a TDI engine running at 200 km/h produces fewer emissions than a TD engine running at 130 km/h! This is the problem.


Regarding the addition of substances: the particle size depends on the atomization of the diesel fuel. There are already many reliable studies showing that the fine particles, which also occur in modern gasoline engines, are orders of magnitude more toxic than the old, large "mega" particles .

The solution is not the tax, but rather the abolition of it and an increase in fuel prices. Then companies will finally be forced to build cars that weigh very little...and you won't have to buy a car where every 60,000 km (if it even lasts that long) a new timing belt needs to be replaced for x-euros, because VW still can't manage to get rid of this ridiculous timing belt from a completely over-engineered diesel...but people want to drive in the upper class. }

Best regards, Christian.

haehnlein wrote:

... The French company fails to meet the standards because the tax is purely political, designed to allow Volkswagen to sell new cars.

"...that's not quite right!! The emission standards apply to the entire Europe, and the HPI FAP is currently the cleanest common rail diesel engine available, and this engine operates well outside those limits."

307 HDI RHS: CO=0.100, NOx=0.339, CH+NOx=0.370, Particles=0.003, D3.
GOLF TDI AXR: CO=0.057, NOx=0.211, CH+NOx=0.225, Particles=0.020, D4.
Standard: CO = 0.5, NOx = 0.25, HC+NOx = 0.3, Particles = 0.025.

The particle emission is remarkably low! But the rest is far away.

Quote:

The combustion process can never be optimized to the point where (almost) no soot is produced, not even with sulfur-free fuels, especially since more and more gasoline drivers and others who don't understand that diesel engines are not designed for speeds above 3500 rpm are switching to diesel . Due to the high fuel prices and the demand for performance, it is automatically ensured that the engines are optimized; therefore, we should not take money from families who cannot afford a PD [presumably referring to a specific type of engine or technology] .

Agreement, but this doesn't just apply to PD models, it applies to all modern EU4 vehicles!

Quote:

@Bertil: The particle emissions have, of course, decreased for a specific speed range... but compare the emission test report (ASU protocol) of a well-tuned TD with a TDI -> the difference is not that significant .

No, the difference is not significant .

1Z TDI last emissions test: Smog value: 1.5 (my previous test was 1.4 – I've also had readings as high as 1.9 in the past, likely due to old injectors).
AXR TDI initial emissions test for opacity: 0.15 (with the new common rail injectors, even 0.12).

Only about ten times!!! The difference isn't really that big.

Quote:

If you calculate the emissions per kilometer, then no one can claim that a TDI engine running at 200 km/h produces fewer emissions than a TD engine running at 130 km/h! This is the problem.

Stop!!! You always have to assume the same conditions, but in principle, you are right.

Quote:

Regarding the particle size: it depends on the atomization of the diesel fuel.

When you're trying to get a good start, the atomization goes completely haywire!

Quote:

There are already many reliable studies showing that the fine particles, which incidentally also occur in modern gasoline engines, are toxic to a power of ten greater than the old, large particles .

I didn't deny it. I see the problem. My comment was also meant to be taken as a joke.

Quote:

The solution isn't the tax, but rather abolishing it and increasing fuel prices.

Doubts.

Quote:

Then the companies will finally be forced to build cars that are lightweight...

"...if the customer is willing to forgo certain features, that's not a problem. Just calculate how much weight things like air conditioning, ABS, airbags, and side impact protection add to the car. Suddenly, the cars are 300-400 kg lighter, and you're back where the Golf II was!"

Quote:

"...and you don't have to buy a service package where you're forced to replace the timing belt every 60,000 km (if it even lasts that long) for x-euros, because VW still hasn't managed to get rid of this ridiculous timing belt in what is essentially an over-engineered diesel engine..."

The timing belt needs to be replaced every 90,000 kilometers (only for a few models was a 60,000 kilometer interval required).
A timing chain also needs to be replaced (due to elongation). I still remember the early 190s Mercedes-Benz models, or even various VW VR6 engines – there, the timing chains were frequently defective, but no one wanted to abolish the chain drive!
Please provide the text you would like me to translate from German to English. I will then give you only the translation.

Quote:

The French person does not meet the standard because the tax is pure politics designed to allow Volkswagen to sell new cars

.

I don't believe it; the French engines probably wouldn't even meet the EU3 standard without particulate filters, and the vehicles wouldn't be approved for registration. How marketing portrays things is a different story; the French have done a good job there. But when these cars reach over 100,000 km (62,000 miles) and the subsequent owners are more economical, 90% of the particulate filters will fail, I guarantee it.

Quote:

It is never possible to optimize the combustion process in such a way that (almost) no soot is produced.

Just wait and see what has happened to diesel engines in the last 10 years. And this development is not going to end anytime soon.

Basically, Volkswagen and other German manufacturers are taking the right approach by focusing on improving combustion to reduce soot emissions.

Best regards, Albrecht.

Bertil wrote:

No, the difference is not significant 1Z TDI last emissions test: Smog value: 1.5 (my previous test was 1.4 -- I've also had readings as high as 1.9 in the past, likely due to old injectors). AXR TDI initial emissions test for opacity: 0.15 (with the new common rail injectors, even 0.12). It's not really that much! The difference isn't actually that big.

Hi Bertil,

"You need to be careful with that!! Mine recently had a turbidity of 0.3 1/m with almost 180,000 km and the original injectors!!! The key thing is what has accumulated beforehand... I can tell you all about thick deposits on the injector nozzles of my old diesel engines from experience as a fuel-efficient driver. Did you drive at full throttle in third gear on the highway for 20 km before this inspection? If so, the test results would have looked much better... and injectors are known to be wear items (wink), but they cost about a quarter of the price of the PD elements!"

The solution isn't the tax, but rather abolishing it and increasing fuel prices.

Bertil wrote:

Doubts.

It's certainly a bit extreme, but we eventually need to get used to the idea that when it comes to sustainable development, we can't just waste fuel. When I see all the idiots on the road, I think the price of fuel still isn't high enough! It seems unfair that a family man who drives an older Golf II TD with a 5-liter consumption has to pay 500 euros in taxes, while someone driving a more modern car only pays 100 euros. Furthermore, we have to consider that huge amounts of energy were invested in the production of a car... and that's never taken into account! It doesn't make much sense to drive a car for only 5 years, even if it only consumes 2 liters!

Bertil wrote:

... if the customer is willing to forgo comfort features, that's not a problem. Just calculate how much weight things like air conditioning, ABS, airbags, and side impact protection... add to the car. Suddenly, the cars are 300-400 kg lighter, and you're back where the Golf II was!!!

No, the A2 TDI also has those features and consumes 3 liters [of fuel], but it's not selling well because the fuel is still too cheap!

Bertil wrote:

A chain also needs to be replaced (due to elongation). I still remember the early 190s Mercedes-Benz models, or even various VW VR6 engines – there, the timing chains were defective one after another, but no one wanted to abolish the chain!!!! ...

Gears that run in oil do not expand!

@Albrecht:

The development cannot exceed the physical limit... and we are very close to it!

Best regards, Christian.

Hi Christean,

I took the liberty of adjusting the post to fit the correct format.

I understand that the AU measures house numbers, but with my AXR, you can't even see a hint of soot at night in the light of the rear lights! Before the AU inspection, the 1Z engine was always revved up very high. The AXR engine was only allowed to warm up on the driveway!
You're right about the nozzles, but I think the pump is also a wear item (in my opinion), and if you include that in the calculation, it looks much better for the PD!

The A2 and the 3L Lupo are good examples, but in this case, price is the deciding factor. Customers are willing to sacrifice some comfort for a higher price, and they don't appreciate it when that's not the case.

While your tax bill is technically correct, consumers need to be educated about environmental awareness (a silly word). Unfortunately, this can only happen through financial incentives! I myself am a "poor" father who has a house to pay for and still has to drive 100km to work every day.
Of course, I'm annoyed by the pollutant tax because my rally car is only equipped with a three-way catalytic converter, which makes it quite expensive!

Now, the gear-based idea from Volkswagen is already being criticized by other manufacturers (too loud, too heavy, unstable, etc.). So, Volkswagen is once again being blamed for pursuing a "special path" (just like with the PD technology).
By the way, Formula 1 engines used to have gears before pneumatic valve control systems!!! Why do you think that was?

Hello Christian,

Quote:

@Albrecht: The development cannot exceed the physical limit... and we are very close to it!

I don't know what physical limits those are supposed to be .
Think about a (nearly) homogeneous mixture distribution and combustion (like in a gasoline engine), then you'll have, at once, less NOx and soot .
And work is being done on that, believe me!
The chemistry must also be right.

Best regards, Albrecht.

Albrecht wrote:

I don't know what physical limits those are supposed to be . Think about a (nearly) homogeneous mixture distribution and combustion (like in a gasoline engine), then you'll have, at once, less NOx and soot . And work is being done on that, believe me! The chemistry must also be right.

Hi Albrecht,

You might be right, but I can't imagine an injector nozzle that overcomes even the Van der Waals forces between individual molecules! These surface forces are greater than those in gasoline! And if it were possible, it would be so fragile that it would only last for 100 kilometers.

Furthermore, the finer the atomization, the higher the formation of NOx, which leads to a higher combustion temperature (but results in less free heat energy released from the diesel).

But I am not certain .

Best regards, Christian.

Hello Christian,

to convince you:
Nowadays, I believe injectors have a maximum of 7 holes. In the future, there will definitely be more, or they might have a completely different design (due to new manufacturing processes, etc.), which would mean even better atomization of the diesel droplets at the same pressure.

Quote:

Furthermore: the finer the atomization, the higher the NOx formation -> higher combustion temperature (but less free heat energy!!!) of the diesel fuel.

"That's not correct! It's the same issue as with the numerous questions about deactivating the EGR system. NOx formation is caused by temperature spikes (locally) due to an excess of oxygen (lean and rich mixture zones in the combustion chamber), which doesn't occur with a homogeneous mixture, unlike when you recirculate exhaust gases. Another thing is that at around 50% load, there isn't even an EGR system active, so you only influence the exhaust gases through mixture formation and subsequent combustion."
Therefore, a gasoline engine with port fuel injection produces very little soot and relatively low levels of NOx, despite the high temperatures in the combustion chamber. Conversely, Otto-DI engines suddenly produce more soot and NOx due to the less homogeneous air-fuel mixture distribution.
Can you also see well when a Mitsubishi GDI in front of you accelerates quickly?

Best regards, Albrecht.