AGR "kaputt machen" technisch riskant? | Posts 16+

Gremlin wrote:

... I don't have the current guidelines readily available, but starting this year, diesel vehicles are also required to support the OBD-II standard. ...

... has been postponed to 01.01.2005 and will be fulfilled with the EU4 standard. The emission values for EU4 and D4 are the same for diesel vehicles, but the OBDII diagnostic requirement is not mandatory for D4.

Hi!

In your opinion, is increased wear and tear due to a disconnected EGR valve more likely to occur with short trips or long trips? I'm still not entirely convinced whether disconnecting the EGR valve would be beneficial for my tractor (1Z) with 94,000 km after an engine overhaul, or whether I should reconnect it.

edward wrote:

In your opinion, is increased wear due to a clogged EGR valve more likely to occur with short trips or with long trips?

Hi.

What effects of a malfunctioning EGR system do you think could potentially lead to increased wear and tear?

Hello Ulf...

I know that this topic has been discussed countless times before, but I still wanted to bring it up again.

I'm still unsure about the extent to which the increase in combustion chamber temperature is affected by the blocked EGR system. I don't believe it can be that small, because a significantly larger amount of fresh combustion air is available (I myself have noticed a faster increase in engine temperature and a maximum engine temperature that is about 5% higher). If these differences are so pronounced outside the combustion chamber, doesn't the better combustion of the diesel fuel then expose the combustion chamber walls to significantly higher temperatures (even if only for a short duration)?

Especially when combined with a 10ct tuning – which is only used occasionally – I could imagine that there might be more wear and tear compared to an engine with a fully functional EGR system. Please correct me if I'm wrong.

edward wrote:

(I myself have observed a faster increase in engine temperature, as well as a maximum engine temperature that is approximately 5% higher).

Hi Edward,

I understand "maximum engine temperature" to be the value reached after a certain distance driven with heavy acceleration. In this case, the (functional) EGR system is anyway closed, so there is no difference compared to a disabled system .

If these differences are observed far outside the combustion chamber, wouldn't the improved combustion of the diesel fuel then expose the combustion chamber floor to significantly higher temperatures (even if they are only of short duration)?

Quote:

AFAIK, the surfaces of the combustion chamber walls, including the piston, assume an average value of the combustion chamber temperature at the interface (reduced by the cooling). As this value increases, the average combustion chamber temperature must also be higher, which, in my opinion, is equivalent to increased engine power. If you use this (hypothetical) partial-load boost instead of reducing the gas accordingly, the engine will (theoretically) warm up faster. However, the temperature peaks that cause NOx formation are likely to occur only within the burning spray jet, which normally should not come into contact with the piston material --> leading to melting damage. "I still believe that a faulty EGR valve is harmless to the engine, regardless of the operating conditions."

edward wrote:

I'm still not clear about which area the increase in combustion chamber temperature falls into, for example, due to a blocked EGR system.

Okay everyone: The combustion chamber temperature will be LOWER when the EGR system is disconnected!!!

Only the peak temperatures around the injected diesel spray increase.

Thank you for listening ).

The 'running down' is definitely a problem because when the engine is stopped, the oil pressure also drops.
I don't know if the storage facilities are suitable for that.
An electric oil pump for the turbo is only used in gasoline engines to prevent coking of the bearings (or was it only an electric water pump?).

The gasoline turbo engines only have an electric water pump because the turbocharger in those engines is subjected to greater thermal stress. That's why, for example, variable turbine geometry (VTG) technology hasn't been implemented in gasoline engines yet.

The issue of a turbocharger winding down when stopping the engine is not the main problem; what's more important is that after driving at full throttle, the engine should not be immediately turned off, but rather allowed to cool down, meaning driving it 'gently' for 2-3 minutes beforehand, or at least letting it idle for a few minutes, so that the exhaust side has time to cool down!

Otherwise, the aforementioned 'coking' will occur, which can quickly lead to premature turbocharger failure due to bearing damage.
This applies to both gasoline and diesel engines, because the electric water pump is only switched on depending on the water temperature. This doesn't make much sense, because while 10-20 seconds of full throttle will make the turbo very hot, the water takes much longer to warm up...

Regards,
Michl.

Tagessuppe wrote:

The combustion chamber temperature is LOWER when the EGR system is disconnected!!! Only the peak temperatures around the injected diesel jet increase.

Hi.

Superficially, the statements seem to contradict each other...

I haven't studied anything related to engines, so for context:

- Lower overall temperature due to the elimination of the hot exhaust gas component in the combustion chamber?

- Higher peaks only occur sporadically (like pinpricks) and are not able to "overcompensate" for the cooler cylinder filling?

Okay, I don't think the two statements contradict each other, but you understood them correctly. Due to the significant loss of hot exhaust gases, the combustion chamber temperature, which is the average instantaneous temperature in the combustion chamber, decreases.

By the way, I find the NoX models more appealing than the CO models;o

Sure, here is the translation of the text from German to English:

"LG" is an abbreviation for "Liebe Grüße," which means "Best regards" or "Best wishes" in English.

Tagessuppe wrote:

By the way, I find the NoX models more appealing than the CO models;o.

CO2, soot, and increased fuel consumption... I agree with that. It's better to drive less aggressively due to higher fuel prices, and also to use a bicycle sometimes... that will also help with NOx emissions .

@ulf:
'First, I might need to correct myself regarding the term 'maximum temperature.' I wasn't referring to the temperature that the engine (or the coolant) reaches after driving many kilometers at full throttle (which, in my opinion, would also depend on various other factors like headwinds, hilly terrain, etc.) - but rather the temperature under normal, meaning fuel-efficient, driving conditions (an average of 120 km/h on the highway) over long distances, specifically not less than 80 km. This value seems to me to be more comparable in the long run than a full-throttle run...'

@tagessuppe:
I have always been under the impression that NOx emissions are only reduced (or should be reduced) through a lower combustion chamber temperature within the scope of the approval process. However, I also think it is possible that they are reduced by a lower flame temperature. Am I interpreting your statement correctly? Could you also address the increase in fuel injection quantity achieved through a '10ct' tuning, which, when the EGR system is disabled, could potentially lead to an exponentially increasing rate of wear and tear, in contrast to a functioning EGR system?

Hello diesel experts!
Finally, someone in this forum is addressing the rumor that a malfunctioning EGR valve leads to an increase in combustion chamber temperature. NO!!! It's the opposite! The thermal load on the engine actually decreases because the partially compressed fresh air in the partial load range is always cooler than exhaust gas.
The amount of heat supplied by combustion is almost independent of the function of the EGR system, because even with a properly functioning EGR system, there is still more oxygen present than is needed for combustion (Lambda > 1).
The addition of exhaust gases is only done because carbon dioxide is an inert gas (similar to shielding gas used in welding) that inhibits oxidation processes. This is intended to prevent the formation of so-called "hot spots" in the combustion chamber. Without this addition of exhaust gases, many such hot spots can form at the edges of the fuel injection streams, which significantly increases NOx emissions. However, the particulate emissions (soot) and the HC/CO emissions are also significantly reduced due to the high local combustion temperatures.

Perhaps someone could conduct a test drive, especially in very low outside temperatures. This should involve driving the same route once with the EGR system active and once with it deactivated. It's important to maintain as similar conditions as possible, such as a cold engine start at the same temperature, and the same driving style (ideally at low to medium load). Then, using VAG-COM, the operating temperatures should be logged over time.
If the above theory is correct, then the engine with a functioning EGR system will warm up faster than the one with the EGR system disconnected. Perhaps a skeptic might want to test this!

Regards,
Alex.

'So, it probably won't be possible to log the data because the initial temperatures are not the same.'

'But I already mentioned this elsewhere: the engine warms up much faster with the EGR system than without it. It's very noticeable on my 12km commute to work.'

It should be mentioned that new diesel engines are once again being equipped with throttle valves (which are then electronically controlled by the EDC system) in order to increase the EGR rate. Oh dear...

CU Gremlin.

[quote="edward Könntest Du zusätzlich auf die Anhebung der Einspritzmenge durch 10ct-Tuning eingehen, die bei abgeklemmter AGR evtl. zu exponentiell ansteigendem Mehrverschleiss im Gegensatz zu intakter AGR führen kann?[/quote]

Hi Edward. I think disconnecting the EGR valve makes sense, especially in combination with a "10 Cent Tuning" chip. This method, like Powerbox tuning, increases the fuel injection amount while keeping the turbo boost pressure and the exhaust gases recirculated by the EGR valve constant. This means that the increased fresh air compensates for the lack of turbo boost pressure, which is different from traditional chip tuning. Only at higher loads do the values approach those of a system with a functioning EGR valve.

@Donalexo. You seem to know a lot about chemistry. Did you study mechanical engineering? What I'm interested in is why the automotive industry is being told to minimize NOx emissions. As far as I know, NO, when combined with rainwater, is a good plant fertilizer. It's probably just a regulation to create jobs in NOx reduction research. ;o)[/quote]

@tagessuppe:
You are absolutely correct in your assumption, as I am a qualified engineer (Dipl.-Ing.) specializing in mechanical engineering.
The major problem with nitrogen oxides is the fact that NOx is converted into ozone near the ground when high-energy UV radiation hits the NOx molecules, causing the oxygen to detach from the nitrogen.
This primarily leads to smog in urban areas, especially during the summer. Consequently, NOx is ultimately responsible for a wide range of respiratory irritations and illnesses.
Therefore, despite being generally non-toxic, nitrogen oxides are definitely not something to take lightly!

At this point, I should perhaps say a few words about the strategy for exhaust gas aftertreatment. In the partial load range, the EGR system actually increases the proportion of all "harmful" exhaust components (CO, HC, and particulate matter), with the exception of NOx. However, it is not the engine's raw emissions that are measured, but rather the exhaust gas that has been treated by the catalytic converter. Therefore, the CO and HC levels can be higher due to the EGR, as the catalytic converter performs after-oxidation, converting them into CO2 and H2O. Overall, this strategy improves emissions; only the particulate matter content is disadvantageous compared to an engine without EGR.

However, this clearly demonstrates that it is better for the engine if it is operated without EGR, as this results in a cleaner combustion process and reduces the formation of deposits in the channels, on the valves, and in the combustion chamber.

It's a matter of conscience that each individual must resolve for themselves: whether they prioritize doing something good for their engine and increasing NOx emissions, or whether they prioritize reducing environmental impact, even if it means subjecting their engine to more "stress."

Regards,
Alex.

donalexo wrote:

So, it's a matter of conscience that each individual must resolve for themselves: whether they prefer to do something good for their engine and burden the environment with more NOx, or whether they want to relieve the environment and subject their engine to more "dirt".

Hi Alex,

I think the key to ecology is not to reduce one thing and accept an increase in another. When I look at the TDI cars on the highway, most of them already have the AGR (heating) system turned on. The only ecologically sensible solution is to raise fuel prices so high that it hurts, thereby reducing overall consumption. What doesn't burn, also doesn't emit. When I look at road traffic, it still doesn't hurt enough. The car manufacturers would then finally be forced to build much more fuel-efficient cars (relative to technological progress). Why does a Passat need four control arms? Because these cars are only designed for heating... and... and...