Exhaust gas recirculation in engines with particulate filters

Hello everyone,

I'm new to this forum and would like some information on the following topic, because I haven't been able to find any suitable answers online or here in the forum.

In modern diesel engines, it is common to find an exhaust gas recirculation system and a particulate filter installed.

How do these two components interact? Does the particulate filter continue to function normally when the EGR system is deactivated, as usual? Does it clog up more quickly, and can it still be regenerated normally?

With my old vehicle, I observed a slight reduction in fuel consumption and decreased soot formation by deactivating the EGR system.

My current vehicle has a particulate filter, and I don't want to interfere with the system without knowing what I'm doing, as I might end up having problems later.

I'm sure you can help me!

If this helps you: I drive a 1.6L HDI FAP with 109 horsepower.

Best regards,
the Peugeot driver

Es macht dem DPF nix, wenn die AGR fehlt. Diese Systeme brauchen sich ned gegenseitig. Nur wird die AGR sicher überwacht, daher wird eine Deaktivierung ohne passende Hard/Software sicher ned gehen.

It goes without saying that the vehicle's registration will be cancelled as a result.

Hello,

Clemens Motorsport in Ulm (a Peugeot dealer/workshop and tuner) responded to my inquiry about deactivating the EGR system, stating that it wouldn't be possible due to the particulate filter... but without providing any explanation. This made me suspicious!

If I simply close the EGR valve with a metal plate, without disconnecting any cables or hoses, shouldn't the electronics basically not notice anything?

Best regards and thank you for your help!

Yes, the engine control unit will detect it and store an error code. If you have the large display, it will inform you of this as the commonly known "Exhaust System Anomaly."

B. t. w.: We know each other, right?

Hello,

Without EGR (where the engine only draws in cold fresh air), exhaust gas temperatures decrease much faster without load compared to when EGR is active (in which case hot exhaust gases are mixed with the intake air).
If the regenerations primarily occur in urban traffic or under low load conditions, then there may be problems because the particulate filter may not reach the necessary temperature to initiate the regeneration process.
Conversely, if you primarily drive on country roads or highways with a constant load, the "cooling" of the exhaust gases when releasing the accelerator or at low loads can be neglected.

-> Whether it works well or not depends on the vehicle and driving style.

Best regards, Rainer.

Sometime after the warm-up phase is complete, the engine control unit will notice and register it...

dieselschrauber wrote:

Without EGR (the engine only draws in cold intake air), exhaust gas temperatures decrease much faster without load than with EGR

. I think this will certainly be compensated for by increased post-injection, or do you agree, Rainer?

TDI-GTI-4-Motion wrote:

dieselschrauber wrote: ohne AGR (Motor saugt nur kalte Frischluft an) fallen die Abgastemperaturen ohne Last viel schneller ab als mit AGR Ich denke, dass wird sicherlich durch mehr Nacheinspritzung ausgeglichen, oder Rainer?

Man kann nicht beliebig viel Nacheinspritzen ohne "Vorwärtsschub" oder übermässige Motorölverdünnung zu produzieren.

Generally, the average exhaust gas temperature is lower when drawing in pure fresh air; therefore, such an engine reaches its operating temperature more slowly, and the DPF also heats up much slower during normal operation. Consequently, depending on the driving profile, the conditions required to initiate a regeneration process are either not met at all or are only fulfilled much later in time.
It won't help if the regeneration process were to compensate for this with increased post-injection, especially if the process doesn't even start in the first place.

Best regards, Rainer.

Why are EGR coolers used then?

The AGR (Abgas Rückführung) system's purpose is to lower the combustion temperature in order to reduce nitrogen oxides. If the combustion temperature is lower, then the exhaust gas temperature is also lower, which, in turn, is not beneficial for the regeneration process within the DPF (Diesel Particulate Filter).

Exactly...that's how I remembered it too. The EGR actually lowers the combustion temperature, it doesn't increase it...otherwise, the NOx emissions wouldn't be lower.

'@Hutfahrer: In my model, all vehicles have a 'large' display, unlike the 206.'

But now, let's talk about a completely different question:
Does it even make sense to disable the EGR system on a modern diesel engine, where everything is controlled and monitored? Perhaps you won't gain any benefits from disabling it, in which case you might as well not bother with the work.

Best regards and thank you for your help!

Unfortunately, this is often misunderstood. While the AGR reduces local peaks in combustion temperature, the overall level is higher in the partial load range.

Okay, that makes sense, because hot air is being supplied, not cold air.

Can it generally be said that deactivating the DPF (Diesel Particulate Filter) is beneficial, or that it offers no advantages? Of course, this assumes that I drive enough long distances to allow the DPF to regenerate properly.

With a functioning EGR valve, deactivating it only results in the disadvantages that the engine takes longer to warm up and runs slightly rougher.

In older engines where blow-by gases were not adequately de-oiled, there used to be significant deposits in the intake manifold, which are often mentioned. However, that is now a thing of the past.

If a motor is experiencing problems such as excessive soot buildup, misfires, or constant regeneration attempts, temporarily blocking the exhaust system can be helpful for troubleshooting. However, this should always be done with a metal plate, not by simply removing the hose.

christians wrote:

With a functioning EGR valve, deactivating it only results in the disadvantages that the engine takes longer to warm up and runs slightly rougher. In older engines where the blow-by gases were not properly de-oiled, there used to be significant deposits in the intake manifold, which are often mentioned. However, that is now a thing of the past. Wenn ein Motor Probleme macht, Rußen, Ruckeln oder andauernd regenerieren will, ist das temporäre Verschließen zur Fehlereingrenzung natürlich angesagt, muß dann aber auf jeden Fall mit einem Blech erfolgen, nicht durch Abziehen des Schlauches.

Okay, here's the translation:

"Could you explain why the AHF/AFN engine tends to experience significant carbon buildup, while the ASV hardly experiences any, even though the AHF is almost identical except for the injectors and MSTG software, meaning the crankcase ventilation systems of the AHF and ASV should be the same?"

Hi,

Regarding the Skoda Superb with engine code BSS and an additive system, I can only offer one observation related to DPF regeneration and EGR.

If you block the EGR valve with a metal plate while maintaining the electrical connection to it, an error will be displayed, but the regeneration process will still occur.
It is important to note that the regeneration cycle is significantly extended compared to a functioning DPF (Diesel Particulate Filter), and it regularly reaches its maximum limit of 1100 km.

If you disconnect the electrical connector at the EGR housing (assuming the EGR valve is properly closed), an error will also be displayed. However, the DPF will no longer regenerate, and a forced regeneration using VCDS login 21295 is not possible.
It is likely that the MSG prevents regeneration if it cannot determine the position of the EGR valve. However, this does not apply in this case, as all the wiring to the EGR valve has been removed, unlike the scenario described in the previous paragraph.

Best regards, Georg.