AGR Off: No More Soot?

Hello!

I jokingly unplugged the connector for the EGR (if it was indeed the EGR connector ) from my AHU today.

The engine feels a bit more responsive, and the partial-load surging is gone (at around 1600 rpm, there was always a jerk in 4th or 5th gear; going 100 rpm higher or lower eliminated it, and it felt like it was about to stall), which is fine so far.

But, before that, it smoked excessively, and I was almost afraid to even touch the accelerator.
Now it only smokes minimally, for example, when I downshift to 3rd gear at 90 km/h.

Normally, the EGR system is used to reduce soot emissions (in the partial load range), right?

What are the connections here?

Thank you and best regards,
Henrik.

Hi,

Read the technical article about the AGR!

The AGR reduces NOx emissions at the expense of increased particulate matter emissions.

In this case, I would suspect a leak in the pressure area (e.g., the low-pressure circuit or the pressure lines), because even with the EGR system active, it shouldn't produce that much smoke.

Otherwise, you now have an error message because you disconnected the plug. A better way to test it is by using a screw in the pressure hose.

But always remember: Driving with the EGR system deactivated is illegal.

Best regards,

Jan.

I have read the article.
That's why I'm so surprised by the low soot emissions.

I should be able to rule out a leak in the turbocharger system, as I have a boost pressure gauge that is showing normal readings.

Thank you!

Henrik wrote:

I have read through the technical article. That's why I'm so surprised by the low soot emissions.

Then you probably didn't quite understand the article.

With AGR; lower NOx emissions, higher particulate matter.

Without AGR: less soot, more NOx.

aah, yes, okay, I'm a bit confused today .

Thank you all!

However, it should be the case that a functioning EGR valve closes completely under full load, meaning when you press the accelerator "hard." Therefore, (...) should not show any differences when accelerating at full throttle.


By the way, does anyone know how the returned exhaust gas volume is regulated in the ASZ system? Is the pressure sensor designed as a proportional valve that regulates the valve's nominal size based on the vacuum level?

joegolf wrote:

By the way: Does anyone know how the returned exhaust gas volume is regulated in the ASZ system? Is the pressure sensor designed as a continuously variable valve that regulates the nominal size of the valve based on the strength of the vacuum???

Yep, that's exactly it (although I haven't heard of a "Stetigventil" before).

By the way, this isn't just happening with the ASZ engine, but in my opinion, it's happening with all TDIs...?

ulf wrote:

joegolf wrote: By the way: Does anyone know if and how the returned exhaust gas volume is regulated in the ASZ? Is the pressure sensor designed as a continuously variable valve that regulates the nominal size of the valve based on the strength of the vacuum??? Yep, that's exactly it (although I haven't heard of a "Stetigventil" before). By the way, not just with the ASZ, but IMO with all TDIs...?

Globe valve: Valve with a variable nominal bore (opening) (also known as a proportional valve, etc.).
Changeover valve: Two switching positions, On/Off.

Okay, good.

Okay, so in our TDI:

Wastegate: 1 solenoid valve (pulsed to simulate something like continuity ).
VTG: 1 Constant valve.
AGR: 1 Solenoid valve.

m;

dieselmartin wrote:

then we have in our TDI: Wastegate: 1 solenoid valve (pulsed to simulate something like continuity ). VTG: 1 Constant valve. AGR: 1 Constant valve

Hi Martin,

Here, it is important to distinguish between EPWs (electropneumatic valves) and membrane valves.

Regarding the latter: I believe the wastegate and EGR valve are types of control valves, while the VTG (Variable Turbine Geometry) is not a valve at all.


The EPWs are all driven by pulsed voltage with a variable duty cycle.

I don't know if the frequency is low enough to fully open and close each valve body with each stroke.

I suspect that, depending on the duty cycle, the valve bodies are driven closer to one limit or the other in a "trembling hovering state."

@ Ulf

Oops, you're right. The pulsed valves (VW German for pressure transducers) actually control the EGR and VTG membranes.

The wastegate valve N75 (the rattling valve in the fender well of the G3) is definitely being pulsed so slowly that the valve is always fully opening.


I had a moment of brain fog.

m;

Could it be that deactivating the AGR (Exhaust Gas Recirculation) system significantly lowers the oil temperature?

'Previously, with constant full throttle, the oil temperature was 140°C (with AXG injectors, increased fuel pressure, but a chip that wasn't properly tuned for it). Now, it doesn't exceed 120°C?'

Henrik wrote:

Could it be that deactivating the EGR system significantly lowers the oil temperature? Previously, with constant full throttle, the oil temperature was 140°C (with AXG injectors, LDerhöhung, but not a chip tuned for it), but now it doesn't go above 120°C?

Hi,

I can only imagine that if the EGR valve wasn't working correctly before.

Best regards, Rainer.

Hello everyone,

Do I need to expect any error messages or even a limp-home mode on my 1999 AJM (85kW) engine if I close off the vacuum hose of the EGR system?
After replacing the mass airflow sensor (MAF), the car is producing such thick plumes of black smoke when accelerating that I'm starting to feel embarrassed.

Thank you very much, and best regards.
Stefan.

@CheBu:

No problem. But if the EGR valve is truly not closing properly, it's questionable whether it will suddenly close correctly - without any external control.

For soot, a whole range of other causes can be considered. Even a longer, more moderate drive can store so much soot in the exhaust system that, later, when the engine is first revved up, the person behind can have their day ruined .

Hello Roger,

Thanks for the information! I don't think I'll have any problems at 70,000 km.
"I'm having issues with the AGR valve. Now that I've replaced the mass airflow sensor (MAF), I'm noticing a problem with soot."
It really caught my attention. However, as you mentioned, I'm a bit slower at the moment.
on the go, and also I'm not sure if I've ever consciously focused on my...
I have paid attention to the exhaust emissions...

I only got scared about AGR because of the technical article, and I want to tell my...
Engine to facilitate breathing.

Best regards,
Stefan.