1.9 TDI vs. 2.5 TDI: Differences in smoke emissions?

Hello everyone!
Is it actually true that a 2.5 TDI engine produces more smoke from the start compared to a 1.9 TDI? I drove behind an older Audi 2.5 103 kW Quattro today, and it was also producing a significant amount of gray-black smoke. It was a bit less than mine . Could the gray smoke be related to the exhaust gas recirculation system? How can I deactivate the EGR system on an AAT engine? Can someone describe how it works and whether it helps with gray smoke?

'Thank you.'

I need to confirm that thing about the 2.5s... most of the ones I encounter tend to misfire when accelerating, and it's noticeable, sometimes even with a smell.

Best regards,

Jan.

Hi.

I also have a 2.5 (AFB) Quattro, and it only smokes when there's an issue with the electronics, meaning the engine control unit isn't reset regularly during inspections.

Just like with the older 1Z or AFN engines, the technology is quite similar.

...or with a chip.

Stefan.

Hello Stefan!

'I also drive an AFB... well, it actually runs pretty well under full load. But I've never heard that you reset the engine control unit during inspections. Sure, you reset the maintenance interval display, but the entire control unit? What's supposed to happen or change with that?' And what exactly does it mean?

DENNIS


Hi.

I also have a 2.5 (AFB) Quattro, and it only smokes when there's an issue with the electronics, meaning the engine control unit isn't reset regularly during inspections.

Just like with the older 1Z or AFN engines, the technology is quite similar.

...or with a chip.

Stefan.

Hi!

As far as I know, the control unit stores dynamic data in memory that it 'learns' itself after a control unit reset.

If these data are not 're-learned' over an extended period, some parameters will no longer be accurate. Whether it's due to wear and tear or other factors, such as modifications.

My experience: Seat Toledo 1Z, after approximately 60,000 km, it started to smoke more and more, and all inspections had been carried out up to that point.
At 75,000 km, I took it to the workshop, and they reset the control unit, and the smoking stopped.

My old Bora (AJM) started smoking like a steam locomotive after about 30,000 km -> I asked a workshop about it, but they didn't know anything. Other workshop: 'Sure, we can do that.' The smoke was gone.

The same applies to the A4 AFB. When it smokes, the workshop knows what's up.

If I've been talking complete nonsense, please feel free to (virtually) slap me or tell me the truth.

Stefan.

Plong....

If such "learning values" were to be stored, they would have to be placed in the EEPROM of the control unit, since relay 109 already draws power from the control unit when the ignition is off.
However, I haven't found anything like that in my VAG documentation for the AHF engine or other TDIs. The only thing that comes to mind for reducing smoke emissions via the engine control unit is to adjust the air mass values. This would reduce the injection amount when there is an insufficient amount of combustion air, which would decrease soot emissions, but it would also reduce the engine's power.
Perhaps Michael knows more about this and can correct me.

Best regards, Rainer.

Hello Rainer,

I can only confirm your opinion.
The learning values for idle stabilization and smooth running control are always determined and adjusted dynamically.
If the car is smoking excessively and you want to try adjusting it using the adaptation channels:

1. Option: Reduce LMM value.
2. Option: Reduce injection volume.

...that hurt...
Okay... WHAT the hell did they do then?

AND: What does the EEPROM do in my control unit if it doesn't have any dynamic data? Data storage?

Stefan.

Stefan . wrote:

...that hurt... Okay... WHAT the hell did they do then?

I have no idea, but did they sacrifice a black cat inside a pentagram next to the car?

Stefan . wrote:

AND: What does the EEPROM do in my control unit if it doesn't have any dynamic data? Data storage? Stefan.

How about the fault memory and data from the adaptation channels?

Best regards, Rainer.

Ha!

Okay, if cats have SUCH an effect, I'm going straight to the animal shelter on Monday and getting some.
I'm actually starting a black cat breeding program!

I looked for it, but unfortunately, I can't find the invoice from back then for my Seat Toledo anymore.

At that time, I called 3 or more vendors and asked if they could do it, and they all said yes, but the prices were different.

Hmph...

Stefan.

Okay, now it's MY turn to give out slaps!

Today, I visited both an Audi service center and an independent workshop equipped with a Bosch diagnostic computer. (It's similar to VAG's 1552, but made by Bosch and compatible with almost all vehicles and brands.)

BOTH told me AND showed me that the engine control unit can be reset to its default settings!

There are even dedicated menu options for it, and certain conditions (engine temperature, air conditioning off, etc.) must be met in order to do it.

So, please, whoever claims that my statement above was incorrect should contact me at Watsch'n.

Stefan.

Hello Stefan,

Sure, you can set the engine control unit into the basic settings-mode.
In this process, only specific actuators (e.g., injection volume adjusters) are supplied with defined signals to adjust the mechanics using a wrench to the desired values.
Timing belt replacement, followed by a basic adjustment to set the injection start of the injection pump. This ensures that in the subsequent operation (non-default mode), the engine control unit can regulate the injection start within the intended range, and that the correct injection timing is maintained during engine start, when the EDC system is not yet active.
Therefore, during the initial setup, it is not the control unit that is adjusted, but rather the mechanical components.
If anyone knows any other secrets of the default settings mode that I am unaware of, please contact me .

Best regards, Rainer.