Mechanical & Electronic EGR Valve Deactivation

I have a question regarding the German Working Conditions Act (Arbeitsschutzgesetz).

If you disable the AGR (Exhaust Gas Recirculation) system mechanically (by blocking it with a plate or disconnecting the hose), will it still be beneficial if you also reduce the AGR rate using VAGCOM?

because someone on http://www.passat3b.de/phpBB2/viewtopic.php?t=3373&highlight=agr+vag+com has the following explanation for it:

'If the EGR valve is disabled by disconnecting the control hose, the engine control unit continues to assume a reduced air mass value for calculating the fuel injection quantity. In reality, however, there is now more air mass available for combustion, but the control unit is not aware of this.'
Therefore, it is necessary to instruct the computer to inject more fuel in this situation.
'Using VAG COM, you can modify the target value, thereby instructing the control unit that the EGR rate (exhaust gas in the combustion air) should only increase when a higher mass airflow sensor (MAF) value is reached.'

Is this reasoning correct, or is there a flaw in it?

Best regards, day trader.

daytrader wrote:

"If the EGR valve is deactivated by disconnecting the control hose, the engine control unit continues to assume a reduced air mass value for calculating the injection quantity. In reality, however, there is now more air mass available for combustion, but the control unit is not aware of this." Is this reasoning correct, or is there a flaw in the thinking?

Hi,

"Of course" there's a flaw in that reasoning: The mass airflow sensor (MAF) measures the actually available fresh air. Therefore, the engine computer knows how much fresh air "really" (= when the MAF sensor is, exceptionally, working correctly ) is entering the cylinders.
And the soot limit applies to the actual LMM value, not the target value.

Thank you for the quick reply, Ulf.
d.h. so, that if you disable the EGR mechanically - the engine gets more fresh air - the MAF sensor also notices this - and therefore also adjusts the fuel injection amount - now I understand
Adjusting the AGR rate further will no longer have any effect.

daytrader wrote:

i.e., so that when you mechanically disable the EGR valve, the engine receives more fresh air - the MAF sensor detects this - and therefore also adjusts the fuel injection amount - now I understand Changing the AGR rate further

has no more influence.

Almost correct: Under normal (part-load!) conditions, the amount of fuel injected will remain the same, meaning it will not be adjusted, regardless of whether the EGR system is active or deactivated.

ok - thank you, Ulf - everything's clear

I once compared the mechanical deactivation with the software method (increasing the LMM value). With both methods, the engine reacts immediately and translates accelerator pedal commands into propulsion (almost) without any delay. Unfortunately, when the hose is disconnected, the turbocharger is very noticeable at idle (about 0.05 bar), which is quite revealing (to those with expertise) and annoying.

However, when I read through all these AGR forum threads, it seems that this whistling noise at idle doesn't bother most people, or am I mistaken?

I once compared the mechanical deactivation with the software method (increasing the LMM). With both methods, the engine reacts spontaneously and translates gas commands (almost) without any delay into forward motion. Unfortunately, when the hose is disconnected, the turbocharger is very noticeable in idle (about 0.05 bar), and that is quite revealing (for experts).

That's true...

and annoying.
but I must strongly disagree with that.

It works best when the engine is running down from 2000 rpm (in coasting mode) and you happen to be passing the front axle at that moment... hehehehehe...

CU Gremlin.