AGR, LMM & VAG-COM: Explained & Troubleshooting

Good morning, everyone.

I have another question. I know it's been discussed a lot.
But I still haven't quite understood it.

So, if, by some dumb "coincidence," the EGR valve is blocked...
If the engine is operating under partial load, it produces no exhaust gases.
"mixed in" As a result, hopefully it will still...
If a working LMM is found to have a value that is too large, it can...
Steuergerät veranlasst, die AGR aufzuregeln. Sure.
not, which means the actual LMM value will always be greater than the specified value.
Setpoint. Okay, so far so good. Now, from that, I would understand...
Since the actual LMM value is higher and there is more fresh air available, then...
increased the injection amount, but only to a limited extent.
regarding the "driver preference" setting and torque limitation.
is stopped, right?

Okay, I think I'm on the right track up to that point. Now, let's get to the questions .

1.) If you increase the target value of the mass airflow sensor (MAF) using VAG-COM,
It avoids a potential error entry, if there even is one.
But what effect does this have on the fuel injection amount?
It should increase, since the actual mass flow rate (LMM) is now higher AND valid, right?
Okay, at this point, the logic should be to increase the AGR (Agricultural Growth Rate).
Chicken or the egg?

2.) What happens if you set the maximum possible target value for the mass flow rate (LMM)?
"How is it recorded? And what is the actual amount?"


As far as I understand, it's also possible to adjust the AGR (Average Good Response) rate.
What impact does this have? And which values make sense in this context?

So, I'm talking about this feedback loop involving the mass airflow sensor (MAF) value and the EGR control.
Injection amount not yet entirely clear. What size should be used here?
What happens if you change something? Assuming that's even possible?!

Thank you and best regards,

Carsten.

Sure, here's the translation:

"PS: This is about a T4, with a 111kW AXG TDI engine."

Hi!

Your initial consideration about the excessively high LM (lambda) target value only applies to partial load conditions. At full load, the EGR (exhaust gas recirculation) would be closed anyway, so the conditions expected by the control system would prevail regardless.
The amount of fuel injected is only increased in a small transitional range, where the EGR valve would normally have to close first (reaction time). This is what the driver perceives as a (slightly) improved response. Otherwise, the amount of fuel injected remains within the range defined by the aforementioned maps, with only the transition during acceleration being characterized by slightly higher amounts.

1. See above. We want to raise it, but can we do that if there's a defect...? As long as there's little load (driver preference!), there's no reason to raise the amount of electricity. And at full load, the AGR is inactive again.

2. The AGR (Active Grille) rate will be lower – if the AGR is working. But it won't be zero. The acceptable value varies from control unit to control unit. In mine, 32768 is the base value. The maximum value it accepts is, as far as I remember, 33368. Just try different values until the highest possible value is accepted.

3. See 2. This is the same parameter.


The main factors influencing the control parameters are the driver's input (throttle position), the mass airflow sensor signal, the boost pressure, and the engine speed. The fuel injection quantity is limited by the known characteristic maps for soot and torque. The exhaust gas recirculation (EGR) system is only active during partial load conditions and is time-limited during prolonged idling. Above a certain load value, the EGR system is closed.

Here's a small tip regarding deactivating the EGR system using a plug-and-play method by simply disconnecting the vacuum hose (for those who find the sealing method too extreme):
I just came from the TÜV, for the initial technical inspection (HU) and emissions test (AU). The inspector's first look during the HU was under the hood, specifically at the EGR vacuum hose . But that had been reattached yesterday .
So, it seems the word has definitely gotten around...

The inspector also immediately looked at the temporary hose attached to the EGR valve and was surprised by the cable tie used to secure it.

[Translating...]

Hello,

A quick question.

Does it make sense to further reduce the adaptation value via VAG-COM if the AGR hose is disconnected?

Best regards,

No!

isi wrote:

Does it make sense to reduce the rate again using VAG-COM, even if the AGR hose is disconnected?

Hi,

Of course, this doesn't change the air mass.
However, the difference between the target and actual air mass changes, which can potentially affect the decision of whether or not to log an error – provided that the EGR system is software-monitored.

Hello,

Thank you for your answers.

I forgot to mention that it's an AFN model, manufactured in 1997. So, it wouldn't make sense to do that here, because the AGR (Abgasrückführung - exhaust gas recirculation) system isn't monitored. Is that correct?

Best regards,

Yes.