LMM Tuning: Optimize Your Engine Performance

Hello?

Was würde wohl passieren wenn man dem LMM einen höheren Luftdurchsatz ermöglicht? Theoretisch mußte der gemessene Wert steigen und die Einspritzmenge müßte angehoben werden. Oder?
Opinions?

best regards
Ronny.

Hello, it's likely that the software will also need to be adjusted. I once experimented with a BMW naturally aspirated engine that had a chip. I removed the grid in front of the mass airflow sensor (MAF). The result was better acceleration across the entire RPM range. According to the speedometer, it reached 220 km/h faster, but then it stopped. With the grid in place, the maximum speed was 10 km/h higher. However, without the grid, fuel consumption increased significantly. I suspect that similar effects occur with diesel engines, which is why the software needs to be tuned differently.

In addition, the standard software includes limits for the LMM (lambda-dependent mass flow measurement). This means that the LMM can display higher values, but above a certain value, the software no longer accepts them and does not use them for calculations; instead, it only uses the pre-defined limits. Therefore, when tuning the engine control unit (ECU), these limits are increased, thereby 'legalizing' higher displayed values. However, I cannot say how much leeway the standard software allows for these displayed values.

Hi,
For the 'older' VE-TDi engines, increasing the mass airflow sensor (MAF) value doesn't achieve anything, as it only reduces the fuel injection amount. The amount is determined first. If there isn't enough air, the amount is reduced again before the fuel pump is activated (soot reduction).
For the PD (direct injection) systems, the mass airflow (MAF) value should be used to determine the injection quantity (so that increasing this value can potentially lead to a limited increase in power).

Rudi wrote:

For the 'older' VE-TDi engines, increasing the mass airflow sensor (MAF) value doesn't achieve anything, as only the injection amount can be reduced based on that value. First, the amount is determined. If there isn't enough air, something is reduced again before the pump is activated (soot reduction). In the case of PD injectors, the mass airflow (LMM) value should be used for determining the injection quantity (so that an increase in this value can potentially lead to a limited increase in power).

Sure, here is the translation of the text from German to English:

"Supplement:"
If the torque map (which determines the maximum fuel injection amount, regardless of the reported mass airflow sensor value) wasn't in the way, an LMM tuning might work – potentially even up to the fuel quantity demanded by the accelerator pedal, although that is also limited: you simply can't exceed the maximum possible amount.

However, a problem would arise if the LMM value were artificially increased:
In the partial load range, the mass airflow (MAF) value also serves as feedback for the exhaust gas recirculation (EGR) rate. Specifically, EGR is used to reduce the MAF value (because when exhaust gas is introduced, the full intake air volume no longer flows through the MAF sensor), until it corresponds to the EGR characteristic map.
If the LMM value is too high, the EGR would be opened further to reach the target LMM value again, and the engine would start to produce more or less soot .
F***ing control systems!

Hello Ulf,

The AGR system makes sense. However, I've always thought that the AGR valve operates digitally, meaning it's either fully open or fully closed. I've never had to replace one myself, but I can imagine that controlling it isn't really simple.
To put it dramatically, I was thinking about a kind of ram-air system for the mass airflow sensor (MAF). Essentially, forcing more airflow. And that within a range of 150-200 mg/h. When a MAF sensor is about to fail, it delivers too low values, and the engine loses power. So, I thought that maybe the opposite could also work...
Okay, it was just a thought.

best regards
Ronny.

However, a problem would arise if the LMM value were artificially increased:
In the partial load range, the mass airflow (MAF) value also serves as feedback for the EGR rate. Specifically, EGR is used to reduce the MAF value to a level that corresponds to the EGR characteristic map (because when exhaust gas recirculation is activated, the full intake air volume no longer flows through the MAF sensor).
If the LMM value is too high, the EGR would be opened further to reach the target LMM value again, and the engine would start to produce more or less soot .
F*** control systems!

What happens then if the AGR is decommissioned?[/quote]

If the EGR system is deactivated, the mass airflow sensor (MAF) value can be increased without causing the engine to produce excessive soot.