LMM Values for 66kW ALH Engine

Hello,

I recently bought a 66kW Golf Variant. The engine code is ALH. I did a performance test and would like to know what you think about the condition of the Mass Air Flow (MAF) sensor.

Measurement block 10:

RPM Mass Air Abs. Pr. Abs. Pr. Load.
/min mg/R mbar mbar %
2583 980 959 2162 100
2835 825 959 1999 100
3087 745 959 1765 100

I have the feeling that the car isn't reaching its full potential, especially in the 3000/min range.

Regards,

Okay, here's the translation:

Achim.

Hi.

I would say that the LMM is providing values that are too low at around 3000 rpm, because the boost pressure is dropping.

The reason for that =

That means checking the intake passages and charging system, etc.

Thank you for your reply.

What do you suggest? How should I proceed?

Regards,

Okay, here's the translation:

Achim.

Hi,
'I also have a similar underpowered ALH engine with 66 kW. It often experiences a noticeable drop in power when the variable turbocharger geometry (VTG) reduces the boost pressure. This is very clearly visible on a boost pressure gauge. The pressure initially rises to 1.45 bar, then drops to 0.5-0.6 bar, and then slowly increases again to 0.85 bar after several seconds. The mass airflow sensor (MAF) then correctly reports the lower airflow, and the engine control unit (ECU) reduces the fuel injection amount.'
That damn car has gotten me into trouble more than once while trying to overtake other vehicles, and I had to abort the maneuver.
The workshop can't or won't find anything wrong, and VW is writing to me saying I shouldn't use biodiesel anymore. However, there was diesel fuel in the tank.
According to the workshop, their diagnostic tool is supposedly unable to write a log file that would display values for RPM, target pressure, actual pressure, and duty cycle. They claim that only a snapshot is taken at 3000 RPM, and at that point, everything should appear to be okay.
The error memory is then (unfortunately) also empty.
The master also said that the turbocharger pressure regulation was not normal, but he couldn't guarantee a replacement based solely on the LDA (lambda датчик адаптер).

If it weren't a company car, I would have returned the thing a long time ago .

If you find anything out, please post it. It might help me too.

Regards,

Eike.

Hello,

I have conducted further measurements. At approximately 3000 RPM, the values for air mass and boost pressure always decrease.

'010 '011
Mass Air RPM Abs. Pressure.

mg/R /min mbar
650 2142 1601
895 2415 2091
890 2688 2060
805 2961 1887
685 3192 1734
735 3402 1867
740 3633 1897
725 3822 1907
720 4011 1918

Is the cause of the drop in boost pressure related to the mass airflow sensor (MAF) value, or is the low MAF value a result of the drop in boost pressure? Where could the fault lie?

Regards,

Okay, here's the translation:

Achim.

ABRA wrote:

Is the cause of the drop in boost pressure related to the mass airflow sensor (MAF) value, or is the low MAF value a result of the drop in boost pressure? Where could the fault be?

Hello Achim,

Unfortunately, boost pressure and air mass affect each other. For example, if the injection amount is reduced due to insufficient air mass, this reduces the 'driving force' for the turbocharger. As long as this can be compensated for by the variable turbine geometry (VTG), the boost pressure will only decrease slightly or not at all; but eventually, it simply won't be enough.
Conversely, if the boost pressure is reduced for some reason, the amount of air entering the cylinders will automatically decrease.
To rule out a faulty boost pressure control (stuck valve) as the cause, please record your above measurement along with the duty cycle of the solenoid valve for the boost pressure control. This will allow us to identify any desperate measures taken by the control unit to regulate the boost pressure (in case something is stuck or, for example, a simple vacuum hose is leaking ).

Best regards, Rainer.

Hello Rainer,

Thank you for your help. I have the values again here, along with the valve's control ratio:

'010 '011
Mass Air RPM Absolute Pressure Absolute Pressure Duty Cycle

mg/R /min mbar mbar %
650 2142 1948 1601 35.1
895 2415 1948 2091 61
890 2688 1948 2060 64.5
805 2961 1948 1887 60.2
685 3192 1948 1734 53
735 3402 1948 1867 54.6
740 3633 1948 1897 54.6
725 3822 1948 1907 55.4
720 4011 1948 1918 55.8

I hope you can make sense of it.


Regards,

Okay, here's the translation:

Achim.

Hi.

I'm having some minor issues with the group header.

For me, "Abs. Pressure" means "absolute pressure," but that value usually can't be almost 2 bar.

I know the distinction between target boost pressure and actual boost pressure in English as "specified" and "actual."

If we interpret 1984 mbar as the target pressure and 1601 to 2091 as the actual pressure, then the whole situation seems to indicate an overshoot (at 2415 rpm) combined with a partially stiff VTG (Variable Turbine Geometry), which results in a correction that is too strong and lasts too long.

Hello,

@Ulf: "Abs. Pressure" is probably an abbreviation for "absolute pressure," so that makes sense. It's just missing "act." or "spec.," which would indicate actual or set value, respectively. But you can see that from the values themselves.
Relative pressure would then be the difference compared to atmospheric pressure.

@ABRA: The 53% drop indicates that the engine control unit wants more boost pressure.
Now we can discuss the strategy of the engine control unit regarding how to get more air into the cylinders.
- The boost pressure should be increased because the mass airflow sensor (MAF) values are too low, and there is insufficient driving force for the turbocharger due to a reduced fuel injection quantity caused by the low air mass.
- or the turbocharger pressure needs to be increased because the current value is too low.
I cannot say which of the two is the case.

Sure, I will. Please provide the text you would like me to translate from German to English.
- A jamming of the VTG (Variable Transmission Gear), causing the adjustment lever to "jump" in steps.
- as well as leaky vacuum hoses,
- leaky adjustment membrane.

Best regards, Rainer.

Rainer K. wrote:

@Ulf: "Abs. Pressure" is, in my opinion, an abbreviation for "absolute pressure," so it's correct. It's just missing "act." or "spec.," which would indicate actual or specified value. But that's evident from the values themselves. Relative pressure would then be the difference compared to atmospheric pressure.

Hi Rainer,

yes, of course: "absolute" and "relative"

My English label files sometimes refer to the charging pressure as Manifold Pressure, and the atmospheric pressure as Barometric .

Hello,

I'm still experiencing these energy dips. I've tried the following so far:
1. LMM (mass airflow sensor) replaced (from eBay) - without success.
2. VTG was addressed using the turn signal method (but did not establish a connection).
3. Hoses were checked for leaks using a vacuum pump/pressure gauge.
4. Adjustable membrane, tested as in item 3.

What I haven't exchanged yet:

Boost pressure control valve.

Could it be due to that? Do you have any other suggestions?

Regards,

Okay, here's the translation:

Achim.

Possibly, the VTG (vertical travel gauge) is set too aggressively.

Can you look HERE } for my values (22kb CSV)?

CU Gremlin.