LMM for 1Z: Refurbished & Optimized:-)

Hello,

The old, bulky Pierburg mass airflow sensor (MAF sensor) (e.g., in the 1Z and AFN engines) appears to perform significantly better in practice than the Bosch HFLM 5.

First, based on general experience, it is likely to be more durable.

However, even if the sensor's output voltage were to decrease to a point where the air mass limiting function is activated, resulting in a loss of power (which can be detected with a VAGCOM diagnostic tool), it can be "rejuvenated" by soldering in a resistor, which will increase its output voltage and restore the full engine power.

More details can be found at https://community.dieselschrauber.org/en/viewtopic.php?t=4258.

Thank you, by the way, to Arne, who sent me a defective Pierburg mass airflow sensor .
I wouldn't have dared to perform the necessary basic measurements and tests on my working part!

Hello,

I wonder why VW stopped using Pierburg mass airflow sensors and now uses Bosch models instead.
On my 1994 car with now 310,000 km, the original mass airflow sensor (MAF sensor) is still installed. It's a Pierburg unit.
According to the VAG-COM diagnostic tool, it is also showing the maximum signal voltage, 850mg/H.
Besides, it's also cheaper.

golf3schrauber wrote:

I wonder why VW stopped using Pierburg mass airflow sensors and now uses Bosch models. On my 1994 Audi A4 with now 310,000 km, the original mass airflow sensor (MAF sensor) is still installed. It's a Pierburg unit. According to VAG-COM, it's also showing the maximum signal voltage, 850mg/H. Furthermore, it is also cheaper.

Hi Oliver,

If one thinks cynically, one might conclude that the Pierburg was too good and therefore .

However, the Bosch sensor is better in terms of "real-time measurement": it reacts so quickly that it can detect pulsating forward and backward flows, allowing the engine computer to accurately determine how much of the reported wind actually enters the engine.

It might be necessary to do this in order to get the TDIs to meet Euro 3 emissions standards... or does anyone here have a Euro 3 car with the large Pierburg mass airflow sensor?

Cool that the old GRANDFATHER is finally being used .

'Really good work, Ulf. Hopefully, the other people will also be brave enough to do the procedure. I will definitely start with 22 ohms for the next broken Pierburg .'

Regards,
arne

Arne wrote:

I will definitely start with 22 ohms when I encounter the next faulty Pierburg

.
Hi Arne,

With a 22 Ohm resistor, the mass airflow sensor would likely behave similarly to the diode in the plug... because the narrowing resistor is in parallel with an internal resistor of approximately 500 Ohms, and reducing that to 22 Ohms would probably cause the electronics to go haywire and overload.

So, for now, it's better to use 22 kOhm, as stated in the technical article .

hehe,

Absolutely right! Of course.

Hi,

a.) Couldn't this also be controlled by software?
"If you adjust the air mass using a characteristic curve so that it theoretically reaches 950 mg/H..."
allows, if the previous maximum flow rate was only about 750 mg/H, then this would...
Do they have the same effect, or not?

b.) If that were the case, couldn't one also achieve a performance increase through that?
"As far as I know, newer turbo diesel engines like the ASZ or ARL allow for a maximum of 1050 mg/H."
What would happen if the AFN map were modified?
Could one predict the advantages and disadvantages of something beforehand, without conducting a test?

Greetings.
Thomas.

Thomas wrote:

a.) Couldn't this also be controlled by software? If you adjust the air mass using a characteristic curve to a value that theoretically allows 950mg/H, whereas the mass airflow sensor (MAF) previously only allowed approximately 750mg/H, shouldn't that have the same effect, or not?

Hi Thomas,

In my own words, I would describe the characteristic curve as...
"LMM voltage + RPM = air mass per stroke."
rephrase it to higher mg/dose. I think that should essentially achieve the same result.
The thing is, for most people here, installing a resistor in the mass airflow sensor (MAF) is easier to implement than a chip tuning-like modification to the engine control unit (ECU). . .

Quote:

b.) If that were the case, couldn't one also achieve a performance increase through that? As far as I know, newer turbo diesel engines like the ASZ or ARL allow for a maximum sulfur content of 1050 mg/kg. What would happen if the AFN map were modified? Could one predict the advantages and disadvantages beforehand, without conducting a test?

Initially, nothing would happen because the throttle motor limiter (and possibly the pedal response curve) would prevent higher fuel injection amounts.
Only after you have adjusted all 3 parameter fields regarding the injection amount upwards will definitely inject more fuel, and specifically, the amount will correspond to the lowest "new" limit in the respective operating condition.

Hi,

Quote:

It's just that for most people here, installing a resistor in the mass airflow sensor is easier to implement than a chip tuning-like modification to the engine computer...

Sure. Absolutely. It wasn't intended as an alternative, but rather as a bridge to point b)!

Quote:

Initially, nothing would happen because the throttle motor limit (and possibly the pedal sensor map) would prevent higher injection amounts.

I should have described that in more detail. I was assuming a certain quantity limit. But to what extent does that relate to the driver's desired performance curve?
Pedal position: 0-100. Nothing goes beyond the floor panel. How is this to be understood?

Let's phrase it differently. If you perform "normal" chip tuning (adjusting boost pressure maps, lambda correction maps, fuel injection quantity, duration, start, etc.), do these 850mg/stroke values then serve as a lower limit if you leave this map unchanged?
That's also why there's a loss of performance if the mass airflow sensor can no longer deliver its maximum values due to defects.

Is the LMM (likely referring to a mass airflow sensor) functioning correctly, and is it reporting a value of 850mg/pulse? If you increase this value by, say, 100mg/pulse, does that mean the next higher setting becomes the lower limit for the injection amount? Am I understanding this correctly?

If that's true, couldn't the LLM signal also be manipulated to make the LLM "measure" a higher value? Or is the characteristic curve the limiting factor?

---

"There are a couple of enthusiasts who run a 1Z engine without a mass airflow sensor (MAF). They must have replaced the MAF with 'maximum fixed values.' This might cause some soot, but it also prevents failures. Hmmm... I need to think about this some more."

Greetings.
Thomas.

Thomas wrote:

To what extent is this related to the driver preference map? Pedal position 0-100. Nothing goes beyond the floor panel. How is this to be understood?

In the sense of "% pedal travel + RPM = driver's desired acceleration (in mg/stroke)".
"Half-throttle" at 1500 rpm might correspond to, for example, 50 mg, while "half-throttle" at 3500 rpm might only correspond to 15 mg (the numbers are arbitrarily chosen).

Quote:

Let's phrase it differently. If one performs "normal" chip tuning (e.g., adjusting boost pressure maps, lambda correction maps, fuel injection quantity, duration, start, etc.), do these 850mg/stroke apply as a lower limit if this map is left unchanged? Then, does that also explain the loss of performance if the mass airflow sensor can no longer deliver the maximum values due to defects?

AFAIK, the aforementioned 850 mg of air is the minimum amount required for the soot emission limit not to apply.

Quote:

If the mass airflow sensor (MAF) is working correctly, it reports a value of 850mg/hub. If you increase this value by, let's say, 100mg/hub, is the next higher setting the lower limit for the injection amount? Am I understanding this correctly?

With the AFN (Air Fuel Needle), it's different: at 850 mg of air and full throttle (at approximately 3000-4000 rpm), the torque limiter is "active."
If you report 950 mg of air to the engine computer, then no more fuel will be injected -> technical article on LLK tuning .

Quote:

If that is true, couldn't one also manipulate the LLM signal to make the LLM "measure" a higher value?

That's exactly what the resistor in the mass flow meter does.

Quote:

or is the characteristic curve then the limitation?

The soot map works like this: "mg of air/stroke + RPM = maximum soot-free injection amount = soot reduction."
I hope my somewhat crude explanation is understandable...

Quote:

There are a couple of "enthusiasts" who drive a 1Z engine without a mass airflow sensor (MAF). They must have replaced the MAF with "maximum fixed values." This does indeed lead to soot, but also avoids any failures. Hmmmm... I need to think about this some more.

In its simplest form, it's the diode on the MAF sensor connector (or soldered directly into the engine control unit) -> MAF sensor technical article.
My AFN accepted it without any problems, so it should definitely work on the older 1Z model as well...

Hi,
Here's some information about the characteristic fields:
from driver preference, transmission protection, and haze characteristic maps.
the smallest value associated with a given speed.
taken.

Driver's Preference Vehicle:
The axes are speed [rpm] and throttle position sensor value [%].
The desired injection amount is specified in the characteristic map.
in mg/stroke volume.
While it's not possible to exceed 100% (and why would you want to?), it does make a difference.
There is a significant difference whether the product contains 48 mg or 53 mg per 100%.
The values specified here are only achieved if not...
The transmission protection or turbidity sensor limits the amount.

Gearbox protection device:
It only has one axis (speed).
Content is also the injection amount in mg per stroke.

Obscuration KF:
The axes are engine speed and air mass [mg/kWh].
The content is again related to the injection quantity.
The higher the power available at a given speed...
The greater the air mass, the larger the permissible fuel injection quantity.
For example, in the first stage (1Z), the maximum value is 850mg of air.
If the language model is now showing signs of weakness, you can, of course, proceed to...
recalculate the values of the air mass axis so that the LMM is for the...
Maximum injection volume, please report only 750mg.

To compensate for the LMM aging error, the method described by Ulf is...
The method using resistance, however, is significantly less complex.


Best regards, Rudi.

Hello Ulf,

I have a few more questions for you, since you've been looking into this in detail recently.
We need to distinguish between the absolute air mass (LM) in mg per unit of time and the relative air mass in mg per piston stroke. The relationship is: absolute LM = relative LM * engine speed. The mass airflow sensor (MAF) likely only measures the absolute LM, as it has no information about the engine speed. So, is it the case that the signal at the MAF is a DC voltage between 0.3V and 4.5V, which is proportional to the absolute LM? If you rev the engine at idle (with AGR off), this DC voltage should increase approximately proportionally to the engine speed. Do you have any comparison values for this?
The values stored in the parameter fields are displayed by VAGCOM, but only the relative LM value is shown. This is the value of 850mg/KH. In other words, the control unit internally divides the mass airflow sensor signal by the engine speed and then uses this value to control the fuel injection quantity and other parameters.
I suspect that contamination of the mass airflow sensor (MAF) changes its signal voltage proportionally, meaning that the 0.3V reading at idle might not change much, but the 4.5V reading will be noticeably affected. Does your resistor reverse this effect? Only then can we ensure that the relative MAF value is shifted by a nearly constant value across all engine speeds.

Hello.
Wolfgang.

So, is it that the signal at the LMM is a DC voltage that is between 0.3V and 4.5V and is proportional to the absolute LM?

something like that...

CU Gremlin.

Wolfgang, syncro16 wrote:

When the engine is running at idle (AGR off), increasing the engine speed should cause this DC voltage to increase approximately proportionally to the engine speed. Do you have any comparison values for that?

Hi Wolfgang,

It doesn't necessarily have to be proportional because the characteristic curve is "non-linear." A high "resolution" is achieved in the lower measurement range (see the Gremlins graphic; the Bosch curve is likely similar in principle to the Pierburg curve), presumably to enable precise control of the EGR system.

Quote:

Does your modification also reverse this? Only then can it be guaranteed that the relative LMM value is shifted by an approximately constant value across all speed ranges.

According to my measurements, 22 kOhm resulted in a change of the mg value per stroke at idle and , increasing it by approximately 100 mg during a logged full-load acceleration.

I would have preferred it if the upper measurement range had been increased, but it seems that's not possible.
It's not that bad, because with aging Lambda sensors, the lower measurement range actually drops. However, you might notice this during operation, at best, by a less pronounced turbo boost.

I also tried a diode trick (the principle is similar to advanced 10c tuning) during my experiments, but unfortunately, the circuit starts to oscillate at a low frequency .