Diode for LMM Simulation

Hi,

I read in an article that the germanium diode 1N60 is supposedly better than the silicon diode 1N4148.

What benefit does it offer?

My LMM (lambda sensor) is also broken, and since I just had a new ESP (Electronic Stability Program) installed for €1400 (which I'll discuss in another question), I want to temporarily fix the issue by disabling the EGR (Exhaust Gas Recirculation) and using the diode trick.

Thank you very much for your help.

Regards,



Okay, I'm going to drive with the mass airflow sensor (MAF) disconnected for now. This gives it significantly more power up to 2000 RPM. After that, it behaves similarly to when the MAF sensor is actually defective.

Hello,

Technically, the diodes differ as follows:

Silicon:
Forward voltage: 0.6-0.7V.
Maximum current: approximately 100mA.
Steeper characteristic curve, lower temperature sensitivity, very low leakage current in the reverse direction.

Germanium:
Forward voltage, active region: 0.3V.
Maximum current: approximately 50mA.
Flatter characteristic, higher temperature sensitivity, lower leakage current in the reverse direction.

Unfortunately, I can't tell you how that manifests itself in the simulation.

The LMM is now only 80 EUR at the friendly store.

I wouldn't waste much time fiddling around with a diode.

Especially since I didn't get any results with the diode, and my colleague barely got anything working with it either.

How do you know that your LMM is broken?
Are you sure about that?

m;

The workshop that installed the ESP performed a measurement.

At 4450 RPM, it should ideally display 850 (target value), but it's only showing a paltry 435.


I already had to borrow 1400 euros for the ESP repair because I only bought the car on installments at the end of January. 80 euros is quite a lot, especially compared to 5 cents for a diode (or 1.15 euros for a germanium diode).

I have the MKB AGR engine in an Octavia... It seems to be the old engine control unit (ECU).


Regards,

Alex.

I have a standard diode (1N4148) in there, and my measurements show an actual voltage of 800+ even at idle. What more could a germanium diode possibly offer? Surely, it can't exceed the maximum!

The 1N4007 diode provides 1125mg/H, which results in the error message 'implausible signal, sporadically.'

The voltage should not be too high, otherwise it will be interpreted as a 'short circuit to positive'.

CU Gremlin.

It should be possible to limit the current using a Zener diode.

Just as a side note:


My 021 AF control unit on the 1Z has a target value of a maximum of 849 mg/H.

I'm not sure, but I don't think the older MSA12 models can handle weights of over 1000.

I once tried the diode trick on an ASV, and it started behaving like a Lanz Bulldog (-> I quickly turned it off).

m;

I have the germanium diode running now, and I haven't noticed anything negative.
It performs wonderfully in city traffic. I haven't yet tried accelerating to its maximum speed, but I'll give it a shot this weekend.

As I mentioned, I have a BMW engine with AGR valves. Initially, I had the AGR system activated, and there was hardly any soot buildup. However, just to be on the safe side, I disconnected the vacuum hose.

Regards,
Alex.

Hi,

I once had a 1N4007 diode in my ASV. As Gremlin mentioned, it provided 1125mg/H, but...
No error entry, the AGR (Abgasrückführung - exhaust gas recirculation) was broken.

@Gremlin
What is the difference between a 1N4007 and a 1N4148 in this application?
They are both silicon diodes, so they should have the same voltage drop. Isn't a germanium diode different?
A lower voltage drop would therefore suggest a higher air mass value, wouldn't it?
Did I misunderstand something?
Please provide clarification.

Achim wrote:

What is the difference between a 1N4007 and a 1N4148 in this application? "They are both silicon diodes, so they should have the same voltage drop. A germanium diode has a lower voltage drop, so it should have a higher air mass value, or have I misunderstood something?"

Basically correct, but:

The "healthy" LMM voltage is typically at its highest when the engine control unit (ECU) starts to reduce the boost pressure, usually somewhere above 4000 rpm.

In this area, the Si diode, with its 0.6V voltage drop, might provide slightly less current than a fully functional LMM, which is why the idea of using a germanium diode was proposed.
Whether this improves performance (e.g., by reducing soot emissions or increasing torque) is detailed on a separate sheet.


Several silicon diodes, such as the 1N4007 and the 1N4148, can indeed exhibit differences in their "voltage drop characteristics" within the "low current range," meaning they can produce different voltage drops.
And the impedance of the LMM input at the engine control unit, combined with the low signal voltages, results in relatively small currents flowing through the diodes.

Similar effects can be achieved by connecting several (identical) diodes in parallel.

Hi,

@ulf
by ulf
In this area, the Si.Diode, with its 0.6V voltage drop, might already provide slightly less than a fully functional LMM, which is why the idea with the Ger.Diode was proposed.

Okay, sure.
My question was more along those lines.
by Gremlin.
The 1N4007 diode provides 1125mg/H, which results in the error message 'implausible signal, sporadically.'

The voltage should not be TOO high, otherwise it will be interpreted as a 'short circuit to +'.

Then, a germanium diode should produce even higher values, and that would be more likely to trigger an error message.

I haven't logged a value of 1125mg/H with a mass flow meter yet, or at least, I don't think I have.

What is the difference between a 1N4007 and a 1N4148 in this application?


simply put: the 4007 has thicker connecting wires (making it easier to install) and was simply the best option in the DIY kit .

@ulf

Okay, my mass airflow sensor has never outputted more than 950mg/H. This maximum value occurs at the engine's maximum torque, which is around 2000rpm at full load. } At higher speeds, the air mass value decreases slightly. } Ultimately, the boost pressure remains constant, but the flow losses increase. } Of course, the absolute amount of air increases with the speed, but when calculated in mg/H, it ideally remains constant. }

Therefore, in my experience, the diode has no influence whatsoever on the maximum speed or final velocity.

CU Gremlin.

Gremlin wrote:

So, my mass airflow sensor has never outputted a value higher than 950mg/H.

And this maximum value occurs at maximum torque, which is around 2000 rpm at full load. At higher speeds, the air mass value decreases slightly. }
Basically, it's the same as mine, except the absolute value is higher for the ASZ: 1156 mg @ 1900 rpm and 2376 mbar (with a slight overshoot).

However, the ASZ also has a different LMM (mass flow meter), with a pipe diameter of approximately 8 cm, and apparently with a higher measurement range.

Hi,

I wanted to test the germanium diode on the highway, but the results were not good.

Above 2000 RPM, it barely accelerated anymore. Then, suddenly, at 4000 RPM, it really started to pull, but then the power quickly faded away.
I think the emergency program was activated, but the light bulb didn't turn on.

The AGR (Abgasrückführung) is 'defective'.

I've now installed the 1N4148 diode. I still need to test it, though.


Best, Alex.

Okay, I'm back... but even with the silicon diode, it's not delivering the correct power output.
Could it be that an emergency program will be implemented after all?

In the first and second gears, the instantaneous fuel consumption during acceleration is still around 13 liters, but from the third gear onwards, it drops to approximately 8 liters, and it actually gets even lower when increasing the engine speed! And that's at full throttle.

What else could it be due to?


a perplexed person.


Alex.