Chip Tuning: Reduced Top Speed Performance?

Hello everyone!

I'm new here, but I still hope to do everything right, so I'm posting my problem now.
I drive an Audi A4 from 1996 with a 1.9 TDI engine (110 hp), specifically the AFN engine.

This weekend, I bought and installed a used engine control unit (with identical part numbers) that has an *** chip inside. Then, I had the immobilizer (VAG 1551) synchronized, and everything worked perfectly at first! The increased power (now 132 hp) was noticeably better during acceleration.

Then I got on the highway to test the top speed.
The suit itself was perfect, but when I exceeded 200 mph (with the tachometer reading over 4000 RPM), I suddenly experienced a loss of power!
But when I got back down below 200 km/h, everything was fine again!
And that's also the case now, which is why I'm only driving up to 200 km/h for now.

Okay, here are my questions:
What is the cause of this decline in performance?
Is it possible that the engine control unit or the chip is defective?
Could it be related to the turbocharger? By the way, it has already been driven over 150,000 kilometers.
The engine is a replacement engine and still has a warranty.
Mir wurde ein Tip gegeben, dass das Getänge im Turbolader in dem hohem Bereich nicht mehr gängig sein soll. KCan that be it?
Was kostet so ein Gestänge und der Einbau? How?
What other causes could there be?
The turbocharger can't be broken yet, right?
Because the full power is available in that suit, and it can reach speeds up to 200 [units - e.g., km/h or mph].

I'm a bit desperate because I don't know how to proceed and whether more things could break! Should I perhaps reinstall the old control unit instead?
Unfortunately, I don't have that anymore; otherwise, I would try it and see if the same error occurs. Everything was fine with the control unit at the final speed.
I'm now hoping to find someone who has experienced something similar before or who is knowledgeable about this topic.

I haven't had the control unit read out yet.
Does this cost money?

Thank you and best regards.
Carsten.

Hello,

Quote:

What is the cause of this decline in performance?

No idea, the crystal ball is broken right now.
What does the engine control unit's fault memory indicate when the problem occurs?

Quote:

Is it possible that the engine control unit, or the chip itself, is defective?

Anything is possible...

Quote:

The engine is a replacement engine and still has a warranty.

You should keep that in mind when doing engine tuning. If something goes wrong, it can get expensive.

Quote:

I was given a tip that the turbine within the turbocharger is not supposed to be operating effectively in the high range. Could that be true?

Yes.

Quote:

Was kostet so ein Gestänge und der Einbau? How?

The support rod is not sold separately. It would also be pointless to replace the lever that moves a stuck mechanism in the turbocharger.
It's like breaking your foot and then buying new shoes.

Quote:

The turbocharger can't be broken yet, right?

No, but soon. What do you mean by "broken"? "Broken" can also refer to a consumption of 1 liter of oil due to defective roller bearings or seals.

Quote:

I'm a bit desperate because I don't know how to act and whether more things can break!??

"If you don't read the error codes while the fault is actively occurring, you won't be able to diagnose anything."
2.) Yes, eventually something can break down.
3.) You should start by reading this:

https://community.dieselschrauber.org/en/viewtopic.php?t=3285

Best regards, Rainer.

Okay, I just went to the Audi dealer and had them read the error codes.
The following error occurred:
00553 028
Air mass meter - G70.
Short circuit to positive.
intermittent error
occasional error
sporadic error

Does that mean the mass airflow sensor is defective?
Or could there be other causes for the error message?
Is it also possible that the shaft in the turbocharger can't handle the higher pressures caused by the chip because it has never operated in that range before? Or would an error message like that be unlikely in such a case?

'Furthermore, I would like to know the difference between the Garrett turbochargers with part numbers 028 145 702 C and 028 145 702 H. I inquired and found that the charger ending in 'C' is for my A4 model year, while the charger ending in 'H' is for the A4 models from the year 1998 onwards. However, both chargers are designed for the same engine code, which is AFN. Would it be possible to install a turbocharger with the designation 028 145 702 H in my car?'

Thank you again for your answers.
and I hope to receive a more competent answer this time than before.

Regards,
Carsten.

Hello,

You've almost already given yourself the answer.
It could be a faulty mass airflow sensor or its wiring to the control unit.

Fix this error first and forget about the boost pressure control for now.
Tip: Try logging the measurement blocks along with the air mass flow readings.

Best regards, Rainer.

Hi,

'And check the fuel supply. If the fuel pressure is incorrect, it will cause the injection timing to shift backwards, which affects the injection timing.'

The effect could be as follows: As the engine speed increases, the ESP (electric fuel pump) draws more diesel. This increases the vacuum pressure in the suction line. If this line is not completely sealed, or if the filter is already somewhat clogged, it will draw in air. This air causes pressure fluctuations/a drop in pressure within the ESP, which affects its injection timing because the ESP's operation is pressure-controlled.

Mine had the exact same thing.


I agree with Rainer that the error entries must be cleared first. If necessary, temporarily replace the mass airflow sensor (MAF) using the diode method to see if it makes a difference.

I don't think it's a turbo, and I also doubt it's a can or rod.
If the turbocharger bearings were to suddenly seize up at full throttle, which corresponds to a power output of approximately 25 kW (!) in the turbo, it would be scrap within milliseconds. If the linkage jams, it is likely to also jam when the system is under 'full pressure,' and the resulting pressure spike would cause the engine control unit (ECU) to shut down the turbocharger at least until the next start-up.

I also doubt it's the motor. But if you already had an original MSG and a guaranteed AT engine, it wasn't smart to give that up. If the engine has problems again and you have the tuned MSG installed, then you essentially sold a modified MSG cheaply and now have to buy another engine!

Let me read how the story continues.

Hello!

How should I log the measurement blocks along with the air mass flow rate values?

And you, 'garth.brooks,' did you also get that exact error message when you encountered your problem?
And what exactly should I do to control the fuel supply?
And what exactly is the diode method, and how does it work?

If the engine ever has a problem, I'll find an original control unit beforehand and only then will I go to the dealer.

Thank you and best regards.
Carsten.

Hello Carsten,

Relaxanz wrote:

Hello! How should I log the measurement blocks with air mass measurement values?

https://community.dieselschrauber.org/en/viewtopic.php?t=3089

Relaxanz wrote:

And you, "garth.brooks," did you also get that exact error message when you encountered your problem? And what exactly should I do to control the fuel supply? And what exactly is the diode method, and how does it work?

I'm going to take the liberty of answering...
Error message: No, that would cause problems with the start of the ESP injection process.
Fuel supply: see the link in my previous posts.
Diode method: Replacing a faulty Hot-Film Mass Flow Meter (HFM) or Laminar Mass Flow Meter (LMM) with a silicon diode (for testing purposes).
https://community.dieselschrauber.org/en/viewtopic.php?t=3347

Best regards, Rainer.

The thing about the error message that says 'everything is okay' is true; it doesn't actually indicate anything, and the workshop will send you back home.
with the comment 'Probably the chip has been deactivated!' !!!???

As a former full-time software developer, I wondered how the MSG could have reprogrammed itself, and I never visited that place again.

Otherwise: Searching is a virtue, especially in this forum...


Okay, one more thing – I can't really imagine an MSG (Message System) defect either. It's possible, of course, but since it mostly involves digital technology, those kinds of issues are also prone to causing digital errors.

So, either it works or it doesn't. Usually, there's nothing in between.

I've also experienced the LMM error a couple of times.

It appeared and then disappeared just as quickly!

Just observe for a moment!

P.S. My turbocharger and mass airflow sensor have 225,000 km on them after being modified/tuned.

Regards,

Manuel.

Good tuners also reduce the power output slightly, even at peak RPM and high speeds, perhaps to the original level, so that the engine can handle full throttle for longer distances... which is what you would expect from a TDI.

Hello everyone!

Regarding the previous comment:
I believe that *** is a reputable tuning company and has considered features like these.
However, the performance at top speed shouldn't drop off that drastically.

And regarding the second-to-last comment:
I'm relieved to hear that someone has experience with this and is reporting positive results.

And to the others:
This weekend, I bypassed the mass airflow sensor using the diode method.
And then the problem was gone, and I could drive at full speed without any issues.
Okay, I'll go ahead and buy a new mass airflow sensor, and then it should work again, right?

The forums and tips here are really very comprehensive and also very good.
However, using a laptop to read the data from my car seems like too much effort for me. It's not that I couldn't do it, but I simply don't have the time, and I'm also not a mechanic or working in the automotive industry.
I think it's great that someone developed something like this and is now using it!
I would really need to delve deeply into those kinds of things, and that's something I'm not able to do right now.

I will definitely post again once I have the new LLM installed in my car and have tested it.

I must give great praise to this internet domain; I wouldn't have thought it was possible to create something so well and comprehensively.

Regards,
Carsten.

Hello,

Thank you for the compliment!

Quote:

But, for example, accessing the data of my vehicle using a laptop seems to go too far for me.

When it comes to the air mass meter , the diode method can be a reliable way to detect a defect.
In many other cases, the only option is to check what's happening inside the corresponding control unit.

Best regards, Rainer.

Hi, I'm not going to leave it like that with the issue of being too complicated for reading data with VAG-COM.

The following needs to be done:

Acquire an interface; if necessary, buy it on eBay and resell it later.
Get a laptop (someone has one).
Download VAGCom shareware.
Find the OBD port in your car.
Pinning.
Let's get started.

If you consider that they're offering to trade something with a 50% success rate, even if it's something that isn't broken, it's still a highly profitable investment.

Hello Garth,

I've already seen that there are cables like that available.
But there are several options, one for OBD, one for OBD2, and also one for USB.
Is an OBD serial connection enough? Or do I need an additional adapter?
What do I need for my Audi A4, year of manufacture 1996, TDI engine?
There's a socket located in the center console, near the ashtray for rear passengers.

You're right, once you have the cable and the connection established...
It shouldn't be a problem anymore.

But why would they exchange something that isn't even broken?
Can I use this to prove something, or to determine what can be ruled out?

Thank you and best regards.
Carsten.

An OBD serial connection is sufficient, provided that the available device still has an RS232 port.
The more sophisticated USB version is specifically designed for the newer, neutered models.

Quote:

But why would they want to exchange something from me that isn't even broken?

What do you think this forum exists for, thankfully?

Quote:

Can I use this to prove something, or to determine what can be ruled out?

Hast du wirklich so große Hemmungen, mal in die Fachartikel zu schauen? Reading educates...
The pressure relief valve of the modules is being stressed.
Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Hello,

Relaxanz wrote:

Hello Garth, I've already seen that there are cables like that available. But there are several options, one for OBD, one for OBD2, and also one for USB.

OBD1 and OBD2 stand for On-Board Diagnostics version 1/2. USB stands for Universal Serial Bus.
USB is a bus system on a computer and has nothing to do with OBD initially. It's simply the physical connection for a diagnostic adapter. Besides USB versions, there are also adapters available for the serial port of the computer.
Your A4 TDI from the year 1996 does not support OBD2. However, you can still read all relevant control unit information using VAG-COM. The software has at least the same functionality as the original VAG diagnostic system, and in some cases it even exceeds it.

Relaxanz wrote:

Is an OBD serial connection enough? Or do I need an adapter for that?

If you have a serial port on your computer or laptop, then yes.

Relaxanz wrote:

What do I need for my Audi A4, year of manufacture 1996, TDI engine?

Current offers in the online shop; for hobby use, I recommend this one. Or you can simply browse a bit through the diagnostic supplies section.

Relaxanz wrote:

But why would they exchange something that isn't even broken?

Because they want to make money, or simply are unable (you keep replacing parts until the problem is gone)?

Relaxanz wrote:

Can I use this to prove something, or to determine what can be ruled out?

If you thoroughly review the technical articles on dieselschrauber.de, the answer is a clear YES.

Best regards, Rainer.