Upgrade Turbo: Wastegate to VTG Turbocharger

Hello fellow mechanics!

Has anyone ever swapped a VTG turbocharger onto an engine that originally came with a factory-fitted wastegate turbocharger?

I have some specific questions about this.

Can the control signal from the MSG (duty cycle), in conjunction with the appropriate electro-pneumatic converter (solenoid valve for boost pressure regulation), be easily used to control a VTG turbocharger? In both cases, the control should function the same way: reducing the duty cycle to increase boost pressure, and vice versa.

As far as I know, VTG turbochargers are only available as a complete unit with the exhaust manifold, whereas with a wastegate turbocharger, there are two separate components (manifold + turbocharger). Does the VTG turbocharger with its manifold fit onto the cylinder head of the AGR engine?

3. What potential for improvement in terms of boost pressure build-up at low engine speeds exists compared to a turbocharger with a wastegate?

4. What modifications to the exhaust system (flexible pipe) are necessary to connect the cargo bed outlet to the existing exhaust system?

5. Are there any differences in the oil supply (and disposal) systems for the two types of loaders?

6. Do the intake and outlet ports of the air ducts match the VTG turbocharger, or are the diameters different?

Thank you for your answers!

Regards,
Alex.

donalexo wrote:

1. Can the control signal of the MSG (duty cycle) in conjunction with the electro-pneumatic converter (solenoid valve for boost pressure regulation) that is suitable for the turbocharger be easily used to control a VTG turbocharger? In both cases, the control should do the same thing, i.e., reduce the duty cycle for higher boost pressure and vice versa!

Hi Alex,

If that works smoothly, I would be very surprised, because the active boost pressure control ranges are different.
In a valve-less turbocharger, the wastegate provides approximately 0.6 bar, while the VTG provides 0.0 bar.
The boost pressure maps are likely to be just as varied.
Regarding the limitation to 1 bar, it might still be possible, as this would reduce the effective current in both valves - but how the overall control behavior will be...

Finally, the VTG valve has a lower resistance than the wastegate component: the target value is 14-20 or 25-45 ohms.
If things go wrong, the EDC (Engine Control Unit) might potentially recognize the VTG (Variable Turbine Geometry) valve as a short circuit – but that's not necessarily the case.

Quote:

As far as I know, VTG turbochargers are only available as a complete unit with the exhaust manifold, whereas with a wastegate turbocharger, there are two separate components (manifold + turbocharger). Does the VTG turbocharger with manifold fit onto the cylinder head of the AGR engine?

No, VTGs also come as "unpowered" versions as well; for example, in my train and at the Ibiza-ALH.
For the Golf 4, the ALH engine actually has a turbocharger, as far as I know...

Quote:

3. What potential for improvement regarding boost pressure build-up at low engine speeds exists compared to a turbocharger with a wastegate?

Based on my gut feeling, I would estimate a maximum of about 20% more torque in the low RPM range, but this should not be considered an official or definitive statement.

4. - 6.: no idea...

Hello.

zu1. Keine Ahnung. Denke aber das funktioniert nicht. See Ulf.

zu2. Gibt es auch einzeln. Volkswagen Golf 3.

More torque in the low RPM range.

'It's a completely different flange. Also, the VTG turbocharger sits slightly higher. You need the flexible pipe with the catalytic converter, or it will need to be welded in place.'

Yes, because the loader sits higher, you will need to replace the oil inlet and outlet lines.

'These fit. However, because the loader sits higher, the pipes don't fit into the previous mounting points.'

Hi,

Take a look at the conversion guide for changing from a 1Z to an AFN engine in an Audi 80; you can find a lot of useful tips there. Just the amount of work involved in converting the exhaust manifold is enormous.
http://www.meckisfaq.de/antworten/motor/diesel/1z_2_afn.htm

@ulf:

Quote:

If that works smoothly, I would be very surprised, because the active boost pressure control ranges are different: In a valve-less turbocharger, the wastegate provides approximately 0.6 bar of pressure, while the VTG provides 0.0 bar. The boost pressure maps are likely to be just as varied. Regarding the limitation to 1 bar, it might still be possible, as this would reduce the effective current in both valves - but how the overall control behavior will be...

It's not a simple yes or no! When you examine the actual ratio (of magnetic valve opening to boost pressure) under various operating conditions, you'll see that even in wastegate turbochargers, this ratio changes continuously, although the magnetic valve only becomes significant when the effective boost pressure reaches approximately 0.6 bar. Before that, the mechanical pre-tension of the spring in the pressure chamber prevents anything from moving!
Therefore, the EDC (Electronic Diesel Control) always attempts to intervene, even with boost pressures below 0.6 bar, although these attempts often prove unsuccessful.
Therefore, I thought that perhaps this continuous signal could be used as an alternative way to control a VTG loader.
The fact that the VTG loader delivers 0 bar with a valve that is not energized is not necessarily a critical issue. Rather, it would be interesting to know whether the ambient pressure or a vacuum is then connected to the pressure sensor!

Otherwise, the mechanical incompatibilities certainly don't speak in favor of a conversion. But I would find the attempt interesting!

@all:
Thank you for the information!

Regards,
Alex.

@Bertil:

I also read Mecki's conversion instructions back then.
This only applies to the Audi 80. In almost all other cars, it probably shouldn't cause any problems. I still don't understand where he has his problem and why he changed everything. The 1Z and the AFN are 100% identical. You just have to somehow adapt the exhaust. So, if there was a 1Z in it before, an AFN will definitely fit. I don't know either?!

Golfmann wrote:

The 1Z and the AFN are 100% identical.

Yes and no!
In terms of physical dimensions, it's already not a perfect fit. The exhaust system from the VTG turbocharger requires a bit more space. The attached components (especially the exhaust manifold) are mounted differently on the AFN engine, which means different brackets are also required.

Quote:

You just need to figure out a way to adapt the exhaust.

"That's where the problem lies! If there's a suitable manifold available, you won't have major issues, but in the case of the Audi 80, the AFN engine with the VTG turbocharger was never produced in series, so there are no corresponding parts available. The wastegate turbocharger is secured with 4 screws, while the VTG turbocharger only has 3 screws - which means you'll have to fabricate a manifold."

Quote:

So, if there was a 1Z engine in it before, then an AFN will definitely fit. I'm not sure though?!

Assuming you can find a suitable exhaust manifold that fits the space, it shouldn't be a problem.

Even if we disregard the manifold and the valve's resistance, I still see problems if the old control unit is used.

The goal of the modification should be to achieve more torque in the lower RPM range through increased boost pressure, right?

However, your engine control unit (ECU) will use a different characteristic curve, specifically the one calibrated for the wastegate turbocharger. This means: even if you were to resolve the installation issues and the VTG (variable turbine geometry) adjustment were working perfectly, you wouldn't gain anything, because the ECU would regulate the pressure via the VTG to precisely match the target pressure defined in the characteristic curve.
The downside of the whole thing is that you've introduced another potential point of failure – the VTG adjustment mechanism, which is prone to contamination.

You will only start to see benefits if you change the characteristic curve for the boost pressure.

*** DUST ***

After a long time, I'm once again having the same idea for a renovation .

Detailed research has revealed that the turbocharger flange diameters and/or mounting positions require new connecting pipes on both the intake and exhaust sides.

The largest mechanical incompatibility is at the connection between the turbocharger outlet and the exhaust pipe, because the VTG turbocharger uses a 3-hole flange where the wastegate normally has a 4-hole flange. Regarding the length, position, and relative installation of the exhaust pipe compared to the wastegate on the EGR system, I (currently) cannot make any statements.
The simplest, but also most expensive, solution would be to replace the entire exhaust pipe, including the catalytic converter, with a suitable replacement. Another option would be to detach the 4-hole flange and weld on a 3-hole flange. Alternatively, it might be possible to have a spacer plate manufactured that acts as an adapter between the 4-hole and 3-hole flanges.

Regarding the control strategy, I imagine that the MSG (Motor Steuergerät - Engine Control Unit) might not have any issues with the VTG (Variable Turbine Geometry) turbocharger, because it continuously outputs changing values for the duty cycle, even though these values have no effect on the wastegate below 0.6 bar.

Is there any experience or information available on whether the existing solenoid valve N108 can also be used for vacuum control?

Please find attached a small diagram that illustrates the potential for torque increase in the lower speed range (difference between the target and actual values).
The extent to which there is actual potential in the low RPM range also depends on the difference between the actual injection amount and the maximum possible injection amount. I will perform a comparative logging between ALH and AGR engines to investigate this further.
I might also want to compare the AGR-MSG (Abgasrückführungsmessgerät) with the magnetic valve from an ALH engine sometime.
Exciting new possibilities with the expanded TDI vehicle fleet .

I am, in any case, confident that it will work .

Regards,
Alex.

EDIT: I've added a diagram that clearly shows the load-dependent (LD) control behavior of the AGR (wastegate) compared to the ALH (VTG). The somewhat sluggish response of the VTG turbocharger in the ALH has improved. However, my main focus is on comparing the control behavior, which can be seen in the curves of the duty cycles. I believe that the AGR control unit should also be able to handle a VTG turbocharger.

Hello everyone!

I'm also interested in another question related to this topic.
Do you think it's possible to get this turbocharger conversion approved? In my opinion, it shouldn't be a problem, because the modified turbocharger only allows the engine to reach the target load values slightly easier, without increasing the maximum power output or worsening the exhaust emissions.
Furthermore, only original VW/Audi parts with the appropriate type approval would be used for the conversion.

Regards,
Alex.

'With every structural modification, the vehicle's approval expires. Since the turbocharger is not standard equipment with this engine, a special inspection is required... and that costs a significant amount of money.'

I wouldn't have that installed if I were you. If it's professionally installed, nobody will probably notice. However, you would then only be allowed to drive the car outside of the traffic regulations.

Hello fellow DIY enthusiasts!

Has anyone here actually tried running a VTG turbocharger using a wastegate control unit?

If you can't get the VTG turbocharger registered for use with the AGR system, perhaps you could completely convert the AGR system to a conventional air-cooled heat exchanger (AHC). That would leave only the injectors and the control unit, resulting in a "normal" AHC system, which was standard in the A3 from 1997 onwards. Okay, to be precise, there are still a few more small parts involved, such as the modified exhaust pipe, the air ducts to and from the turbocharger, the magnetic valve for boost pressure control, the vacuum reservoir, and a few other minor components.
Could that possibly work?

I actually find variant 2 even more appealing, because you officially get the increased performance registered, and the way is open for further performance enhancements with an ABE (German approval) towards 130-140 horsepower.

Regards,
Alex.

@donalexo

I think it's often the small, seemingly insignificant details that cause problems with the TÜV (German technical inspection authority). Therefore, I would suggest visiting them beforehand and getting a feel for how they view such modifications.

Enjoy your meal!

In the PRG.

http://www.prga.de/

It has a VTG turbocharger, but the swirl chamber engine doesn't have an exhaust gas recirculation system anyway.
The adjustable valve is set to maximum boost pressure in its default state and is adjusted using...
As the pressure increases, a pressure relief valve directs the flow towards an area of lower pressure.
It probably wouldn't be very useful for a regular road vehicle.

Alternatively, the VTG (variable geometry turbine) could be controlled separately using a vacuum cylinder/solenoid valve and a...
"Connect to a self-built circuit; there were some considerations about this on www.fmso.de."
because some of us (including myself) would like to have a VTG inside.

I cannot say to what extent this solution is compatible with control units, etc.

Hi, Jockel.