Turbocharger for Audi A4/VW Passat AFN, AJM (VNT 15)

I finally installed the large VNT 17 turbocharger from Garrett, and I'm totally thrilled with it!

Almost no boost overshoot, directly 1.1 bar, and the power delivery is incredible!

Here's a brief guide for anyone interested! I'll be revising it again next week. I've now driven almost 1000 km with it, and I'll be able to provide more information then!

http://www.seifert-online.de/passat/VNT17_AFN.pdf

I just measured the cruising speed at 80-120 km/h in fifth gear!

After 3 measurement cycles, I've found that it's 0.8 seconds faster with the VNT 17.

Why? Nothing has been changed in the software!

It's very simple. The turbocharger boost has noticeably improved!

My old VNT 15 turbocharger quickly built up boost pressure to approximately 1.2 bar immediately after the full load command, then reduced it to around 0.9 bar, and slowly increased it again to 1.1 bar.

The new, large VNT 17 turbocharger goes directly to 1.1 bar and stays there!

I never thought it would have such a noticeable effect!

Cool stuff.

I described the process of changing the AFN engine in a transverse configuration before, and I think it wasn't as much work then. Do you know if it's the same with the A6 regarding the intercooler piping? To be honest, I don't have that information memorized.

Regards,
arne

Yes, it's the same with the A6!

Regards,

Manuel.

Hey, great. Do you also have the T4 nozzles installed?

arne

Hello.

Have you measured the fuel consumption to see if it's noticeably lower now?

I would like to know the exhaust backpressure for a specific boost pressure.

Does anyone have any data here?

I believe that the (too) small VNT 15 loses efficiency at high pressure and RPM, and consequently generates more back pressure than the VNT 17.

I'm still missing some evidence for this theory, but it would explain why your AFN is performing so much better now, even though nothing was actually changed in the injection amount. The increase in performance should be measurable through a decrease in fuel consumption.

What about the 'turbo lag'? Is it noticeably worse now?

By the way, great documentary!

I've only driven 170km since the conversion. It's too early to say much about the diesel consumption yet!

Next up are the T4 injectors. Whether I replace the original ones with new ones due to wear and tear at 250,000 km, or use T4 injectors, it makes absolutely no financial difference!

Regarding turbo lag, I have already expressed my opinion in my PDF document. Since the boost pressure is available 200 RPM earlier, there is no evidence of turbo lag!

I don't think there's any extra power there. The larger turbocharger simply provides boost pressure faster and more consistently!

Doch eines ist Seltsam. Der Verdichter vom 17ner ist nicht doppelflügelig wie der vom 15ner! Why?

http://www.edv-schreiber.at/audi4ever/fdb/pics/489_cd5c9fd3c65a217df4b634198459884f.jpg

Here's the compressor from the 17-inch model:

http://www.edv-schreiber.at/audi4ever/fdb/pics/489_65c515110402d930d1eaafd62a4581ee.jpg

Regards,

Manuel.

Hello Manuel Thomas!

Schöne Doku hast Du da verfasst. Compliment!

Do you perhaps have any data logs taken with VAG-COM that show the different rates at which boost pressure builds up? It would be really great if you could provide them here .

One thing that greatly surprises me is this: Normally, I would expect that a larger loader, whose undercarriage has a significantly higher moment of inertia (since the diameter is raised to the fourth power!), would accelerate more slowly in the lower speed range and only be able to demonstrate its advantages at a medium speed level.

For me, there are really only the following logical explanations for this:

1. The VNT15 loader (what is the mileage?) may have been difficult to operate (possibly due to a carbon-fouled shaft, bearing damage, etc.).

2. The VTG (Variable Turbine Geometry) adjustment of the VNT15 is stuck in the area of one end stop, which corresponds to the most aggressive airflow (maximum torque at the turbine shaft), and therefore cannot provide optimal airflow to the turbine wheel when the engine is running at low RPM.

3. You have created different settings for the actuator rod between the vacuum sensor and the VTG (Variable Turbine Geometry) mechanism in the VNT15 and VNT17 models.

4. The maximum possible range of inlet angles for the VNT17 is greater than that of the VNT15.

5. The design of the VNT17 turbine nozzle is aerodynamically more efficient, resulting in a higher overall efficiency (turbine + compressor).

What do you think about that?

@all:
Does anyone know the reason why a standard AFN engine is set to a boost pressure of 1.1 bar, while a standard AHF/ASV engine, with the same power output, only regulates to a boost pressure of approximately 0.9 bar?

Regards,
Alex.

My series AFN (Air Flow Number) regulates the boost pressure at 0.948. This should also be the general target value for the AFN!

Hello Manuel Thomas!

You've written a beautiful documentary. Congratulations!

Thank you!


Do you perhaps have any data logs taken with VAG-COM that show the different rates of boost pressure build-up? It would be really great if you could provide them here .

Unfortunately, no. My measurements are based on using two different instruments: a tachometer for one eye, and a pressure gauge for the other.


One thing surprises me greatly: Normally, I would assume that a larger loader, whose undercarriage has a significantly higher moment of inertia (since the diameter is raised to the 4th power!), would accelerate more slowly in the lower speed range and only be able to demonstrate its advantages from a certain mid-range speed level onwards.

Well, that surprises me just as much. I was expecting a significant turbo lag! But there's nothing. I think this rule might only apply to turbochargers with a wastegate.


The VNT15 loader (what is the mileage?) may have been difficult to operate (possibly due to a carbon-fouled shaft, bearing damage, etc.).

The VTG (Variable Turbine Geometry) adjustment of the VNT15 is stuck in the area of one end stop, which corresponds to the most aggressive airflow (maximum torque at the turbine shaft), and therefore cannot provide optimal airflow to the turbine wheel in the low-speed range.

You have created different settings for the actuator rod between the vacuum sensor and the VTG (Variable Turbine Geometry) mechanism in the VNT15 and VNT17 models.

The maximum possible inlet angle range for the VNT17 is greater than that of the VNT15.

The design of the VNT17's turbine nozzle is significantly more aerodynamically efficient, resulting in a higher overall efficiency (turbine + compressor).

What do you think about that?

The old loader has reliably covered 226,000 km. It is also still fully functional. The shaft is a bit harder to turn on the old one, but the VTG is easier to move there! Overall, there are many, many
@all:
Does anyone know the reason why a standard AFN engine is calibrated with a boost pressure of 1.1 bar, while a standard AHF/ASV engine, with the same power output, is only calibrated to a boost pressure of approximately 0.9 bar?

Oh, I completely forgot to mention that mine is chipped, which is why it has 1.1 bar of boost!

I'm going to disassemble and clean the old loader this week. Let's see what I find!
Regards,

Manuel.

Hi,

@donalexo:

How do you conclude that the ASV (Abgasrückführungssystem) only regulates to 0.9 bar? In my VAG-COM tests, the target value was always 1999, and the regulated values were slightly above 2000, with overshoots up to 2200.

Even on the LDA, you can see the gauge, which reads just above 1 bar when running at full throttle.

Of course, my ASV (Anti-Slip Valve) is completely unmanipulated, meaning it has no chip, no box, no modification with a 10-cent piece, and no tampering with the VTG rod.

Best regards,

Jan.

I was on the highway today and I need to call my mechanic on Monday.

The car runs cleanly without producing any smoke, but at full throttle and 170 km/h, it's generating a boost pressure of 1.35 bar?

That would mean my old charger was already broken, since it was only producing 1.15 bar of pressure!

Is that okay?

Regards,

Manuel.

Manuel Thomas wrote:

The car runs cleanly and doesn't produce any more soot, but at full throttle, it reaches a boost pressure of 1.35 bar starting at 170 km/h!?

Hi Manuel,

It's possible that the VTG rod is too short for the new turbocharger, which could prevent the boost pressure from being properly limited in the Pmax range.

This should be detectable using data logging with VAGCOM.
If the duty cycle at the solenoid valve is at its maximum (IMO display shows 97%), try extending the VTG rod slightly.

Otherwise, it could also be a software adjustment designed to reduce soot emissions.
But if the VNT 15 was supposed to consistently produce 1.35 bar at the top end, that would have been quite stressful for it .

The strange thing is that it only reproduces when driving in 5th gear, at a speed of approximately 170 km/h!

If it were due to the VTG (variable turbine geometry), shouldn't I experience this issue in all gears within that RPM range? Am I making a mistake in my thinking?

Could 1.35 bar be harmful to the AFN? The VNT15 also had short overboosts into that range!

I still have 300 km of highway ahead of me! I'll try to document everything as much as possible without using VAGCOM.

I'll have someone check the duty cycle. Unfortunately, I don't have a VAGCOM.

First of all, thank you.

Manuel.

Manuel Thomas wrote:

The strange thing is that it only reproduces when in 5th gear, at approximately 170 km/h! If it were indeed due to the VTG, shouldn't I experience that issue in all gears within that RPM range? Am I making a mistake in my thinking here?

From a normal perspective, probably not, but occasionally, the EDC behaves in an unusual way.

Quote:

I'll have someone check the duty cycle, I guess! Unfortunately, I don't have a VAGCOM!

Tapping into the pressure control valve and measuring the voltage (using an analog multimeter!) also seems to work -> a reading below approximately 1 volt indicates that it's fully engaged.

ULF, you're awesome!

I'll try to get to it sometime this week!

I just hope the VTG (variable torque generator) isn't too short. There was so much sealant on it that I'll probably only be able to extend it once the loader is removed!

Regards,

Manuel.

What's actually going on with the ABE?
Does this also expire when...?
VTG is being discontinued from the standard print run.
even if a VNT 17 is installed in the car.