Strange questions about VTG turbocharger pressure regulation!

We all know how the charge pressure control system works on a VTG turbocharger, but I still have a question that I just can't figure out on my own!

When I start the engine, the VTG rod is pulled inwards by the vacuum that is then applied.

Now, the loader is essentially in the max. charging pressure build-up position!

But why isn't it building any boost? Even with the exhaust gases at idle, it should actually start building a small amount of boost! Or are the exhaust pressures at idle too low?

Furthermore, there's the boost pressure control valve, also known as the pressure transducer, which costs around €80. Alternatively, there's also an N75 pressure transducer available for around €30! (Vehicle identification number dependent).

What's the difference there?

Can I install the N75 myself if it's defective? The 130PS TDI engine, for example, hasn't been changed, but depending on the vehicle's chassis number, either the pressure sensor or the N75 valve is installed.

Regards,

Manuel.

But why isn't it building any boost? Even with the exhaust gases at idle, it should actually start building a small amount of boost! Or are the exhaust pressures at idle too low?
You have answered that question excellently yourself. Yes, at idle, the amount of exhaust gas is simply too low. The turbocharger can only function properly when significantly more exhaust gas comes out than fresh air goes in. The more diesel is injected, the hotter the exhaust gases become. And this either results in more pressure or more volume. This allows them to better power the loader.
The amount of fuel injected during idle is simply not enough to drive the turbocharger. Even if you keep the engine running at 3000 RPM in neutral, so little diesel is injected that, in my opinion, it probably wouldn't be enough to build up significant pressure.

Unfortunately, I don't have any information about the pressure transducer.

Regards,
Private.

Sure, here is the translation of the text from German to English:

ad 1.
I also think that the exhaust gases at idle are too slow and too weak to provide enough pressure to the turbocharger.

Regarding point 2: Is the N75 sensor NOT the pressure sensor?! Do you have part numbers that indicate a difference?

For Wastegate chargers, the N75 valve is that clattering metal thing (part number 028 906 283 F) that regulates overpressure. And for VTGs (Variable Turbine Geometry), it's the same or a similar component as found in all AGRs (which regulate underpressure).

I haven't noticed any difference so far.

m;

Hi,

With a warm turbocharger, I see a boost pressure of around 10...20 mBar at idle, so the turbocharger is already spinning a bit. When it's cold, the pressure is approximately -10 mBar.

I'll test what's causing the 3000 RPM idle tomorrow when the car is warm.

Even at 55 km/h with 1100-1200 RPM in 5th gear, the turbocharger boost pressure is relatively low, around 70-80 mBar.

Best regards,

Jan.

Regarding point 2: Is the N75 sensor NOT the pressure sensor?! Do you have part numbers that indicate a difference?

m;

Sure: My example car: Skoda Octavia, model year 1998, engine code ASV, 110 horsepower, TDI.

Up to part number FGNr 1U-X-208 700: Pressure sensor 1H0 906 627A, approximately €80.
Starting from part number 1u-x-208 701: Pressure sensor N75, part number 1J0 906 627A, approximately 30€.

Regards,

Manuel.

I suspect it's simply related to warehouse logistics.

The first three digits indicate the vehicle type.

1H refers to the golf model produced up to 1998.
The Golf Jetta is the model designation starting in 1998.

therefore: both valves are exactly the same.

It is similar in many tax-related devices.

CU Gremlin.

Hoelle, those people at VW must be crazy!

I had someone look for the valves for the 2001 ASV.
I can confirm the change from registration number 1J-X-999 000 to 1J-Y-000 001.

1H0 906 627 (AGR valve) - EUR 83 (already installed in the 1Z model).
1J0 906 627 (AGR valve) - EUR 33.

1H0 906 627 A (VTG Valve) - EUR 111 (from AFN models).
1J0 906 627 A (VTG Valve) - EUR 33

It's also interesting to note that in the AGR engine, the N75 valve, which controls the wastegate, was also changed with this part number.

028 906 283 J EUR 32
on
028 906 283 N EUR 30 (or 028 906 283 P)

1Z, AHU, and ALE were offering the 028 906 283 F for 32 EUR.

m;

It's interesting that the part number 1HO, which originally came from the Golf 3, was still used in the Golf 4, at least until 1999. That probably only applies to a few parts.

Why is there such a price difference then? To my knowledge, the supplier is still Pierburg. Or are the valves actually different (e.g., with a different cross-section, different timing, etc.)?

Consequently, one would also expect to find changes in other components within the vacuum system: (vacuum pump, pressure vessel, vacuum sensor from the turbocharger/EGR valve). Perhaps the software in the control unit has also been modified.

Given the price difference, it's probably worth buying the cheaper one first.

The only indication of the manufacturer is:
028 906 283 N is from Pierburg, while 028 906 283 P is from BOSCH, but they cost the same.

The reason for its use is likely also due to the fact that models G4 and G3 were produced simultaneously (in 1999, the G3 was the only variant available).

But even in the G2, there are still 1987 "G1" parts installed, for example, the rubber ball in the gear linkage has a part number 171!!!

I would also buy the cheaper one, especially considering the price difference of 111 to 33 EUR!

m;

Hi,

"These parts are all manufactured by Pierburg, and each one has a different part number within the Pierburg catalog, for example:"

AFN 04.96 - 08.97 7.21903.75.0 Electrical/Pneumatic. Wastegate (EPW) boost pressure.
AFN 04.96 - 08.97 7.21903.70.0 Electrical-Pneumatic. Converter (EPW) AGR.
and
GOLF IV VARIANT (1J5)
1.9 TDI (81 kW)
Part No. >1J-X-999 000 AHF/ASV 05.99 - 06.01 7.21903.75.0 *6) Electric-Pneumatic Converter (EPW)
Part No. 1J-Y-000 001 > AHF/ASV 05.99 - 06.01 7.22903.04.0 *6) Electrical/Pneumatic. Converter (EPW)
Part No. >1J-X-999 000 AHF/ASV 05.99 - 06.01 7.21903.70.0 *7) Electro-pneumatic. Converter (EPW)
Part No. 1J-Y-000 001 > AHF/ASV 05.99 - 06.01 7.22903.01.0 *7) Electrical/Pneumatic. Converter (EPW)
*6 Turbocharger boost pressure
*7 Exhaust Gas Recirculation (EGR)

The list comes from the Pierburg website, and the parts should be available with those numbers from parts suppliers, making them likely cheaper than buying them directly from VW.
Since Pierburg uses different part numbers as the manufacturer, I assume that the parts are actually different.

greetings
dieter

"Hey, does anyone know if the part number N75 1H0 906 627A is the same?"
How to replace the AGR valve (exhaust gas recirculation valve) with part number 1H0 906 627, without the "A".

I need to swap them around for troubleshooting purposes. The things look completely the same except for the A.

Steffarn wrote:

Do you know if the N75 1H0 906 627A is the same? how the AGR valve

1H0 906 627 without A.
According to Tec Doc:

NOT the same, despite A.
1H0 903 627A = 7.21 903.75.0 replacement for 7.21 903.05.0, also compatible with 903.15.0, 903.25.0, 903.25.1, 903.25.2, 903.25.5.
1J0 906 627A = 7.22 903.04.0 replacement for 7.22 903.25.0...903.25.2

Another one.
without A = 7.21 903.70.0 ers. 7.21903.20.1.., 20.1, .20.2, ..20.3, ..20.5
I hope I've been helpful.
derteileklaus