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Boost Pressure Limiter: Explained & Benefits

 
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mm7637



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Post04-01-2007, 15:59    Subject: Boost Pressure Limiter: Explained & Benefits Quote

Hello,
I drive a SEAT Ibiza TDI with 90 horsepower, manufactured in 1997, which has a wastegate turbocharger.
Er hat nun folgenden Fehler: Beim Beschleunigen im 5. Gang wird ab ca 2700U/min schlagartig die Leistung deutlich dauerhaft reduziert. Wird die Zündung abgeschaltet, ist der Fehler wieder behoben und kommt erst wieder beim Erreichen der 2700U/min. Im 4. Gang wird bei ca 3000U/min abgeregelt. Nachdem ich mich in diesem Forum eingelesen habe, habe ich vermutet, daß das Ladedruckregelventil N75 nicht korrekt funktioniert und die Motorsteuerung den Motor vor zu hohen Drücken schützt. Heute habe ich das Ventil demontiert. Im Schlauch zur Druckdose und im Ventil selbst befand sich Öl. Den Schlauch habe ich temporär nach unten verlegt und mit Druckluft versehen. Das Öl wurde dadurch herausgeblasen. Die Regelstange hat sich auch bewegt, allerdings kann ich nicht sagen bei welchem Druck. Ich habe jetzt die Druckdose direkt mit dem Ladedruck beaufschlagt und das Ventil N75 elektrisch angeschlossen aber nicht mit den Schläuchen. ( bei der Demontage habe ich leider einen Anschluss abgebrochen). Bei der Probefahrt konnte ich keinen Fehler mehr feststellen, Leistung war vorhanden, konnte aber auch nicht Höchstgeschwindigkeit prüfen sondern nur die Geschwindigkeit an einem Berg im 4. Gang.
Are there any disadvantages for the engine due to this simplified regulation?
Does the modification affect fuel consumption or exhaust emissions (ASU)?
Best regards,
Martin.


Translated on 19-10-2026, 22:04.
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dieselmartin
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Post04-01-2007, 16:29    Subject: Boost Pressure Limiter: Explained & Benefits Quote

What exactly did you do?

What does "relocated downwards" mean?

Are you now connecting the pressure hose directly from the turbocharger compressor to the pressure sensor?
If you've created this "short circuit," you'll only be running with 0.6 bar of boost pressure instead of 0.9 bar, and therefore not at full power, because it's definitely being regulated by the Russian border.

Which nipple did you break off?

Please describe your process in more detail.
- "nach unten" sagt nichts, denn Schlaeuche kann man verlaengern bis in den 2. Stock icon_smile.gif
- Which nipple did you break off?
- for N75 -> buy new.
- on the compressor - It's just a bolted flange, but it's made of metal, how do you break it off?
- on the pressure sensor - that was stupid because it was expensive == new turbo!

Pictures often speak louder than words.

m;

EDIT: Sorry, I had to read the unstructured text twice before I understood it. You now have 0.6 bar of boost pressure (assuming the turbocharger, including the pressure sensor and wastegate, is functioning correctly), which means you're no longer producing 90 horsepower, more likely around 70 or so.
Transparency, Teamwork
... there was another T.

I don't know what the f*ck it was.


Translated on 19-10-2026, 22:07.
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Rudi
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Post04-01-2007, 17:24    Subject: Boost Pressure Limiter: Explained & Benefits Quote

Whatever icon_twisted.gif.

The N75 valve is the cause of the error 99.5% of the time!
Neu kaufen und gut. Costs approximately 33€.

Best regards,
Rudi

P.S. And please fix that short circuit.

edit: @Martin:
The pressure canister for the waste compactor is available separately (for somewhere between €120 and €150).


Translated on 19-10-2026, 22:09.
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dieselmartin
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Post04-01-2007, 17:54    Subject: Boost Pressure Limiter: Explained & Benefits Quote

@ Rudi

Good luck to Martin, but...

Quote:
Starting 03.02.07: Passat Variant Sportline 2.0 TDI 16V DPF with 170 horsepower.


icon_mrgreen.gif
Transparency, Teamwork
... there was another T.

I don't know what the f*ck it was.


Translated on 19-10-2026, 22:10.
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Post04-01-2007, 18:27    Subject: Boost Pressure Limiter: Explained & Benefits Quote

Sure (traitor icon_mrgreen.gif).
It referred to the possibly detached nipple icon_wink.gif.


Translated on 19-10-2026, 22:10.
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simsoni



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Post17-01-2007, 7:05    Subject: N75 Valve: My Experience and Tuning Guide Quote

Hello everyone.
I also have a Golf 3 with a 1Z engine, and I'm experiencing the same symptoms around 3000 RPM. In the forums, people often point to the boost valve. I tried it, but it didn't do anything. In my case, the engine doesn't stall; it just loses power. If I release the accelerator and then press it again, it starts working again. You can keep doing this until you reach the top speed.
By the way, the error memory continues to show error code 575.

Greetings to the rest of the nation.


Translated on 19-10-2026, 22:11.
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