Beiträge von RobertRO

Zitat von AndiG

NOACK is determined at 250° and constant air flow over a period of one hour

where in the engine do you have such "conditions"?

English: Allow me to quote from the "Optical measurement of the valve temperature" article of Mr. Johannes Wüst and Mr. Maximilian Fischer (I wonder why would they write in English, but never mind):

Measurement range from up to approx. 500 degrees Celsius for intake valves and approx. 900 degrees for exhaust valves, with a sensor ambient temperature of max. 125 degrees centigrade.

Correlated with information from other sources, I conclude that it is actually quite common for the intake valves to reach temperatures of 250° or more. Regarding the constant air flow, while it is not constant, there sure is a lot of air flow over those valves. Bottom line, the NOACK test cannot be ruled out as irrelevant in a GDI engine.

Regarding the Addinol Super Light 0540 oil, since you mentioned that its has a fairly high NOACK value, this actually sustains the second opinion in the first post: the higher the NOACK value, the lower the valve deposits.

German, automatic translation by Google: Erlauben Sie mir, aus dem Artikel "Optische Messung der Ventiltemperatur" von Herrn Johannes Wüst und Herrn Maximilian Fischer zu zitieren (ich frage mich, warum sie auf Englisch schreiben, aber egal):

Messbereich bis ca. 500 Grad Celsius für Einlassventile und ca. 900 Grad für Auslassventile, bei einer Sensorumgebungstemperatur von max. 125 Grad Celsius.

Korreliert mit Informationen aus anderen Quellen schließe ich, dass es tatsächlich ziemlich üblich ist, dass die Einlassventile Temperaturen von 250° oder mehr erreichen. In Bezug auf den konstanten Luftstrom, obwohl er nicht konstant ist, gibt es sicher viel Luftstrom über diese Ventile. Unterm Strich kann nicht ausgeschlossen werden, dass der NOACK-Test in einer GDI-Engine irrelevant ist.

In Bezug auf das Öl Addinol Super Light 0540, da Sie erwähnt haben, dass es einen ziemlich hohen NOACK-Wert hat, stützt dies tatsächlich die zweite Meinung im ersten Beitrag: je höher der NOACK-Wert, desto geringer die Ventilablagerungen.

(sorry, this is in English)

I start this thread to discuss about two divergent opinions regarding the relationship between NOACK oil volatility (evoporation) and intake valve deposits on gasoline direct injection engines.

The main (which is also the intuitive) opinion is that an engine oil with a lower NOACK evaporates less, therefore there will be less deposits on the intake valves.

However, there's the other (opposite) opinion, stating that intake valve deposits are not actually caused by the oil vapors (gas), but by the oil droplets (liquid) that escape the positive crankcase ventilation (PCV) system. According to this theory, the lower the NOACK, the more time the liquid droplets spend on the intake valves (due to slower evaporation), thus giving enough time to the oil components and contaminants within the droplets to deposit on the valves. Going ahead with this logic, it means that in order to reduce the intake valve deposits it is best to use the oil with the highest NOACK and lowest SAPS. It may be counter-intuitive, but I must admit that it does make sense.

What is your point of view on this subject?