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      08-03-2013, 10:13 PM   #21
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Drives: 2011 335i X-Drive
Join Date: Apr 2012
Location: Colorado Springs

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N55 Data Sheet

Overall I would recommend reading the data sheet for the engine to determine the differences yourself and make your own call. I will try to attach a copy. When discussing reliability it appears that the connecting rods to the pistons have been redesigned to better distribute the load placed on them. The VANOS oil passages in the engine are less complex, the oil management of the engine has had multiple overhauls compared to the n54 with changes to the crankcase and oil pan, and oil pump. It mentions that the HPFP is still the same design as the N54, and covers the difference in the fuel injectors from the Piezo-electric ones to Bosch.

Overall I would be willing to bet that the N55 would be more reliable as mentioned earlier for the simple fact that they took data from the N54 and improved upon many systems. I can't say whether or not the change in forged parts will affect reliability when tuned. Seeing as the engine is currently having issues reaching 400hp due to the twin scroll turbo limitations I doubt you will ever run into power levels that would make these parts a necessity. That is speculation tho. Only time will really tell
Attached Images
File Type: pdf N55 Engine.pdf (3.22 MB, 6652 views)