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Originally Posted by XutvJet
The N55 in M235 and M2 have forged cranks. All other N55s do not. All EWG equipped N55s (mostly beginning in 2014) have S55 forged rods and the S55 rod bearings which are way better than the prior parts used in the earlier PWG N55s.
The open deck of the N55 isn't an issue unless you have plans to push 600whp+.
Same goes for fueling. Unless you plan to push 400whp+, fueling isn't an issue. Luckily, it's a cheap fix if you need the capacity.
The main reason BMW went with the N55 in the 2016-2018 was because the B58 did not meet their requirements for track usage, specifically oiling under high Gs. The N55 in the M2 has the S55 oil pump and sump system allows the motor to handle sustained high G loads. Many of the S55 parts are interchangeable with the N55, but not the B58 as it's an entirely difference generation of motor.
The reason the B58 uses a closed deck block is not because of all out power potential, but rather it's the same block used in the diesel variants. The block of the B58 is super stout, but other expensive internal parts need replacing if you want to push 600whp in the B58 over the long term. The B58, just like the N55 or N54, aren't designed for huge power like so many try to push through. The S55s and S58s are specifically designed to handle big power.
The N55 in the M2 weakest link is intercooling on the track. If you plan to track these cars, a larger intercooler is a must. Cheap and easy fix.
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Well said. So stock for stock there isn’t much difference betweeen the two. Yes the b58 has more power but it also has a difficult to access timing chain and vanos if something goes wrong and yes the N55 sounds much better. Open vs closed deck doesn’t matter day to day until you tune it.
If you plan to track it, yes the N55 can suffer in tight turns but the N55-M2 solved that.
I’m not sure how good the B58 oiling system is, can someone chime in?
There are many high mileage N55 engines, especially with the updated bearings