Unless you are a Bimmerhead that title probably makes no sense, but if you are a Bimmerhead you probably know all about it…..except maybe for one little detail.

That little detail is that the N54 isn’t actually going away. But more on that in a second. First some background for the non-bimmerheads:
The N54 is the engine currently in BMW’sY35 models (insert 3,5,Z4 etc.. for Y). We have one in our long term 335 and love it. In simplified form it is a twin turbo 300 (maybe more….depending on rumors) horsepower 6 cylinder engine.
The N55 is a single turbo 300 horsepower 6 cylinder engine. It is also going to replace the N54 engine.
The reason BMW is doing this is not really known. It may have to do with weight (the N54 weighs about 50lbs less). It may have to do with cost (there are rumors that it is cheaper to make….one turbo…less material cost….). It may have to due with HPFP (do your self some Google’ing…there have been problems with fuel injection on the N54). I may be that the N%% doesn’t match to the DCT transmission that well (but that seems strange).
The point is we really don’t know why they are making the change. We had figured BMW had a good engioneering reason to do this and that some how it was a better performance solution. We hoped it wasn’t just an accounting move. We also had thought that when this was first announced (announced may be wrong….rumored) a few months ago that the N54 would be going away. But that bring us back the the little detail we were talking about. The N54 isn’t actually going away.
The N54 will just be used in performance applications. Wait? What?
Yep. The N54 will now be found in the new ISes (Flandereseses). We first told you about the Z4 IS the other day. Basically the new IS versions will be uprated versions of current cars to slot in between them and their M brethren (or in the case of the Z4 as the top model). In that application the N54 will produce according to BMW 340 horsepower and have overboost that brings the torque up to 369lbft.
So that is where the mystery lyes. If the N55 is a better engine, why are they still using the N54 in performance applications? Or is BMW not a performance car company any longer?
The N54 has widely been hailed as a great engine. It is easy to modify and add lots of power to. BMW itself seems to think it is the best choice for a performance car. So why the change?
We don’t know.

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The N54 is also spec’d for the brand new 740i and 740Li, per a press release that called the engine a “twin turbocharged” I6, rather than the using the amusing “Mono Turbo” or “TwinPower Turbo” monikers.
I don’t buy the excuse that “the N55 doesn’t need two turbos because its single turbo is a twin scroll unit.” It has to be a cost and weight savings thing, right? Because basically, all the serious BMWs are keeping the N54, and it’s not just existing models – newly introduced serious BMWs are geetting the N54.
It is also worth noting The N54’s 300hp/300lb-ft numbers are widely thought to be underrated. I think I’m on pretty safe ground predicting that the N55’s 300hp/300lb-ft numbers are not.
I pretty much agree with you….that is why it is somewhat concerning to see them switching to the N55. BMW is supposed to be the ultimate driving maching. But maybe now the M models and IS models will be, but not all of them.
BMW has always offered varying degrees of power, and cost has been a factor in the content of the vehicles since the 1st Lexus LS400 debuted. So I don’t think this development tarnishes the Ultimate Driving Machine mantra. An EU market E38 728i was arguably underpowered, but was still a satisfying drive for an enthusiast minded individual.
Big power is nice, and I certainly want my BMW to have an N54 rather than an N55, but big power isn’t an essential part of the Ultimate Driving Machine recipe
Fair enough. You could still make the argument that the popular EU models are all underpowered (i.e. they sell a hell of a lot more 318’s than 335s)
So which engine is the 2010 335i Sedan using?
The 2010 335i Sedan has the N54 (i.e. the twin turbo) engine. The 2011 though will have the N55 engine (the new single turbo).
Sounds good, because I just went out today and ordered a 2010 335xi Sedan. I hope I’m making the right decision.
I have the fastest, quickest N54 on the planet, in a 135i, according to Dragtimes.com and the enthusiast forums: 11.2 ET @ 127 MPH …. over 500 WHP with stock turbos and a bunch of bolt-on mods. I can say the N54 has a lot of potential … but stock is not overrated at 300 crankshaft HP. Stock, my 135i recorded only 258 HP at the rear wheels. Add the JuiceBox3 tune, and other items, and it goes up from there.
Think about this one people…already talk from the big wigs, through the grapevine, as to why the replacement…not only to comply with better emissions standards as well as the public’s yearning for better mpg, but it’s all about the money! Cheaper to produce and potentially maintain. If they could, they would’ve put n55 with more power in the IS cars but the N54 performance kits have passed US and international emissions standards long ago…meaning they have paid their dues for standardizing it already. That just means they’re trying to get the last invested drops out of this powerplant because it is cost effective and they don’t need to pay to re-standardize an n55 with more power (it costs millions of dollars to do this). Car companies are being very careful how they spend their money these days. A little birdie already told me a stock N55 is out performing the N54 /w an oem performance kit on the track,,,45lbs lighter and more responsive out of the corners…not to mention it runs much cooler than an n54
Yowza!
Interesting info