Quote:
Originally Posted by mkoesel
I've been a bit skeptical of this claim since it was first published.
First of all he asserts that the older engine - the N54 is the only one he could be referring to based on his words - is no longer in production which we all know is flat out wrong. It is still in use in the Z4 35i and 35is.
Secondly, with Valvetronic, the B3 engine is no more an N54 than an S55 is, which is to say not an N54 at all really. If you remove everything bolted to the head, its basically an N55, no? I mean, I don't know whether they use a bone-stock N55 long-block or upgrade some of the internals such as timing assembly or cams or what have you, but why even talk about the N54 at all? In my mind they've taken an N55, removed the turbocharger and all supporting equipment, and replaced it with a twin-turbo setup.
If I recall there was some claim elsewhere about them using an N54 block casting, but it's not clear why that would even be necessary, and even less clear that it would effect the character of the engine anyway. And for that matter, it's not even clear what the difference is between an N54 and N55 block to begin with - or indeed if there is any difference at all. I guess I could easily answer that last part by looking it up in one of the parts databases.
In the end, if this engine has Valvetronic (and by the way, I don't know if Alpina even states anywhere that it does, do they? Not sure TBH), then its an N55 with TT setup much like the S55 although without the new closed deck block and other reengineering BMW has done to the rest of the long-block.
That all being said, there is every reason to believe that the S55 will be as responsive if not more so than the B3's TT N55. I just don't like the wonky over-romanticized embellishment about rescuing the N54 from the trash bin or whatever.
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Yeah, that quote is probably inaccurate at best
My interpretation is that they have the tooling to cast the exhaust manifolds.
The official thread on the Alpina B3 also states that it's a N55 with twin turbos:
Quote:
The prerequisite for these impressive values is a high-tech engine which exhibits its own unique characteristics thanks to a significant number of stand-alone features. The goal of the engineers from Buchloe was to achieve excellent responsiveness, high output across the entire rpm range and an improvement in fuel consumption. The ‘Bi-Turbo’ engine configuration arose not only out of tradition. More to the point, this type of turbocharging has the advantage of providing very good response and pick-up due to the low mass moment inertia of the turbocharger’s running gear and sufficient rate of air-flow for spontaneous power delivery.
The design and construction of the excellent BMW 3.0 litre straight-six cylinder (N55) engine serves as a starting-point for a specially cast aluminium crankcase with Bi-Turbo capable flanges. These enable the mounting of two turbochargers along with required oil and water connections and a close-coupled catalytic converter arrangement. ALPINA specific NGK spark plugs and a forged steel high-strength crankshaft guarantee long-lasting stability.
Always-on power delivery and excellent throttle response are aided by an electronically controlled bypass valve system. Specially constructed and de-throttled, i.e. flow and cross-section optimised, air intake ducts guide the air with minimal losses from the air intake via the air filter housing to the turbochargers. On the fuel side, a high-performance high-pressure fuel pump ensures the right throughput. Optimal utilisation of the output is provided by a high-capacity intercooler with flow-optimised collector boxes made from aluminium. Coolant cooler, addi- tional separate coolant and engine oil coolers as well as a high-performance 850w cooling fan ensure the thermal stability of the cooling system in all conditions.
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http://www.f30post.com/forums/showthread.php?t=811899
So, the B3 N55 has many of the S55 features such as twin turbos, electronic wastegate and forged crank.