Quote:
Originally Posted by red-sauerkraut
The N55 has 1 Variable Turbo, being dubbed the Twin-Power, because of it's Duel Function.
The N54 [Twin-Turbo] will be replaced by the N55 [SINGLE Twin-Power TURBO] because of the fuel saving it is capable of.
The new series of High-Revving Turbo 4 Bangers, most likely will see the same Twin-Power Single Turbo application.
The 2011 X3 being built on the up and coming 2012 3er Platform, may indeed see the first application of the new N55 Motor.
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Wrote an article on the N55 for the local chapter BMW CCA mag. it incorporates Valvetronic (they managed to squeeze it into the cylinder head with double Vanos, spark plugs and direct injectors - phewwww!).
The Twin-Power turbo is basically the same turbo that's used on the V8 - it's a twin scroll (two chamber) on the exhaust side. So rather than an exhaust pulse arriving every 240 degrees of crank rotation (as on the individual turbos of the N54) an exhaust pulse arrives every 120 degrees of crank rotation. That allows peak /RPM/ should read
torque/ to occur at 1200 RPM, so it is less 'lagy' then the N54.
The Valvetronic allows the engine to go 'throttleless' after startup, that's where the fuel savings comes in.