2012 Z4 35is

N54: two turbos. N55: one turbo, siamesed inlet scroll. "Twin Power Turbo" is BMW-Speak for "They'll Pay More If They Think There Are Two!"

If your service writer thinks the Z435is has only one twin-scroll turbocharger, then he is an idjit. Or I am. Or I was drunk and passed out when they changed everything.

Here is the confusing data on the Z435is engine:

Here is the N55 Z435i: No, wait---I can't even find a similar page!

But if you go to the link above, you'll see an image of the N54 engine. See those two manifolds? Each feeds a different turbocharger. Count the ehausts and cats.

Well, you have to admit that BMW seems intent on obscuring the differences between the N55 and the N54 engine, and their "Twin Power" bullshit doesn't help. At first I thought the N20 four might have two turbos, because BMW makes a two-liter four-cylinder DIESEL with twin turbos, but noooo---the N20 is sort of an N55 with two cylinders lopped off.

Here's what BMW said when the N55 engine came out for the 2011 models:

Beginning with model year 2011 production, several BMW models (135i, 335i, 535i, 535i Gran Turismo, X5 xDrive35i, and X6 xDrive35i) will switch to the new, single twin-scroll turbocharged inline-6 “N55” engine. The newest BMW inline-6 engine is the first BMW inline-6 to combine turbocharging, High Precision direct fuel injection, and Valvetronic variable intake technology. It features a single, mid-sized turbocharger with a “twin-scroll” housing to boost performance and minimize the response lag. Together, this combination produces the same at 300hp and 300 lb-ft of the previous N54, but the fuel efficiency improves and the emissions are reduced.

A further advantage of turbocharging is that this is the most weight-efficient method to boost engine power and performance. The N55 turbocharged inline-6 weighs approximately 150 lbs. less than an equally powerful eight-cylinder engine displacing 4.0 liters. This lower weight means a significant advantage not only in fuel economy, but also in balancing the car's weight distribution.

Using Valvetronic for the first time on a turbocharged inline-6 allows the engine to “inhale” air for combustion with virtually no delay and with reduced pumping losses. As a result, the engine makes power more quickly than ever before, and this is proven by the N55’s ability to reach peak torque at 1200rpm, 200rpm earlier than its twin-turbo predecessor [N54].

They also mention the "turbocharger system" for the Z435is, but again carefully avoid mentioning the difference between the N54 and the N55 engine. Since the N4 is now reserved only to the 1 Series M coupe and the Z435is, you have an extremely rare BMW ("rare" does not necessarily imply valuable, just scarcity). And your particular car in Atacama Yellow (part of the Citrus Yellow package) is the only BMW extant that had me pondering a new car---except that it was unavailable with a six-speed manual.

Maintain it religiously and drive it forever. You got a good one!

Heh! I'm laying out the flame designs already! (Ghost flames using just a hint of red pearl; they'd be invisible until seen in exactly the right light, when they would appear a reddish oarange. . .)

I must admit that when we redid the Motorsport stripes on my white car, and laid ghost flames over the stripes, Party A was rather insistent that they be subtle. That's why I have to point them out to people who otherwise would never see them! "See? See? Just bend your head over this way. . . now squint. . . ."

You have an N54 E89 that's faster than my M roadster and you want MORE PERFORMANCE?!

As soon as you're out-driving the car beneath you, then we'll talk. And no #$%! air filter enters into this conversation. I'd ask Stevie D if the programs he wrote for the N54 335i will work in the Z4...

Oh.
My.
God.
I just got it: BEE MW because it's YELLOW! Like. . . like a BEE!
Somebody shoot me...