[ocarioca1m]

So the N55 is the single turbo engine that came after the N54 wich was a monster when tuned. So they removed one of the turbos and made a very reliable and cleaner running engine. Nice, or not so much. Since when tuned the N54 would make easilly over 50bhp over the N55. Now every performance N55 that is breaking the 400bhp barrier is a twin turbo like the M3/M4 and the Alpina. So how come there hasn't been a thread discussing this here? I mean there are ongoing big turbo projects going on but none working properly so far. So how come no one has been looking at this. The N55 is present throughout the entire BMW range.
So anyways I just wanted to start a little discussion on this. I'd love to hear what everybody thinks about this.

[Billetboosted]

Except for the new M3 and M4 the N55 is the same for all other BMWs. Some guys are over 400hp and theyre still single turbos.

[FeckinSpaceman]

Pretty sure the new M3 and M4 are the S55

[nemith]

The number of turbos doesn't really matter. The twins on the N54 were way undertuned to not compete with the M3 of the times so there was just a lot of room for way more boost.

There are 500+ hp N54 cars that have switched to a single large turbo for even more power. The amount of effort it would take to do twin turbos in the N55 wouldn't be worth it. I would imagine the N55 and the S55 being quite different in many regards so there probably isn't a whole lot to do here.

I know there are some efforts to fit a larger turbo to the N55. That is probably your best bet outside of buying an older e90 with the N54 or the new M3/M4 with the S55.

It took years for newer turbos to work with the N54. There is a lot of work to be done, so just be patient.

[RoundelM3]

Other options for increasing power on the N55 would include a more efficient turbine design and possibly a variable-vane design as well. The new M3/M4 engine is more of an evolution of the N54 and will likely stay with two turbos for the additional tuning capabilities.

Much larger turbos, such as seen on 18-wheelers and other diesel applications is that you have to balance the turbine size to the engine's displacement and compression ratio. Turbos are exhaust-driven, and there's just so much exhaust pressure that can be generated by a 3.0-liter engine. The bigger the turbo, the more mass the turbine itself contains and thus the more energy it takes to spin it up to where it provides significant boost. Ceramic turbos have some potential in that regard, but they're significantly harder to manufacture with a resultant higher cost.