[Nati0n]

Haven't found much information online about this, I know manufacturers don't readily publish this type of information outside of internal documentation, but what are the specifications on the N55 turbo in the M235i? I know it's a twin-scroll unit but not much other than that. I also saw a thread suggesting these were made by MHI? Do these differ between the N55B30O0 in the M235i and the N55B30M0 in the 335i and other 35i platforms?

Thanks.

[BMW GENIUS]

I believe they are of Borg Warner Turbo Systems but I'm not 100% sure which model they are.

[allthatisntnow]

I think the unit is a Borg Warner B03

http://www.borgwarner.com/en/News/Pr...wGasEngine.pdf

Not sure if the compressor was increased in size for the higher output variants of the N55 though.

[Nati0n]

From this Australian website http://australiancar.reviews/bmw_N55.php :

The N55 engine had a journal bearing Borg Warner ‘B03’ turbocharger which had a custom version of the smallest Borg Warner EFR billet compressor wheel (62 mm) and custom inducer sizing. For the N55 engine, maximum boost pressure is understood to be around 0.61 bar (8.8 psi).

In vehicles fitted with a twin-scroll turbocharger, the exhaust manifold separates the channels for cylinders that can interfere with each other, so that the pulsating exhaust gases flow through separate spirals (or scrolls). For the N55 engine, cylinders 1-3 (bank 1) and cylinders 4-6 (bank 2) were paired together. As a result, the low pressure tail component of an exhaust pulse could be used to extract all the combustion products from the cylinder head, and, induct the intake charge during periods when both intake and exhaust valves are partially open.

Because of its turbocharging, the N55 engine had a pressure-limiting crankcase breather so that oil would not be drawn in through the breather into the intake manifold as a result of high vacuum pressures.

Below they list the N55B30O0, the upper output model in the M235i, as being relevant to this white-paper. So seems like that information above is correct. Interesting that it runs the same boost at 8.8 psi as the N54, I believe.