BMW N55

BMW N55 engine
Overview
Manufacturer	BMW, Bayerische Motoren Werke AG
Production	2009–Present
Combustion chamber
Configuration	Straight-6
Chronology
Predecessor	BMW N54

The BMW N55 is a turbocharged direct injection straight-6 DOHC piston engine which has been in production since 2009, being initially launched in the BMW 535i Gran Turismo (F07).^[1]

The N55 generally replaced the N54 in most applications, especially after the release of the N55HP in 2011 for 2012 models, but high-output versions of the N54 remain in production.^[2][3]

While having the same displacement and peak power output as the N54, the N55 is 15% more fuel efficient, has lower emissions, less turbo lag and better low-rev torque.^[4][5]

Design

While its N54 predecessor uses parallel twin-turbochargers, the N55 uses a single twin scroll turbocharger.^[6][7] BMW has used the term "TwinPower Turbo" to describe both twin-turbo and (single turbocharger) twin-scroll systems.

The exhaust manifold design, called Cylinder-bank Comprehensive Manifold (CCM) by BMW, aims to reduce the pressure fluctuations to reduce throttle lag and exhaust back-pressure.^[8] The N55 also adds Valvetronic variable valve lift, a feature missing in the N54.^[4]

The N54's gasoline direct injection system uses piezo injectors, also used in the naturally-aspirated N53 (mostly European markets only), the N55's direct injection uses Bosch solenoid-type injectors. The piezo injectors were more expensive and BMW decided they were not worthwhile in North America, in contrast to Europe which they could perform lean burn to reach their full potential.^[4]

The N55 is mated to ZF's 8-speed automatic transmission in most applications such as the 2011 535i and 2013 BMW 740i,^[9] and a 6-speed manual is usually available for sedans (excluding the 7-Series), but not crossover the X3, X5 and X6.^{[citation needed]} The N55 engines in the 2011 BMW 135i and 2013 BMW 135is are mated to Getrag 7-speed Dual-clutch transmission or a 6-speed manual transmission.^[10][11]

Models

N55 (225 kW)

• 2010-current E92 335i Coupé (2011 model year)
• 2010-2011 E90 335i Sedan (2011 model year)^[12][13]
• 2009-current F07 535i GT (2010 model year)
• 2010-current E82 135i
• 2010-current E70 X5 xDrive 35i
• 2010-current F25 X3 xDrive35i
• 2013-current E84 X1 xDrive35i
• 2010-current F10 535i (2011 model year)^[5]
• 2012-present BMW F30 335i Sedan (2012 model year)
• 2011-present E71 X6 xDrive 35i (2013 model year)

N55 (235 kW)

• 2011-current F12 640i Coupé, Cabriolet (2012 model year)^[14]
• 2012-current F12 640i Gran Coupé (2013 model year)
• 2012-current F20 M135i^[15][16]
• 2012-current F01 740i/Li Sedan (2013 model year)
• 2012-current US-Spec E82/E88 135is Coupe/Convertible (2013 model year)^[17]

N55HP (240 kW)

• 2013-current F22 M235i Coupe (2013 model year)

N55HP (250 kW)

• 2013-current E89 Z4 sDrive35is (2013 model year)

See also

• List of BMW engines

References

External links

• http://www.bmwblog.com/2010/09/12/dyno-test-bmw-335i-and-335is-n54-vs-n55-engine/ comparison of N54 and N55 dyno results