So, you’ve been sitting around wondering what are the differences between the BMW N54 and N55 engines. Well, I am happy to say that together we can look at what changed between these two engines. I won’t cover everything, but the major differences and what that means to you.
What has remained the same
Displacement remains unchanged with a total displacement
of 2,979 cc utilizing a 84 mm bore and a 89.6 mm stroke
Compression ratio is unchanged at 10.2:1
Use of an air-to-air intercooler for charge air
Open deck block design with an aluminum block
and iron cylinder sleeves
Both are still direct injected, but with a change
in injectors on the N55
Now the Fun Stuff, What Has Changed
Most significantly is the use of a twin-scroll
turbocharger on the N55 instead of the parallel twin to help improve turbo
response and reduce turbo lag. BMW has
seen 15% improvements in fuel economy and lower emissions with this more
The addition of 3rd Generation
Valvetronic. Valvetronic is BMW’s name
for variable valve lift which allows for precise adjustment of valve lift and
duration. This adjustment allows for improved
efficiency across various engine operating conditions.
Crank and connecting rods are now cast compared
to forged in the N54. However, the N55
crank is 3 kg lighter.
Diverter valve is changed to an electronic
actuator from the pneumatically actuated found in the N54.
The fuel injectors were changed to the Bosch solenoid
valve fuel injector (HEDV5.2) from the piezo style HPI injectors found in the
N54. This change was primarily driven by
cost and reliability issues outweighing the lean-burn advantages of the piezo style.
VANOS (BMW’s variable valve timing system) is
retained but the adjustment ranges are increased on the N55. The N55 sees an additional 15 degrees of
adjustment on the intake side, and 10 degrees on the exhaust.
Engine operations are now controlled with the
MEVD17.2 ECU from the MSD80/81 found in the N54.
Additional webbing has been incorporated around
the cylinder sleeves for improved cooling.
N55 has a lower emission output by approximately
There were also various improvements to cooling,
oiling and integration of a blow-by pipe on the crankcase ventilation system.
For the most part you can see that the N55 is really an evolution of the N54 engine. From a performance standpoint the N55 outperforms in stock form, but the N54 seems to be a better and easier tuning platform. This is primarily a result of the differences in rotating assemblies and the capability of N55 turbo setup.
Regardless of what BMW engine you have under the hood, remember at Alex’s Autohaus we are always here to help you with BMW repairs, maintenance and performance upgrades. Give us a call at (801) 566-6115 to discuss what we can do for you.
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