BMW N54 vs. N55 Comparison

BMW created two incredible engines for drivers with the N54 and N55 designs. If you have the option to choose one, which provides the best results?

Although BMW offered turbocharged engines before the N54 and N555, the focus was on creating naturally aspirated designs before 2006. Some examples of popular choices in that category include the M106 and M102.

The N54 was BMW’s first effort to create a mass-produced turbo-style engine as part of the NG6 family. Only a few vehicles got to use it, but the idea would set the stage for future turbo efforts.

What makes the most sense for vehicles today in the BMW N54 vs. N55 comparison debate?

The primary difference between the BMW N54 and N55 is the turbocharger design. The N54 offers a true twin turbocharger, while the N55 provides a twin-scroll option. That means the N55 has a single turbo, but the exhaust housing uses two openings, shaped like a formed scroll, to deliver results.

The N54 and N55 engine use an all-aluminum block. They’re a 3.0L inline six-cylinder option that features heavily in sedans and sports models.

Both engines were recipients of the International Engine of the Year Award.

When comparing the N54 and N55 directly, the turbocharger design is the difference that most drivers, critics, and commentators discuss.

Having twin turbos is a significant advantage for some vehicles, especially since the N55 uses a single with a twin-scroll exhaust.

A closer look at this particular feature shows that each provides potential advantages when getting behind the wheel of a BMW.

Advantages of Twin Turbo Engines	Advantages of Single Turbo Engines
The twin-turbo setup helps with lag reduction. It produces the same boost with half of the required cylinders when compared to a single turbo design.	A single turbo engine takes up a little less space than those with twin designs without sacrificing much speed or acceleration while driving.
Engine functionality tends to be smoother with the dual design. Vehicles operate more efficiently when using two smaller turbos than one larger one.	The setup process for a single turbo engine is more efficient and streamlined than for a twin, ensuring that drivers receive cost-efficient results.
The visual aesthetics of a twin-turbo design are impressive under the hood while delivering a consistent and positive overall experience.	A single turbo design like the N55 can produce a maximum boost at higher RPMs than what a twin-turbo option usually produces.
There is an excellent throttle response that comes from the N54, offering a suitable acceleration profile because it achieves a rapid and significant airflow.	This engine style can cool faster and more efficiently because the air intake is significantly higher in a centralized area while minimizing exhaust reversion with the scroll design.

What Are the Differences Between the BMW N54 and N55?

The BMW N54 engine debuted in 2006, launching with the 335i model in the E90+ series. Once the N55 was released in 2009, the automaker started phasing out the older engine.

You can still get the N54 in the BMW E89 Z4 Roadster, which the automaker produced until 2016.

It won five consecutive International Engine of the Year awards, and it comes in two versions with a bore of 84 mm, an 89.6 mm stroke, and a compression ratio of 10.2:1.

The N55 stayed in production from 2009 to 2015 before it started being phased out for the updated N58 design.

It was initially introduced in the F07 5 Series Gran Turismo. Several versions are available, with a few still offered in models still produced by BMW.

There is also an S55 variation that’s a high-performance version of the original.

When looking at the N54 vs. N55 comparison, BMW implemented several changes between the two engines that are worth reviewing. Here’s a closer look.

1. The Crank and Connecting Rods

BMW used forged crank and connecting rods with the N54 engine. When they moved to the N55, the decision was to cast them instead.

That makes the crank about six pounds lighter. Although that might not seem like much, every weight reduction matters when working toward a fuel-efficient design.

2. Fuel Injection

When BMW released the N55 engine, they changed the fuel injectors from the N54 design.

The updated approach uses Bosch solenoid valves, while the earlier model incorporated piezo-style HPI injectors.

That means the N54 burns leaner than the N55, but the updated design is slightly more reliable and less expensive to operate for drivers.

3. Diverter Valve Change

BMW uses a pneumatic actuator for the N54 engine design. When you look at the N55 update, you’ll find an electronic diverter valve.

4. Third Generation Valvetronic

BMW uses Valvetronic for the in-house variable valve lift. This system provides precision for valve adjustment and duration, ensuring efficient operations across various conditions and environments.

The N55 uses the third-generation design of this technology, while the N54 does not.

5. Webbing Additions

BMW offers more webbing around the N55 cylinder sleeves compared to what you’ll see with the N54 engine.

The goal of this update is to improve cooling and temperature regulation while driving.

6. ECU and Emission Output

BMW updated the ECU in the N55 engine to a MEVD17.2, while the N54 comes equipped with an MSD80/81 model.

The update allows the N55 to deliver 20% fewer emissions output compared to its predecessor, reducing the owner’s overall carbon footprint from their driving activities.

7. Variable Timing System

VANOS is the variable valve timing system that BMW uses with its engines. The N54 and N55 have it, but more adjustment ranges are available with the latter design.

The N55 comes with 15 extra degrees of adjustment for the intake and ten degrees on the exhaust side.

This benefit works with small improvements in engine lubrication and cooling, including a new blow-by pipe in the crankcase, to encourage performance benefits.

BMW N54 vs. N55 Comparison: Which Is the Better Engine?

The N55 is a superior design to the N54 because it updated the various flaws and user concerns that plagued vehicles with it over the years.

Although the N54 won numerous awards for its innovation, the N55 creates consistency for the driving experience.

The first two years of the N54 were its worst, triggering recalls and repairs that forced BMW to offer extended warranties since it was a bit unreliable.

The N55 has a few quirks of its own to manage, but the risk of requiring repairs because of them is significantly lower.

Here’s a closer look at the common problems that both engines encounter.

List of BMW N54 Engine Common Problems	List of BMW N55 Engine Common Problems
N54 oil filter housings are prone to leaking and cracking incidents. This issue can cause oil to mix with the vehicle’s coolant, cause fluids to spray on the drive belt, and lead to severe problems.	The N55 engine encounters issues with the charge or boost pipes breaking or detaching. There’s a small clamp that connects it to the throttle, and it doesn’t do a great job of withstanding a high-pressure boost.
The serpentine belt on the N54 engine in 2007 and 2008 models can fail due to the motor mounts developing flexibility as they age. It causes the pully to contact the subframe, damaging the belt and potentially causing engine failure.	Gasket and valve cover leaks have been known to happen with the N55 engine. This issue sometimes causes the positive crankcase ventilation valve to crack, causing rough idling.
Fuel injectors on N54 engines have failed so often that BMW revised the design nearly a dozen times. It is still less reliable than other designs, including the N55, causing power loss and misfires.	Water pumps are known to fail on the N55, although this problem is something that most BMW engines encounter as they age. Most models require a replacement around 30,000 miles, but you’ll want to verify things on your service schedule.
Soot buildup in the N54’s cylinders occurs because of the direct fuel injection design. This issue creates throttle lag while reducing the fuel economy if periodic cleaning doesn’t occur.	Solenoid failure occurs at times with the N55 engine because this component is always working. As the engine ages, the risk of this issue increases. The bolts for the VANOS system were recalled in the 2010-2012 designs to improve this issue.
HPFP (high-pressure fuel pump) failure is a common problem with the N54 engine. When this component fails, the symptoms include power loss, engine stuttering, and failure to restart.
The valve covers on N54 engines are known to crack, with reports of the component failing after 25,000 miles. This issue causes burning oil smells to come into the cabin.

N54 vs. N55 Comparison: Which Is Better?

Drivers in the market to purchase a BMW vehicle can choose from the N54 or N55 engine, especially with an older model. The N54 delivers power benefits, but it requires more maintenance and care than the N55. Additional lag occurs in the N55, though it delivers more consistency.

Despite the issues that it creates for some people, I prefer the N54 engine. There’s nothing like the feeling of stomping on the accelerator and feeling the twin turbos deliver enough gravity to throw you back into the seats.

I’ve driven the N54 and N55, and both are suitable for the average daily needs of professionals, travelers, and families. When you want consistency, the N55 delivers.

If you want power, the N54 is what delivers.