Ultimate BMW N55 Engine Guide
Austin graduated from the University of Colorado Denver in 2021 with a degree in technical writing and remains in the Denver area. Austin brings tons of automotive knowledge and experience to the table. Austin worked as a Technical Product Specialist at BMW for over 5 years and drives a heavily modified E30 325i with a stroker kit, all of which he built from the ground up.
Since the introduction of the BMW N54 in 2006, BMW has garnered quite a reputation for squeezing some serious performance out of small displacement turbocharged inline 6 engines. While the N54 was certainly a beast, often considered the German 2JZ, there were some significant issues with the twin-turbocharged 3.0L inline 6 that wouldn’t be ironed out until the engine that succeeded it. Enter the BMW N55 engine.
Like the BMW N54, the N55 is a 3.0L turbocharged inline 6 that was placed in cars like the BMW E90 335i, E82 135i, and F10 535i. The N55 came at a time when BMW was introducing a new generation of most models, including the F30 3-Series, F22 2-Series, and F15 X5. The BMW N55 filled the void left by the BMW N54 from the generation prior.
The N55 introduced some very significant BMW engine technology to the fleet, including BMW Valvetronic and BMW twin-scroll turbochargers. Both of these advancements continue to be integral parts of modern BMW turbocharged engines to this day. It is clear to see how the BMW N55 influenced future engines like the prize-winning B58.
In this ultimate N55 engine guide, we’ll cover everything you need to know about the 3.0L turbocharged inline 6, including N55 engine specs, popular N55 engine modifications, and N55 reliability.
BMW N55 Engine Specs
|Engine||BMW N55 Engine|
|Displacement||3.0L (2,979 cc)|
|Valvetrain||DOHC, Dual VANOS w Valvetronic|
|Bore x Stroke||84 mm × 89.6 mm (3.30 in × 3.50 in)|
|Weight||Long Block ≈ 427 lbs|
|Horsepower||302-445 hp @ 6,000 RPM|
|Torque (lb-ft)||295-502 lb-ft @ 4,000-5,000 RPM|
In terms of the BMW N55’s specs overall, they are quite similar to the BMW N54 engine that preceded it. There were a few notable advancements in BMW engine technology that were introduced on the BMW N55. For example, the BMW 3.0L inline-6 was the first turbocharged engine to implement BMW’s Valvetronic variable valve lift system. This is combined with BMW VANOS variable valve timing as well on the N55. It was also innovative on the turbocharger front, as the BMW N55 was also the first engine to utilize BMW’s now famous twin-scroll turbocharger technology. While the twin-scroll arrangement isn’t as good for aftermarket shenanigans as the N54’s twin-turbo arrangement, the twin-scroll is more efficient overall.
The BMW N55 features an entirely aluminum construction, including both the head and block. Unlike the BMW N54 which featured a forged crank, the N55’s rotating assembly is primarily cast iron. This changed later, as BMW revised the N55 engine for use in the F87 M2. Additionally, BMW learned quite a bit from the initial problems with the previous N54 engine and remedied common problems like failing high-pressure fuel pumps and wastegate rattle.
BMW N54 vs N55 Engine
Since the BMW N54 and N55 share a similar design and have a lot in common overall, comparisons were bound to spring up. The BMW N54 vs N55 debate is one that has been raging since the introduction of the N55 in 2009. Ultimately, it is hard to say that either engine is better, as they both have their strengths and weaknesses. If you are really trying to dive deep into the topic, we have actually already written an entire article about the BMW N54 vs N55, so we won’t be too longwinded here.
There are a few key differences between the 3.0L N54 inline-6 and 3.0L N55 inline-6 that have a noticeable impact on drivability, modifiability, and power delivery. The turbos are one of the main differences between the two engines, with the N54 utilizing a true twin-turbo setup while the N55 introduced the BMW twin-scroll turbocharger. The N55’s twin scroll is more efficient, has very little spool time, and allows the cylinders to run cooler. With that being said, the N54’s twin-turbo arrangement is far more tunable and modifiable, leading to more power potential overall.
After the BMW N54’s release, BMW was able to learn a lot about their turbocharged inline-6 formula and improve on it before releasing the N55. For that reason, the N55 is also the more reliable engine of the two. Fueling issues were very common on the N54, which was resolved with the introduction of new BMW high-pressure fuel pumps and injectors on the N55. While the N55 has better reliability overall, the N54 has a forged crankshaft that allows it to withstand more horsepower in stock form.
What Cars Use the S54 Engine?
When it comes to the list of vehicles that came factory equipped with the N55 engine, the list is pretty extensive. The BMW N55 has 5 different base variants, and even more if you loop the S55 into the mix. The 3.0L N55 is a very versatile engine, as BMW decided to use it in nearly every series between 2009 and 2019.
The BMW N55B30M0 is by far the most common N55 variant out there. Just look at that list below. The M0 was also the first N55 variant released in the BMW 335i. In its initial form, the N55B30M0 shared even more in common with the N54, including a front timing cover-driven high-pressure fuel pump. The B30M0 received a refresh in 2014 that changed the fuel pump design, added an electronic wastegate, and allowed for a larger turbocharger.
- 2009–2017 F10/F11/F07 535i
- 2010–2013 E90/E91/E92/E93 335i
- 2010–2013 E82/E88 135i
- 2010–2017 F25 X3 xDrive35i
- 2011–2013 E70 X5 xDrive 35i
- 2011–2015 F30/F31 335i
- 2011–2014 E71 X6 xDrive 35i
- 2012–2015 E84 X1 xDrive35i
- 2013–2016 F32/F33/F36 435i
- 2014–2018 F15 X5 xDrive 35i
- 2014–2019 F16 X6 xDrive35i
- 2014–2016 F26 X4 xDrive 35i
- 2011–2018 F06/F12/F13 640i
- 2012–2013 E82/E88 135is
- 2012–2015 F20/F21 M135i
- 2012–2015 F01/F02 740i/Li
The N55B30O0 came along in 2013 as a performance-focused version of the N55B30M0. Due to the fact that the B30O0 was used in M-performance models, BMW reinforced the N55 a bit more. The N55B30O0 came with a forged steel crankshaft. Combined with a larger intercooler and radiator than the N55M0, the N55B30O0 is ready for additional modifications and tuning.
- 2013–2016 F22/F23 M235i
- 2015–2016 F20/F21 M135i LCI
The N55B30T0 is the top-of-the-line variant of the N55, produced by BMW at least. While the N55B30O0 was built for M-performance models, the N55B30T0 was built primarily for the full-blown M2. As such, the B30T0 is a no-nonsense engine. The B30T0 borrows rods, pistons, spark plugs, and its oil pan from the M-spec S55 engine.
- 2016–2018 F87 M2
- 2015–2018 F26 X4 M40i
It is important to note that there is quite a big discrepancy between N55 engine variants. For example, there is a 60 horsepower discrepancy between the initial BMW N55B30M0 and the newer and technically updated N55B30T0. While we aren’t including it on this list, there are also some additional Alpina-tuned N55 variants as well. Alpina’s first N55, labeled the N55R20A, was essentially an N55B30M0 with a twin-turbo arrangement borrowed from the N54B30. Alpina would continue to improve on the N55, eventually creating examples pushing 445 horsepower.
Stock N55 Engine Performance
There are quite a few common conclusions that people make about the N55 engine in factory form. For one, there’s plenty of power. It’s no secret that BMW has a history of fibbing about their stock horsepower figures, with the actual figure being significantly higher than what is advertised. It is generally said that N55s make somewhere in the ballpark of 379 crank horsepower, which is more than enough for most people.
BMW’s inline-6 engines are notorious for delivering power in a linear, smooth, and even fashion. Despite introducing forced induction into the mix, the N55 still abides by those overarching characteristics. Both the BMW N54 and N55 are based on the design of the M54 naturally aspirated inline-6, which gives the turbocharged engines similar characteristics to the N/A M54. In comparison to the N54, the N55’s twin-power turbo is also beneficial for smooth acceleration, as there is very little turbo lag.
In the dyno chart above, you’ll notice a couple of things. Firstly, it is nearly impossible to have a more consistent and linear power and torque curve than the one that the N55 produces. A very consistent amount of torque is produced by the N55 from 2,000 RPM to 5,000 RPM with only a slight drop off near the very peak of the rev range.
It is a similar story in terms of horsepower, with power building at a steady trajectory until it reaches its peak at around 5,500 RPM. Generally, with a turbocharged engine, you’d expect to see very little torque low in the rev range leading to a massive power and torque spike later in the rev range. That is due to the spool time that is typically associated with a turbo engine.
As far as how that equates to real-world performance, the moral of the story is that when you put your foot down, you know exactly what to expect. That makes stock BMW turbocharged engines unique.
That type of predictable power delivery is fantastic for performance driving, as there’s no guesswork to be done as far as engine performance is concerned. You don’t have to worry about building and staying in boost or sketchy torque spikes, just silky smooth German horsepower.
BMW N55 Engine Mods and Upgrades
Due to the fact that the N55 engine has been around for 14 years at this point, there isn’t much that hasn’t been done to the N55. That is even more the case since the N54 is a very similar engine and has been around for even longer. Both of the BMW 3.0L inline 6 engines have amassed a die-hard fanbase that swears by the engine’s capabilities.
The massive amount of love for the N54 and N55 has directly translated into aftermarket support. In terms of German engines, the BMW N5X engine series has one of the largest aftermarket communities hands down. While the N54 is the more popular engine to modify due to its internal strength and factory twin turbos, the N55 also shares in the spoils. Generally speaking, if there is a modification that you want to do to your BMW N55 engine, there are not only tons of vendors to choose from, but also countless support forums that will guide you through the process.
Best BMW N55 Piggyback Tune: Burgertuning.com
Best BMW N55 Flash Tune: MHDTuning.com
N55 Tune Power Gains: 60-80whp w/o additional modifications
This N55 modification shouldn’t come as a surprise at all. In fact, it’s such common sense to install a tune on your N55 that it is almost not worth mentioning here. Alas, we want to give you some options at least. If you aren’t familiar with N55 tuning, it is hands down the easiest way to gain some extra power without any additional modifications. When it comes to N55 tunes, you generally have two options, piggyback tunes and flash tunes. As we have already written multiple guides about both types, we won’t go into exhaustive detail here.
Both piggyback and flash tunes have their benefits, but both are very easy to install on a BMW N55. To quickly summarize, flash tunes essentially re-write the DME to target more aggressive boost targets. They also allow for control of fueling, load, ignition advance, etc. Piggyback tunes, on the other hand, trick the factory DME into believing that the N55 is still running stock boost. Flash tunes generally give more customization options, as piggyback tunes are still confined to factory DME parameters. MHD is unquestionably the most popular N55 flash tune option on the market and for good reason. For the N55 piggyback route, the Burger Motorsports JB4 is the best option.
While an N55 tune can net an additional 60 horsepower or so without any additional modifications, the real power is unlocked when a tune is paired with other N55 performance parts, like an N55 catless downpipe, N55 intake, or N55 FMIC.
N55 Catless Downpipe
Best BMW N55 Catless Downpipe: VR-Speed.com
Best BMW N55 High-Flow Downpipe: VR-Speed.com
When it comes to exhaust components, downpipes are one of the most crucial components. The downpipe is the first exhaust component to follow the turbocharger. Ensuring that exhaust gasses can escape with ease is of utmost importance, and an upgraded N55 downpipe can increase flow substantially. BMW’s factory N55 downpipe design could certainly be better. The factory downpipe has restrictive catalytic converters built-in, making it harder for exhaust gasses to escape.
When it comes to upgraded BMW N55 downpipes, there are typically two paths. There are catless N55 downpipes and high-flow, catted N55 downpipes. While catless downpipes will unquestionably yield the best power gains, they aren’t road legal and will cause you to fail emissions. High-flow N55 downpipes retain catalytic converters but replace the restrictive factory ones with less restrictive ones. High-flow N55 downpipes are road legal and will allow you to pass emissions, depending on where you live.
You can expect to gain around 20-25whp from an N55 catless downpipe when paired with a tune. Since high-flow N55 downpipes still have cats, the power benefits will be slightly less, somewhere around the 15-20whp mark. VRSF is a brand that we swear by due to their high-quality constructed downpipes at a reasonable price.
N55 Front Mount Intercooler Upgrade
This mod is a departure from power-focused mods and instead focuses on reliability and efficiency. If you are planning on going wild with your BMW 3.0L straight 6, you need to make sure that everything surrounding your N55 power mods are up to snuff. One, often overlooked, modification in that category is your N55 intercooler. On high horsepower builds, regardless of the engine, heat is always one of the main considerations. Heat is the most taxing force acting on an engine’s internals, so the cooler you keep your N55’s internals, the longer your engine will last and the better it will perform.
An upgraded N55 intercooler comes with numerous benefits over the stock arrangement. An N55 FMIC will lower intake air temps, improve ignition timing, decrease the risk of detonation, and allow you to aim for higher boost targets. The primary benefit is even and steady power delivery, free from power loss from heat soak. That is especially noticeable if you track or drag race your N55 BMW.
There are multiple different N55 front mount intercooler sizes to choose from, with most ranging from 5” to 7.5.” Larger N55 intercoolers tend to cool air more efficiently due to their larger volume. However, choosing an N55 FMIC that is too large can lead to boost lag.
BMW N55 Engine Problems
There’s absolutely no question that the BMW N55 is a more reliable engine than the 3.0L N54 that preceded it. In fact, the N55 was really the engine that began BMW’s run of extremely reliable turbocharged engines that continues to this day. With that being said, there is no such thing as an engine without problems. The N55 is no exception. Here are the most common BMW N55 engine problems:
- VANOS Solenoid Failure
- Valve Cover Oil Leak
- Water Pump Failure
- Leaking Oil Filter Housing Gasket
Most of the BMW N55’s common problems align with many other modern BMW engines that are equipped with dual VANOS. BMW engines are also notorious for oil leaks as well. Despite the couple of issues that we’ll outline below, the N55 as a whole is very dependable as long as you stay on top of regular maintenance and servicing.
BMW N55 VANOS Problems
While BMW’s VANOS variable camshaft timing system unquestionably makes the BMW driving experience more enjoyable, especially high in the rev range, it does come with some sizable drawbacks as well. While we won’t get into the nitty-gritty about how BMW’s VANOS system works (if you are interested, we wrote an article about it), it is important to note that there is an internal solenoid that controls the amount of oil pressure being applied to the auxiliary components to move the cam gears.
VANOS solenoids are notoriously finicky on newer turbocharged BMW engines, which is certainly the case for the N55 as well. There are some telltale warning signs that your N55 VANOS solenoids are on their way out. Some common symptoms include sluggish acceleration below 3,000 RPM, rough idle with frequent hiccups, cold start issues, limp mode, and 2A82 and 2A87 BMW engine codes. VANOS issues tend to manifest near 50,000-mile intervals, with the solenoids needing to be replaced every 70,000 miles or so.
N55 VANOS Replacement Costs
Unlike earlier single VANOS units on older BMW engines, dual VANOS systems are significantly easier to work on. That means that replacement costs and DIY VANOS repairs can actually be done for relatively cheap. Modern dual VANOS systems are very easy to work on and don’t require any special tools. Overall, depending on your skill level, it is possible to replace N55 VANOS solenoids in under an hour.
N55 VANOS Failure Symptoms
Symptoms may vary depending on the exact issue with the VANOS system. However, a few typical symptoms to look out for include:
- Power Loss (especially in the lower RPM ranges)
- Hesitation and Bogging
- Rough Idle
- Poor Fuel Efficiency
- Cold Start Issues/Long Cranks
- SES (Service Engine Soon) Light
BMW N55 Valve Cover Oil Leak
Similar to the N54, a leaking valve cover, valve cover gasket, or PCV valve are among the most common problems with the BMW N55 engine. Due to the fact that all of the gaskets are made from rubber, they are prone to cracking over time. There isn’t necessarily a set mileage or time when this issue arises, but you can expect most of the rubber seals to be in less-than-ideal shape after around 100,000 miles.
The polymer compound that comprises the BMW N55’s valve cover faces a similar issue. As a general rule, if you have to replace a leaking valve cover gasket, it is a good idea to also replace the valve cover at the same time.
If you opt to do the repair at a certified BMW repair facility, the labor is quite expensive due to the fact that the valve cover is time-intensive to remove.
N55 Valve Cover Gasket Leak Symptoms
It will likely be pretty obvious when your N55 valve cover is leaking. With that being said, it can be difficult to pinpoint the exact origin of an oil leak. Once the valve cover begins leaking, expect some of the following symptoms:
- Low engine oil light
- Burning oil smells, or smoke coming from the valve cover area
- Oil on spark plug threads
Most of the symptoms of a leaking N55 valve cover gasket are in line with other similar oil leaks in the engine bay. While technically part of the valve cover, the N55 PCV valve is another potential source of an oil leak. A PCV valve uses the engine vacuum to pull any blow-by gases out of the crankcase, and is integrated into the valve cover. Continued stress can lead to an eventual N55 PCV failure.
BMW N55 Water Pump Failure
Water pumps are one of the most central and important elements in an engine’s cooling system. Unfortunately, BMWs do not have a very good reputation as far as water pump lifespans are concerned. The main reason is that BMW uses electric water pumps with plastic impellers to circulate coolant through the N55’s cooling system. BMW thermostats have a similar reputation of failure, so if you do need to replace your N55 water pump, it is a good idea to also replace your N55 thermostat.
It is hard to give a definitive time frame in terms of how long an N55 water pump will last. Some examples can last to the 100,000-mile mark, while others have been known to fail as soon as the 30,000-mile mark. To a certain extent, it is luck of the draw. With that benign said, if you haven’t replaced your N55 water pump in over 100,000 miles, expect to encounter issues with it in the near future.
Failing N55 Water Pump Symptoms
- Engine overheating significantly – usually rapid over-heating once the pump fails
- Cooling Fan running full speed (noisy)
- Coolant boiling out of coolant cap
Unfortunately, there are rarely preemptive warning signs before an N55 water pump fails completely. It isn’t a part that fails gradually. Instead, it will work one day and not the next. It is extremely important that you pay attention to your BMW’s temp gauge, as a failed N55 water pump can cause your car to rapidly overheat, potentially doing significant damage to the engine.
BMW N55 Engine Summary
The BMW N55 was a massive leap for BMW engine technology. Not only was it the engine that introduced Valvetronic to modern BMW engines, but it was also the engine that set a precedent for reliable BMW turbocharged engines in the years to come.
The 3.0L turbocharged inline 6 took the reigns from the wildly popular BMW N54, which was a tough act to follow. Since the BMW N55 utilizes a single twin-power turbo instead of a true twin-turbo setup like the N54, the N55 has slightly less power potential out of the box. With that being said, the twin-power turbo also makes the N55 more dependable and smoother with its power delivery.
Like the BMW N54 engine, the N55 is an extremely modifiable engine. There is massive aftermarket support for the BMW N55, making it extremely easy to tack on some additional power modifications. An N55 tune alone can garner around 60whp without any additional modifications. An ungraded N55 downpipe is another solid power modification for the N55, as they remove significant exhaust restrictions. While an N55 FMIC upgrade isn’t the best mod for raw power, it will aid in reliability and provide excellent support for other N55 power mods.
Defined by reliability, strength, and modifiability, the BMW N55 will remain one of the most important engines in the BMW catalog for many years to come.