BMW S55 Engine – 3.0L Twin-Turbocharged Inline-6
BMW’s S55 engine is a 3.0L inline-6 twin-turbocharged, direct injection gasoline engine produced from 2013 to the present day (in the M2 CS Racing). The S55 marked a reintroduction of the inline-6-cylinder engine to the BMW M division after the S65 V8-powered E9X M3. While many M-enthusiasts would likely have preferred a naturally aspirated inline-6 under the hood of the M3, the S55 signaled that BMW was committed to forced induction as the way forward for all M-cars to come.
Like most of the other engines that found their way under the hood of a true BMW M vehicle, the 3.0 twin-turbocharged S55 engine borrows heavily from its non-M counterpart, the BMW N55 engine. Like the N55, the S55 is an aluminum 3.0L inline-6 engine equipped with double-VANOS and Valvetronic variable valve timing. The BMW S55 returned to a true-twin turbo arrangement which was popularized on the earlier BMW N54 engine.
Throughout the BMW S55’s build cycle, it was used in a number of BMW M models including the F87 M2, F80 M3, and F82 M4. Depending on the model, power from the S55 ranged from 359 horsepower to 493 horsepower. Since the S55’s release, it has quickly become one of the fan-favorite BMW engines from an aftermarket potential standpoint.
This page is the ultimate resource for everything BMW S55. We provide a general overview and technical information on the engine in addition to problems, performance modifications, FAQs, and various other resources. Whether you own an S55-powered BMW or are looking to purchase one, we have the most comprehensive S55 information on the internet.
S55 Engine Overview
The BMW S55 is a 3.0L twin-turbocharged inline-6 engine that was designed for the explicit purpose of powering BMW’s coupe and sedan M vehicles including the F87 M2, F80 M3, and F82 M4. Prior to the BMW S55, the BMW M3 was powered by the naturally aspirated S65 V8 engine, which was a major departure from the inline-6 engines that powered both the E36 and E46 generation M3s. A massive reason for the switch to a twin-turbocharged inline-6 for the M3 was efficiency. While the S55 only produced 15 more horsepower initially, it provided a 30% increase in torque and a 28% improvement in fuel efficiency over the previous S65 V8.
Over the course of the S55’s build cycle, it has been released in a number of variants producing different levels of power. While the S55’s overall construction is widely the same across the board, the engine’s tune was modified depending on which model it was placed in. For example, standard M3 and M4 models received 425 horsepower variants of the S55 while M3 and M4 Competition models received a 444 horsepower S55 variant.
Unlike many of the other turbocharged inline-6s that came before it, the S55 is known as an exceptionally reliable engine. BMW undoubtedly learned from the N54 and N55 engines and made necessary changes to improve the reliability of the S55. While the S55 does have typical BMW engine issues, like valve cover and oil filter housing gasket leaks, it has very few unique issues outside of crank hub failure at high-horsepower thresholds.
The S55 is one of the most popular BMW performance engines in the aftermarket community. Due to the S55’s high tolerance for power and its true twin-turbo arrangement, it has tremendous aftermarket support and a massive tuning scene.
BMW N55 vs S55 Engine Differences
The BMW S55 shares approximately 75% of its components and overall design with the N55 engine found in non-M BMW models from 2009 to 2019. However, BMW made some key changes to the S55’s internal components and overall engine architecture to be able to withstand the higher power output and demand. The primary differences between the S55 and earlier N55 engines can be seen in their block design, cooling system design, turbocharger arrangement, and internal components.
One of the most notable performance-affecting differences between the engines is the difference in their crankcase design. The N55 engine uses an open-deck design, like its N54 predecessor, while the S55 utilizes a closed-deck crankcase. The N55’s open-deck block has the advantage of improved cooling properties, as they feature cooling channels surrounding the cylinders. While the S55’s closed-deck block doesn’t provide the same cooling efficiency, it is far more structurally rigid, allowing it to withstand far more strenuous forces.
In part due to the S55’s closed deck block, as well as the engine’s twin-turbo arrangement and higher overall performance ceiling, it needed a far more comprehensive cooling system than the N55. As a result, the S55’s cooling system is split into two circuits. One is an engine cooling circuit and the other is a charge air cooling system. It also includes oil cooling for the engine oil and transmission.
The S55’s use of a true twin-turbo arrangement is a massive difference between the N55 and S55 and plays the most significant role in how the two engines perform differently. The S55 moved away from the single twin-scroll turbocharger used on the N55 in favor of a more traditional twin-parallel Mitsubishi TF035 mono-scroll turbocharger arrangement.
The S55’s internals and auxiliary systems were also improved including a revised crankshaft, pistons, rods, and oiling system.
BMW S55 vs S58
In 2019, the BMW S58 took the reigns as the premier BMW M engine found in a number of vehicles ranging from the F97 X3M to the G80 M3. Like the S55 which was based on the non-M N55 engine, the S58’s overall architecture and construction was based heavily on the celebrated BMW B58 engine.
Overall, the two engines are pretty similar in terms of their overall design. Both engines are closed deck, aluminum, twin-turbo inline-6 engines with double-VANOS, direct injection, and Valvetronic variable valve timing. While the S58 is still considered a 3.0L engine, it does feature a slightly higher displacement of 2,993cc compared to the S55’s 2,979cc. That is due to the S58’s slightly longer stroke of 90mm which benefits top-end power.
One of the most important differences between the two engines is the S58’s lower 9.3:1 compression ratio, which plays a significant role in the S58’s larger power potential and more linear boost characteristics. Due to the S58’s lower compression ratio and larger turbos, it has more turbo lag than the S55 due to its higher boost threshold. However, that also means that there is more performance to be extracted from the S58, as it isn’t as highly strung from the factory and the larger turbos are capable of providing more boost.
Ultimately, the BMW S58 is an engine built with top-end power in mind and outperforms the S55 higher in the rev range. However, the S55 is more peaky and aggressive earlier in the rev range due to its smaller turbos and lower boost threshold. For more information about the two engines, take a look at our dedicated BMW S55 vs S58 article below.
General BMW S55 Information & Resources
S55 Engine Specs
|Aluminum, closed deck
|DOHC, Valvetronic, Dual VANOS
|Bore x Stroke
|84 mm × 89.6 mm (3.30 in × 3.50 in)
|359-493 hp @ 6,000 RPM
|295-443 lb-ft @ 1850–5500rpm RPM
Over the course of the S55’s build cycle, the engine was released in six factory trim levels. The primary difference between the S55 variants is the factory tune, which created a wide variety of horsepower outputs depending on the model. All S55 engines are nearly identical in construction regardless of the model, with the exception being the highest-output S55 found in the F82 M4 GTS which featured a water injection system. Here is a list of all of the vehicles that made use of the BMW S55 engine:
275-359 bhp BMW S55
- 2020–present F87 M2 CS Racing
405 bhp BMW S55
- 2019–2021 F87 M2 Competition
425 bhp BMW S55
- 2014–2018 F80 M3
- 2014–2020 F82/F83 M4
444 bhp BMW S55
- 2016–2018 F80 M3 with Competition package
- 2016–2020 F82/F83 M4 with Competition package
- 2020–2021 F87 M2 CS
453 bhp BMW S55
- 2018 F80 M3 CS
- 2017–2020 F82 M4 CS
493 bhp BMW S55 (Water Injected)
- 2015–2016 F82 M4 GTS
- 2017 F82 M4 DTM Champion Edition
We have compiled some of the most commonly cited BMW S55 engine problems. Overall, the BMW S55 is seen as a very reliable engine, even 10 years after it was released. With that being said, there are still some problem areas with the 3.0L turbocharged inline-6. In addition to some unique issues with the S55, including crank hub issues, the S55 shares quite a few common problems with the N55. S55 oil filter housing gasket leaks, oil pan gasket leaks, and chargepipe failures are the most common issues with the S55 and are good to know about if you drive an S55-powered BMW.
Take a look at the dropdown menu below to learn more about these problems or check out the more in-depth problem and maintenance guides featured below.
S55 Problems & Maintenance Guides
We have the most comprehensive resources for S55 performance upgrades. This section includes some of the most popular, cost-effective, and value-focused modifications for the BMW S55 engine. At this point in time, 10 years after the release of the S55 in the F80 M3, the 3.0L BMW inline-6 has one of the largest aftermarket communities of any modern BMW engine. From tuning information to performance parts suggestions, we have you covered as far as BMW S55 modifications are concerned.
Click on each modification to get a brief rundown of the mod, the benefits, and our best product recommendation. Additionally, we have full in-depth guides for each of these modifications that you will find within the sections. Furthermore, a list of general performance and modification-related content can be found below, covering power limits, boost levels, and various other S55-specific topics.
Additional S55 Performance Guides
We have a comprehensive article that covers performance upgrades, power levels, general maintenance, problems and reliability, and more for the S55. We’ve included a few performance and reliability-related questions below but recommend reading our full BMW S55 engine guide for more extensive questions and details about the BMW S55 engine.
How much power can the S55 handle?
The S55 can handle around 700wtq on the stock engine block and internals. Horsepower isn’t really the issue here, as low and mid-range torque is what truly does damage to engine internals on highly tuned S55 engines. With the right tune, the S55 engine is capable of withstanding upwards of 800 horsepower on the stock block and internals. The most common place for a BMW S55 engine to fail is its connecting rods, which tend to bend beyond the 700wtq mark.
How much boost can the stock S55 turbos handle?
The factory S55 turbos are capable of making up to roughly 30psi. In most cases, the factory S55 turbos are good for low-600 horsepower figures before a turbo upgrade is needed. However, for reliability and longevity reasons, we recommend limiting boost to about 25-26psi. Much over 25psi pushes the turbo well outside its efficiency range for minimal performance gains. Even at that boost level, reliability is questionable. Additionally, altitude increases cause the turbo to work harder.
How reliable is the BMW N55?
The S55 is known for its impressive reliability, even now, 10 years after its initial release. There are very few truly common problems with the S55 engine, with the majority of issues springing up as a result of age or extensive tuning and modifications that the factory engine can’t handle. Most of the S55’s problems revolve around wear-and-tear components like the valve cover gasket and oil filter housing gasket. However, some issues like crank hub failure and charge pipe failure are generally caused by fatigue from high horsepower and torque levels. With proper maintenance and diligence, the S55 engine is one that should last a very long time under the hood of an M2/M3/M4.
In-Depth FAQ Guide
8020 Media S55 Videos
Other Helpful S55 Videos
We have dozens of guides on the BMW S55 – check out all of our S55 content below or use the tabs to find our articles on specific modifications, and so on. However, there is also a ton of good content elsewhere around the S55. Check out a few of our favorites here: