A Beginner’s Guide to the BMW S55 Engine
The BMW S55 Engine: What You Need to Know
The BMW S55 engine is one of the most well-known performance engines to come out of Bavaria in recent years. Introduced in 2014 as the high-performance variant of the N55, the S55 was designed specifically for the F8X generation BMW M3, M4, and later the M2 Competition and M2 CS. With a twin-turbo inline-six layout and significant cooling upgrades over the N55, the S55 is a powerhouse that has earned both praise and criticism from enthusiasts and tuners alike.
What People Love About the S55
There’s no denying the S55 delivers serious performance straight from the factory. With 425 horsepower in its base form (and up to 444 hp in Competition models and 453 hp in the M2 CS), the engine is a beast even before modifications. The twin-turbo setup provides strong mid-range torque, making acceleration effortless, whether on the street or track.
Enthusiasts also love how well the S55 responds to tuning. With basic bolt-ons and a tune, it’s common to see these engines pushing well over 500 wheel horsepower; with upgraded turbos and forged internals, the sky's the limit. The aftermarket support for the S55 is massive, making it an attractive choice for those looking to extract more power.
Additionally, BMW made significant improvements in cooling compared to the N55, with an air-to-water intercooler, improved oiling system, and additional radiators to handle track abuse. For those who want a powerful and well-supported platform, the S55 checks a lot of boxes.
Common Complaints and Issues
While the S55 is impressive, it’s not without its downsides. The most infamous issue is the dreaded crank hub failure. The factory design uses a press-fit, non-pinned crank hub, which can slip under high loads, throwing off engine timing and potentially leading to catastrophic failure. Many owners preemptively upgrade to a pinned crank hub solution to avoid this expensive problem.
Another significant concern is excessive rod bearing wear. To address this, we offer Coated Rod Bearings, designed specifically for high-performance applications. These bearings feature a friction-reducing, wear-resistant coating that enhances durability under extreme conditions. Whether you’re pushing big power or simply want peace of mind, upgrading to these coated bearings can help protect your engine from premature failure.
On the BMW S55 engine, the accessory belt is situated in an area where coolant and oil leaks are common. When the accessory belt is affected, even by a mild leak, it can begin moving off of the crank pulley, causing the belt to fray. The tiny shards of rubber created by a fraying belt then work themselves into the crank seal, where they are picked up by the timing chain and begin to cause detrimental problems. To prevent this, we offer the 5150 Crank Seal Guard, which acts as a protective barrier to stop debris from entering the crank seal and causing catastrophic engine damage.
Vehicles That Used the S55
The S55 was featured in several high-performance BMW models:
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F80 M3 (2014–2018)
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F82/F83 M4 (2014–2020)
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F87 M2 Competition (2018–2021)
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F87 M2 CS (2020–2021)
These cars quickly became favorites among enthusiasts for their balance of power, handling, and aggressive styling. The M2 Competition and CS, in particular, brought the S55 into a smaller, more nimble chassis, making it an exciting alternative to the larger M3 and M4.
The S55 in Performance Applications Today
Today, the S55 remains a favorite among tuners, track day enthusiasts, and competitive racers. Many owners push these engines well beyond their stock limits with upgraded turbos, built internals, and advanced fuel setups to achieve 700+ hp on pump gas and even higher with ethanol blends or race fuel.
On the motorsport side, the S55 continues to be used in various racing applications, including time attack, endurance racing, and drifting. Its ability to produce reliable, consistent power makes it a solid choice for those looking to build a competitive track car.
Final Thoughts
The BMW S55 is a fantastic engine with huge potential, but it does come with some known pitfalls. If you're considering buying an S55-powered car or modifying one, it's crucial to be aware of its common failure points and take the necessary precautions. With proper maintenance and the right upgrades, the S55 can deliver serious performance and reliability, making it one of BMW’s most exciting modern powerplants.