What Engine Is In The Bmw M4 – A Deep Dive Into The S55 And S58
The BMW M4 utilizes a 3.0-liter twin-turbocharged inline-six engine, specifically the S55 in the first generation and the S58 in the current G82 generation. These engines are celebrated for their high-revving nature, forged internals, and incredible tuning potential for enthusiasts and DIY mechanics alike.
If you are a performance enthusiast or a prospective buyer, you have likely asked yourself, what engine is in the bmw m4? Understanding the heart of this machine is crucial for proper maintenance, tuning, and long-term reliability. In this guide, we will break down the technical specifications, common issues, and DIY tips for both the S55 and S58 powerplants.
Whether you are looking to change your own oil or planning a stage 2 build, knowing the nuances of these engines will save you time and money. We will explore why BMW chose these specific configurations and how they differ from the standard 3 Series engines. Let’s dive into the mechanical soul of the M4.
The Evolution of the M4 Heart: S55 vs. S58
To understand what engine is in the bmw m4, we first have to look at the timeline of the M4 nameplate. The M4 replaced the M3 Coupe in 2014, introducing the world to the S55 engine. This was a significant shift from the high-revving V8 found in the previous E92 M3.
The S55 was based on the N55 engine but featured a closed-deck block design for added strength. It utilized two mono-scroll turbochargers and a water-to-air intercooler system mounted right on top of the engine. This setup allowed for better thermal management during track sessions.
In 2021, BMW introduced the G82 M4, which debuted the S58 engine. While it shares the same 3.0-liter displacement and inline-six layout, it is a completely different beast. The S58 is based on the B58 modular engine architecture, known for its extreme durability and efficiency.
The S58 brings 3D-printed cylinder head cores and a forged crankshaft to the table. It also features a more advanced cooling circuit and higher fuel injection pressures. These upgrades allow the current M4 to produce significantly more power than its predecessor right out of the box.
what engine is in the bmw m4? Breaking Down the S58 Architecture
The current generation of the BMW M4 is powered by the S58 engine, which is widely considered one of the best modern performance engines. It is a 3.0-liter, twin-turbocharged inline-six that produces between 473 and 543 horsepower depending on the specific trim level. This engine is designed to handle high boost pressures with ease.
One of the most impressive features of the S58 is its forged chrome-molybdenum steel crankshaft. This component is incredibly light and strong, allowing the engine to rev freely up to its 7,200 RPM redline. For DIYers, this means the bottom end is built to last even under heavy load.
The S58 also utilizes a closed-deck design, which means the area around the cylinders is solid rather than open. This provides maximum rigidity and allows for higher combustion pressures. If you are planning on adding a flash tune or larger turbos, this structural integrity is a massive advantage.
Furthermore, the S58 features two single-scroll turbochargers that feed three cylinders each. This “twin-power” setup minimizes turbo lag and provides a linear power delivery that feels almost like a naturally aspirated engine. It is a masterpiece of modern automotive engineering.
The Cooling System of the S58
Managing heat is the biggest challenge for any turbocharged engine. The S58 uses a sophisticated indirect intercooling system. This system uses a dedicated low-temperature coolant circuit to cool the intake air, ensuring consistent performance even in hot weather.
There are also multiple radiators tucked behind those large kidney grilles. One main radiator and two smaller outboard radiators handle the engine’s thermal needs. If you drive your M4 on the track, keeping these radiators free of debris is a critical maintenance task.
The oil system is also track-optimized. It features a map-controlled oil pump and a suction-optimized oil sump. This ensures that the engine receives proper lubrication even during high-G cornering where oil might otherwise slosh away from the pickup tube.
Technical Specifications: S55 vs. S58 Comparison
When discussing what engine is in the bmw m4, it helps to see the numbers side-by-side. The S55 was no slouch, but the S58 has moved the goalposts significantly. Below is a quick comparison of the key metrics for both engines.
- S55 (2014-2020): 425–493 hp, 406–443 lb-ft torque, 7,600 RPM redline.
- S58 (2021-Present): 473–543 hp, 406–479 lb-ft torque, 7,200 RPM redline.
- Bore/Stroke: The S55 is more “undersquare” while the S58 moves toward a more “square” bore and stroke for better balance.
- Fuel Injection: The S58 uses 350-bar high-pressure injection, compared to the 200-bar system in the S55.
The S58’s increased fuel pressure allows for better atomization of fuel. This results in more efficient combustion and more power. It also helps the engine meet stricter emissions standards without sacrificing the raw performance BMW M fans expect.
Another key difference is the valvetrain. Both engines use VALVETRONIC variable valve lift and Double-VANOS variable camshaft timing. However, the S58’s system is more refined, offering smoother transitions and better throttle response throughout the rev range.
Common Issues and Maintenance for the S55 Engine
If you own an older M4, you are likely working with the S55 engine. While generally reliable, it has a few “Achilles’ heels” that every DIY mechanic should know. The most famous issue is the crank hub failure, which can lead to catastrophic engine timing issues.
The S55 crank hub is a friction-fit design. Under high torque or aggressive downshifts, the hub can spin, causing the engine to go out of time. Many owners choose to install a “pinned” or “keyed” crank hub as a preventative measure before adding power mods.
Another common point of failure is the plastic charge pipes. These pipes carry pressurized air from the turbos to the engine. Over time, the plastic becomes brittle and can burst under boost. Replacing these with aluminum versions is a standard “Day 1” mod for most owners.
Oil filter housing gaskets (OFHG) are also known to leak on the S55. If you see oil pooling near the front of the engine, this is the likely culprit. It is a tedious job but manageable for a weekend DIYer with a good set of sockets and some patience.
DIY Maintenance Tips for S55 Owners
- Oil Changes: Use a high-quality 0W-30 or 5W-30 synthetic oil. Change it every 5,000 miles, regardless of what the onboard computer says.
- Spark Plugs: Turbocharged engines are hard on plugs. Replace them every 20,000 to 30,000 miles to prevent misfires under high boost.
- Coolant Levels: The S55 has two coolant reservoirs (one for the engine, one for the intercooler). Check both regularly, as the intercooler can develop internal leaks.
Reliability and Performance of the S58 Engine
So far, the S58 has proven to be incredibly robust. Because it was designed with lessons learned from the S55 and B58, many of the previous generation’s flaws were engineered out. For example, the S58 features a much stronger crank hub design that has not shown the same tendency to slip.
However, no engine is perfect. One thing to watch out for is the oil cooler location. On the G82 M4, the oil cooler is mounted horizontally at the very bottom of the front bumper. This makes it vulnerable to road debris or speed bumps.
Many enthusiasts install a protective mesh or a reinforced skid plate to prevent a stray rock from puncturing the cooler. If the oil cooler is punctured, you will lose oil pressure almost instantly, which can destroy the engine if you don’t shut it down immediately.
The S58 also uses a very complex PCV (Positive Crankcase Ventilation) system integrated into the valve cover. If you notice excessive oil consumption or a whistling sound at idle, the PCV diaphragm may have failed. This usually requires replacing the entire valve cover.
Maximizing S58 Longevity
To keep your S58 running perfectly, always allow the engine to reach operating temperature before driving aggressively. These engines have tight tolerances, and the oil needs to be warm to flow correctly through the turbocharger bearings. This simple habit can add years to the engine’s life.
Additionally, stick to high-quality fuel. The S58’s high compression and high boost levels require 91 or 93 octane (AKI). Using lower-grade fuel will cause the knock sensors to pull timing, reducing power and potentially causing long-term damage.
DIY Guide: Changing the Oil on a BMW M4
Performing your own oil changes is the best way to get familiar with what engine is in the bmw m4. Both the S55 and S58 follow a similar process, though the filter locations and oil capacities vary slightly. You will need a 17mm socket, a 27mm oil filter housing tool, and a torque wrench.
Start by jacking up the car and securing it on jack stands. Never work under a car supported only by a floor jack. Locate the drain plug on the oil pan. On the S55, this is often behind a small plastic trap door in the under-tray.
Drain the oil into a suitable container. While it drains, remove the oil filter from the top of the engine bay. Replace the filter element and the large rubber O-ring on the housing cap. Lubricate the new O-ring with a bit of fresh oil to ensure a proper seal.
Reinstall the drain plug with a new crush washer and torque it to 25 Nm. Lower the car and fill it with the recommended amount of oil (usually around 6.5 to 7 liters). Use the iDrive system to check the oil level once the engine is warm, as there is no physical dipstick.
Tuning Potential: Unlocking More Power
One reason people are so curious about what engine is in the bmw m4 is the massive tuning headroom. The S58, in particular, is a “tuning monster.” With just a simple ECU flash and high-quality fuel, it is common to see gains of 100 horsepower or more.
For those going further, “downpipes” are a popular modification. These replace the restrictive factory catalytic converters, allowing the turbos to spool faster and lowering exhaust gas temperatures. Note that this may not be street-legal in all jurisdictions.
The fuel system on the S58 is also very capable. It can handle E30 (a blend of 30% ethanol) without any hardware changes. Ethanol has a higher octane rating and a cooling effect, which allows for even more aggressive timing and boost.
If you plan on tuning, always monitor your data logs. Use a tool like MHD or Bootmod3 to keep an eye on ignition timing, knock, and air-fuel ratios. This ensures that your quest for more power doesn’t end in a “ventilated” engine block.
Frequently Asked Questions About what engine is in the bmw m4
Is the BMW M4 engine a V6 or an Inline-6?
The BMW M4 has always used an inline-six engine. BMW is famous for this configuration because it is naturally balanced and provides a smooth, vibration-free power delivery that V6 engines often struggle to match.
Does the BMW M4 have a turbocharger?
Yes, all BMW M4 models are twin-turbocharged. The S55 and S58 engines use two separate turbochargers to provide high levels of torque across a wide RPM range, virtually eliminating the lag associated with older turbo engines.
How long does a BMW M4 engine last?
With meticulous maintenance, an M4 engine can easily last over 100,000 miles. The key is frequent oil changes, addressing cooling system issues early, and not over-tuning the engine beyond its safe limits.
Is the S58 engine better than the S55?
In terms of pure performance and reliability out of the box, the S58 is considered superior. It has a stronger crank hub, better cooling, and higher power potential. However, the S55 is still a legendary engine with a massive aftermarket community.
Conclusion: Respecting the Power Under the Hood
Understanding what engine is in the bmw m4 is the first step toward becoming a better owner or mechanic. Whether you are dealing with the raw, aggressive nature of the S55 or the refined, overwhelming power of the S58, these engines represent the pinnacle of BMW M engineering.
Always remember that high-performance engines require high-performance care. Don’t skip on maintenance, use the best parts available, and always prioritize safety when working in your garage. If you treat your M4 engine with respect, it will reward you with years of exhilarating drives and track-day glory.
Stay safe, keep your wrenches turning, and enjoy every mile behind the wheel of your ultimate driving machine!
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