Overview
The BMW S55 engine is a high-performance inline-6 twin-turbocharged engine developed by BMW M GmbH. Based on the N55, it powers models such as the F80 M3, F82/F83 M4, and F87 M2 Competition. The S55 emphasizes track capability, durability under sustained loads, and increased power output.
Key Specifications
- Engine Code: S55B30
- Configuration: Inline-6
- Displacement: 2979 cc
- Turbocharging: Twin mono-scroll turbos (vs. single twin-scroll in N55)
- Fuel System: Direct injection with increased rail pressure (200 bar)
- Compression Ratio: 10.2:1
- Max Power Output: Up to 500 hp (varies by application and tune)
- Max Torque: ~550 Nm (405 lb-ft)
- Redline: 7600 RPM
- Cooling System: Additional radiators, dedicated transmission and oil cooler
- Exhaust System: Integrated with electronic valves for sound modulation
Engine Enhancements
- Closed-deck block: For improved strength under boost
- Forged crankshaft and pistons: High durability for track use
- Valvetronic and Double VANOS: Variable valve timing and lift
- Lightweight magnesium sump and components: Reduces mass
- Active Sound Design (ASD): Digital augmentation of engine note
Performance Features
- Track-oriented cooling system
- Dry-sump-like oil scavenging
- Stiffer engine mounts
- ECU tuning potential is significantly higher than N55
- Meets Euro 6 emissions
S55 vs. N55 – Key Differences
| Feature | S55 | N55 |
|---|
| Turbocharger | Twin mono-scroll turbos | Single twin-scroll turbo |
| Block Design | Closed-deck | Open-deck |
| Crankshaft | Forged steel | Cast steel |
| Pistons | Forged alloy | Cast aluminum |
| Redline | 7600 RPM | 7000 RPM |
| Max Rail Pressure | 200 bar | 170 bar |
| Cooling System | Multi-radiator, oil, trans coolers | Single radiator |
| Engine Sound | ASD-enabled, dual-valve exhaust | No ASD in most models |
| ECU | Custom BMW M DME (MEVD17.2.G) | Standard Bosch DME (MEVD17.2.6) |
| Track Use Readiness | High | Moderate |
S55 vs. N55 – Commonalities
| Component / Feature | Notes |
|---|
| Engine Layout | Inline-6, longitudinal |
| Engine Mounting | Same locations on block, upgraded mounts and subframe |
| Base Architecture | Both based on BMW modular I6 design |
| Fuel System | Direct injection |
| Valvetrain | Double VANOS, Valvetronic |
| Displacement | 2979 cc |
| Materials | Aluminum alloy block/head |
| ECU Tuning Capabilities | Supported for both, higher ceiling on S55 |
