The Mercedes-Benz M271.946 is a 1,796 cc, inline-four petrol engine produced between 2008 and 2015. It features a DOHC 16-valve configuration with variable valve timing (VVT) and direct fuel injection, delivering 135 kW (184 PS) and 270 Nm of torque. This evolution of the M271 series introduced spray-guided direct injection for improved efficiency and responsiveness, particularly in urban driving conditions.
Fitted to models such as the W204 C-Class, W245 B-Class, and CL203 C-Class Coupe, the M271.946 was engineered for dynamic performance with enhanced throttle response and mid-range torque. Emissions compliance was achieved through a three-way catalytic converter and oxygen sensor feedback, allowing Euro 5 compliance across its production run, verified under EU Regulation (EC) No 715/2007.
One documented concern is carbon buildup on intake valves due to the absence of fuel-washing effect in direct-injection systems. This issue, referenced in Mercedes-Benz Service Bulletin 02.2012.01, can lead to rough idle and reduced volumetric efficiency. From 2012, revised intake manifold designs and updated ECU mapping were implemented to mitigate deposit accumulation.
All production years (2008–2015) meet Euro 5 emissions standards (VCA UK Type Approval #VCA/EMS/5679).
The Mercedes-Benz M271.946 is a 1,796 cc inline-four petrol engine engineered for compact and mid-size platforms (2008–2015). It combines spray-guided direct fuel injection with variable valve timing to deliver strong mid-range torque and responsive urban performance. Designed to meet Euro 5 standards, it balances performance with regulated emissions control and improved fuel stratification.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,796 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, DOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 82.0 mm × 85.0 mm | |
| Power output | 135 kW (184 PS) @ 5,500 rpm | |
| Torque | 270 Nm @ 3,000–4,600 rpm | |
| Fuel system | Spray-guided direct injection (ME 9.7 ECU) | |
| Emissions standard | Euro 5 | |
| Compression ratio | 10.7:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven (double-row, non-interference) | |
| Oil type | MB 229.51 (SAE 5W-30) | |
| Dry weight | 146 kg |
The direct injection system provides precise fuel control and improved low-end torque but requires regular intake valve cleaning to prevent carbon buildup, especially in short-trip driving. MB 229.51 (5W-30) oil is essential due to its enhanced detergency and shear stability, protecting the high-pressure fuel pump and variable valve timing system. Extended idling or frequent cold starts can accelerate deposit formation in the intake tract. The ME 9.7 ECU is sensitive to fuel quality; use of low-sulfur petrol meeting EN 228 standards is required to prevent injector coking. Post-2012 models feature revised intake runners; pre-2012 units should undergo periodic intake cleaning per Mercedes-Benz SIB 02.2012.01.
Oil Specs: Requires MB 229.51 (5W-30) specification (Mercedes-Benz SIB 02.2012.01). Supersedes ACEA C2 requirements.
Emissions: All units meet Euro 5 certification (VCA Type Approval #VCA/EMS/5679) under EU Regulation (EC) No 715/2007.
Power Ratings: Measured under DIN 70020 standards. Output remains consistent across fuel grades (Mercedes-Benz TIS Doc. A027104).
Mercedes-Benz Technical Information System (TIS): Docs A027100, A027101, A027102, SIB 02.2012.01
VCA Type Approval Database (VCA/EMS/5679)
DIN Standards: DIN 70020 Engine Power Measurement
The Mercedes-Benz M271.946 was used across Mercedes-Benz's W204/CL203 platforms with longitudinal mounting and adapted for transverse applications in the W245 B-Class. This engine received platform-specific adaptations-shorter intake manifolds in the W245 and revised engine mounts in the W204-and from 2012 the updated W204 facelift adopted revised intake runners and ECU mapping, creating service part interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front of the cylinder block near the timing cover (Mercedes-Benz TIS A027106). The 8th VIN digit indicates engine family ('A' for M271 series). All M271.946 units have black valve covers. Critical differentiation from M271.820: Original M271.946 uses Bosch ME 9.7 ECU with 104-pin connector and high-pressure fuel pump, while M271.820 uses ME 2.8 with 80-pin. Service parts require production date verification - intake manifolds for pre-2012 models are incompatible with post-facelift units due to revised port geometry per Mercedes-Benz SIB 02.2012.01.
The M271.946's primary reliability risk is intake valve carbon buildup, with elevated incidence in urban driving and short-trip usage. Internal Mercedes-Benz quality reports from 2013 indicated a significant portion of pre-2012 engines required intake cleaning before 100,000 km, while UK DVSA records show a notable share of emissions-related MOT failures linked to misfires from clogged ports. Frequent cold starts and low-RPM operation increase deposit formation, making maintenance intervals and fuel quality critical.
Analysis derived from Mercedes-Benz technical bulletins (2010–2014) and UK DVSA failure statistics (2015–2023). Repair procedures should follow manufacturer guidelines.
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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