The Porsche M 55.01 is a 2,687 cc, dual-overhead-cam flat‑six petrol engine produced between 2005 and 2008. It featured Bosch Motronic ME7.8.1 sequential fuel injection, an aluminum block with Nikasil-coated cylinders, and a dry‑sump lubrication system. In standard form it delivered 180 kW (245 PS) and 290 Nm of torque, offering increased displacement and refinement over the previous M 48 architecture while retaining mid-engine balance.
Fitted exclusively to the 987-generation Boxster and Cayman (2005–2008), the M 55.01 was engineered to improve torque delivery and high-RPM response over the 2.5L variant. Emissions compliance was achieved through a secondary air injection system, wideband oxygen sensors, and a close-coupled three-way catalytic converter, meeting Euro 4 standards across its production life.
One documented concern is rear main seal (RMS) leakage, a continuation of M96/M48-era design sensitivity. Porsche Technical Bulletin PTB/987/05 notes that the M 55.01 retained the dual-lip RMS but remains vulnerable to improper installation torque or elevated crankcase pressure from a degraded PCV system.
Production years 2005–2008 meet Euro 4 standards (TÜV Certificate TÜV/05/M55/11).
The Porsche M 55.01 is a 2,687 cc flat‑six petrol engine engineered for the mid-mounted 987 Boxster and Cayman (2005–2008). It combines DOHC architecture with sequential fuel injection and dry-sump lubrication for stable oil supply during high-g cornering. Designed to meet Euro 4 emissions standards, it integrates catalytic converters and secondary air injection for regulatory compliance while improving on prior-generation torque and smoothness.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,687 cc | |
| Fuel type | Petrol (RON 95 min, RON 98 recommended) | |
| Configuration | Flat‑6, DOHC, 24‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 89.0 mm × 72.0 mm | |
| Power output | 180 kW (245 PS) @ 6,400 rpm | |
| Torque | 290 Nm @ 4,750 rpm | |
| Fuel system | Bosch Motronic ME7.8.1 sequential injection | |
| Emissions standard | Euro 4 | |
| Compression ratio | 10.9:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven DOHC | |
| Oil type | Porsche C3 5W‑40 (API SM/ACEA C3) | |
| Dry weight | 158 kg |
The larger 2.7L flat-six provides stronger mid-range pull and smoother high-RPM delivery than the 2.5L, ideal for spirited driving. The dual-lip rear main seal reduces—but does not eliminate—leak risk if flywheel bolts are overtightened or the PCV system is neglected. Use RON 98 fuel to prevent knock under load. Oil changes every 10,000 km with Porsche C3 5W‑40 are essential to protect bearings and catalytic converters. Per PTB/987/05, RMS replacement requires strict torque control on the flywheel bolts (18 Nm + 90° angle). Nikasil bores remain sensitive to glycol contamination—any coolant leak must be addressed immediately.
Oil Specs: Requires Porsche C3 5W‑40 meeting ACEA C3/API SM (Porsche Lubricants Bulletin LB-987-05). Low-SAPS formulation is mandatory.
Emissions: Euro 4 compliance applies to all 2005–2008 models (TÜV Certificate TÜV/05/M55/11).
Power Ratings: Measured under DIN 70020; verified on dynamometer (Porsche PTB/987/05).
Porsche Technical Information System (TIS): Docs 987-03, 987-1120, 987-2210
Porsche Technical Bulletin PTB/987/05
TÜV Certificate TÜV/05/M55/11
Porsche Lubricants Bulletin LB-987-05
The Porsche M 55.01 was used exclusively in Porsche's 987 platform with mid‑mounted, longitudinal flat-six mounting and no external licensing. This engine received platform-specific tuning—revised oil galleries in the 2006 Boxster S and updated exhaust manifolds in 2007 Cayman—and from 2008 was succeeded by the M 97.22 2.9L with VarioCam Plus and higher output, creating clear generational boundaries. All adaptations are documented in OEM technical bulletins.
Engine code 'M 55.01' is stamped on the rear crankcase flange near the flywheel housing (Porsche TIS 987-1120). The 10th VIN digit indicates model year ('5' = 2005, '6' = 2006, etc.). Visual cues: black valve covers with “Boxster S” or “Cayman S” script, twin exhaust outlets, and absence of VarioCam Plus (introduced in 2009). The engine uses a dual-lip RMS (part #987 101 076 01) and retains the single-row IMS bearing from earlier M96/M48 designs.
The M 55.01's primary reliability risk is rear main seal (RMS) leakage due to installation sensitivity and PCV system degradation, with elevated incidence in high-mileage or track-used vehicles. Porsche internal data (2006) noted a 9% RMS replacement rate in 987 S models before 120,000 km, while TÜV Germany MOT records show elevated oil consumption in engines with neglected PCV systems. Extended high-load operation without maintenance accelerates seal stress, making RMS protocol and oil quality critical.
Analysis derived from Porsche technical bulletins (2005–2008) and TÜV Germany failure statistics (2007–2017). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE M-55-01.
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