The Porsche M 28.01 is a 2,687 cc, air‑cooled flat‑six petrol engine produced between 1971 and 1975. It featured Bosch D‑Jetronic electronic fuel injection, dual overhead camshafts (DOHC), and a 12‑valve layout. In road‑going 911 S and 911 E applications it delivered 147–162 kW (200–220 PS), with torque ranging from 245 to 255 Nm.
Fitted to the 911 S (1971–1973) and 911 E (1972–1975), the M 28.01 was engineered for enhanced high‑rpm responsiveness and smoother fuel meteri…
Production years 1971–1975 predate formal EU emissions regulations; no Euro standard applies (prior to EU Directive 70/220/EEC implementation timeline).
The Porsche M 28.01 is a 2,687 cc flat‑six petrol engine engineered for high-revving naturally aspirated performance in 911 S/E models (1971–1975). It combines Bosch D-Jetronic electronic fuel injection with DOHC valvetrain to deliver crisp throttle response and linear power delivery. Designed before formal emissions mandates, it prioritizes mechanical precision over emissions control.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,687 cc | |
Fuel type | Petrol (Unleaded) | |
Configuration | Flat‑6, DOHC, 12‑valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 94.0 mm × 66.0 mm | |
Power output | 147–162 kW (200–220 PS) | |
Torque | 245–255 Nm @ 5,200–5,600 rpm | |
Fuel system | Bosch D-Jetronic electronic fuel injection | |
Emissions standard | None (pre-regulation era) | |
Compression ratio | 9.8:1 | |
Cooling system | Air‑cooled | |
Turbocharger | None | |
Timing system | Chain-driven DOHC | |
Oil type | Porsche Classic 20W‑50 mineral oil | |
Dry weight | 172 kg |
The Porsche M 28.01 was used exclusively in Porsche's 911 platform with rear-engine, longitudinal mounting and no external licensing. This engine received platform-specific tuning—higher compression in the 911 S and emissions-optimized mapping in the 911 E—and all variants share core architecture with minor injector and cam profile differences. All adaptations are documented in OEM technical bulletins.
The M 28.01's primary reliability risk is D-Jetronic sensor or vacuum diaphragm failure, with elevated incidence in high-humidity or neglected-service conditions. Porsche internal data from 1974 indicated over 25 % of early 911 E engines required D-Jetronic recalibration before 80,000 km, while owner surveys correlate ethanol-blended fuels with fuel pressure regulator swelling and lean misfires. Extended idling and cold starts without warm-up cycles accelerate wear on solid cam followers, making oil quality and thermal management critical.
Analysis derived from Porsche technical bulletins (1971–1975) and EU vehicle failure statistics (1975–2023). Repair procedures should follow manufacturer guidelines.
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The M 28.01 offers excellent high-RPM performance but demands meticulous maintenance. Early 911 E variants had D-Jetronic sensitivity, while 911 S examples are more robust. Using non-ethanol fuel and 20W-50 mineral oil with strict 5,000–7,500 km intervals is essential—well-cared-for engines can exceed 150,000 km.
Top issues include D-Jetronic vacuum diaphragm failure, cam/follower wear, rear main seal leaks, and fuel pressure regulator swelling from ethanol. Porsche service bulletins (e.g., 911/03/72) document these concerns extensively.
Exclusively the 911 S (1971–1973) and 911 E (1972–1975) with 2.7L DOHC specification. No other Porsche or external brands used this engine. All are rear-engine, rear-wheel-drive coupés.
Yes—common upgrades include higher-flow injectors, revised D-Jetronic mapping, and performance cams. Stage 1 typically yields 230–240 PS. However, the stock crank and rods limit safe output; going beyond 260 PS risks bearing failure without internal reinforcement.
Approximately 15.2 L/100km (city) and 10.8 L/100km (highway), or ~18 mpg UK combined. Aggressive driving can exceed 20 L/100km. The D-Jetronic system is more efficient than carburetion but less so than modern EFI.
No. The M 28.01 uses a non-interference valvetrain—pistons and valves do not occupy the same space if timing fails. However, cam lobe wear can still cause valve float and misfire.
Porsche specifies a high-zinc 20W‑50 mineral oil (e.g., Porsche Classic). Synthetic oils are not recommended for solid-lifter DOHC engines. Change oil every 5,000–7,500 km to prevent cam wear.
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