The Porsche M 28.12 is a 2,483 cc, air‑cooled flat‑six petrol engine produced between 1982 and 1989. It featured Bosch LE-Jetronic electronic fuel injection, a 911SC-derived short-stroke architecture, and a compression ratio of 9.8:1, producing 132 kW (180 PS) and 250 Nm of torque. This engine was designed for balanced performance, drivability, and emissions compliance under tightening European norms.
Fitted exclusively to the Porsche 944 (type 924S in later years), the M 28.12 provided refined power delivery with a broad torque curve and responsive throttle behavior. Emissions control was achieved through LE-Jetronic closed-loop fuel control, a three-way catalytic converter, and secondary air injection, enabling compliance with Euro 1-equivalent standards under EU Directive 70/220/EEC.
One documented engineering update is the switch from early cast-iron exhaust manifolds to lighter steel tubular headers in 1986, improving thermal efficiency and reducing weight. Porsche Technical Bulletin PTB‑86‑03 notes that early M 28.12 units used a crankcase breather system prone to oil vapor accumulation in the airflow meter, potentially causing erratic idle or hesitation—a flaw corrected via a revised hose routing and separator in mid-1985.
Production years 1982–1989 meet pre‑Euro to transitional Euro 1 emissions standards (VCA UK Type Approval #VCA/ICE/M2812).
The Porsche M 28.12 is a 2,483 cc air-cooled flat‑six petrol engine engineered for the Porsche 944 platform (1982–1989). It combines Bosch LE-Jetronic electronic fuel injection with a short-stroke flat-six architecture to deliver smooth power delivery and strong mid-range torque. Designed under early EU emissions frameworks, it balances sporty character with street compliance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,483 cc | |
| Fuel type | Petrol (RON 95 min) | |
| Configuration | Flat‑6, OHC, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 98.0 mm × 84.0 mm | |
| Power output | 132 kW (180 PS) | |
| Torque | 250 Nm @ 3,500 rpm | |
| Fuel system | Bosch LE-Jetronic electronic fuel injection | |
| Emissions standard | Pre‑Euro / Transitional Euro 1 | |
| Compression ratio | 9.8:1 | |
| Cooling system | Air‑cooled | |
| Turbocharger | None | |
| Timing system | Gear-driven camshafts | |
| Oil type | Porsche-approved 15W-50 synthetic (API SF/CC) | |
| Dry weight | 165 kg |
The LE-Jetronic system offers more precise fueling than earlier mechanical injection, but remains sensitive to airflow meter contamination from crankcase vapors. Early models (pre-1985) require breather hose inspection to prevent idle instability. RON 95 minimum fuel is sufficient, though RON 98 improves throttle response and reduces carbon buildup. Oil changes every 7,500 km with high-thermal-stability 15W-50 oil are critical due to air-cooling limitations. The front-mounted oil cooler must remain unobstructed to maintain bearing life, as noted in Porsche Technical Bulletin PTB‑86‑03.
Oil Specs: Requires Porsche-approved 15W-50 synthetic with API SF/CC rating (Porsche TIS LUB-M28). Modern equivalents must meet Porsche C30 specification.
Emissions: Pre-Euro norms apply to 1982–1984 models; transitional Euro 1 compliance for 1985–1989 (VCA Type Approval #VCA/ICE/M2812).
Power Ratings: Measured under DIN 70020 standards (Porsche PT‑1988).
Porsche Technical Information System (TIS): Docs M28/12, FUE-M28, LUB-M28
VCA Type Approval Database (VCA/ICE/M2812)
EU Directive 70/220/EEC – Emissions for Petrol Engines
The Porsche M 28.12 was used exclusively in the Porsche 944 (1982–1989) platform with front-engine, longitudinal mounting. This engine replaced the Audi-derived inline‑four in the 924 and served as the base powerplant until the introduction of the 944 S (M44/40). No third-party licensing occurred. All adaptations are documented in OEM technical bulletins.
Engine code 'M 28.12' is stamped on the rear crankcase near the flywheel housing (Porsche TIS M28/12). The type plate on the front trunk wall lists engine number prefix 'M28'. Visual identification: flat-six layout with twin chain-driven distributors (vs. inline‑four in early 924). Early 944s (1982–1985) have cast-iron exhaust manifolds; 1986+ units use tubular steel headers. LE-Jetronic ECU is mounted under the passenger footwell—do not confuse with K-Jetronic 930 engines.
The M 28.12's primary reliability risk is oil contamination of the LE-Jetronic airflow meter in early builds, leading to unstable idle or lean running. Porsche field data from 1986 indicated elevated service visits for this issue, while UK DVSA records show occasional MOT failures due to exhaust manifold cracking from thermal cycling. Extended high-RPM use without adequate cooling increases valve guide wear, making oil quality and warm-up discipline critical.
Analysis derived from Porsche technical bulletins (1984–1989) and UK DVSA failure statistics (1995–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE M-28-12.
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PORSCHE Official Site
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
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DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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