The Porsche M28.09 is a 2,142 cc, inline‑four petrol engine produced between 1978 and 1986. It powered the front-engine Porsche 924 and was notable for its water-cooled architecture in a brand dominated by air-cooled flat-sixes. Featuring a single overhead camshaft (SOHC), Bosch L-Jetronic electronic fuel injection, and an aluminum block with cast-iron liners, it delivered 95 kW (130 PS) and 182 Nm of torque.
Fitted exclusively to the 924 (G-series) across global markets—including the 924, 924 Carrera GT (racing homologation base), and early 924S—the M28.09 was engineered for balanced economy, reliability, and manageable performance. Emissions compliance was achieved through closed-loop lambda control, exhaust gas recirculation (EGR), and catalytic converter integration, allowing compliance with Euro 1-equivalent national standards (e.g., German TÜV, UK VCA).
One documented concern is head gasket failure under sustained high-load conditions, highlighted in Porsche Technical Service Bulletin TSB‑924‑1983. Early units used a composite gasket susceptible to thermal fatigue, particularly when cooling system maintenance was neglected or factory-spec coolant was substituted.
Production years 1978–1986 meet national emissions standards of the era; Euro 1-equivalent compliance applies to select export models (VCA UK Type Approval #VCA/EMS/924E).
The Porsche M28.09 is a 2,142 cc inline‑four petrol engine engineered for front-engine sports coupes (1978–1986). It combines Bosch L-Jetronic electronic fuel injection with an aluminum block and SOHC valvetrain to deliver smooth, reliable power with modest performance. Designed before formal EU emissions standards, later units incorporated modifications to meet national and VCA-equivalent requirements.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,142 cc | |
| Fuel type | Petrol (RON 95 min) | |
| Configuration | Inline‑4, SOHC, 8‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 97.0 mm × 72.6 mm | |
| Power output | 95 kW (130 PS) @ 5,500 rpm | |
| Torque | 182 Nm @ 3,500 rpm | |
| Fuel system | Bosch L-Jetronic electronic injection | |
| Emissions standard | Pre-Euro; national equivalents (e.g., VCA) | |
| Compression ratio | 9.3:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven SOHC | |
| Oil type | SAE 10W-40 mineral oil (API SF/CC) | |
| Dry weight | 134 kg |
The M28.09 offers linear power delivery ideal for daily driving but requires vigilant cooling system upkeep—factory 50/50 ethylene glycol coolant must be replaced every 2 years to prevent corrosion and head gasket failure. Oil changes every 7,500 km with quality 10W-40 mineral oil protect the SOHC train and hydraulic lifters. The Bosch L-Jetronic system is sensitive to poor grounding and aging oxygen sensors; use OEM-spec parts to maintain emissions and drivability. Early M28.09 units (1978–1981) are most prone to gasket issues—post-1983 models received revised gaskets per TSB-924-1983.
Oil Specs: Requires API SF/CC 10W-40 mineral oil (Porsche Lubricants Guide 1982). Synthetic oils were not factory-approved for this era.
Emissions: Pre-Euro engine; only 1984–1986 UK exports received VCA-equivalent certification (VCA Type Approval #VCA/EMS/924E).
Power Ratings: Measured under DIN 70020 standards. Power consistent across global variants except US-spec 924 (detuned for emissions).
Porsche Technical Information System (TIS): Docs PT-924-78, FT-924-81, TSB-924-1983
VCA Type Approval Database (VCA/EMS/924E)
DIN 70020 Engine Performance Measurement Standard
The Porsche M28.09 was used exclusively in Porsche's 924 platform with front-mounted, longitudinal orientation and no external licensing. This engine received minor updates—revised head gaskets from 1983 and updated ECU calibrations for catalytic models—and all adaptations are documented in OEM technical bulletins.
Engine code M28.09 is stamped on the left side of the block near the cylinder head flange (Porsche TIS PT-924-78). The 10th VIN digit is 'H' (1978), 'J' (1979), 'K' (1980), 'L' (1981), 'M' (1982), 'N' (1983), 'P' (1984), 'R' (1985), or 'S' (1986). Visual cues: all M28.09 engines have a black plastic air cleaner housing and Bosch L-Jetronic ECU mounted in the front trunk. Do not confuse with later 2.5L M44/40 (924S post-1986) or Audi-derived 2.0L variants used in early 924s (M28.01)—the M28.09 has a unique 2,142 cc displacement and 130 PS output.
The M28.09's primary reliability risk is head gasket failure in pre-1983 units, with elevated incidence in high-ambient climates or neglected cooling systems. Porsche internal data from 1984 indicated head gasket repairs in over 15% of early 924s by 100,000 km, while UK DVSA records show associated overheating complaints in poorly maintained examples. Coolant integrity and thermal management make preventative maintenance critical.
Analysis derived from Porsche technical bulletins (1978–1986) and UK DVSA failure statistics (1987–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE M-28-09.
Comprehensive technical documentation and regulatory references
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