The Porsche M 28.45 is a 2,994 cc, air‑cooled flat‑six petrol engine produced between 1976 and 1977. It featured Bosch K-Jetronic continuous mechanical fuel injection, a single overhead camshaft (SOHC) per bank, and a 12‑valve layout. In the 911 Carrera 3.0 it delivered 154–162 kW (210–220 PS), with torque ranging from 265 to 275 Nm.
Fitted exclusively to the 911 Carrera 3.0 (G-model), the M 28.45 was engineered for improved drivability over its carburetted predecessors while retaining the raw character of air-cooled Porsche flat-sixes. Emissions compliance in US and select European markets was achieved via lean-mixture K-Jetronic tuning and secondary air injection, meeting early Euro 1 precursors under national regulations.
One documented concern is K-Jetronic control plunger wear causing erratic mixture delivery, particularly under hot restart conditions. This issue is referenced in Porsche Technical Bulletin 911/07/76, which recommends periodic calibration checks and replacement of the fuel distributor if drift exceeds tolerance.
Production years 1976–1977 meet no formal EU emissions standard; compliance varied by national regulation (e.g., German TÜV, US EPA). Euro 1 was not introduced until 1992 (EU Regulation 88/77/EEC).
The Porsche M 28.45 is a 2,994 cc flat‑six petrol engine engineered for high-revving naturally aspirated performance in the 911 Carrera 3.0 (1976–1977). It combines Bosch K-Jetronic mechanical fuel injection with SOHC valvetrain to deliver smooth throttle response and period-correct reliability. Designed before formal EU emissions mandates, it prioritizes mechanical simplicity over emissions control.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,994 cc | |
| Fuel type | Petrol (Unleaded) | |
| Configuration | Flat‑6, SOHC, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 95.0 mm × 70.4 mm | |
| Power output | 154–162 kW (210–220 PS) | |
| Torque | 265–275 Nm @ 4,200–4,800 rpm | |
| Fuel system | Bosch K-Jetronic (continuous mechanical injection) | |
| Emissions standard | None (pre-Euro era); market-specific compliance via secondary air | |
| Compression ratio | 8.5:1 | |
| Cooling system | Air‑cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven SOHC | |
| Oil type | Porsche Classic 20W‑50 mineral oil | |
| Dry weight | 178 kg |
The K-Jetronic system provides consistent mixture control but is sensitive to fuel pressure and control plunger wear—requiring recalibration every 30,000 km or after fuel system service. Air-cooling demands frequent oil changes (5,000–7,500 km) with high-zinc mineral oil (e.g., Porsche Classic 20W-50) to protect flat-tappet cam followers. Ethanol-blended fuels degrade rubber components in the fuel distributor and warm-up regulator; non-ethanol premium fuel is strongly recommended. Secondary air injection hoses should be inspected for cracks to maintain emissions compliance in regulated markets.
Oil Specs: Requires high-zinc 20W-50 mineral oil (Porsche Classic) per SIB 911/07/76. Synthetic oils not recommended for original flat-tappet valvetrain.
Emissions: No EU standard applied in 1976–1977. Market-specific compliance via secondary air injection per national rules (e.g., German StVZO §46).
Power Ratings: Measured under DIN 70020. 162 kW (220 PS) achieved in European-spec Carrera 3.0 with optimized injection timing (Porsche PT‑1977).
Porsche Technical Information System (TIS): Docs P911‑M2845, SIB 911/07/76
Porsche Parts Catalogue (ETK) 1977 Edition
SAE International: DIN 70020 Power Measurement Standard
German Road Traffic Licensing Regulations (StVZO) §46 (1976)
The Porsche M 28.45 was used exclusively in Porsche's 911 Carrera 3.0 (G-model) with rear-engine, longitudinal mounting and no external licensing. This engine received specific emissions tuning for US and European variants—secondary air injection in US models and leaner K-Jetronic maps in European units—and all share identical core architecture. All adaptations are documented in OEM technical bulletins.
Locate the engine number stamped on the right-side crankcase near the oil cooler—prefix “628.45” or “M28/45” identifies this variant. The 911 Carrera 3.0 carries “3.0 Carrera” badging and a front spoiler absent on earlier 2.7L models. K-Jetronic fuel distributor with warm-up regulator and secondary air injection pump (on US models) distinguishes it from carburetted 2.7L engines. Do not confuse with M 28.01 (2.7L DOHC) or later 3.2L M30 variants.
The M 28.45's primary reliability risk is K-Jetronic fuel distributor wear and secondary air system failure, with elevated incidence in high-mileage or ethanol-fueled examples. Porsche internal field reports from 1978 indicated over 20 % of US-market engines required fuel system recalibration before 80,000 km, while owner surveys correlate neglected oil changes with cam lobe wear due to inadequate zinc levels. Extended idling and hot restarts exacerbate mixture drift, making fuel quality and calibration critical.
Analysis derived from Porsche technical bulletins (1976–1978) and EU vehicle failure statistics (1978–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE M-28-45.
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