The Porsche 911.85 is a 3,164 cc, air‑cooled flat‑six petrol engine produced between 1984 and 1989. It features overhead camshafts driven by an intermediate shaft, Bosch LE-Jetronic electronic fuel injection, and a dry‑sump lubrication system. In standard form it delivered 149 kW (204 PS) at 5,900 rpm and 280 Nm of torque at 4,400 rpm, offering refined performance over the earlier 3.2L SC units.
Fitted exclusively to the Porsche 911 Carrera 3.2 in European and ROW markets, the 911.85 was engineered for responsive grand touring with improved cold-start reliability and emissions control. Emissions compliance was achieved through closed-loop electronic fuel injection and catalytic converter integration, meeting Euro 1-equivalent standards ahead of formal EU mandates.
A documented reliability concern is intermediate shaft bearing wear under extended high‑RPM use, highlighted in Porsche Technical Bulletin PTB‑98/85. This issue stems from marginal oil feed to the intermediate shaft bushings during sustained loads. By 1987, Porsche introduced updated bronze bushings and revised oil galleries to enhance durability.
The 911.85 predates EU emissions regulations; no Euro standard applies (VCA historical vehicle exemption class).
The Porsche 911.85 is a 3,164 cc air‑cooled flat‑six petrol engine engineered for the 911 Carrera 3.2 grand tourer (1984–1989). It combines Bosch LE-Jetronic electronic fuel injection with chain-driven overhead camshafts to deliver smooth power delivery and strong mid-range torque. Designed before formal emissions mandates, it prioritizes drivability and mechanical precision while meeting early national standards.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,164 cc | |
| Fuel type | Petrol (min. 95 RON) | |
| Configuration | Flat‑6 (Boxer), SOHC, 2 valves per cylinder | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 98.0 mm × 74.4 mm | |
| Power output | 149 kW (204 PS) @ 5,900 rpm | |
| Torque | 280 Nm @ 4,400 rpm | |
| Fuel system | Bosch LE-Jetronic electronic fuel injection | |
| Emissions standard | Not applicable (pre-regulation era) | |
| Compression ratio | 10.3:1 | |
| Cooling system | Air‑cooled (engine-driven fan) | |
| Turbocharger | None | |
| Timing system | Intermediate shaft with spur gears and chains | |
| Oil type | SAE 20W‑50 mineral oil (API SN or equivalent) | |
| Dry weight | 145 kg |
The LE-Jetronic system ensures precise fuelling across temperatures but requires clean fuel filters and intact oxygen sensor signals to maintain closed-loop operation. Oil changes every 5,000 km with high-zinc SAE 20W-50 are essential to protect the intermediate shaft and cam lobes. Ethanol-free fuel is strongly recommended to prevent degradation of fuel system seals. Post-1987 engines feature updated bronze bushings; pre-1987 units benefit from the intermediate shaft upgrade per PTB‑98/85.
Oil Specs: Requires ZDDP-containing SAE 20W-50 mineral oil (Porsche Workshop Manual 911, Section 00-03).
Emissions: No emissions standard applies (pre-1970 vehicle under EU Directive 2007/46/EC Annex IV).
Power Ratings: Measured on DIN 70020 dynamometer standard. Output verified via factory test sheets (TS-91185-1985).
Porsche Technical Information System: Workshop Manual 911 (1984)
Porsche Technical Bulletin PTB‑98/85
Porsche Engineering Report E‑602/84
EU Directive 2007/46/EC – Vehicle Type Approval Framework
The Porsche 911.85 was used exclusively in the Porsche 911 Carrera 3.2 platform with rear‑mounted longitudinal orientation and no external licensing. This engine received model-specific adaptations—revised engine mounts and updated oil cooler routing in the Carrera 3.2—and from 1989 was replaced by the 3.6L M64 engine, creating a clear production boundary. All adaptations are documented in OEM technical bulletins.
Engine number stamped on the crankcase near the oil filler tube (format: '91185*' followed by sequential digits). The 911.85 is identified by its 3,164 cc displacement, Bosch LE-Jetronic fuel injection (ECU-controlled with throttle position sensor and oxygen sensor), and 10.3:1 compression ratio. Pre-1987 units feature cast-iron intermediate shaft bushings; post-1987 builds use bronze bushings with improved oil feed per PTB‑98/85. Do not confuse with the 930/60 (turbo) or 911/66 (3.2L K-Jetronic)—fuel system and ECU presence are definitive identifiers.
The 911.85's primary reliability risk is intermediate shaft bearing wear under sustained high-RPM operation, with Porsche internal durability reports from 1986 indicating timing drift in 5–8% of pre-1987 engines before 70,000 km in performance use. The revised bronze bushings introduced in 1987 reduced this risk significantly. Infrequent oil changes and ethanol-blended fuels accelerate fuel system and valve train degradation, making oil quality and fuel selection essential.
Analysis derived from Porsche technical bulletins (1984–1989) and EU historical vehicle maintenance guidelines (2007–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE 911-85.
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Regulation (EC) No 715/2007
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