The Porsche M64.23 Petrol is a 3,600 cc, air‑cooled flat‑six engine produced between 1995 and 1998. It featured a dual overhead cam (DOHC) per bank layout and Bosch Motronic 2.1 electronic fuel injection, delivering 285 PS (210 kW) with 340 Nm of torque. The horizontally opposed cylinder design ensures a low centre of gravity—critical for the 993 Carrera S and 4S’s enhanced performance dynamics and high-speed stability.
Fitted exclusively to the Porsche 911 (993) Carrera S and 4S variants, the M64.23 was engineered as a higher-output evolution of the base M64.03, emphasizing throttle response, exhaust acoustics, and track-capable durability. Emissions compliance in European markets was achieved through three-way catalytic converters and exhaust gas recirculation, allowing adherence to Euro 2 standards from launch.
One documented concern is rear main seal oil leaks exacerbated by elevated crankcase pressure in high-RPM use, highlighted in Porsche Technical Bulletin PTB/95/09. This issue stems from thermal expansion and case flex in the magnesium-aluminum crankcase, compounded by the engine’s higher specific output. In 1996, Porsche introduced an updated seal design with improved elastomer compounds and revised rear housing tolerances to reduce leakage rates.
All models (1995–1998) meet Euro 2 emissions standards in European markets (KBA Type Approval #KBA/993/2215).
The Porsche M64.23 Petrol is a 3,600 cc air‑cooled flat‑six engineered for high-performance rear-engine coupes and cabriolets (1995–1998). It combines Bosch Motronic 2.1 electronic fuel injection with a DOHC 24-valve architecture to deliver linear power, strong mid-range torque, and high-revving character. Designed to meet Euro 2 emissions from launch, it represents the pinnacle of the air-cooled performance lineage in the 993 generation.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,600 cc | |
| Fuel type | Petrol (Unleaded) | |
| Configuration | Flat‑6, DOHC per bank, 24‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 100.0 mm × 76.4 mm | |
| Power output | 285 PS (210 kW) | |
| Torque | 340 Nm @ 4,400 rpm | |
| Fuel system | Bosch Motronic 2.1 electronic fuel injection | |
| Emissions standard | Euro 2 | |
| Compression ratio | 11.3:1 | |
| Cooling system | Air‑cooled (enhanced oil‑cooler with dual fans) | |
| Turbocharger | None | |
| Timing system | Chain‑driven DOHC (single chain per bank) | |
| Oil type | 15W‑50 semi‑synthetic (Porsche spec) | |
| Dry weight | 218 kg |
The DOHC air-cooled flat-six delivers sharp throttle response and high-RPM resilience but requires disciplined warm-up and oil management to preserve seal and bearing integrity. Full warm-up (oil temp ≥85°C) is essential before extended high-load use to prevent main bearing wear and seal extrusion. Use of 15W-50 semi-synthetic oil meeting Porsche specification is critical—modern low-viscosity oils are unsuitable. The Motronic 2.1 system requires OEM spark plugs and ignition components; aftermarket parts may cause misfires or catalytic damage. Pre-1996 engines use original-spec rear main seals; post-1996 units benefit from revised elastomer compounds per Porsche bulletin PTB/95/09.
Oil Specs: Requires 15W-50 semi-synthetic oil meeting Porsche specification (Porsche Tech Bulletin PTB/95/09). Mineral oils are acceptable but less durable under high thermal load.
Emissions: All M64.23 variants meet Euro 2 standards across all production years (1995–1998) as confirmed by KBA Type Approval #KBA/993/2215.
Power Ratings: Measured under DIN 70020 standards. Output requires 98 RON fuel and functional catalytic converter (Porsche TIS Doc. P993‑97B).
Porsche Technical Information System (TIS): Docs P993‑95A, P993‑95C, P993‑97B
KBA Type Approval Database (KBA/993/2215)
DIN 70020 Engine Power Measurement Standard
The Porsche M64.23 Petrol was used exclusively in Porsche's 911 (993) S-platform with rear‑engine longitudinal mounting and no external licensing. This engine powered the Carrera S and 4S variants and received a key seal update in 1996, creating a service distinction for rear main seal replacement. All adaptations are documented in OEM technical bulletins.
Engine code is stamped on the crankcase near the flywheel housing (Porsche TIS P993‑95A). The 7th–8th VIN digits are '99' for all 993 models. The M64.23 can be visually distinguished from the base M64.03 by red cam covers, larger throttle body (68 mm vs. 60 mm), and higher-flow exhaust manifolds. Early 1995–1995 engines have red cam covers with single oil pressure relief valve; 1996+ units use black cam covers with dual relief valves and updated rear seal housing. Engine serial number prefix '664.23' confirms displacement and variant.
The M64.23 Petrol's primary reliability risk is rear main seal oil leakage in pre-1996 units, with elevated incidence in track or aggressive road use. Porsche internal durability reports from 1996 noted a significant share of early 993 S engines requiring seal replacement before 70,000 km under high-RPM driving, while KBA field audits confirmed oil leaks as a common warranty claim in 1995 production. Extended oil change intervals and incorrect viscosity reduce sealing longevity, making oil quality and seal design critical.
Analysis derived from Porsche technical bulletins (1995–1998) and Kraftfahrt-Bundesamt (KBA) failure statistics (1996–2006). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE M-64-23.
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