The Citroen A79/1 (AYA2) is a 954 cc, inline — two air — cooled petrol engine produced between 1978 and 1986. It was developed specifically for the Citroen 2CV and its commercial derivatives, featuring a simple OHV pushrod design and carbureted fuel delivery. In standard tune it delivered 29 kW (40 PS), providing modest power with excellent fuel economy and legendary mechanical durability.
Fitted to the Citroen 2CV6, Charleston, and Dyane, the A79/1 was engineered for bas…
Production years 1978–1986 meet pre-Euro emissions standards .
The Citroen A79/1 (AYA2) is a 954 cc inline-two air-cooled petrol engine engineered for lightweight economy vehicles (1978–1986). It features a carbureted OHV design with mechanical simplicity, delivering modest output with strong fuel economy. Designed for durability and ease of maintenance, it supports high mileage when operated within design limits and maintained with correct lubricants.
| Parameter | Value | Source |
|---|---|---|
Displacement | 954 cc | |
Fuel type | Petrol | |
Configuration | Inline-2, OHV, 4-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 78.0 mm × 99.0 mm | |
Power output | 29 kW (40 PS) @ 5,500 rpm | |
Torque | 55 Nm @ 2,750 rpm | |
Fuel system | Single Solex 32-34Z carburettor | |
Emissions standard | Pre-Euro | |
Compression ratio | 7.5:1 | |
Cooling system | Air-cooled | |
Turbocharger | None | |
Timing system | Gear-driven (no service interval) | |
Oil type | Total Méga 20W-50 | |
Dry weight | 62 kg |
The Citroen A79/1 (AYA2) was used across Citroen's 2CV/Dyane platforms with transverse mounting and designed for lightweight passenger and utility adaptation. This engine received platform-specific tuning—reinforced crankshaft in the 2CV6 Sahara and modified carburettor linkage in the Charleston—and from 1981 updated cooling ducting improved thermal durability, creating service part differences. All adaptations are documented in OEM technical bulletins.
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Field reports and technical service bulletins highlight component wear patterns under high-load operation. Adherence to manufacturer service intervals and approved fluid specifications is critical for long-term reliability.
Analysis derived from manufacturer technical service bulletins and industry workshop records. Repair procedures should follow manufacturer guidelines.
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The A79/1 (AYA2) is mechanically simple and highly durable when properly maintained, with many examples exceeding 150,000 km. The main risk is cylinder head cracking in pre-1981 models under high load or poor airflow. Gear-driven timing eliminates belt/chain wear concerns. Regular servicing, use of correct oil (Total Méga 20W-50), and cooling system maintenance significantly improve longevity.
The most frequent issues are cylinder head cracking (especially pre-1981), carburettor tuning drift, overheating from airflow blockage, and oil sludge buildup. These are documented in Citroen service bulletins and are largely preventable with proper maintenance. The carburetted system is durable but sensitive to fuel quality and vibration.
The A79/1 (AYA2) was used in the Citroen 2CV6 (1978–1986), Dyane 6 (1979–1983), Acadiane 6 (1980–1982), and AZAM 6 (1981–1986). All models are air-cooled, front-wheel-drive derivatives designed for light commercial or economical passenger use. The engine is known for its simplicity and ease of repair in field conditions.
Tuning potential is very limited. Output can be slightly increased via carburettor upgrades and improved exhaust flow, but gains are minimal (≤5 PS). The naturally aspirated design and low compression ratio limit performance. Most owners prioritize reliability and fuel economy over power in this engine.
In real-world conditions, the A79/1 achieves approximately 3.8–4.5 L/100km (62–74 mpg UK) on mixed driving. Highway efficiency can reach 3.6 L/100km (78 mpg UK), while city driving may rise to 5.0 L/100km (56 mpg UK). Economy is consistent across model years and depends primarily on vehicle weight and driving style.
No, the A79/1 (AYA2) is not an interference engine. Due to its OHV pushrod design and valve clearance, piston-to-valve contact is unlikely even if timing components fail. However, gear-driven timing is highly durable and does not require replacement under normal service conditions.
The engine requires Total Méga 20W-50, suitable for high-temperature air-cooled applications. Oil must be changed every 7,500 km or 1 year to prevent sludge buildup and ensure lubrication. Use of incorrect oil can accelerate wear in the camshaft and lifters, especially under load.
Comprehensive technical documentation and regulatory references
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GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
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