Home 2CV History Engines

The car featured an air-cooled, flat-twin, four-stroke, 375 cc engine, with the notoriously underpowered earliest model developing only 9 bhp DIN (6.5 kW). A 425 cc engine was introduced in 1955, followed by a 602 cc (giving 28 bhp (20.5 kW) at 7000 rpm) in 1968. With the 602 cc engine the tax classification of the car changed so that it became in fact a 3CV, but the commercial name remained unchanged. A 435 cc engine was introduced at the same time in replacement of the 425 cc, the 435 cc engine car was christened 2CV 4 while the 602 cc took the name 2CV 6 (although a variant did take the name 3CV in Argentina). The 602 cc engine evolved to the M28 33 bhp (24 kW) in 1970; this was the most powerful engine fitted to the 2CV. A new 602 cc giving only 29 bhp (21.5 kW) at a slower 5750 rpm was introduced in 1979. Despite being less powerful, this engine was more efficient, allowing lower fuel consumption and better top speed, at the price of decreased acceleration. All 2CVs with the M28 engine can run on unleaded petrol, but attention is needed to ensure that valve clearances are maintained.

The 2CV also pioneered the use of the now common wasted spark Ignition System, also known as the DIS (Distributorless Ignition System) ignition using a double ended coil fired on each revolution, (on the exhaust and compression stroke), by just a contact breaker.

The engine's design concentrated on the reduction of moving parts. The cooling fan and dynamo were built integrally with the one-piece crankshaft, removing the need for drive belts. Instead of using the usual two-piece crank bearings, one-piece items were pressed onto the crankshaft with a hydraulic press once the crankshaft had been submerged in liquid nitrogen to cause it to contract (thus providing enough clearance to press the bearings on). Similarly, the contact breaker was driven directly off the end of the camshaft, meaning that the ignition timing remained accurate for years.

These design features made the 2CV engine highly reliable (test engines were run at full speed for 1000 hours at a time- equivalent to driving 50,000 miles (80,500 km) at full throttle). They also meant that the engine was very much 'sealed for life' - the main bearings, for example, could not be replaced individually- the entire crankshaft had to be replaced. However, the engine is very under-stressed and long-lived, so this is not a major issue. Until the 1960s it was common for other car manufacturers engines (British Fords especially), to need full strip downs and rebuilds at as little as 50,000 mile intervals - unrebuilt 2CV engines are still running that are passing 250,000 miles.

When asked about the 2CVs performance and acceleration, many owners said it went "from 0-60 in one day". Others jokingly said they "had to make an appointment to merge onto an interstate highway system".

The last evolution of the 2CV engine was the Citroen Visa flat-2, a 652 cc featuring an electronic ignition. Citro├źn never sold this engine in the 2CV, however some enthusiasts have converted their 2CVs to 652 engines.