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CitroŽn 2 CV (engine)



Assignment

The development of the first prototype dates back to the year 1937. The outbreak of the Second World War caused the market introduction to be delayed until 1949. While some money was to be spent on the development of a comfortable chassis, to combat the bad French country roads at that time, they had to be thrifty with the engine. Thus, for the rest of its life the performance of the engine was very moderate, indeed, so was the fuel consumption. The advantage of the good chassis could never really be exploited.

Function

At first glance, the straight-mounted, air-cooled boxer engine, apart from having only two cylinders, did not indicate thriftiness, the modest cubic capacity of only 375 cm≥ did. The cam shaft was mounted underneath the crankshaft, driving the valves via push rods and rocker arms. The crank-case respectively the camshaft housing and the cylinder heads were made from aluminium, the cylinders from cast iron. In the first two pictures the flanges for the common intake tube can be seen. On top of it, in the middle, the carburettor was mounted, in front of the comparatively enormous oil filler. It was supplied with fuel by the diaphragm pump, well visible in fig. 2.

The cooling air was drawn in from the front by the fan-wheel, then without thermostatic regulation, blown past the two cylinders. In front, just above the crank case, an oil cooler (see fig. 3) was mounted. The entire cooling air passage was of course, guided by appropriate sheet metal plating, which has been removed in figures 1 and 2. In the end, the air ducts led the air either into the interior as heating or out into the open. A so- called fresh-air heating as was found in the Volkswagen Beetle would never be offered.

The engine had one somewhat unconventional characteristic. Because the valves were not parallel to each other the combustion chambers were slightly half-spherical, the spark plugs protruded into the combustion chamber in the proximity of the exhaust valves. Despite being a push-rod engine, due to its small stroke, the engine was quite happy at high revs, although, to hold out better when climbing hills it had to be supported by a relatively large flywheel. This was big enough, e.g., to cause a slight wheelspin when shifting from first to second gear because the flywheel tried to maintain the high revs at the end of the first gear.

That thriftyness also has advantages, can be seen by the two starter devices in the 2 CV. For years the car did not have a solenoid. The starter was mechanically engaged, manually per cable. Have a closer look at fig. 2, in the middle of the fan-wheel you'll see the alternative to the electric starter. Here, the standard issue crank-handle could be applied, its disengaging when the engine started, was guaranteed. This feature was important, so that the crank-handle didn't remain joined to the engine when it fired. Thus, a French farmer would have been able to reach the next workshop - or carry on driving - even if the battery and starter were defect, indeed, only until the generator also gave up the ghost.

While we're on the subject of workshops, the legendary simplicity of repairing the engine must be mentioned. This was mainly due to its exposed position. The side-covers could also be dismantled in a very short time. The cylinders and cyl. heads could be dismantled without removing the engine. The removal of the engine was only necessary for replacing the crankshaft. The con-rods with their needle bearings, could not be screwed off, the new crankshaft was supplied with the already mounted two con-rods. Due to the danger of remaining metal shavings, the new crankshaft was only available together with a new oil cooler. 07/12


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