No matter how many V8s the Americans may have thrown on the market, we dare to say that the most common internal combustion engine is a four-cylinder. It is partly the Americans' own fault, because the first car that went around the world from there was powered by a four-cylinder. We're talking about the Ford T and, for the most part, also A.

Even after that, the company had sometimes returned to the four-cylinder, e.g. in the second series of the Mustang, of all things, after an initial six-cylinder. And it's back with the current one. The VW Beetle spoilt the plans of the Model T by pre-empting it with its boxer engine.

But we are focusing on the in-line engine, liquid-cooled from the basic construction, so to speak, although there were also very few air-cooled engines. It appeared very early in vehicle development, but initially as a double two-cylinder. One was just not able to cast four cylinders with a crankcase in one piece like the one in the picture above.

You can see it here on this four-cylinder with 15.4 liters (175 mm * 160 mm) and 81 kW (110 PS) at 1080 rpm, two of which were built by Daimler-Motoren-Gesellschaft for Count Zeppelin's LZ6 in 1908/09. Two cylinders are cast together. However, the crankshaft inside the two cylinders must not look like it is usual in a four-stroke two-cylinder.

If the two parts of the crankshaft were also cranked in this way, then at most the engine on the left would be possible. Therefore, they have to be shaped like in case of a two-stroke, which results in the engine on the right. The crankshaft is then one-piece because it is located in the crankcase common to all cylinders.

Here you can see one possibility of increasing the performance of the four-cylinder, namely via the displacement. A displacement of 21.5 liters provides 147 kW (200 hp) at 1600 rpm and 353 Nm at 1000 rpm. The car was built by Benz in 1909 and proved to be only suitable for record drives. Bob Burman achieved 228 km/h in the USA in 1911, a record that was not surpassed in the following 13 years.

The picture shows the stormy development using the example of this Mercedes, which won the last Grand Prix before the First World War in Lyon on July 4, 1914. It did not get its power from the displacement, which was 'only' 4.5 liters, but from 77 kW (105 hp) at 3100 rpm, i.e. more speed with a camshaft driven by a vertical shaft and four valves per cylinder.