Actually, this engine was an aberration, since it had two cylinders in line and its pistons didn't carry out the same movements. It would have been suitable as a two-stroke engine, it was however, thought of for the heavier Benz vehicles. It was designed by August Horch, who managed the construction of motor cars at Benz and it was developed together with the Contramotor, a somewhat more complex, indeed as a four-stroke, very much more sensible construction.
Both engines, by the way, were, prototypes. Only the Contramotor would be further developed, It only appeared however, 2 years later in the Benz vehicles. This in-line twin was never in question as a four-stroke, because it inevitably had an unfavourable firing order. After two strokes, in which the available cylinders could ignite, the following two strokes did nothing at all. It is possible that this could have escaped someone like August Horch?
The whole thing clears up a little, if one has a good look at the following engine below. This is Horch's development for his own first car in 1901. He called it the 'impact-free' engine. Here once again, are two cylinders in line, although not in alignment with each other. Horch's aim was to offset the mass despite the four-stroke principle. Hereby, the large left-hand piston functioned as a type of charging piston and the small left-hand piston was degraded to a sort of moveable sealing.
Both pistons do the work, but only in the right-hand cylinder is there an uncontrolled, through vacuum opening intake- and an exhaust valve which is controlled by a type of camshaft (controller shaft). At least we can now imagine where Horch wanted to go with the construction shown at the top. Apparently, the engine ran quite smoothly, despite only igniting once in two revolutions. The cost of producing it was however, too high, which finally resulted in Horch giving it up.
Thus, once again, we find ourselves back at the above prototype, because the engine performance of the two-cylinders was no longer sufficient, indeed, in the beginning, one was not in a position the cast four cylinders in line in one piece. Suddenly, a great number of engines looked just like the one shown above, only doubled. Below you can see an early Daimler-four-cylinder from the year 1894. 07/14