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The most common car engine is a 4-cylinder 4-stroke engine. The car manufacturers have a great pressure to lower the cost of the cars and this deal also with the engines. The challenges are the coming new emission norms (for example EURO-6) and also the custom acceptance, because of the fact, that the car drives are used to the 4-cylinder engine and they want to have the same driving fun also from the new engines. A 2-cylinder 2-stroke engine has the same power output and torque as a 4-cylinder 4-stroke engine and thus it offers the same driving fun. Equal balancing is easy to make without some big additional costs, if the gas exchange of the engine is made by using poppet valves and camshafts. As there are only about 70% of the moving parts in the engine, its acceleration is even better than by a 4-cylinder engine. One of the latest development in 2-stroke engines is the Z-engine, having the compression partially transferred outside of the working cylinders.

The most common car engine is a 4-cylinder 4-stroke engine. The car manufacturers have a great pressure to lower the cost of the cars and this deal also with the engines. The challenges are the coming new emission norms (for example EURO-6) and also the customer acceptance, because of the fact that the car drives are used to the 4-cylinder engine and they want to have the same driving fun also from the new engines. A 2-cylinder 2-stroke engine has the same power output and torque as a 4-cylinder 4-stroke engine and thus it offers the same driving fun. Equal balancing is easy to make without some big additional costs, if the gas exchange of the engine is made by using poppet valves and camshafts. As there are only about 70% of the moving parts in the engine, its acceleration is even better than by a 4-cylinder engine. One of the latest developments in 2-stroke engines is the Z-engine, having the compression partially transferred outside of the working cylinders.

A light duty downsized engine, named as “z-engine”, was developed, built and tested on the experimental rig. This engine is a two-stroke diesel with a split compression process and poppet valve for the gas exchange. The split compression process provides sufficient time for the longer exhaust process (over 180 CA degrees). The first stage of fresh air compression takes place in a turbocharger, the second part of the compression takes place in the mechanically driven piston compressor with PR of about 4.5 - 5.5. A very brief induction period, which lasts for about 10-22 CA degrees, is followed by a short final compression in the cylinder in which mixing occurs. The external piston compressor which provides all cylinders with a fresh charge, has relatively cold walls and its outlet is connected to an intercooler, so the total compression work is reduced and the fresh charge has a considerably lower temperature in comparison with a conventional diesel engine.