Over decades, research has been carried out and prototypes presented, but it is only now, perhaps just before the end of the piston engine, that it comes to the market with variable compression. Infiniti has been working on this since 1996 and promises it for 2018 in the new QX 50 SUV. Of course, once again the Japanese, which are professionals to bring good ideas to the series production.

At the same time, neither the cylinder head has different distance towards the block, nor the crankshaft is changed in its position. It also still consists of fixed main- and connecting rod bearings. But on these the connecting rods do not run directly, but via attachment points adjustable from the shaft below.

The fact that the compression can only be adjusted between 8 and 14 : 1 is surprising, because earlier designs implemented much more in certain operating modes. However, they also had no supercharging as an additional instrument of control. One would have to know how additional is controlled by the boost pressure.

You shouldn't compare the power values of 200 kW and 390 Nm e.g. with an AMG engine also with 2 liters displacement and 280 kW and 475 Nm, because only power was not the only design target, but low fuel consumption and pollutant emissions, too. Both can be optimized as much as possible along the limit of knocking combustion. By the way, perhaps also different strokes over the whole working cyclus (Atkinson) is possible.

Disadvantages are more effort and height. Otherwise, the engine has any technical advances on board, with regard to engine control, mixture formation and rapid exhaust gas detoxification. 05/17

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