Computed Curves

The first two curves, which are based on calculated quantities, should not be confused with measured quantities, which would surely have produced much more unevenness. Both proceed as petrol engines of 500 cm³ single displacement, but this time uniformly going out from 0.85 pressure (absolute) at the beginning of the compression stroke.

However, curve 1 shows a naturally aspirated engine with a compression of 13: 1 and curve 2 a motor charged with 1 bar (1000 hPa) with reduced 10: 1. You see, the latter starts 1 bar higher and can not be obtained despite a smaller geometric compression.

Now one could ask the question, why the measured compressive pressures in the petrol engine are always far below 20 bar, even if the engine is really in order. Please take into account the hole of the spark plug completely or partly to the final volume, and the piston can let escape pressure because of the low rotational speed of the starter.

In addition, it should be pointed out that this calculation of the isentropic change in the state is based on an absolute heat resistance of the engine, which is not the case even with a slow starting speed. The charge e.g. by turbochargers does not develop at all in the compression measurement, which would then result in a smaller value.

Below the diagrams for the diesel engine, here again without and with charging. You can see how the turbocharger makes the diesel fly, but also has to be limited, because the 145.3 bar could not be sensibly recorded. How it can be promoted even more can be seen below on the video. The diagrams in the background also show that the charging pressure of the diesel engine must be limited to a certain torque. 03/17