model test engine was used in the experiments. The technical specifications
of the test engine are given in Table 1.
It is hoped that the thermal efficiency of six-stroke engines is
higher than four stroke engine due to extra expansion stroke with
water injection. More energy can be converted to the useful work
via the extra expansion stroke [13–15]. Cam shaft should be redesigned
and the water injection system should be mounted in the
engine in order to convert four-stroke engine to the six-stroke
engine. The structural differences are seen between four- and
six-stroke engines in Fig. 1.
Cam-crank gear ratio was changed in the test engine. For this
purpose, new cam profiles were determined and designed at original
valve timing of the test engine. Partial exhaust process was
added to the valve timing diagram of the test engine as exhaust
valve opened twice in a cycle. The view of the modified six-stroke
engine is seen in Fig. 2.