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There arm two kinds of rotational speed changes in running of internal combustion engines - rotational speed fluctuation within each working cycle and rotational speed change of successive cycles. Application of transient rotational speed nφ of each crank angle and average rotational speed nc of any working cycle can rationally demonstrate the change of the rotational speed of I.C.E.. Conventional speed-measure instruments may not be used to measure nφ and nc. Therefore authors take work on this measuring technique. This paper introduces the measuring principle and instrument and analyses the accuracy of measure. The developed instrument has been used on 5 types of diesel engines, such as 6135, 6130Q, R4100, etc. Measured results at steady condition, low speed radomrunning, sudden loading, free acceleration and starting process are given in this paper.

In this paper, the authors analyse the effect of combustion process upon the combustion noise and working stability of 6130Q D.I. diesel engine, and point out that the higher combustion noise is caused by excessive premixed combustion. In order to improve engine noise it is need to decrease the injection quantity in delay period. The fluctuation of working cycles is mainly effected by the injection pump rack shaking and auto-advancer oscillating. By improving the matching of spring rigidity and mass the working stability can be improved.

The authors of this paper have experimented on four and six-cylinder engines of ϕ 0102 x 125mm with shallow W-type combustion system, showing satisfactory results. In a 1200-2800 r/win speed range the prototype engine showed excellent performance characteristics, moreover, it required less accuracy in making their inlet ports. Based on fuel injection and combustion heat release pattern measured under various matches of combustion chamber, injection system and inlet port, the authors have studied each effect of design parameters on combustion characteristics and put forward the key points for optimum combustion match.