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RESULTS of an investigation directed toward determining why deposits increase antiknock requirement are discussed here. Data are presented which indicate that substantially 100% of the increase in octane-number requirement caused by deposits results from a combination of thermal and volume effects. An analysis procedure is given which indicates that deposit-thermal effects may result entirely from the heat that is stored in the deposits. Thus, the deposits absorb heat during the combustion process in one cycle and transfer it to the fresh charge during the intake and compression portions of the next cycle. The findings reported in this paper show that those engines with the smallest area of combustion-chamber surface, for a given displacement, would be expected to have the smallest thermal effects and hence should have minimum deposit effects.

AN improved method, applicable to either motored or fired engines, for evaluating energy release rate occurring during preflame reactions is described in this paper. A unique feature of this method is the use of a mechanical computer to handle calculations. A smooth energy-release-rate curve can be obtained with this improved analysis technique-something not possible with two previous methods. However, the mean rate of energy release as determined by all three methods is in general agreement.

DESIGN details for many of the passenger-car engines being built in Britain are presented here. Illustrations are used, wherever available, to make the details clear to the reader. The author points out that the well-known Royal Automobile Club formula is no longer used in determining the British vehicle tax. This formula was considered by many British designers a millstone around their necks. It is based on piston area, and so they were almost forced to design their engines with small bore and long stroke to keep down taxes on the car. Thus, the author reveals, the present tendency seems to be toward cylinder proportions approaching square and, in some cases, even over-square.

Previous procedures for estimating diluent in used railway diesel lubricating oils all have drawbacks. Precision is limited in simple procedures. A research procedure is time consuming and requires specialized equipment and highly skilled personnel. The authors describe a graphic correlation for estimation of amount and type of diluent as functions of decrease in flash and viscosity. Also included are empirical methods for development of the dilution chart without recourse to experimental blends of the oil with diluents.

High speed photographs of the combustion process in an engine equipped with a quartz window, in the cylinder head are described. The optical path was so arranged that direct and shadowgraph images of flames could be separately photographed on the same film at the same time in conjunction with flywheel timing marks. Simultaneous pressure-time records were also obtained. The photographs confirm the well-known fact that knock occurs immediately after the portion of fuel still unreached by the flame spreading from the spark plug spontaneously ignites and begins to burn very rapidly. Cylinder pressure then rises so fast that acoustic resonance develops in the combustion gases and is heard as knock. Four types of combustion phenomena in the engine were investigated: normal flames, “cool” flames, “hot” flames, and knock. With no spark ignition, cool flames start at the valve end of the L-head combustion chamber and end at the far side over the piston.