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The distribution of air mass flowrate between the cylinders of a 4-cylinder, carburetted automotive engine has been measured using a propane injection technique. The results show that over a wide range of operating conditions the engine has acceptably uniform distribution of air flow. At low- and medium-speed conditions the insertion of quite large obstructions into individual limbs is shown to have little effect on the air mass flows through these limbs. Only at high engine speeds and loads do these resistances have significant effect. The measured data are compared with corresponding predictions from a computer model of the engine and good agreement is shown.

A four-stroke, spark-ignition engine is described that seeks to achieve high expansion ratio and low throttling losses at light load, whilst retaining good knock resistance at full load operation and without the need for expensive mechanical changes to the engine. The engine does, however, incorporate a second inlet (transfer) valve and associated transfer port linked to the intake port. The timing of the transfer valve is different from that of the main inlet valve. Load modulation is achieved by control of the gas outflow from the transfer port. A computer model of the engine is first validated against measured data from a conventional engine. Comparisons are made of incylinder pressure at part load conditions, total air flowrate through the engine and intake port air velocities as a function of crank angle position.