Paper 6: Turbocharging the Automotive Two-Stroke Cycle Engine

Abstract
The paper deals with the problems of turbocharging the two-stroke cycle engine. Obtaining a sufficiently rapid drop in the pressure of the cylinder contents after exhaust port opening is chiefly dependent on obtaining a high turbocharger efficiency. However, exhaust-pipe design can be very important in this process, and a system is described which permitted the use of simple turbocharging from light load to 200 lb/in2 b.m.e.p. Good starting and acceleration demanded that energy be fed into the charging system and so the normal engine-driven Roots blower was then fitted as a second stage. This spoiled the good natural match of the turbocharger and engine but it was discovered that by control of air recirculation through the Roots blower a good match could be obtained. The work showed that the best match leads towards a constant horsepower type of engine torque curve, and this fact should be recognized for future vehicle design. The use of two turbochargers in series offers very high outputs with good efficiency but will require a new generation of engines to withstand the high pressures and thermal loading.

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