Torque Boosting of 4-Stroke Cycle Spark-Ignition Engines by Crankcase-Supercharging

4 crankcase-supercharged 4-stroke spark-ignition engine was made and tested in both the motoring and firing modes.

It was found that a 20 to 30 % torque rise compared with the naturally-aspirated baseline engine was obtained in the low and middle engine speed ranges without any sacrifice in brake specific fuel consumption.

Additionally, the throttle response of the modified engine was better than that of the naturally-aspirated baseline engine, and there was no deterioration in part-load brake specific fuel consumption.