The two stroke Detroit Diesel engines that are naturally aspirated have compression ratios about 19:1. The turbocharged engines are about15:1. All of these engines are equipped with roots style surcharges. The blower is required for the engine to move air into it. Small two strokes are piston ported. Each rod throw is sealed in the crank case from the others. When the piston travels up the bore, pressure under it is lowered which allows atmospheric pressure to push air into the crankcase. As the piston travels down the bore, the crankcase is pressurized a bit. The exhaust sort is uncovered a few degrees before the intake port to blow down cylinder pressure. When the intake port is uncovered, the pressure under the piston is allowed into the cylinder.

Dale Davies

Excellent description Dale.

Paul Lamar


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