Simple- Because there is no intake valve in the two-stroke Detroit Diesel. That is why it needs a blower to run.
In a normal four-stroke engine, there are intake valves that allow air to come into the chamber of the engine. In two-stroke Detroit diesel engine, there is no intake valves, so the blower serves as intake valves which allows air to come into the engine. Although, the blower is not a supercharger because it doesn’t compress the air as much as a supercharger, it still works like a supercharger.
The Detroit 53, 72, 92, and 149 Series all are 2 stroke cycle diesel engines. Although they stopped manufacturing in 1998, there are still thousands of these engines powering throughout the world.
How it works?
When the air comes in from the blower, the sleeve of the liner of a two-stroke Detroit diesel engine has holes around it. The hole allows the air to come in.
As the air comes in, the piston will be at the downwards position, alowing the air to come in. So, by the time the piston comes off, it compresses the air and blocks the hole at that particular time. You will notice that in two-stroke Detroit diesel, the piston is usually long, so that it can also serve as a valve. So, when it compresses the air, it blocks the intake hole around the cylinder so that air cannot come in.
And when it goes down, it allows air to come in. That’s why two-stroke Detroit diesel engines always need a blower. Though some confuse the blower and call it a supercharger, it is not, because it doesn’t compress the air. It is also not a turbocharger because it is not driven by smoke.
