Unlike a gasoline engine, a diesel engine does not adjust air intake. A carburetor in a gasoline engine adjusts and mixes both fuel and air. A diesel engine injects fuel through an injector or pump, and takes air in by creating a vacuum as the piston moves down during the intake stroke.

On larger engines, aftermarket turbochargers and superchargers actually compress air and force it into the chamber, improving combustion.

On a small diesel engine, there is nothing.

This handmade ramscoop below has been replaced with an improved sweptback air pipe leading to a 44mm carburetor which controls water flow, ending in a 70mm air filter. This allows better control of engine vacuum which controls the water intake process