Because the engines do not need to control air volumes, they lack a butterfly valve in the intake tract.

This is simply a spring-loaded rod that, when depressed, manually pushes the float down and allows excess fuel to fill the float bowl and flood the intake tract.

The reed valve is a simple but highly effective form of check valve commonly fitted in the intake tract of the piston-controlled port.

This engine was so small that very little room was available for smooth intake tracts.

Good optimisation of enrichment fuel is essential otherwise the fuel can 'drop out' and puddle in the intake tract, potentially causing a backfire.

The A1 Samurai motor was lubricated by the Superlube system, with 2-stroke oil directly injected in the intake tract.

By 1973, an EGR valve controlled by manifold vacuum opened or closed to admit exhaust to the intake tract only under certain conditions.

The PCV system just diverts a small percentage of this air via the breather to the crankcase before allowing it to be drawn back into the intake tract again.

The MAF may pose a physical restriction across the vehicle's intake tract, thereby reducing airflow into the engine.

Allow smooth and even entry of air at high velocities into the intake tract with the flow stream adhering to the pipe walls.