In a normal engine, when the pistons go down, the admission valves open and the mixture is sucked-in, after going through the carburettor and within the admission pipe. This means than in 1200 cc for example, each cylinder of 300 cc must be filled up with 300 cc of the mixture when the piston arrives down. This is the theory. In fact, the fill up does not exceed 85 % because of the successive stranglings that slow down the gaz. At low and high rating, the percentage even dramatically diminishes, this bad filling up capacity being typical of the VW engine that this way, willingly, does not take laps and is therefore more reliable.

The final power is therefore determined by the filling up capacity. If the cylinders are partially filled up, the power will be weak. On the contrary, if they are completely filled up, the power will increase, on the condition that the ignition is also capable to burn all these gaz.

	On this Karmann Ghia, the most recent kit with one notch pulley. Also, the owner has installed an additional system of tension.

A blower, which in fact is only a pump moved by the engine itself, forces the mixture air-gas within the cylinders, increasing the filling up capacity up to 100 %, or even more. In this last case, the engine behaves as if it was larger. As the engine burns more mixture, its power is increased , the torque at low rating taking the advantage to increase.