With this blower cooling, the heat is transferred to the outside air, this is done by a blower wheel driven directly by the crankshaft past the heat-intense parts. Part of the air should serve the vehicle heating. This kind of the cooling does not appear in todays vehicles any more. Therefore, what is shown here is an example of one of the last (and largest) boxer engines made by VW.
The four-cylinder boxer engine is shown with the flywheel below. The blower wheel extracts the air from above right and left, past the cylinders to the bottom. Well defined cooling fins and deflectors provide for specific heat transfer. On the right in the air exit there is a ribbed-gaiter thermostat which when filled with lighter simmering gas causes an expansion when a certain temperature is reached. When the engine is cold the air supply is thus regulated to the engine by the two red air-flaps on the top. When a certain opening temperature is reached, both are opened by a push rod and the (not shown here) connection. With vehicles the cooling air can not be used for the heating, rather, a part of it must be diverted beforehand and be heated by the counter current of the hot exhaust pipe.
The above figure 2 shows a flat-four cylinder engine with one carburettor on either side, which are operated by a lever/linkage. Above that, is the air filter with a connection to both cylinder banks. The air box, with ribbed-gaiter, for cool air induction is especially prominent. Behind it is the, not so easy to recognise, aluminium casing with air ducts to both cylinder rows. Air is taken in, in each case, on the far outside by two black sheet-metal pipes, rubber connections and clamps, the air is then diverted past the exhaust pipes, into the passenger compartment.