The VW engines have had two cooling arrangements: one using propelled air as coolant and the other using water, with radiator, pump, thermostat and fan.
The air-cooled VW engines, as you all know, with millions built and in service, is one of the most popular car engines on planet Earth. They were all built in the last century and they have pulled war vehicles, small planes, small electric power generators, water pumps, boats, motorcycles, etc., sometimes as factory set ups and other times as owner’s adaptations. Although being a four-cylinder, some people have cut it in half and made a two-cylinder light and powerful engine out of it, other people have coupled two or more beefed-up engines to add horsepower. And, quite logically, some other have transformed the four-cylinder into a two-cylinder all-purpose air compressor powered by the other two cylinders.
But, yes, a large part of the persons that listen daily to the unmistakably unique sound of the VW air-cooled engine are the VW car drivers. The VW air-cooled engine is found in almost all bugs, convertibles, Karmann-Ghias, busses, Things, Fridolins, trikes, Hebmüllers, Rometsch, Schwimmwagens, Porsche 914s and some other models and types I don’t remember right now.
The VW engine, in its three variants type 1, type 3 and type 4, is an engine of modest power output, by concept. Within the boundaries of the metallurgic knowledge of the days when it was projected, the choice of power vs. longevity fell on the latter. In other words, on the drawing table decisions were already taken to create in 1938 an engine slightly “stuffed” to avoid a high rev. regime and, thus, be more reliable for a longer service life. In the production decades that followed, the VW engine underwent many upgrades during its manufacture, with several increases in capacity and consequent power output, accompanied by the necessary reinforcement and redesign of many component parts, such as engine casing, crankshaft, heads, pistons, manifolds, etc, to name but a few. The latest revamp included a catalytic exhaust muffler coupled with fuel injection to use unleaded petrol. This was towards the end of the 20th century, circa 1988.
What was said above is not of total application in the case of the type 4 engines, designed in the 70ies with high power output specifications. But, no doubt this engine, too, was sturdily designed with a large margin of reliability. VW engine rebuild enthusiasts know it and the type 4 VW engine is a common choice for dragster strip, street-rods, bajas and sand rails.
The World War was over, Germany was recovering from the nightmare, VW was selling well world wide, the model became popular in our Planet already in the fifties.
Automobiles, as a whole, started their run up for the throne of Consumerland. In those days Mankind needed steel, paved roads and ships. Oil was being extracted in an ever increasing yield and, with the arrival of the atomic energy in the electricity production industry of the western world, the steam engines, the trains and coal, both as fuel as a mining industry, initiated a decline period. Jet planes were preparing the assault of the skies. This near-poetical part of my description wants to depict the large-scale economical and industrial context of the years in which air-cooled VWs were everyday every person’s car and sales were booming towards top levels in the western world. In some countries, if you sat by the road you could count cars passing, one VW, one other brand, one VW, one other brand, one VW … and so forth.
By the mid fifties, some VW owners found out that the “bug” (or kuplavolkkari in Finnish, if you prefer) was disappointing them in terms of power. They started finding the car dull. It lacked that brisk pull some of its competitors provided: the minis, some alfas and bmws not to mention the small English roadsters, some of them supercharged. Of course the bug was reliable, it would start bellow freezing temperature without problem, it lasted for years on end, it was safe, stable and roadworthy, but … well, it was slow.
Many manufacturers of car accessories and aftermarket equipment noticed this, too. And many came up with various solutions to the problem: double carburetion, special cylinder/piston kits, full flow heads and superchargers.
Almost without exception, the superchargers suitable for VW engines retailed on the market were offered as complete kits. According to the construction of the blower and the principle of operation, they are classified in two main types: vanes and lobes. A third type of superchargers exists, the centrifugal blowers (also named negative displacement superchargers) of which odd units have been mounted on VW engines in the sixties in the US, with modest enough results to scrap any project of commercial kit sales.