air-cooled engine Air-cooled engines rely on the circulation of air directly over hot parts of the engine to cool them.
A cylinder from an air-cooled aviation engineMost modern internal combustion engines are cooled by a closed circuit carrying liquid coolant through channels in the engine block, where the coolant absorbs heat, to a heat exchanger or radiator where the coolant releases heat into the air, and so on, ad infinitum. Thus, while they are ultimately cooled by air, because of the liquid-coolant circuit they are known as water-cooled. In contrast, heat generated by an air-cooled engine is released directly into the air. Typically this is facilitated with metal fins covering the outside of the cylinders which increase the surface area that air can act on.
Many motorcycles use air-cooling for the sake of reducing weight and complexity. No current production automobiles have air-cooled engines, but notable past models include the Volkswagen Beetle and related models, Citroën 2CV, the Chevrolet Corvair, the Porsche 911 and others.
Most aviation piston engines are air-cooled, including most of the engines currently (2005) manufactured by Lycoming and Continental and used by major manufacturers of light aircraft Cirrus, Cessna and so on. Notable exceptions have included the Allison V-1710 and Rolls-Royce series of (most well known, the Merlin V-1650) liquid-cooled V12 engines which powered P-51 Mustangs, Avro Lancasters, Hawker Hurricanes and Spitfires.
It is worth noting that in all combustion engines, a great percentage of the heat generated (around 44%) escapes through the exhaust, not through either a liquid cooling system nor through the metal fins of an air-cooled engine (12%). About 8% of the heat energy finds its way into the oil, which although primarily meant for lubrication, also plays a role in heat dissipation via a cooler.

Beetle customisation

The Beetle is popular with customisers throughout the world not only because it's cheap and easy to work on, but because its iconic looks can be personalised and the flat four motor is so tunable. Its very ubiquity make even subtle changes noticeable; everybody knows what a Beetle is supposed to look like.

Exterior

There are many popular Beetle styles, from a 'Cal Looker' to a 'Rat Rod'. They vary between themselves but are very similar in many ways. Also the California Look has changed during the 30+ years of its lifespan. The most typical way to customise the exterior is to change the wheels and lower the suspension of the car. The favorite wheels are period-style EMPI 5- or 8-spokes, Speedwell BRMs, or Porsche factory rims like Fuchs from classic 911. One of the original California Look modifications is to replace or remove the bumpers and trim, either to give a cleaner look or to reduce the kerb weight; if bumpers are removed, pushbars are common. The stock bumpers are usually chromed or polished, sometimes painted or powdercoated. For 'Resto Cal' look, a roof rack and similar accessories can be added. There are many other aftermarket parts that can be added to the Beetle, including wing mirrors, chrome wipers, stone guards, mud flaps and badges. Rear light and front indicator lenses can also be changed. This is as far as a 'Cal Look' or 'Resto Cal' car will go.
VW Beetle modified in 70's California Look styleFor a more custom look, smoothing and shaving the body (removing trim and other parts) is done, including doorhandles, badges and driprails, and replacing taillights and front indicators with smaller, simpler units. Frenching (tunnelling) headlights, frequent in non-VW customs and rods, is not usual, but dramatic lowering (in low rider fashion) is, and unusual hood and trunk hinging is commonplace.
Interior Many Beetle owners try to keep their Beetle interior stock. Others will fit a sound system, which usually consists of a head unit and possibly some speakers and a subwoofer (usually mounted in the front of the car). Aftermarket steering wheels can be added along with auxiliary gauges. For a true race look, the interior can be stripped and a full roll cage installed, along with bucket seats and race harnesses.

Power

The Type 1 is astonishingly flexible in this area. Because most parts of the flat-four engine other than the crankcase are bolted on, they are easily exchanged with larger or more high-performance items. The standard VW engine has been modified from 1600 cc (the largest factory-produced Type 1 engine) to configurations well over 2300cc using larger piston/cylinder kits and other performance-enhancing parts. A variety of other powerplants, including the VW Type 4 ( also used in the 914) 2-liter flat four, Chevy Corvair and porsche 911 flat sixes have been used. Even the turbocharged flat 4 from Subaru has been used. Turbocharged Type 1 flat fours have appeared. These variants tend to be mated to the stronger Type 2 (Bus, Combi) transmission. Dual carb setups are very common on Beetles (especially the 1600 cc dual port engine). Also a wide range of exhaust systems are available. Headers and straight pipes are very popular because, since Beetles have a reputation for being extremely loud, cops usually ignore the excessive noise these muffler-less systems create. Dune buggy style pipes are also very popular for people who remove the hood from their cars.

KitCars

The VW Type 1 chassis, being easily separated from its original body without removal of engine, transmission, or suspension, has provided the basis for countless custom re-bodyings, usually of fiberglass and usually replicating other, less humble vehicles. Mercedes, MG and Porsche replicas are among the popular choices. These "kit cars", although derided by many for their lack of authenticity, provide to their owners a much cheaper, often more-reliable means of enjoying a dream vehicle.

The Beetle in developing countries

The Beetle in developing countriesOther countries produced Beetles from CKD (complete knockdown kits): Thailand, Indonesia, South Africa, Australia, and Nigeria have assembled Beetles under license from VW .

Beetles produced in Mexico and Brazil had several differences:

The Brazilian version retained the 1958-1964 body style (Europe and U.S. version) with the thick door pillars and small quarter glass; this body style was also produced in Mexico until 1970. Brazilian CKD kits (complete knockdown) were shipped to Nigeria between 1975-1987 where Beetles were locally produced. The Brazilian-produced version have been sold in neighboring South American nations bordering Brazil, including Argentina and Peru. The Brazilian VW Bug have four different sized engines: 1200cc, 1300cc, 1500cc and, finally, 1600cc. In the 70's Volkswagen made the SP-2 (derived from the VW Bug chassis and powertrain) that used an air-cooled VW engine with 1700cc. In Brazil the VW Bug never received electronic fuel injection, but retained single or double carburetion throughout its life.

The production of the air-cooled engine finally ended in 2006, after more than 60 years. It was last used in the Brazilian version of the VW Bus, called the "Kombi", and was replaced by a 1.4-litre water-cooled engine with a front-mounted cooling system. Beetles produced in Mexico (since 1964) have the larger door and quarter glass between 1971 — 2003 with the 1958 vintage back glass until the mid-1970s. This version, after the mid-1970s, saw little change with the incorporation of electronic ignition in 1988, an anti-theft alarm system in 1990, and electronic fuel injection, hydraulic valve lifters and a spin-on oil filter in 1993.

Production boom

Production of the Type 1 grew dramatically over the years, with the one-millionth car coming off the assembly line by 1954. The Beetle had superior performance in its category with a top speed of 115km/h (72mph) and 0-100km/h (0-60mph) in 27.5 seconds on 31mpg for the standard 25kW (34hp) engine. This was far superior to the Renault 4CV and Morris Minor and even competitive with more modern small cars like the Mini. The engine fired up immediately without a choke and could only be heard in the car when idling. It had excellent road-handling for a small car. It was economical to maintain and, for many, a joy to drive. However, the opinion of some in the United States was not as flattering. Henry Ford II once described the car as 'A little shit box' out of frustration that it was the top-selling foreign car in the US market.

During the 1960s and early 1970s, innovative advertising campaigns and a glowing reputation for reliability and sturdiness helped production figures to surpass the levels of the previous record holder, the Ford Model T, when Beetle No. 15,007,034 was produced on February 17, 1972. By 1973 total production was over 16 million, and by June 23, 1992 there had been over 21 million produced.

The military Beetle

Prototypes of the Kdf-Wagen appeared from 1935 onwards — the first prototypes were produced by Daimler-Benz in Stuttgart, Germany. The car already had its distinctive round shape and its air-cooled, flat-four, rear-mounted engine. However, the factory had only produced a handful of cars by the time war started in 1939. Consequently, the first volume-produced versions of the car's chassis were military vehicles, the Jeep-like Kübelwagen Typ 82 (approx. 52,000 built) and the amphibious Schwimmwagen Typ 166 (approx. 14,000 built).

The car was designed to be as simple as possible mechanically, so that there was less to go wrong; the aircooled 985 cc 25 hp (19 kW) motors proved especially effective in actions of the German Afrika Korps in North Africa's desert heat. This was due to the built-in fan-cooling and the superior performance of the flat-four engine configuration. The innovative suspension design used compact torsion beams instead of coil or leaf springs.
A handful of civilian-specific Beetles were produced, primarily for the Nazi elite, in the years 1940–1945, but production figures were small. In response to gasoline shortages, a few wartime "Holzbrenner" Beetles were fueled by wood pyrolysis gas producers under the hood. In addition to the Kübelwagen, Schwimmwagen, and a handful of others, the factory managed another wartime vehicle:
the Kommandeurwagen; a Beetle body mounted on the 4WD Kübelwagen chassis. A total of 669 Kommandeurwagens were produced until 1945, when all production was halted due to heavy damage sustained in Allied air raids on the factory. Much of the essential equipment had already been moved to underground bunkers for protection, allowing production to resume quickly once hostilities had ended.

Engine cooling - Basic principles

Most internal combustion engines are "air-cooled" or "liquid-cooled". Each principle has advantages and disadvantages, and particular applications may favor one over the other. For example, most cars and trucks use liquid-cooled engines, while most small airplane engines are air-cooled.
Most liquid-cooled engines use a mixture of water and other chemicals such as antifreeze and rust inhibitors. Some use no water at all, instead using a liquid with different properties, such as propylene glycol or the combination of propylene glycol and ethylene glycol. Although the term "liquid-cooled" is used here, most air-cooled engines also use some liquid oil cooling, and most liquid-cooled engines subsequently cool the hot liquid with air.
Conductive heat transfer is proportional to the temperature difference between materials. If an engine metal is at 300°C and the air is at 0°C, then there is a 300°C temperature difference for cooling. An air-cooled engine uses all of this difference.
In contrast, a liquid-cooled engine might dump heat from the engine to a liquid, heating the liquid to 150°C which is then cooled with 0°C air. Thus, in each step, the liquid-cooled engine has half the temperature difference and so may need as much as twice the cooling area.

The Kdf-Wagen

The Kdf-Wagen was a project of the Kraft durch Freude organisation in Nazi Germany.
Kdf stands for Kraft durch Freude, or "Strength through joy".
For the construction of the Kdf-Wagen, a new town now known as Wolfsburg was created in Lower Saxony.
The Kdf-Wagen had initially been called the Porsche 60 by Ferdinand, but it was officially named the Kdf-wagen when the project was launched. Later simple known as the Type 1, it became more commonly known as the Beetle after the Second World War.
In the period of the Second World War, two notable variants of the Kdf-Wagen were produced for military use: the Kübelwagen and the Schwimmwagen. A number of short-run and innovative (although ultimatly doomed) variants known as "Holzbrenner"s also existed, including charcoal and woodburning versions, intended to cope with the extreme fuel shortage experienced throughout Germany (the world) during WWII.
The designer of the Kdf-Wagen (Ferdinand Porsche senior) is often confused with his son Ferdinand "Ferry" Porsche. Ferdinand Porsche (senior) was the founder of the Porsche car company, which his son worked for and later went on to run after his death.