Type 1 - 1.1-1.6 litres
Like the Volkswagen Beetle, the first VW Transporters (bus) used the Volkswagen air cooled engine, a 1100cc DIN-rated 24kW (24PS, 24bhp), air-cooled four-cylinder boxer engine mounted in the rear. The 22KW (29PS; 29bhp) version became standard in 1955, while an unusual early version of the engine which developed 25KWs (34PS; 34bhp) debuted exclusively on the Volkswagen Type 2 (T1) in 1959. This engine proved to be so uncharacteristically troublesome that Volkswagen recalled all 1959 Transporters and replaced the engines with an updated version. Any examples that retain that early engine today are true survivors - since the 1959 engine was totally discontinued at the outset, no parts were ever made available.
The second-generation Transporter, the Volkswagen Type 2 (T2) was slightly larger and considerably heavier than its predecessor, and lost its distinctive split front windscreen - which gained it common nicknames of Breadloaf, Bay-window, Loaf or Bay for short. The engine was also slightly larger - at 1.6 litres and 35KWs (48PS; 47bhp). A T2b Type 2 was introduced by way of gradual change over three years. The 1971 Type 2 featured a new, 1.6 litre engine, now with dual intake ports on each cylinder head, and was DIN-rated at 37KWs (50PS; 50bhp).
The Volkswagen Type 3 (saloon/sedan, notchback, fastback) was initially equipped with a 1.5 litre engine, displacing 1493cc, based on the air-cooled flat-4 found in the Type 1. While the long block remained the same as the Type 1, the engine cooling was drastically changed to allow for a much lower engine profile. This resulted in increased area for cargo stowage with the so-called "Pancake" or "Suitcase" engine. This engines displacement would later increase to 1.6 litres. Originally a single or dual-carburetted 1.5 litre engine (1500N, 33KWs/45PS/44bhp or 1500S, 40KWs/54PS/54bhp), the Type 3 engine received a larger displacement (1.6 litre) and was modified in 1968 to include Bosch D-Jetronic electronic fuel injection as an option, making it one of the first mass production consumer cars with such a feature (the first was the Type 4 VW 411).
Type 4 - 1.7-2.0 litres
In 1968, Volkswagen introduced a new vehicle, the Volkswagen Type 4. The model 411, and later the model 412, offered many new features to the Volkswagen lineup. While the Type 4 was discontinued in 1974 when sales dropped, its engine became the power plant for Volkswagen Type 2s produced from 1972 to 1979: it continued in modified form in the later Vanagon which was air-cooled from 1980 until mid-1983. For the Volkswagen Type 2, 1972's most prominent change was a bigger engine compartment to fit the larger 1.7 to 2.0 litre engines from the Volkswagen Type 4, and a redesigned rear end which eliminated the removable rear apron. The air inlets were also enlarged to accommodate the increased cooling air needs of the larger engines. The engine that superseded the Type 4 engine in late 1983 retained Volkswagen Type 1 architecture, yet featured water-cooled cylinder heads and cylinder jackets. The wasserboxer, Volkswagen terminology for a water-cooled, opposed-cylinder (flat or 'boxer engine'), did not enjoy the reputation for longevity that the original air-cooled design had forged. From the very start, the engine suffered cylinder-to-head sealing problems, mostly due to galvanic corrosion, often a result of slack maintenance schedules. Volkswagen discontinued the engine in 1992, upon the introduction of the Eurovan.
The Type 4 engine was also used on the Volkswagen version of the Porsche 914. Volkswagen versions originally came with an 80 horsepower (60 kW) fuel-injected 1.7 litre flat-4 engine based on the Volkswagen air cooled engine. In Europe, the four-cylinder cars were sold as Volkswagen-Porsches, at Volkswagen dealerships. This "tainted" the car in the opinion of many automotive critics of that era, and a little of that attitude persists to this day. Slow sales and rising costs prompted Porsche to discontinue the 914/6 variant in 1972 after producing 3,351 of them; its place in the lineup was filled by a variant powered by a new 95 metric horsepower (70 kW; 94 bhp) 2.0 litre fuel-injected version of Volkswagen's Type 4 engine in 1973. For 1974, the 1.7 litre engine was replaced by a 76 metric horsepower (56 kW; 75 bhp) 1.8 litre, and the new Bosch L-Jetronic fuel injection system was added to American units to help with emissions control. 914 production ended in 1976. The 2.0 litre engine continued to be used in the Porsche 912E, which provided an entry-level model until the Porsche 924 was introduced.
In the Type 2, the Volkswagen Type 4 engine was an option from 1972. This engine was standard in models destined for the US and Canada. Only with the Type 4 engine did an automatic transmission become available for the first time in 1973. Both engines displaced 1.7 litres, rated at 66 metric horsepower (49 kW; 65 bhp) with the manual transmission, and 62 metric horsepower (46 kW; 61 bhp) with the automatic. The Type 4 engine was enlarged to 1.8 litres and 68 metric horsepower (50 kW; 67 bhp) in 1974, and again to 2.0 litres and 70 metric horsepower (51 kW; 69 bhp) in 1976. As with all Transporter engines, the focus in development was not on motive power, but on low-end torque. The Type 4 engines were considerably more robust and durable than the Type 1 engines, particularly in Transporter service.