The Volkswagen air-cooled engine is an air-cooled, gasoline-fuelled, boxer engine with four horizontally opposed cast-iron cylinders, cast aluminum alloy cylinder heads and pistons, magnesium-alloy crankcase, and forged steel crankshaft and connecting rods. There are two distinct families/variations of the aircooled engine namely Type 1 and Type 4. The Type 3 engine is a variation of the Type 1 engine with pancake cooling arrangement. Variations of the engine were produced by Volkswagen plants worldwide from 1936 until 2006 for use in Volkswagen's own vehicles, notably the Type 1 (Beetle), Type 2 (bus, transporter), Type 3, and Type 4. Additionally, the engines were widely used in industrial, light aircraft and kit car applications.

Type 1: 1.0–1.6 litres

The Type 1 engine got its name from the Type 1 Beetle it originally came with. It evolved from the original 985cc in the KdF wagen in 1939 to the 1600cc dual port fuel-injected engine that came in the 2003 Mexican Beetle. The very last Type 1 engine came in the 2006 Type 2c built in Brazil. In most applications, the Type 1 engine came with an upright cooling shroud and a belt driven fan. When equipped with crank mounted cooling fan, the Type 1 engine may be referred as Type 3 engine. These engines came only in 1500cc and 1600cc configurations in Volkswagen Type 3 based vehicles. The Type 1 engine was also used in Type 2 vehicles with additional engine mounting provisions. The term "universal engine case" refers to an engine case that can be used for all three applications. All Type 1 engines used lighter magnesium alloy for the engine case even though late model engines used stronger alloys for durability. The bore spacing on Type 1 engine is 112mm. A clean sheet re-design of the Type 1 engine was introduced in 1968 in the Volkswagen Type 4. It came to be known as the Type 4 engine. It was larger and powerful and shared almost nothing with the Type 1 engine other than the general architecture of the longblock.

1000

1100

Like the Volkswagen Beetle produced after the war, the first Volkswagen Transporters (bus) used the Volkswagen air-cooled engine, a 1.1 litre, DIN-rated 18 kW (24 PS, 24 bhp), air-cooled four-cylinder "boxer" engine mounted in the rear. The 22-kilowatt (29 PS; 29 bhp) version became standard in 1955, while an unusual early version of the engine which developed 25 kilowatts (34 PS; 34 bhp) debuted exclusively on the Volkswagen Type 2 (T1) in 1959. 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.

1200

The 1.2-litre engine is called Type 122 and has a displacement of 1192 cc. As industrial engine, its rated power is 22.8 kW at 3000 min−1 without a governor, the highest torque 81.4 Nm at 2000 min−1. With a governor set to 8% accuracy, the rated power is 21.33 kW at 3000 min−1, the highest torque is 69.63 Nm at 2000 min−1. For other applications, the power and torque output may vary, e.g. On the Beetle produced 41 PS at 3900 rpm and 88 Nm of torque at 2400 rpm.

1300

1285cc Single port 1966, type 1, beetle only. With Higher compression, it developed 50 bhp. It was a problematic engine, and so only used in the North American market in type 2 vehicles for model year 1966.

Type 4: 1.7–2.0 litres

From 1968 to 1983, the Type 4 engine was produced in 1.7, 1.8 and 2.0 litre variants.

Other applications

Beginning in 1987, Dunn-Right Incorporated of Anderson, South Carolina has made a kit to perform the conversion of a VW engine to a compressor.

Industrial

Volkswagen AG has officially offered these air-cooled boxer engines for use in industrial applications since 1950, lately under its Volkswagen Industrial Motor brand. Available in 18 kW, 22 kW, 25 kW, 31 kW, 33 kW and 46 kW outputs, from displacements of 1.2 L to 1.8 L, these Industrial air-cooled engines were officially discontinued in 1991.

Aircraft

The air-cooled opposed four-cylinder Beetle engines have been used for other purposes as well. Limbach Flugmotoren has since 1970 produced more than 6000 certified aircraft engines based on the Beetle engine. Sauer has since 1987 produced certified engines for small airplanes and motorgliders, and is now also producing engines for the ultralight community in Europe. Especially interesting is its use as an experimental aircraft engine. This type of VW engine deployment started separately in Europe and in the US. In Europe this started in France straight after the Second World War using the engine in the Volkswagen Kübelwagen that were abandoned by the thousands in the country side and peaked with the JPX engine. In the US this started in the 1960s when VW Beetle started to show up there. A number of companies still produce aero engines that are Volkswagen Beetle engine derivatives: Limbach, Sauer, Hapi, Revmaster, Great Plains Type 1 Front Drive, Hummel, the AeroConversions AeroVee Engine, and others. Kit planes or plans built experimental aircraft were specifically designed to utilize these engines. The VW air-cooled engine does not require an expensive and often complex gear reduction unit to utilize a propeller at efficient cruise RPM. With its relative low cost and parts availability, many experimental aircraft are designed around the VW engines. Formula V Air Racing uses aircraft designed to get maximum performance out of a VW powered aircraft resulting in race speeds above 160 mph. Some aircraft that use the VW engine are: • Aerosport Quail • Airdrome Bleriot Model XI • Airdrome Dream Fantasy Twin • Airdrome Fokker DR-1 • Airdrome Fokker D-VI • Airdrome Fokker D-VII • Airdrome Fokker D-VIII • Airdrome Nieuport 11 • Airdrome Nieuport 24 • Airdrome Taube • AirLony Skylane • Airmotive EOS 001 • Akaflieg München Mü23 Saurier • Altair Coelho AC-11 • Alvarez Polliwagen • Aurore MB 04 Souris Bulle • Bensen B-8 • BK Fliers BK-1 • Bounsall Super Prospector • Boyd G.B.1 • Bradley Aerobat • Cassutt Special • Circa Reproductions Nieuport 11 • Circa Reproductions Nieuport 17 • Corby Starlet • Denney Kitfox • Druine Turbulent • Evans VP-1 Volksplane • Evans VP-2 Volksplane • Falconar F9A • Falconar F11 Sporty • Fisher Avenger V • Fisher Youngster • Flaglor Sky Scooter • Flitzer Z-21 • Great Plains Easy Eagle • Grob G 109 • Harmon Der Donnerschlag • Harmon Mister America • Hummel H5 • Hummel Ultracruiser Plus • JDT Hi-MAX • JPM 01 Médoc • Junqua Ibis • Just Superstol • Mignet Pou-du-Ciel • Mini-Hawk Tiger-Hawk • JDT V-MAX • Kolb M3X • Leger Pataplume 1 • Light Miniature Aircraft LM-5 • Milholland Legal Eagle – half VW and full Type 1 VW engines • Monnett Sonerai • Nicollier Menestrel • Parker Jeanie's Teenie • Parrish Dart • Pazmany PL-4A • Plumb BGP-1 • Pober Pixie • Pottier P.40 • Pottier P.130 Coccinelle • Preceptor STOL King • Preceptor Ultra Pup • Preceptor Stinger • QAC Quickie Q2 • RagWing RW1 Ultra-Piet – half VW and full Type 1 VW engines • RagWing RW7 Duster – half VW and full Type 1 VW engines • Rand Robinson KR-1 • Rand Robinson KR-2S • Scheibe Falke • Sisler SF-2A Cygnet • Sonex Aircraft Onex • Sonex Aircraft Sonex • Southern Aeronautical Renegade • Southern Aeronautical Scamp • Stewart Headwind • Stolp SA-500 Starlet • Taiwan Dancer TD-3 • Tervamäki ATE-3 • Tipsy Nipper • Taylor Monoplane • Thatcher CX4 • Vidor Champion V • Viking Dragonfly • Zenair CH 100

Half VW

For aircraft use, a number of experimenters, who were seeking a small, two-cylinder, four-stroke engine, began cutting Type 1 VW engine blocks in half, creating a two-cylinder, horizontally opposed engine. The resulting engine produces 30 to 38 hp. Plans and kits have been made available for these conversions. One such conversion is the Carr Twin, designed by Dave Carr, introduced in January 1975, in the Experimental Aircraft Association's Sport Aviation magazine. The design won the John Livingston Award for its outstanding contribution to low cost flying and also was awarded the Stan Dzik Memorial Award for outstanding design. Other examples include the Total Engine Concepts MM CB-40 and Better Half VW. Some aircraft that use the Half VW engine are: • Belite Ultra Cub • Duane's Hangar Ultrababy • Hummel Bird • Hummel Ultracruiser • Milholland Legal Eagle – half VW and full Type 1 VW engines • Pop's Props Pinocchio • Preceptor N3 Pup • RagWing RW1 Ultra-Piet – half VW and full Type 1 VW engines • RagWing RW4 Midwing Sport • RagWing RW7 Duster – half VW and full Type 1 VW engines • Spacek SD-1 Minisport • Ultravia Pelican