End of an Era: The Last Air-Cooled Automobile Engines

by James Kraus

Air-Cooled Engine

Air-cooled horizontally-opposed 12-cylinder powerplant

I have always been a fan of air-cooled engines. I even enjoy the mechanical noises that emanate from their insides, unmuffled by water jacketing and walls of cast metal. It serves as a reminder that the car is powered by an engine containing many precision parts moving in high speed synchronization, akin to an Audemars Piguet running on high octane fuel.

Air-cooling offers advantages in simplicity, light weight and low cost. Automotive air-cooled engines are actually cooled by both air and oil. Basic cooling is provided by generous fins on the cylinders and cylinder heads which expose as much surface area as possible to the cooling air forced across them by an engine-driven fan. Located in the airstream is a heat exchanger to control the temperature of the engine oil. Flow though the cooler is generally controlled by an oil pressure valve that flows oil through the cooler only when the viscosity drops below a pre-determined threshold, indicting that the oil is has reached operating temperature.

A major limitation of air-cooling is that above an engine output of around 100 Kw (135 DIN hp), supplementary external oil cooling in the form of remote heat exchangers is needed. This significantly detracts from the inherent design elegance of air-cooling and diminishes the cost and weight saving advantages. The Porsche 356’s powered by the 4-cam Fuhrmann engine used two such remote oil coolers mounted in front behind the horn grilles. The 911 incorporated a much larger integral cooler mounted on the crankcase; nonetheless, even in original 2.0 litre form, Porsche recommended fitting an additional cooler when using the car for “Sports Purposes.” As the power output of the 911 steadily increased, a front-mounted cooler eventually became standard fitment.

1936 Tatra T97

1936 Tatra T97

Air-cooling was quite rare before World War II. In the 1940’s only the Czechoslovakian Tatra flat-four and V8 and the VW flat-four were being produced. Following the war, both Tatra and VW restarted manufacturing of their air-cooled engines. The original Tatra V8 stayed in production though 1975 and the prewar VW flat-four powered the Beetle until the autumn of 1960, at which time it was replaced with a updated air-cooled engine design.

After the war Citroën and Panhard joined the air-cooled club with the 2CV and Dyna X and the Porsche 356 débuted with a redesigned version of the VW engine. Numerous small cars were developed powered by modified one and two-cylinder motorcycle engines, culminating in the BMW 700. Fiat introduced their Nuova 500 with an air-cooled twin. The new 500 was also produced under license in Austria by Steyr-Puch who developed their own engine for the car; a horizontally-opposed air-cooled twin with hemispherical combustion chambers. The Styer-Puch 650TR, using a high-output version of this engine, won the Group 2 European Rally Championship in 1966. Finally, in 1959, Chevrolet introduced the Corvair with a horizontally-opposed air-cooled six-cylinder engine.

Then came the final generation of air-cooled powerplants. The decade of the sixties represented the peak of development of air-cooled engine designs, with significant advancements over those created earlier. Most of these engines reflected the latest design currents of the time with overhead camshafts, hemispherical combustion chambers and the ability to rev to 7,000 rpm or higher.

NSU 1000

1967 NSU 1000

NSU 1000, 1963-1973

The first genuine 1960’s design to come to market was the NSU Prinz 1000 launched in 1963. This was the world’s first inline four-cylinder to incorporate air-cooling since the ill-fated 1923 Chevrolet, and the first mass-produced air-cooled automotive engine with an overhead camshaft.

NSU 1000 Engine

NSU 1000 engine

The engine was constructed of an aluminium block with two sets of iron cylinders cast in pairs, and a pair of twin cylinder heads. The cooling fan was built into the flywheel and a single overhead camshaft was driven by a chain from the nose of the crankshaft. 1.0, 1.1 and 1.2 litre versions were built. Uniquely, the rear-mounted engines were mounted transversely, just behind the rear axle.

NSU 1000 TTS Engine

NSU 1000 TTS engine

It was a robust engine with a strong and rigid crankshaft supported by five main bearings. Soon after introduction, the sporting TT variant was launched with twin carburettors and later, the fabled TTS. The TT and TTS versions would happily spin up to 7000 rpm in stock form and were a favourite of sedan racers of the period, facing off against Mini-Coopers and Fiat-Abarths. The NSU’s won many European Touring Car Challenge Division One awards including 1st at Spa in 1967 and 1971 and 2nd at Zandvoort in 1968 and 1970. They also achieved class victories in the 1968 Marathon de la Route and the 1974 German Hillclimb Championship.

Porsche 911

1967 Porsche 911S

Porsche 911, 1964-1998

Probably the most iconic air-cooled engine among enthusiasts was introduced in the Porsche 911 of 1964. Designed by Paul Hensler and Hans Mezger to supersede both the standard 356 engine and the 4-cam Furhmann engine, the horizontally-opposed six cylinder was originally produced as a 2.0 litre with an aluminium crankcase and aluminium cylinder barrels with cast-iron liners. Each cylinder was topped with its own aluminium cylinder head with a fully machined hemispherical combustion chamber. The single overhead camshafts were chain driven. Cooling was provided by a belt-driven cast magnesium fan surrounding the alternator. The air ducting was moulded from fibreglass-reinforced resin.

Early Porsche 911 Engine with Dual Triple-Throat Weber Carburetors

Early Porsche 911 2.0 engine with dual triple-throat Weber carburettors

The crankcase had a dry sump, with a single dual-chamber pump handling both pressure and scavenging functions. An eight-litre oil reservoir and full-flow filter were located behind the right-rear wheel. In 1970, oil spray jets were added to cool the underside of the pistons, a feature which became commonplace on turbocharged engines in the years following.

The 911 also featured a new and unique fuel system. Conventional carburettors relied on a very accurate fuel level in the float chamber to control the final fuel mixture. This worked very well in a stationary vehicle, but once subject to the centrifugal and inertial forces of cornering, acceleration and braking, the sloshing fuel caused the mixture to vary considerably. This is a concern in any engine but especially critical in an air-cooled application since running lean can cause operating temperatures to soar to dangerous levels in short order.

To address this issue, Porsche and Solex engineers developed a radically new fuel delivery arrangement for the new 911. Each bank of the engine was equipped with three single-throat Solex “Spill-Tube” carburettors which shared a single fuel reservoir mounted below the carburettor base.

An electric pump delivered fuel from the tank to the reservoirs. An engine-driven double fuel pump (one chamber for each bank) continuously recirculated fuel from the reservoirs to the carburettors. The fuel chambers in the carburettors were kept 100% full at all times, the excess fuel exiting through the spill-tubes and back into the reservoirs. It was a brilliant concept, but unfortunately Solex were never able to perfect the system and Porsche had to switch to conventional carburetion.

911 2.8 RSR Engine with High Butterfly Mechanical Fuel Injection with Magnesium Velocity Stacks and Dual Ignition

911 2.8 RSR engine with high-butterfly mechanical fuel injection, magnesium velocity stacks and dual ignition

Porsche immediately took this new engine to the track, installing tuned versions in the 904/6 in 1965 and the 906 the following year. In 1967 a near-identical version to the 906-spec powerplant was made available in the 911R that developed 210 DIN hp at 8000 rpm, an output that would not again be available to the public in a 911 until the Carrera 2.7 RS of 1972.

In the fall of 1968, E and S versions incorporated mechanical fuel injection and electronic ignition. Over the ensuing years the engine grew in steady increments from the original 2.0 litres to 3.6 litres and was developed in both normally aspirated and turbocharged form. It went on to win almost every major race in the world in which it was entered including the Monte-Carlo Rallye in 1968, 1969, 1970 and 1978, the Tour de France in 1970, the Targa Florio in 1966 and 1973, and Le Mans in 1979.

Volkswagen 411

VW 411/412, 1968-1974

Volkswagen 411/412, 1968-1974

1968 saw the introduction of the VW 411 with a newly-designed 1.7 litre air-cooled flat-four. This was actually the second new VW engine of the sixties. The first was introduced in the fall of 1960 in 1.2 litre form in the Beetle, Bus and Karmann-Ghia, and later powered the 1500/1600 Series.

Unlike all other air-cooled engines debuting during the decade, VW’s new motors retained pushrod-activation for the valves. The new 1.7 litre engine, initially equipped with twin single-throat carburettors, would later be offered with Bosch D-Jetronic and L-Jetronic fuel injection.

VW Type 4 1.7 litre twin-carburettor form installed in 411 Variant

VW 1.7 litre with twin-carburettors installed in 411 Variant

There were some refinements over the smaller VW motor. The crankcase was cast in slightly heavier but more robust 319 aluminium-silicon alloy, and the larger-capacity lubrication system featured VW’s first full-flow oil filter. The cylinder heads incorporated a full cross-flow design for the first time, with exhaust ports exiting at the bottom rather than out from the sides.

Gijs van lennep and Jooks Klein in their VW 411 finishing 16th overall at the Rallye Monte-Carlo, 1969

Gijs van Lennep and Jooks Klein in their VW 411 finishing 16th overall at the Rallye Monte-Carlo, 1969

Besides powering the 411 and 412, the new engine found its way into the VW-Porsche 914, the VW Bus, and finally, in its most prestigious application, the Porsche 912E. In 2.0 litre high-output form, Porsche-designed cylinder heads boosted power to as much as 100 hp DIN; the pinnacle for Volkswagen air-cooled engines.

Porsche 917

Porsche 917, 1969-1975

Porsche 917, 1969-1975

One of the most legendary racing cars of all time, the Porsche 917 was powered by a air-cooled horizontally-opposed 12-cylinder DOHC engine of between 4.5 and 5.6 litres, in both normally aspirated and turbocharged form. Another Paul Hensler and Hans Mezger design, the basic architecture was largely based on Paul’s eight-cylinder Porsche Formula One engine of 1962.

917 Engine

917 engine: 4.5 litres, naturally aspirated, 1969

To reduce torsional stresses on the long 12-cylinder crankshaft, all takeoffs for power and ancillary drives were taken from the centre of the crank. In 911 fashion, each cylinder had its own individual aluminium head. These were topped with a common camshaft carrier, one per bank. The dual overhead camshafts, four in all, were gear driven.

Low weight, both in terms of the complete engine, and the rotating masses within, was a key priority. The crankcase was aluminium-magnesium alloy and the cam carriers and cam covers were magnesium. Cylinder barrels were aluminium with Nikasil liners. The connecting rods, rod bolts, fan drive shaft, auxiliary and output shafts and other miscellaneous hardware were made of titanium. The fan shrouding, cooling fan and intake stacks were fibreglass. The cooling fan displaced up to 148 cubic meters of air per minute.

917 Engine Cross Section

917 engine cross-sectional view

Like the 911, the 917 employed a dry sump oiling system. This one utilized no less than seven pumps. A triple unit in the sump provided pressure and scavenging of the front and rear of the crankcase, and four small pumps located at each end of the exhaust camshafts allowed for scavenging oil from the cylinder heads. The system held 30 litres of oil. Each cylinder had dual spark plugs, ignited by two separate distributors. Fuel was supplied by Bosch mechanical injection. The initial batch of 4.5 litre versions produced 520-580 hp at 8500 rpm, the turbocharged versions generated up to 1580 hp on full boost.

The 917 won Le Mans and the World Sportscar Championship title in 1970 and 1971, the Interserie Championship from 1970-1973 and the Can-Am Championship in 1972 and 1973. During the 1973 season, it won every single race. In 1975 a 917 set a closed course speed record of 356 kph/220 mph at Talladega Speedway, hitting over 400 kph/250 mph on the straight sections.

Citroën GS

Citroën GS, 1970-1986

Citroën GS, 1970-1986

Finally, the last mass-produced automobile introduced with a clean-sheet air-cooled engine design; the Citroën GS. The GS went into production in 1970 and garnered the European Car of the Year award in 1971. In accordance with traditional small-Citroën practice, it made use of an opposed engine driving the front wheels, this time with four cylinders. Initially just 1.0 litre in displacement, it was ultimately enlarged to 1.3 litres. The crankcase and heads were cast of aluminium and the cylinder barrels were cast iron. The cooling fan mounted directly to the nose of the crankshaft in the manner of the earlier Citroën twins. Following another practice dating back to the original 2VC, the connecting rods were one-piece and installed on a built-up crankshaft.

GS Engine

GS engine

Like the NSU and Porsche 911 engines, the GS employed single overhead camshafts, but toothed belts rather than chains drove them. Another revver, the engine produced its maximum power at 6750 rpm.

A distinctive feature of the engine was that the crankcase incorporated a double oil pump; an internal section for the engine oil and an external one to supply fluid pressure for the GS’s hydropneumatic suspension system. The engine’s compact layout allowed for the spare wheel to be stored in the engine bay, a Citroën tradition.

GS Engine Cross Sectional View

GS engine cross-sectional view

While largely renowned as an economical family sedan, the GS also enjoyed a career in rallying, finishing 6th overall at Caledonia in 1973, 4th at the Rally Torre del Oro of Spain in 1975 and 3rd at Cyprus in 1977.

There are two I left out as they sold only in small numbers but are worthy of mention: the Honda air-cooled twin of the 360/600 (1967-1972) and the air-cooled in-line four of the short-lived but technically intriguing Honda 1300 and 1300/9 Coupe (1969-1973) developed under the direction of none other than the majordomo himself, Soichiro Honda. The 1300 engine was an inline-four with a flywheel fan in the style of the NSU 1000. What made it unique was that unlike other air-cooled engines that utilized sheet metal or fibreglass ducting to contain and direct the flow of cooling air over the engine, the cooling passages of the 1300 were cast into the block and head in the manner of a liquid-cooled design. This served to considerably reduce engine noise from the level normally associated with air-cooling. Installed in the Honda 1300/9, the quad-carb dry-sump unit produced 110 DIN hp at 7300 rpm.

The Citroën GS motor would prove to be the last automotive air-cooled engine design. With the increasing emphasis on quiet operation, low emissions, fuel efficiency, larger displacements and heat producing ancillaries; air-cooling was no longer an attractive option.

Air-cooled engines traditionally ran slightly rich to reduce combustion temperatures. Unfortunately, this both reduces fuel efficiency and increases hydrocarbon emissions. In addition, the cooling system of most modern cars has to cope not only with engine heat, but the heat generated by air-conditioning condensers, forced induction intercoolers and transmission fluid coolers. These additional loads tip the balance well in favour of a liquid cooling system. Finally, it is quite difficult to design a multi-valve cylinder head for an air-cooled engine as space quickly runs out for adequate fin sizing and airflow.

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43 thoughts on “End of an Era: The Last Air-Cooled Automobile Engines

  1. Hi,

    I think you forgot to mention that Tatra built their T613/700 series from 1975-1998. They were fitted with 3.5 litre V8 DOHC air-cooled engines.

    Best regards,
    Kees Smit

  2. Kees,

    You are correct. I was not aware that the T613 received a new motor; I always assumed it was a carry-over from the T603 with new cylinder heads. Nonetheless, the T613 was a somewhat low-volume vehicle (11,000 built in 24 years) with only limited numbers being available to civilian consumers.

    Regardless, kudos to Tatra for sticking with air-cooling in the new powerplant!

  3. Another advantage of air cooling in the 1960’s was not having a cooling system. While water hoses and pump seals in contemporary cars can often last ten years; back then it was a different story. Periodic replacement of water and heater hoses was a normal maintenance procedure. Otherwise, they could fail at the most inopportune time – usually the hottest day of the year.

  4. J Kraus, do you ever see the return of the air cooled engine?

    Comedian Jerry Seinfeld, reportedly, has a real fetish for such engines. When both VW and Porsche discontinued their respective air cooled engines he went into a rage and bought up whatever air cooled models that he could store in his garage.

    Does the general public feel the same?

    I once owned a 1978 Porsche 911 Targa. I get goose bumps just remembering how that engine sounded when I revved it up in the morning before work. Oh, the days!!

    Will

  5. It would be interesting to know whether Tata engineers ever considered air-cooling for the Nano in the early design stages.

  6. Not only 3,5l V8 but also 4,5 V8 Tatra was made in late 1990’s.

    Also the Tatra trucks, Tatra is making air cooled V12’s up today.

    http://www.tatra.cz/en/zajimavosti/Press%20ReleaseEURO5.pdf

    VW/Porsche made them known worldwide, but still it was Tatra development which was stolen during Nazi era. I recommend you to find out how Hitler personally assured Porsche to use knowhow from Tatra V570 and Tatra T97 as he was promising to “solve all law issues after taking Czechoslovakia over”.

  7. Some points to note:

    The 1. air-cooled “Peoples car” was designed by Hans Ledvinka,manufactured in Tatra Koprivnice as the official type line of the 1920’s (1924, 1925,…) Because they made the trip through the Tatra Mountains, they were honored with the name of Tatra. This was the change from the original name of Ringhofer-Neseldorfer Mfg.

    Early in 1930’s Ing. Hans Ledvinka introduced the first of the totaly new look and whole line of revolutionary novelties- the production line of “Streamlined-shape passenger cars”. As the #1 was officially named the Family Car V 570. I would not discuss the patent rights and so on. The carrosserie and another technical properties of the car’s mechanicals become property of Dr. Porsche, due the diversified circumstances, and partly the cooperation of Ing. Hans Ledvinka and Dr. Porsche, together with Nazi ocupation of the whole Czechoslovakia 1938/39 to 1945.

    After war through the high amount of “finance” the VW/Porsche Co. bought from Tatra the Product Rights and so became the Tatra-originated Concept/product the property of the new Owners. So the different is the Original Product x Bought/borrowed product. Unfortunately due the Communist puch and the following development, the Czechoslovakians in 1948 lost the Marketing and personal-commercial contacts with the West/Free Market.

    It is forgotten today that in the Years 1947-1949 the “Real World Travelers,” Ing. Hanzelka and Ing. Zikmund, with the Tatra 87 succeeded to travel through the 3 continents: Europe, Africa (to Cape Town) through the real jungle….and by boat to Buenos Aires. In the new Continent (South America) – Argentina, from Buenos Aires to the Top of the Andes (Cordilliers) to 15-16,000′ on to Mexico and the Mid-American States, and by boat back to Europe…….a Grand Success: was mentioned in print and spoken on radio…..

    Prior to the war, the driver’s were Prague University students, working during the war in Tatra Mfg, and fluently spoke “35 LANGUAGES, INCLUDING AFRICAN DIALECTS”… After returning home, they made the 2nd complete trip of the Eastern half of the planet…(Eastern Europe, Complete Asia, New Zealand and Australia… with two vans, a Tatra 805 (+2 wheel small trailers).

    Something that should never be forgotten from our memories!!

    Andy

  8. You are quite right: The globe-trotting Tatra journey by Jiří Hanzelka and Miroslav Zikmund that Jerr S. (Andy) describes is quite fascinating and bears further study.

  9. One of the advantages of an air cooled engine is that is cheaper to maintain due to the absence of antifreeze.

  10. I have an aircooled v-4, 108ci flathead engine that is cast iron, cast steel , so I have ruled our a Mighty Mite AMC (pre Jeep). Any ideas?

  11. The AMC Mighty Mite V4, developed to power a lightweight, helicopter-transportable Jeep for the United States Marine Corps in the 1950’s was made of aluminium for light weight. It was discontinued in 1962. Since it was 1.8 litres (108 ci); the same size as yours, possibly what you have is an early iron prototype. Or more likely, you might have a Wisconsin VH4D industrial engine. The Wisconsin is a cast iron flat-head air-cooled V4 of 107.5 ci. which goes back to the 1940’s and is still in production.

  12. J-
    What are the specs on the aircooled flat six that was introduced in the Corvair prior to Porsche’s introduction of their flat six ?
    Dwight
    PS..great article as always.

  13. The Corvair flat-six engine was quite similar in configuration and basic architecture to the original 1938 VW 4-cylinder motor except for the horizontal top-mount cooling fan driven by the infamous twisted belt, hydraulic valve lifters and full-flow oil filtration.

    The most noteworthy aspect of the Corvair powerplant was the turbocharged variant of 1962, covered in detail in my earlier post; Genesis of the Automotive Turbocharger.

  14. I have an old Porsche motor. It’s air cooled, opposing pistons, with dual carbs. Can anyone tell me what my engine is by looking at a picture, or a way I can find out what I have? Thanx

  15. If it is a six cylinder engine, it is some variant of the 901 engine which powered the 911 and numerous racing vehicles.

    If it is a four cylinder with a single distributor and a dynamo slightly offset to the right, it is a 356/912 motor. If it is a 4-cylinder with dual distributors and a centrally-mounted dynamo, then you have a Carrera 4-cam Fuhrmann engine. If that is the case, you can consider moving up your retirement date or embarking on a lavish holiday excursion.

  16. Hello Mr J Kraus.

    The air cooled motor is waning in production, but it still is a desirable piece.

    I have worked with Porsche automobiles and drivetrains for some years and do have a fetish for high performance air cooled types.

    I have built many high performance engines over the years and the durability from design of the Porsche flat six is what sets it apart.

    Since I build motors and have seen them fail, I In my own mind, I had to design and build a 4 cylinder 911; and not one but many. I had not heard of Paul Hensler until an article in Excellence Magazine in Feburary 1997.

    He wrote that is was in Porsche’s program to build a 4 cylinder 911 type motor. Because of the limitations of fixed dimensions and displacement size Porsche declined to build it.

    I have a crankcase for a 4 cylinder 911 that will allow for 1600cc to 2700cc. I also have the crankshafts and camshafts. All other parts are of Porsche origin.

    I think your insight and knowledge is refreshing knowing I have gone down that road.

    Thank you for your writings,

    Dean Polopolus, Adv. Perf. Eng.

  17. Now we have covered air cooled petrol engines thoroughly how about air cooled diesel engines? Not necessarily automotive but transport orientated.. any offers?

  18. Think laterally… The company once made motor cycles and was eventually sold to India. The engine a WW2 design and is indeed air cooled but is in a boat.. so you ask yourself why its not water cooled. But these boats have to be able to have their engines running on the davits i.e. NOT in the water. They are needed to do this when the sea water is below a certain temperature and you cannot take a chance of having starting problems if you do need to put it in the water as particularly north of the Arctic Circle and towards the White Sea for instance. The application is military…. I’ve had one running so long we had to top up the fuel tank several times…

    Eoin Sloan

  19. All I know is that if my camper engine blew, that really would be the last of the air-cooled engines!

    Great blog! Took me 15 mins to read and 10 minutes to read the comments! Never has a webpage held me for so long!

  20. Without a doubt, liquid cooling is the best. But I love air cooled. I think with todays materials industry could do it. And — look at the size of cars now. They are getting smaller and could use a smaller engine.

    Brock

  21. A great page.

    Dear Mr. Kraus, lets add to the list of air cooled engined cars: germans of the 50’s; 60´s NSU Prinz, Glas (now BMW) 400 and 700, BMW 700, Japanese microcars of the 60´s: Mazda, Daihatsu, Suzuki, Subaru, and the Dutch DAF with a flat twin, the world´s first car with a CVT.

    The popularity of the Beetle has been lately a matter of subjective and acrimonious desire to cast a shadow of doubt about Porsche merits on the general design of the car. Undeniably Ledwinka was a clever designer in its own right but, by the time the Tatra prototype appeared, Porsche´s own design was already made in the form of the NSU Typ32; as well as Mercedes-Benz W17. It is also worth mentioning that the matter was amicably settled with Ledwinka receiving a worthy economic compensation. Let´s take into account that Hitler had meetings with both, Porsche and Ledwinka, discussing the formula of a people´s car.

    The air-cooled engine has a hope in the case of the air-oil cooling (Deutz), extra oil of the new synthetic formulas can make the difference for a totally new design.- Tatra´s air-cooled diesel meets the stringent Euro 5 norms, which include noise emission. The general auto industry option for water-cooling was more based on cost than for technical reasons, which as we can see, are not an obstacle for designing a decent air-cooled plant, which, has plenty of virtues, including longer life span, because air, as it is in the case of water, doesn´t degrade metal.

    • Dear Roger you are omitting that the first air-cooled Tatra was made in 1921, long before NSU32 or MBW17. http://en.wikipedia.org/wiki/Tatra_11 So Tatra V570/77 were preceded by a long line of air-cooled FR cars.

      You are right that NSU Typ32 appeared at the same time as Tatra 77, both sharing RR air cooled design. More important are the problems Tatra had with efficient air cooling of RR layout (and which he was able to solve). Tatra registered a number of patents on this, and that is what Porsche copied.

      Porsche might have eventually found solutions on his own, but he did not, so we can safely say that without use of Tatra’s knowhow VW Käfer would be overheating unreliable piece of scrap metal.

      • Dear Bungameng: 1923 Tatra´s T11 had an air-cooled front engine.- Mercedes-Benz had a rear engined air-cooled prototype already under test in 1929.

        Let´s not forget about Zündapp prototype with a 5-cyl. (water). I don´t see how we have to argue about it, because we, as Ferdinand and Hans, like Air-cooling.

  22. Air cooled engines are sadly disappearing; maintenance and metallurgy are really the deciding factors. Small plane engines are even seeing this due to better high-power water cooled designs.

    The thermocycle process that shortens the air cooled engines life will finally be its down fall. If you’ve ever spent a lot of time with these engines as I have you will soon see their drawbacks and see that Porsche and Citroen went the distance to try to solve these issues. One of the big ones I dealt with was the ambient temperature effects on the engine. 100 degrees F in July at 3000 ft above sea level, the engine temps and ability to shed heat differ from winter below zero times. Cleanliness and ensuring no oil leaks are paramount to long lasting engines.

    Many early VW/Porsche engines I worked with had followed the same demise: oil leaks led to dirt build up on cooling fins which led to overheating. VW owners found it difficult to replace the cooling seals around the engine which would allow hot air from under the car to recirculate through the engine causing temperature rises. As engine temps rose you would heat the fuel pump mounted on the case and that could lead to lean mixtures then vapor lock. Early 911/912s had noise damping insulation in their engine compartments that would break down and get into the cooling air and lodge against the oil coolers blocking cylinders 3 and 4 from getting adequate air. I found that maintaining an air cooled engine was a high maintenance operation in order to ensure that the engine could make it past the 100k miles barrier.

    Consumers today also want cars with every imaginable gadget and ridiculous levels of comfort leading to excessive electrical and cooling requirements that require as little maintenance as possible. Yes I do miss air cooled designs and still have a ’69 912. I always liked the compact designs and light parts, they are just enjoyable to work on.

  23. The story states that the 1960’s NSU Prinz was the first in line four cylinder air cooled automotive engine. The Franklin automobile company of Syracuse, New York, USA built and sold cars with in line air cooled four cylinder engines starting in 1903.

    Franklin built a total of about 70,000 air cooled cars between 1903 and its demise in the 1930’s. The engines ranged from the inline four to an air cooled V12 designed and built in 1930.

    • The article actually states that the NSU had “…the world’s first inline four-cylinder to incorporate air-cooling since the ill-fated 1923 Chevrolet…”

      To the best of my knowledge, Franklin’s 4-cylinder engine was extinct by 1923 (at least as to automotive applications) with the Series 10 and up all having at least six cylinders. If you can tell me which production Franklins with inline 4-cylinder power were produced in ’23 or later, by all means please let me know, and I will update the article accordingly.

  24. Don’t forget the old Fiat 500, the Cinquecento… 500cc, vertical twin, with pistons moving in tandem. The engine lived on in the 126, then later in the Panda 750, in to the 80s, I believe.

    • The stalwart 500 engine was not forgotten; like the original VW, Porsche, Citroën, Panhard and Puch air-cooled engines, the 500 motor was a 1950s design and not one of the final 1960s powerplants introduced in the twilight years of air cooling.

  25. Well, the last aircooled Citroën was NOT the GS(A), but the Visa Club, launched in sept 1978. And btw, one of the first cars with solid state breakerless ignition. Though the engine is similar to the late Dyane6/Ami8/2CV engine, it differs radically from it as well. Having alloy barrels, a displacement of 652cc and 36PS (DIN) at 5500. And 30% higher torque than a 602cc 29hp 2CV engine.

    One could argue that the Citroen Axel, introduced in 1985, was the last air cooled Citroën… But the engine is the same as in the GS.

    • Thank you for commenting. The Club was launched after the premier of the original GS, but the engine, as you point out, while heavily modified, was still based on 2CV architecture that dated back to the 1940s. The engines I focused on here were all-new 1960s designs.

      The standard fitment electronic ignition was likely the first in a supermini, but trails the high output version of the 6.5 litre Chevrolet V8 (1965), Dino V6 (1966), Porsche six-cylinder models (1968) and North American Chrysler models (1972).

    • It doesn’t fit your definition of a new air-cooled car (newly designed air cooled engine) but the Volkswagen Gol must have been one of the last air cooled cars to enter the market. It went on the market in Brazil in 1980 with the venerable Volkswagen 1.3 liter air cooled engine. The displacement was increased to 1.6L during its production run, then the air cooled engine was replaced with a water cooled engine in 1985. It was an interesting car, as far as I know, it was the only air cooled front engine, front wheel drive Volkswagen ever produced.

  26. The Franklin Automobile Co. in Syracuse, New York, U.S.A. produced air cooled automobiles from around 1900 to 1936. Their chief mechanical designer John Wilkenson, a Cornell graduate, put into use many concepts that became widely used in automobiles, such as automatic spark advance.

    Early Franklin autos broke many records in the U.S.A. for speed and durability. All were air cooled with the engine in the front. There is a museum in Tuscon, Arizona, U.S.A. that has a large collection of Franklins; The docent mentioned an astounding, little known fact… that Ferdinand Porsche visited the Franklin Automobile factory in the mid 1930’s. He may have come away with ideas that would contribute to the development of the Volkswagen engine.

    Air cooled engines are commonly used in private aircraft…I’m glad that the technology is still being put to use. Too bad that it’s not for cars. I love my Volkswagen bus and will never willingly part with it.

    Someone needs to write a good history book about the development of air cooled engines for automobiles.

  27. I guess technically it’s a water cooled engine but do you see a resurgence in the radiator-less motor with the possibility of 6-cycle water injected engines?

    • Indeed, most every 6-cycle design uses total-loss water cooling (although the cooling effect is secondary to the generation of steam pressure from the water), hence there is no need for a radiator. I do not see a 6-stroke engine coming to market anytime soon.

      Another radiator-less design was the gas turbine engine which many auto manufacturers experimented with in the 1960s. Due to the massive amount of air passing through the engine to facilitate the combustion process, they needed no additional cooling system of any sort.

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