For fans of military wheeled vehicles, it is known that behind every large American vehicle of the 70s, 80s and 90s often beat a superquadro heart. A precise technical choice, perfect for the long American roads, hydraulic transmissions and the need for high reliability.
The bore (cylinder diameter) was larger than the stroke (vertical movement of the piston), which was ideal for maximizing displacement - 5.7L, 7.0L and beyond - without creating engines that were too tall. These engines were well suited to sturdy frames, such as those of pickup, work SUVs or military vehicles.
American supersquare engines favored low-end torque, between 2.000 and 3.000 rpm, essential for towing heavy trailers, driving on difficult terrain, and reducing the risk of overheating. Their characteristic sound, deep, full-bodied and pleasant - the classic American "rumble" - recalls that of a tank.
Concrete examples
In 1985 the first HMMWVs or Humvee (High Mobility Multipurpose Wheeled Vehicle). Here too, the super-square architecture found its ideal home with the GM 8L V6.2 diesel engines derived from civilian production, with a bore of 103,1 mm and a stroke of 88,9 mm, such as to guarantee elasticity at low revs and plenty of torque, perfect for extreme environments.
During the Gulf War (1990-1991), American convoys traveled thousands of kilometers in the Kuwaiti desert. The 6.2L proved to be extraordinarily resistant and capable of running for days at temperatures of up to 50°C and in extreme conditions without the need for technical stops, thanks to the supersquare design philosophy that reduced thermal and mechanical stress. Maintenance required was minimal.
The European Concept: A Different Philosophy
In Europe, a different engine approach developed, based on long-stroke engines, both diesel and petrol. This configuration favored low-end torque and optimized fuel consumption, which were essential on narrower and more varied roads than the highways American.
The use of lightweight materials, such as aluminum – much less common in the United States at the time – allowed for reduced weight and operating temperatures. The result was more compact engines, often with 4 or 5 cylinders, sometimes mounted transversely to optimize space and improve weight distribution.
However, the oversquare engine can be considered extremely versatile, depending on the context of use and the design configuration. In military vehicles, trucks and American work vehicles, the oversquare is used to obtain a great torque at low revs, thanks to a large bore that allows the use of large diameter valves and large combustion chambers, ideal for delivering power at low revs. In the sports field, however, the oversquare philosophy is used to maximize power at high revs: the large bore favors abundant air flows, essential for powering engines capable of exceeding 8.000 rpm with extreme performance, as demonstrated by famous examples such as the Ferrari F8 and BMW S136 V65s. In these contexts, the comparison between automotive oversquares and high-performance motorcycle engines is particularly apt.
It can therefore be stated that superquadri engines have two performance keys: if designed for heavy work, they favor torque delivery at low revs and thermo-mechanical robustness; if oriented towards pure performance, they enhance maximum power at high revs.
American OHV Engines
The OHV (Overhead Valve) or HEMI (Hemispherical Engine, like the Chrysler engines with hemispherical combustion chambers), with camshaft in the crankcase and pushrods, typical of the USA, offered a lower specific power than the more refined European or Japanese engines. This was due to moderate compression ratios (necessary to handle low-octane gasoline, around 87 AKI) and a simpler and heavier distribution: perfect for robustness, less so for high revs and inertia. However, these V8s proved to be workhorses: long-lived, easy to maintain and ideal for heavy-duty use.
2000s and turbo
With the widespread use of turbochargers in Europe, interest in oversquare engines declined. Turbos allowed high power and torque – low down – even from long-stroke engines, without the need for extreme bores.
Current philosophy and modernity
Today, heavy vehicles such as MRAPs (Mine-Resistant Ambush Protected) still use robust diesels with large bores, although not always purely oversquare. duramax The 6.6L V8 Diesel has a 103mm bore, 99mm stroke (nearly square), the Ford 6.7L Powerstroke Diesel, 99mm bore, 108mm stroke (slightly undersquare)
Even in the new generation of Humvee civilians, such as the AM General NXT 360, continues the tradition of large-bore turbodiesel V8s. In the civilian field, engines such as duramax e Powerstroke They can easily tow over 15 tons, inheriting the philosophy of robustness and reliability.
American and European engine philosophies represent two distinct approaches to balancing power, torque, efficiency and reliability. While America favors robust engines for long distances and heavy loads, Europe focuses on dynamic efficiency and low fuel consumption.
The differences between American supersquare engines and European long-stroke engines are not simply design choices, but the reflection of two operational visions. Where it was necessary to resist the desert, tow armored vehicles or ensure autonomy in hostile territories, the supersquare V8 became synonymous with survival and longevity. Where precision, agility and efficiency were decisive, Europe developed an equally refined motoring art. In both cases, the technique followed the strategy.
The technological revolution
Even in the civilian sector, Ford Mustang modern has adopted the 10-speed 10R80 automatic transmission with torque converter, born from the collaboration between Ford and General Motors. This transmission combines the muscular character of the oversquare engines with an unprecedented management of efficiency and responsiveness.
Depending on the version, the 10R80 is paired with three engines that reflect different technical philosophies: the 5.0L V8 "Coyote", virtually square (93x92,7 mm), powerful and full-bodied; the 5.2L V8 "Predator", oversquare (94x93 mm), designed for extreme performance, and the 2.3L EcoBoost, undersquare (87,5x94 mm), close to the European school, aimed at efficiency and response at low revs.
Even the modern one Mustang, a muscle icon, represents the perfect synthesis between the American tradition of supersquares and the technical rationality of European undersquares, today offering a balance between power, torque, efficiency and innovation.
Photo: US DoD / Italian Army / web
