The technical evolution of the Sukhoi Su-2 was defined by a critical shift in propulsion philosophy, transitioning from liquid-cooled to air-cooled radial engines to meet the demands of mass production and battlefield reliability. While early design stages for the "Ivanov" project in 1935 originally centered on the 1,025 hp Mikulin M-34FRN liquid-cooled engine, Pavel Sukhoi made a decisive turn toward air-cooled radial powerplants. This decision was influenced by the potential for higher performance at altitude and the inherent simplicity of air-cooled systems for military operations.

Early Powerplants and Prototypes

The first flying prototype, the SZ-1 (ANT-51), took to the air on August 25, 1937, powered by an air-cooled, nine-cylinder radial Shvetsov M-62 engine producing approximately 800 to 830 hp. Although the aircraft displayed good stability and handling, the M-62 eventually reached its development limit, and subsequent prototypes like the SZ-3 utilized the more powerful M-87 series. By 1939, the M-87A and M-87B engines, offering 950 hp, were integrated into series production models, though these early engines were frequently plagued by failures in the supercharger and carburetor systems.

The M-88 and M-88B Series

The M-88 engine became the primary powerplant for the series-produced Su-2, increasing output to 1,000–1,100 hp. The most refined production variant was the M-88B, which featured significant structural improvements over its predecessors, including increased cooling fin surfaces on the cylinder heads and liners, as well as reinforced cylinder walls. Despite these enhancements, the M-88 series suffered from a persistent "motor crisis" involving chronic overheating, oil leakage, and unreliability, which at times forced the suspension of aircraft deliveries and led to the arrest of technical personnel at manufacturing plants.

Modernization and the M-82 Engine

In 1941, efforts to drastically improve the Su-2's performance led to the installation of the Shvetsov M-82, a sophisticated 14-cylinder, two-row air-cooled radial engine. This engine delivered between 1,330 and 1,400 hp, increasing the aircraft's top speed to approximately 486 km/h and significantly improving its rate of climb. Later experimental versions even tested the M-82FN with direct fuel injection, which promised even greater performance, though the cessation of Su-2 production in November 1941 prevented these variants from seeing wide service.

Fuel and Oil Systems

The Su-2's engine was supported by a robust fuel system consisting of three tanks: a primary fuselage tank (capacity varying between 405 and 594 liters) and two wing tanks (approx. 168–175 liters each). A notable safety feature was the use of cooled exhaust gases to pressurize these self-sealing tanks, creating an inert environment that protected them from ignition when struck by enemy fire. The oil system utilized an external radiator, typically mounted in a tunnel under the engine or, in modernized versions, integrated into the wing center section.

Operational and Propeller Equipment

Engine power was delivered through a three-blade metal variable-pitch propeller, such as the VISh-6 or VISh-23, with a diameter of 3.25 meters. In the harsh conditions of the Eastern Front, maintaining these engines required significant effort. During winter, crews used specialized APL-1 lamps to pre-heat the engine and oil before starting. Furthermore, the M-88B engines utilized castor oil, which presented maintenance challenges; it was consumed in high quantities and, if leaked, would harden on the fuselage, creating a rough surface that degraded the aircraft's aerodynamics.