"Koba Dzhugashvili" - the difficult fate of the first domestic automobile diesel engine
Developers and testers of "Koju"
The Endeavor
The Soviet Union of the 30s is somewhat reminiscent of modern Russia. The policy of accelerated import substitution unites the two eras. However, Soviet Russia actually had it easier—the Americans were happy to collaborate with the Kremlin on industrialization. For example, Ford built the Gorky Automobile Plant according to its own design, something that seems unthinkable today. Frankly, it's not really needed these days.
Despite Western assistance, sometimes paid for in gold, the USSR needed its own solutions. In the transportation industry, the main problems lay in engine manufacturing. To be fair, the challenges with domestic engines have not disappeared in the 21st century—Russia has lagged behind global progress in this area, and continues to do so.
Many people believe that the first domestic diesel engine for transport was tank The B-2. It can't be called strictly military, as from the very beginning of its development, the vehicle was intended for use as a tractor. The first truly civilian diesel engine is considered to be the "Kodzhu," which stands for "Koba Dzhugashvili."
To understand the technical and conceptual level of the Soviet Koju diesel engine, it is necessary to place it in the context of the global development of diesel engines at the turn of the 1920s and 1930s. By this time, the diesel engine, invented by Rudolf Diesel in the late 19th century as a highly efficient compression-ignition heat engine, had already become widely used in stationary power generation, marine applications, and other applications. navy and in railway traction. But these were heavy and low-revving engines. An automotive diesel engine required a completely different approach—comparatively lightweight and with a high crankshaft speed.
By the early 1930s, leading industrial countries already had diesel engines for trucks and buses, primarily with pre-chamber or swirl combustion and a specific power of about 20–30 hp per liter of displacement.
Koju
The Koju cannot be called the very first diesel engine in the Soviet Union—the first experimental locomotive diesel engines were used as early as the 1920s, although before the war they were represented by single units and small-scale production runs. It is safe to say that there was some technological advancement in diesel engine design in the Soviet Union.
Given the current situation, it was decided to design a domestic diesel engine for a truck. The country's leadership recognized the importance of dieselization in transport and agriculture. The key document was the decree of the Council of People's Commissars of the USSR of May 15, 1931, on comparative testing of domestic and foreign diesel engines, which called for a broad competition involving numerous engines on domestic chassis.
In late 1930, the management of economic bodies also paid special attention to the introduction of diesel engines into the national economy, including for tractors and trucks with a payload capacity of over 2,5 tons. A decree of the Presidium of the Supreme Council of the National Economy of the USSR explicitly stated this. "absolute necessity" to establish production of high-speed diesel engines, especially for heavy trucks and tractors, in the shortest possible time.
Kodzhu diesel engine under the hood of the Ya-5
In full keeping with the spirit of the times, the decision was made to develop the Kodzha in one of Stalin's sharashkas. The Yaroslavl Ya-5 truck, capable of carrying five tons—a very substantial load at the time—was chosen as the basis for the future diesel engine. Development was entrusted to the Special Design Bureau of the OGPU Economic Directorate, where Professor Nikolai Romanovich Briling, who had been arrested but was a recognized authority on thermal engineering and engines, worked.
The goal was ambitious: to design a unique, entirely domestic diesel engine with a displacement of approximately 10 liters, producing 80–90 hp at 1700 rpm, suitable for installation in five-ton trucks and, potentially, heavier vehicles. This meant that Soviet designers intended to compete with leading foreign companies that had already mastered similar units, but to do so within the context of a still-developing metallurgical and mechanical engineering base.
Everything for industrialization
A little about the father of the future diesel engine, Nikolai Romanovich Briling. The scientist entered history as one of the founders of the domestic science of piston internal combustion engines.
Born in 1876, he rose from an engineer and researcher in pre-revolutionary Russia to a leading scientist in the USSR, making fundamental contributions to the theory of piston engines, thermal engineering, machine dynamics, and the development of steam and gas turbines. His work laid the foundations for the national school of automotive and tractor engine design, and his teaching contributed to the training of an entire generation of engine engineers. After the revolution, he, a professor at the Moscow Higher Technical School, was appointed deputy chairman of the Central Automobile Section of the RSFSR, which later transformed into the Scientific Automobile and Motor Institute (NAMI). Nikolai Romanovich headed this specialized institution until 1925.
Nikolai Romanovich Briling
From 1930 to 1933, the professor was imprisoned in a sharashka, where he worked on the design of the Koju. Fortunately, Briling was not executed, and he lived a long and productive life after his imprisonment.
But let's return to 1931, when the Special Design Bureau of the OGPU Economic Directorate began work on a high-speed diesel engine. The key parameters were determined in 1931: a four-stroke cycle, six cylinders in line, a displacement of approximately 10 liters, and a power output of 82–87 hp at 1700 rpm. An innovative solution was an aluminum cylinder block with wet insert steel liners and a common head—on par with the best foreign designs. Implementation relied on a three-pronged collaboration: the OGPU Design Bureau (development), the Yaroslavl Automobile Plant (manufacturing and installation on the Ya-5 chassis), and NATI (testing and refinement).
The Koju's evolution spanned three stages: the 1933 experimental diesel engine—90 hp at 1600 rpm; the NATI Koju variant—105–110 hp at 1800 rpm; and the pre-production MD-23 for the Ufa Motor Plant—133 hp. Over several years, power increased by almost half without changing displacement. The inline-six design ensured good balance, and the four-stroke cycle provided better fuel economy than two-stroke designs.
An aluminum block with steel cylinder liners equipped with transverse stiffeners was a bold move for the early 1930s, given the limitations of metallurgy. In this respect, the Koju resembled the B-2 tank. Aluminum reduced weight, improved heat dissipation, and allowed for increased power, but required careful structural rigidity. This was addressed in a comprehensive manner: a crankcase split below the crankshaft axis formed a robust lower flange; transverse partitions in the main bearing planes served as stiffeners; and ribbed cylinder liners improved coolant turbulence. Main and connecting rod bearings made of bimetallic strip combined a durable steel core with an antifriction layer.
Koju undergoing testing at NATI
This combination of materials placed the highest demands on manufacturing precision. Aluminum-steel and aluminum-cast iron joints were particularly sensitive to differences in thermal expansion. For Soviet industry, which was just beginning to master the mass casting of aluminum alloys, this posed a serious challenge. Nevertheless, prototypes were manufactured in November 1933—a testament to the rapidly growing technological school.
Difficulties with Koju
The diesel engine's success was largely determined by its fuel injection system. Early on, imported Bosch units with high injection pressure and precise cyclic delivery were used. However, dependence on foreign supplies conflicted with strategic objectives: imports were expensive, limited by quotas, and nationwide service was extremely difficult. The need arose to switch to domestic fuel injection pumps and injectors, which required the creation of an entire production culture: high-precision machining, heat treatment, and lapping of plunger assemblies.
The Koju fuel pump is a classic in-line plunger pump with an individual element per cylinder. Flow was regulated by rotating the plunger, which altered the opening of the shutoff port. The transition to domestic equipment was also a scientific challenge: it was necessary to select materials resistant to cavitation and wear on unstable fuel, and to develop refinement methods. During long runs, the Koju served as a kind of mobile laboratory, accumulating experience for future generations of diesel engines.
In 1934, Yaroslavl trucks equipped with Koju were sent on a Moscow-Tbilisi-Moscow run for comparative testing with imported counterparts. The route included flatlands, mountain climbs, and sections with poor pavement. Fuel consumption, speed, failures, and starting performance in various climates were recorded.
The results were impressive: first place for starting ease and second for fuel consumption. Overall, among 40 engines from 15 companies in 8 countries, Koju placed sixth, and third for starting performance. The German MAN D-0540 took first place, followed by the French LC-3 and the Hungarian OML-65.
The Moscow–Tbilisi–Moscow diesel rally of 1934
Preparations for serial production of the MD-23 then began at the Ufa Motor Plant, located far from the western borders and boasting an industrial base. However, as work progressed, system limitations were revealed.
The aluminum block—a design advantage—became the Achilles' heel. Mass casting of large-sized blocks required a developed foundry base, which did not yet exist. Issues with machining accuracy manifested themselves in the cylinder liners, heads, and bearing seats. While these challenges were overcome with prototypes, transferring this level of production to mass production proved impossible given the labor shortage and deadline pressures.
Fuel injection equipment was particularly complex: the production of injection pumps and injectors required ultra-precise machining at the micro level. Any deviations resulted in a drop in injection pressure, uneven flow, and deterioration in starting and fuel economy. For imported units, this level of precision was achieved through decades of experience; Soviet factories were just beginning to master high-precision mechanics.
Bringing the Koju into production required enormous resources and time. With international tensions mounting and resources being redistributed toward military projects, priorities shifted, and the promising diesel engine was relegated to the background. With a major war ahead, engines of a completely different class were required.
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