Tank M84A is one of the most used armored vehicles in the Croatian army. It uses a 12- cylinder Diesel engine V46-TK which develops a power of 735 kW. One of the ways of increasing mobility of M84A tank is increasing its engine power. Today, it is common for tank engines to have a power of 1100 kW. At that engine power, the M84A tank would have a specific power of 26,2 kW/t which is better than the most modern present tank, the Russian Armata (22.8 kW/t). The increase in engine power is often achieved by increasing the density of energy entering the engine, more specifically by increasing the mass of air charging system with higher capacity) and increasing the mass of fuel. In order to ensure efficient combustion, which also means lower fuel consumption and greater vehicle autonomy, it is necessary to have an injection system that can achieve high injection pressures, and thus good mixing of fuel and air. Modern systems that enable precise control of the amount of fuel injected and injection pressure are Common Rail systems. The V46-TK engine has a direct injection system which could be replaced by modern Common Rail system that would reise engine power to 1100 kW and would reduce noise and enviromental pollution. The most important components of fuel supply system are: high-pressurepump, injectors, pipelines, etc. To make the modernization successful, it is necessary to adequately replace these parts. A math calculation would result in certain values of mass and volume flow and power per cylinder. The calculation shows that the LP11.2 high – pressure pump and LI1 injectors from Liebherr are the most suitable ones for instalationin V-46TK engineof M84A tank.