Abstract
According to the FSAE and Formula Student rules, only a car fitted with an engine not more than 610cm3 of displacement can take part in the contest and also the intake manifold should be fitted with a 20mm diameter restrictor. This restrictor changes the whole operation of the engine, spoiling the torque characteristics and the fuel consumption. That is why the working parameters must be changed, and the gas exchange process must be optimised. One of the best and most effective changes is redesigning the valve timing and displacement, adjusting it to the new circumstances.
In this work, after building the model of the engine in a simulation programme it turned out, that the volumetric efficiency of the cylinders drops down to 45% because the original opening time of the intake valves is too wide. The valve opened too early, when the pressure was still high enough to make the exhaust gas flow into the intake runner, than it got again in the cylinder when the piston sucked it back. The valve closed too late when the piston was far in compression phase and the piston pushed the intake gas out of the cylinder. This caused torque and power drop on a wide revolution range and could not be solved with optimised intake runner length. That is why a new cam profile was created based on the engine simulations, which had a shorter open interval and safe enough to work in the engine without making damages in the cylinder head.
The simulations showed, that the new cam profile improved not only torque in the mid rpm range, but highered the maximum power too. This was caused by decreased loss of gasexchange and the higher volumetric efficiency.
Keywords: valvetrain, camshaft, cam, Formula Student, engine