This paper reports the results of engine development for our Formula SAE competition vehicle. To utilize growth rate effect of power train weight on overall vehicle weight, single cylinder engine, Honda CRF450, was chosen as the base unit. However, as this base engine is naturally aspirated and its piston displacement of 0.45 1 is much less than the regulation upper limit, we installed a turbocharger unit for a three cylinder engine having 0.6 1 piston displacement installed on Suzuki mini-cars because of its size and price.
In the first step, we estimated the engine performances using gas exchanging process simulation using AVL Boost because the software has convenient function of modeling turbocharger. Because of the lack of both our experience and data base, we discarded the idea of driving the turbocharger dynamically following the engine operating conditions precisely. Instead, a somewhat large capacity surge tank was installed in between the turbocharger and the intake manifold. By selecting a suitable volume of the tank, the engine can breathe practically enough amount of air at almost all the engine operating conditions. We believe that this intake system design method with a surge tank helps engine designers installing a turbocharger without precise design database.
To evaluate the above mentioned design, a chassis dynamometer test was conducted. In this test, a turbocharger with much larger capacity that is for 1.2 1 engine was also tested as a reference. The measured maximum power reached to 75 kW, and the maximum torque was 70 Nm from 5,000 rpm to 7,000 rpm. By tuning the power-train final gear ratio, the vehicle almost achieved the aimed acceleration performance.