Improvement of Formula Student Racecar Performance with Rotary Variable Runner Length for the Intake System

The purpose of this research is to implement the variable intake manifold on a Formula Student racecar to achieve a lower overall Autocross lap time. A previous version of the linearly adjustable variable intake manifold prototype was able to deliver an improved engine performance in the form of wider range of engine RPM with high torque, but its dimension did not conform to the FSAE regulation. This research focuses on developing a physically compact rotary variable intake system to achieve a favorable characteristic while conforming to the FSAE rules. The engine is expected to perform better than the previous one by comparing the range of engine RPM which produces torque greater than 48.47 N-m, representing 90% of maximum torque or our 2015 car with a conventional intake system. The optimum runner length is determined using the pressure wave tuning method. CFD analysis is performed to determine the inlet-plenum diameter ratio to ensure uniform mass flow distributions among four runners. The plenum housing is constructed using carbon fiber composites with an allowable maximum displacement of 1 mm during operation. Finally, a rotary variable intake system is built and installed in the 2016 racecar. Test results from a chassis dynamometer between 4,000-11,500 engine RPM at all possible runner lengths show that the rotary variable intake system is able to deliver torque above 48.47 N-m over the range of 7,035-9,307 RPM (range of 2,272 RPM), which is 69.17% wider than the previous car’s power band between 5,784-7,127 RPM (range of 1,343 RPM). The maximum power achieved by the rotary variable intake system is 50.175 kW, which sees an increase of 7.66 kW. The results have successfully shown that the rotary variable intake system can enhance the car performance and ultimately help reduce the lap time at the Autocross event by 1.07 second or 1.53%.