1. Engine Mounting
Engine Center of Gravity Experiment
The engine being the heaviest component of the car its position and mounting on the chassis has a significant effect on the dynamics of the car. The weight of the engine with all the fluids is around 40 kg which is nearly 25% of the total weight of the car. Knowing the Centre of Gravity of the engine with the help of the COG experiment we were able to position the engine in such a way that the CG of the engine remains as low as possible. After trying different orientation of the engine within the chassis we opted to mount the engine at an angle of 5⁰ with respect to vertical. This has allowed us to have the COG of the engine to be as low as 480 mm above the ground. The front engine mounting point also incorporates the Anti-Vibration Mounts made of Polyurethane. The mounting is designed in such a way to avoid any metal to metal contact with the chassis thereby resulting damping of vibration in all 6 axial directions. All the engine mounts were designed using structural analysis.
Structural Analysis with 120N of downward force acting on the engine mounts. Maximum deformation = 0.1236 mm
2. Air-Intake System
With a restrictor limiting the air flow, the air-intake manifold was designed in a manner to compensate for the power losses. Keeping in mind the available space and the envelope around the chassis, apt plenum volume and design was required for higher volumetric efficiency and diffusion of air. The intake manifold was designed in a manner such that the power-band was widened and utilizes torque in the most effective means. We tuned the intake manifold to obtain a flatter torque curve between 5000-7000 RPM with the runner length tuned for 6500 RPM for better response. A constant taper plenum of volume 2.3 litres was designed to get a better throttle response. Its shape was optimized by analyzing it using transient Computational Fluid Dynamics to determine the flow of air in the intake during the complete engine cycle. The outlet pressure boundary condition was obtained by performing one-dimensional engine analysis on Ricardo software. A simulation code was prepared on MATLAB with all the engine specifications for developing the combustion model and accurately predicting the CA 50 combustion values. The intake system was manufactured using the Selective Laser Sintering Process for achieve higher dimensional accuracy which increased the volumetric efficiency of the engine.
1-Dimensional Engine Model on Ricardo
Intake Transient and Structural Analysis
Air-Intake System Analysis
3. Fuel System
The main goal of the fuel system was to have a variable pressure fuel system so as to improve the tuning hence increasing the power output of the engine. Other goals were to decrease the sloshing, minimize dead fuel and to eliminate the bubbling while filling the tank while keeping an optimum volume. An inline fuel pump was incorporated along with a variable pressure regulator. To overcome the issue of fuel sloshing and increase the fuel efficiency of the car, the system was analyzed on Star CCM+ using the data obtained from the accelerometer mounted on the car. This analysis helped me determine the positioning of the baffles which reduced the sloshing and increased the efficiency of the car from 2.6 liter/22km to 2 liter/22km. A compact fuel tank was designed along with the inline fuel pump which was mounted on the Center of Gravity of the car in order to maintain the dynamic balance of the vehicle.
Fuel System Assembly and Fuel Tank Layout
Fuel System CAD
Accelerometer Data used to Perform Fuel Sloshing Analysis
Fuel Sloshing Analysis at different G-Force
Speed Density method was used to tune the engine. The performance Electronics PE3 ECU was used as a microcontroller. The aim was to have different maps for each event i.e. Acceleration, Skidpad and Endurance. Tuning maps are optimized by logging the engine data and other sensors, using DAQ system and chassis dynamometer testing. In order to improve the dynamic performance of the car, clutch-less upshift has been implemented. More theoretical approach was followed to make good base fuel maps and ignition maps. The maps were further fine-tuned using the closed loop Lambda Sensor data. With this done further time was spent on improving the drivability. Acceleration, Barometric, Temperature and Ambient pressure compensations were applied to make engine performance consistent in different conditions.
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