Formula SAE Implications

FSAE rules mandate restrictions on the engines used during the competition. In order to limit the power capability from the engines, a single, circular, 20mm restrictor must be placed in the intake system between the throttle and the engine and all engine airflow must pass through the restrictor. Any device that has the ability to throttle the engine downstream of the restrictor is prohibited. 

Turbochargers or superchargers are allowed if the competition team designs the application. The restrictor must be placed upstream of the compressor but after the carburetor or throttle valve. Therefore, the only sequence allowed is throttle, restrictor, compressor, engine.

Despite the heavy breathing that a motorcycle engines require when making power, a 600cc naturally aspirated engine cannot provide a large enough pressure drop to cause even a high-subsonic condition through the 20mm restrictor throat. There are two ways to provide a greater mass flow into the engine: wave tuning and turbocharging.

Wave tuning works off the principle of resonance. By accurately placing pressure nodes along the intake and exhaust tracts, it is possible to induct and expel gasses at greater rates than otherwise. This however is very difficult to both design and implement for any given rpm range.

Turbocharging uses the principle of conservation of energy. Energy from the exhaust gas is extracted, converted to mechanical work, and reentered into the system in the form of compressed air into the engine intake. Through this process, it is simple to produce a larger pressure drop across the restrictor, and thus a higher mass flow into the engine.

More air means more power!

To accomplish this project, we used a Garrett GT12 variable wastegate turbo. The exhaust manifold, tailpipe, intake and coolant plumbing were all produced to utilize current race-engine principles. The engine management is done using a MoTeC M4 ECU. This microprocessor allows for accurate ignition and fuel timing as well as ease of tuning. The tuning was done on a Stuska water brake dynamometer.

The rules of the official rules of FSAE can be found at: http://www.sae.org/students/formula.htm