Weight has a direct impact on the efficiency and speed of a racing car; lighter weight is more desirable. Lighter engine parts help the car transfer energy more efficiently, which reduces the power lost in the transfer.
Professional race cars are almost completely handmade using lightweight materials designed for maximum efficiency. The frame is made from a steel tubing, and the body is constructed in lightweight sheet metal, all surrounding a bare block engine. Lightweight construction combined with aerodynamic design combine to generate downforce, which allows the race car to go through tight turns quickly with as little resistance as possible.