When a go-kart racer knows the density of dry air entering the engine, he can tune his carburetor's efficiency accordingly and maximize performance. The problem is weather is always changing. To avoid any guesswork, John Cashon built an on-board weather station for go-karts. It monitors three atmospheric parameters (barometric pressure, relative humidity, and temperature), does the required math, and displays the dry air density on a PDA for quick, on-the-fly carburetor adjustments.