Abstract: An apparatus includes an application pump that pumps water through a water application line. Fast-acting valves control a flow of different chemical concentrates into the water application line, and a controller is connected to each of the valves and programmed with a chemical injection pulse solenoid algorithm for optimal control of the chemical concentrate. The apparatus provides direct chemical injection into vehicle wash systems through the use of the fast-acting solenoid valves which rapidly turned on and off, creating an accurate and variable means of metering highly concentrated chemicals. Algorithms are used to control operation of the fast-acting solenoids, “pulsing” them in accordance to chemical type and application. The particular algorithm used preferably balances end performance and consistency with mechanical considerations such as actuation lag time, valve longevity, and wash equipment variables.