Solenoids, Valves and Lines
Of course, there's more to an air suspension system than just a simple bag. Here are the parts the help make an air suspension system work.
Lines carry the compressed air to the bags. The lines are similar to common high-pressure air lines and are routed along the frame of the vehicle. While most lines are a rubber/polyurethane composition, they can be replaced with custom steel lines, offering a cleaner look and a more rugged construction.
Valves are the gateways for the air to enter various parts of the system. In today's air suspension system, valves play a critical roll in isolating and controlling where air is directed and how. Early generation air suspension systems were two-way setups. Essentially, each left and right air bag was connected by a line and shared air. As the vehicle cornered, one air bag compressed its air and pushed it through the line to the other air bag, which was expanding. This resulted in severe body roll and accounted for part of the reputation air suspension systems had for causing a terrible ride. Now, systems use a series of valves that control this tendency and offer bettering handling.
Solenoids are used in electronically-controlled systems to fill and vent each air bag. As the system adjusts for different conditions, it commands each solenoid to open or close, changing the amount of air in each of the bags.
Electronic systems are managed through an electronic control module. The controlling software can be very basic, almost a digital version of analog on/off controls, or it might run a more sophisticated software, monitoring pressure and ride height in real time. The modules receive information through a variety of inputs, including ride-height sensors, and toggle the compressor on and off as needed. The electronic side of the system is where most innovation has occurred, and where changes will likely happen in the future. These systems generally remain separate from the vehicle's on-board modules and communications.