Originally Posted by ColdCase
The suspension compressor is tiny, is light duty and does not have much capacity. It is designed more to move a little air and produce high PSI. It has trouble keeping up with even a minor leak without overheating. You't have better performance with a $20 12VDC plug in air compressor.
BTW QL is not an entirely closed system. It will draw air in to make up for losses.
Where did you read that?
According to every piece of literature and info I have seen it's completely self contained and does not draw in or expel any air/gas.
Jeep Grand Cherokee WK2 - Quadra-Lift Air Suspension system
"A closed system - because it's better
Quadra-Lift is a closed system so adjustments are much faster than other systems that must draw in or exhaust air for operation. It is the first SUV to use the latest air suspension technology utilizing a closed type design.
The closed type system does not draw in fresh air during vehicle lifting or leveling-up, or pump air out to the atmosphere during lowering or leveling down. Instead it moves stored pressurized air from the reservoir to the air springs and back again.
Since the system's compressor is working with pre-pressurized air, and not air at atmospheric pressure, the compressor can be smaller which translates into reduced power consumption and weight as well as improved NVH characteristics. Pressurized air is moved between the reservoir and the springs by way of an air supply unit (ASU). The ASU consists of an air compressor and a valve block assembly that is plumbed to the springs with a network of lines. The ASU valve block provides six color-coded pneumatic connections to the system. Four connections distribute or retrieve air from each of the air springs. One connection is the inlet from the compressor, and the last connection exhausts the system. The ASU also contains an intake / exhaust assembly with filter, onboard desiccant, a reversing valve, a temperature sensor, and a pressure sensor. It is important to note that the ASU is not designed to fill an empty system. The ASU's main function is to pressurize and move air that is already there.
Front and rear height sensors measure the distance between the body and suspension, and provide feedback to the control system to constantly monitor vehicle height. The air suspension control module (ASCM) contains the logic that controls ride height during all driving and loading conditions. The ASCM controls the ASU compressor and valve block, and is influenced by many other modules and systems. The powertrain control module (PCM), anti-lock brake system (ABS) control module, cabin compartment node (CCN), and drivetrain control module (DTCM) are all primary inputs to the ASCM.
By working with pre-pressurized air, the closed air suspension system also provides additional benefits to the customer:
Reduced time to change vehicle height
A significantly greater number of repeated lifts without lift time deterioration
System performance that is unaffected at higher altitudes when compared to an open type air suspension"