The I-S Internal Ride Height...
The I-S Internal Ride Height Sensor is built into the ShockWaves. Pre-calibrated, it needs only to be plugged into the LevelPro wiring harness.
There's no question that using air suspension under a street rod offers a number of advantages when compared to leaf or coil springs. However one of it's major strong points, adjustable ride height, can also be a source of frustration.
Air spring systems provide the best performance in a factory-determined range of operating height. In their basic form air ride systems are controlled by a manual valve or valves-the system's air pressure, and the resultant ride height, is monitored by one or more pressure gauges. If a change in ride height is desired, or if the vehicle's load is increased or decreased, the pressure in the system is manually altered accordingly.
When external ride height sensors for aftermarket air spring systems became available, they provided a new level of sophistication-ride height adjustments were taken care of automatically. Something minor such as filling the gas tank, or more extreme situations like back seat passengers and a trunk full of luggage, were compensated for thanks to the sensors and a computerized control system.
While external sensors work well, they do take up space in a usually already crowded street rod chassis. As Bret Voelkel, owner of Air Ride Technologies points out, allowances for tire clearance and suspension component interference must be made and the sensors must be synchronized and calibrated. According to Bret, to work properly the ride height sensor must accurately track the entire movement of the suspension. When you are dealing with multiple moving parts this can get tricky. Even at best you are looking at a few hours to get all four sensors installed and calibrated. OEM cars use external sensors because they are inexpensive and are installed on thousands of identical cars. The OEM's don't have to deal with custom installations and installers.
Although external ride height sensors get the job done, Bret felt there had to be a better way to control air suspension systems, and thanks in part to the military, he found it. As Bret explains it, a few years ago Air Ride Technologies had a military customer who demanded an integrated, accurate ride height sensor to compliment the air suspension and leveling system on their project. They figured soldiers might have higher priorities than looking at an air pressure gauge to see if their vehicle was at ride height. They also wanted a solution that would eliminate damage by debris or improper installation. Since there wasn't a control that met those requirements, the crew at Air Ride Technologies had to invent one and, after much testing and refinement, a version is available to the street rod market.
Called the I-S Internal Ride Height Sensor, it uses infrared technology to measure the height of a ShockWave internally. That measurement is sent to a computer, which adjusts air pressures as needed.
Currently the I-S sensor is only available for ShockWave applications. Those using air springs will have to rely the external sensor system, at least for now. For those who want to retrofit their existing ShockWaves, the installation must take place at the factory but Air Ride has a program for that as well. Since the output of the I-S sensor is a standard 0-5 volt signal it is compatible with most other aftermarket leveling systems in addition to the Air Ride Technologies LevelPro system. Think of it as military benefits without enlisting. (Ed.'s note: Keep your eyes peeled for a full-length feature on the complete install in a future issue).
The I-S sensor works on an...
The I-S sensor works on an infrared light module that is built into the top of the ShockWave. It bounces a beam of light off the top of the shock and measures how long it takes to return. This is done once every few milliseconds. The internal circuitry translates this reading into a 0-5 volt signal that is then read by the LevelPro electronic leveling system computer. That ECU then decides if the air spring needs to be deflated or inflated to achieve the proper ride height. All this happens in less than one second.
Several years of evaluations...
Several years of evaluations and refinement have proven the sensors are unaffected by the oil and grime that may accumulate. Testing has shown that this unit is accurate even down to 2 percent reflectivity. That means even with a layer of flat black paint on the top of the shock it would be able to compensate and maintain an accurate ride height within .050-inch
While the tried and true external...
While the tried and true external sensors perform well, they do complicate air spring installations.