The new Bendix AD-HFi air dryer features the same design as the AD-HF dryer, which was launched...

The new Bendix AD-HFi air dryer features the same design as the AD-HF dryer, which was launched in 2019, but incorporates a solenoid-operated valve that replaces the traditional mechanical governor.

Photo: Bendix

Bendix said it developed its new AD-HFI air dryer with electronic pressure control capabilities to provide more dry air for the systems today’s trucks depend on, increase energy efficiency, and improve air system diagnostics.

The AD-HFi features the same design of the Bendix AD-HF dryer, which was launched in 2019, but incorporates a solenoid-operated valve that replaces the traditional mechanical governor. The company announced it in conjunction with the American Trucking Associations' Technology & Maintenance Council meeting in Cleveland, Ohio.

“An electronically controlled governor means we precisely regulate the dryer’s charge and regeneration cycles using Bendix’s Electronic Air Control (EAC) software,” said Rich Nagel, director of marketing and customer solutions, Air Supply and Drivetrain, in a news release.

“This function enables the dryer to operate under different parameters in different conditions, increasing its dry air processing capability and saving energy,” he continued. “That same software also provides diagnostics that help fleets and owner-operators get the most out of their dryers and cartridges.”

According to the company, while a mechanical governor’s status operates within two fixed pressure settings, the AD-HFi’s solenoid is controlled by Electronic Air Control (EAC) software, which monitors a range of data broadcast across a truck’s J1939 network, including speed, engine torque, and RPM.

“With EAC software, the AD-HFi unit can modify its charge cycle based on air system and engine demands,” Nagel said. “If the software determines that the air system requires extra drying capacity – let’s say you’re hauling multiple trailers or have extra axles, for instance – then it can command additional short purge cycles. This patent-pending technology is called Interrupted Charge Regeneration. This enhanced purge capability provides significantly more dry air for vehicles that need it.”

Bendix said efficiency and energy savings are also built into the EAC software in the form of Overrun and Overtake functions. When a compressor is building pressure, it consumes approximately 8 to 10 horsepower from the engine. EAC software uses the vehicle’s operating information to determine optimal compressor run times.

Of overrun and overtake

“Overrun is when you’re in what we call a ‘favorable energy state,’” Nagel explained. “If you’re going downhill or idling, then the engine has ‘free energy,’ which would otherwise be wasted and can now be used for charging. In those situations, the EAC temporarily increases the cut-in and cut-out pressures because the compressor can charge above the standard, programmed pressure without the driver losing engine power.

“Overtake is the opposite,” he continued. “If I’m trying to pass or climbing a hill, then I don’t want the compressor to charge because I need that horsepower. In this case, the EAC lowers the cut-in and cut-out thresholds, so the compressor won’t try to build pressure. And ultimately, that’s an energy savings since you’re running the engine more efficiently.” The software is programmed not to reduce the cut-in pressure below a safe setting, per FMVSS-121 regulation.

The EAC software provides air dryer-related status messages over the J1939 network, with the capability to monitor excessive air demand, which can indicate system leaks or other issues, said Bendix. It also monitors regeneration cycles and the amount of air processed during the service life of a dryer cartridge. Using this information along with other data from the compressor, the EAC can signal when it’s time to replace the cartridge.

“Our Electronic Air Control software is loaded with parameters tied to which compressor and engine are on the truck,” Nagel said. “The software is programmed to know what a nominal duty cycle is for that compressor and how much air it should be producing, so it can send a diagnostic code if something isn’t operating correctly. As far as cartridge life goes, it only makes sense that measuring by the amount of air actually processed is better than using mileage as a guideline.” A message that broadcasts the remaining life of the dryer cartridge can be reset after replacement using Bendix ACom Pro diagnostic software.

The Bendix AD-HFi air dryer is available for order through several major North American commercial vehicle manufacturers.