Contributed by Bob Chabot
Keep Vacuum Simple
New Dayco Products technology provides many vacuum solutions
In this modern era of increased electrification and intensified light weighting, automakers and their suppliers are continually seeking new solutions that can be applied to as many vehicle models as possible. Recently, Dayco Products introduced new vacuum generation system (VGS) technology, called Activac VGS, which uses a profoundly low-tech approach that the company believes will revolutionize how vehicles will operate.
Dayco’s Activac VGS technology is a less costly, lighter and more efficient solution that can essentially replace any mechanical or electrical vacuum pump by rerouting the air that flows naturally into the engine. (All images — Dayco Products)
Physics Leveraged to Replace Heavier, Expensive and Inefficient Pumps
Activac VGS leverages a fluid dynamics principle known as the “Venturi effect,” named after Italian physicist Giovanni Venturi. This involves creating a reduction in air or fluid pressure by forcing it through a constricted section of a pipe, or choke, to produce a vacuum.
"When Dayco first began developing Venturi-based actuators in 2011, all we had at the time was a basic pneumatic actuator," noted Jim Miller, Dayco's director of valve and actuator technologies, who has been with the product since its inception. “After a year or so of development, we were experiencing success with valve and actuator technologies — an area the company had never developed previously. From those early encouraging results, the full ACTIVAC system gradually emerged, which is now protected by six current patents and others patents pending.”
How you go about designing constriction is the differentiator. For example, our Venturi tube design features an elliptical throat and hyperbolic wall, in addition to other proprietary details.” The system includes an array of stand-alone components, such as aspirators, ejectors, flow control valves, check valves and noise attenuators, all built to amplify or create vacuum, while reducing vehicle weight and/or parasitic engine loss.
It’s an ideal solution capable of replacing more costly, heavy and fuel-guzzling conventional mechanical and electrical vacuum pumps found in systems on many of today’s engines, such as vacuum brake assist, fuel vapor purge and crankcase ventilation. The Activac braking system technology also replaces the need for vacuum pumps to run auxiliary systems in vehicles, which is a growing issue as engines are being boosted by either superchargers or turbochargers, according to Paul DiLisio, Dayco senior vice president, Automotive and Industrial OE Sales.
"As more and more engines are becoming boosted, most auto makers must have some kind of auxiliary vacuum system,” DiLisio explained. “Typically, in the past, they've been either using mechanical vacuum pumps or an electrical vacuum. Both of those products have disadvantages. The disadvantage of a mechanical vacuum pump is that it's always running, and that drains power from the engine. An electrical vacuum pump only runs on demand, but is typically expensive."
"The key breakthrough for Dayco was discovering how to apply the concept to mass-produced vehicles to address the push for weight reduction and the engineering desire to limit how much engine — or electric battery — power is drained away to run component systems. Our solution is as close to no-compromise as you can get. It can result in lower systems cost, better fuel economy and better braking performance.”
The ACTIVAC system weighs just 1.82 pounds. When compared to mechanical vacuum pumps, the Dayco ACTIVAC system reduces weight between 1.1 and 6.2 pounds, depending on whether the pump is cam-driven or belt- driven. The system also improves fuel economy by an estimated .3 percent over the mechanical vacuum pump. In addition, when compared to electrical vacuum pumps, Dayco’s ACTIVAC reduces weight by approximately 5.1 pounds.
“In all cases, this results in a significant cost savings per vehicle depending on the type and size of vacuum pump currently being used,” DiLisio added. “These p>me-changing technologies also directly result in benefits for the driver. For example, our vacuum brake assist assembly, featured in the Ford F-150 pickup, results in a lower and more consistent brake pedal force. The driver doesn’t experience a hard pedal during multiple brake application, as might be felt during a parking maneuver, providing an overall better feel to the driver.”
Dayco's James Miller stands next to a Ford F-150 equipped with the supplier's Activac system, shown under the hood in blue. The Activac braking system technology replaces the need for vacuum pumps to run auxiliary systems in vehicles.
A Successful Launch Takes Teamwork
After years of development, the Activac VGS pumps debuted last fall on the brake system for more than 188,000 2017 Ford F-150s equipped with the second-generation 3.5-liter V-6 EcoBoost engine. The pickup had previously used a mechanical vacuum pump. Dayco engineers harnessed the Venturi effect to create an engineered system that evacuates air from a vehicle's brake boost canister to provide brake assist without any compromise to fuel economy.
“The EcoBoost engine's induction airflow creates the required pressure differential across the venture orifice, a key component within the Activac system,” Miller advised. “The 1.82 lb. Activac vacuum-generation system, including hoses, replaced a 2.27 lb. (1.03 kg) cam-driven mechanical pump. The mechanical pump runs constantly, so it was pulling power from the engine all the time,” Miller said, noting the pump’s 0.3% fuel economy penalty. “Activac is also lighter than the 6.3 lb. (2.86 kg) electric pump that pre-dated the F-150’s mechanical pump for brake assist.”
“Another of the system's key components is a 4.96 in. long injection-molded thermoplastic part that creates and amplifies the Venturi effect,” Miller continued. “The component’s throat geometry is unique; it’s an ellipse, not a circle. Its basic design increased the speed of a fluid’s flow and decreased the air pressure at the point of constriction. Once we saw that an ellipse of a certain height and width worked well, we then varied width and height to see if it got worse or improved until we reached the optimal design. Finally, to optimize the hissing noise that Activac’s two noise attenuators created, without unduly restricting the flow of air, we added a stainless steel mesh, packaged within the Venturi assembly, to serve as a noise muffler.”
“Ford opted to replace the previous cam-driven mechanical pump because "as a vacuum source, a large, thermally efficient aspirator with a shut-off valve was lighter, more fuel efficient, and less expensive," added Ross Pursifull, Research Specialist in Ford's Powertrain Controls Research and Advanced Engineering Group. While the Venturi part’s design provided part of the optimal solution, the Ford team ran thousands of computation fluid dynamic (CFD) iterations and evaluated hundreds of different wall and throat profiles. They also looked at optimizing the design of other components, such as gate valves.
“For example, a tight tolerance is desirable between the gate and the housing to prevent air leak when the gate is closed, but it can't be so overly tight that it’s difficult to move,” Pursifull advised. “The solution was a fluorosilicone spring between the gate plates, which keeps the normal force low and consistent, the size of the solenoid small and maintains a tight fit when the gate is closed. During brake-assist operation scenarios, boosted air pressure passes through a tiny hole to further expand the fluorosilicone spring and prevent boosted air from leaking.”
The first application of Activac VGS technology was in 188,000 Ford F-150 pickups. The automaker, which calls the technology Vacuum-on0Demand, is looking at other vacuum-dependent vehicle applications. In addition, Dayco says other automakers are planning to use the simpler, more cost-effective innovation.
Brake Systems Were Just the Opening Act; More Activa Apps are Coming
“The collaboration between Ford and Dayco was a resounding success,” said Jiyan Cadiz, Ford North America Truck Communications Manager. “Ford was interested in the system because it is less expensive and lighter than its existing vacuum-generation technologies. In addition, it created no additional parasitic loss for the engine and it's electronically controlled and easily adjusted. That’s a win-win for everyone."
Dayco expects to reach annualized production of 500,000 ACTIVAC units by the end of MY2017 at its 100,000-square-foot facility in Springdale, Arkansas,” noted DiLisio. “Activac VGS is one of our highest-growth product lines right now and has the potential to grow to more than 20 percent of our global automotive business in the very near future.”
According to Dilisio, Dayco currently has six other projects using ACTIVAC technology scheduled for launch between MY2018 and MY2022. The first will be another vehicle, also equipped with an Activac VGS on a brake system that will be introduced later this year. The other projects will expand to other manufacturers, other types of engines and other vehicle systems.
"There’s a lot of growth ahead," Dilisio stated. “Dayco intends to put Activac technology to use in fuel vapor purging, crankcase ventilation, recirculation valve control, turbocharger compressor and even smaller turbocharged engines, which produce less vacuum than larger natural aspirated engines and require mechanical and electrical pumps to run auxiliary systems in the vehicle."
[Editor's note: Visit MOTOR.com for the latest diagnostic and service insights.]