AUBURN HILLS, Michigan: Valeo is introducing its new, steering system-integrated, hydraulically driven engine cooling fan system (HDFS) in the 2001 Jeep Grand Cherokee. The company claims that hydraulic fans substantially improve fuel economy, air conditioning performance and towing capacities, while reducing engine compartment operating temperatures.

The industry has long known that hydraulic systems can meet all cooling fan needs and a hydraulic fan, powered by the power steering pump, was used on some V6-engined Toyota Camry models in the early 1990s.

Valeo says, however, that hydraulic systems were previously too costly and heavy for practical application. By integrating the HDFS with the power steering pump, the Valeo design eliminates the cost, weight and efficiency losses of a separate hydraulic circuit with its own pump.

“Our hydraulic team worked closely with the engineers from Valeo to make this system standard on our V-8 WJ," said Steve Johnston, supervisor of DaimlerChrysler's Jeep cooling systems. "The HDFS reduces the consumption of horsepower as compared to current engine-driven fan cooling systems -up to 19 horsepower -- and returns that power to the rear wheels.

"These power savings will be seen in both fuel economy and performance. This new fan, which runs only on demand, allows us to reduce heat exchanger sizes for the transmission, power steering and engine while also allowing the grille area size to decrease."

Valeo thinks its biggest market for steering-integrated HDFS is light trucks and SUVs, according to James Neville, general manager of the Air Flow Division.

He said: "Our system is much quieter and more efficient than traditional fans that connect directly to the engine through a clutch. Vehicles with engine-driven fans lack the refined aerodynamic features we see in passenger cars that use electric fans. But electric fans are seldom an option in trucks because their low air flow hampers towing capacity, under-hood cooling and air conditioning performance. Our system permits improved aerodynamic designs in the truck and SUV markets."

In the Valeo design, a common hydraulic pump driven by the engine accessory belt powers both the fan and power steering system. A dual displacement motor drives the fan and efficiently transfers power levels greater than 10 horsepower from the pump.

The maximum air moving power is 20 to 30 times higher than is typically available from electrically driven fans and an electronic link to the engine controller closely matches fan speed to the vehicle's cooling demands, minimising noise and power draw.

A special valve feature gives the steering system priority during brief periods when both systems demand high power.

Valeo claims HDFS provides much higher airflow at idle and low speeds than a traditional engine-driven fan, giving the engine cooling system a cushion of safety for long, heavy towing.

Thus, engine cooling requirements are no longer the limiting factor in determining trailer capacities. HDFS also allows much better heat dissipation for the air conditioning condenser. This results in improved air conditioning performance in comparison to traditional engine-driven fan systems whose lower air flow often result in poor air conditioning performance under severe high temperature.

Top photo: Shown is a new, hydraulically driven fan system (HDFS) that is integrated with power steering. Manufactured by Valeo, it provides substantial improvements in fuel economy, acceleration, air conditioning performance and towing capacities over traditional clutch-driven fans. Its maximum air moving power is 20 to 30 times greater than is typically available from electrically driven fans. Bottom photo: Shown is the 2001 Jeep(r) Grand Cherokee Limited which uses the Valeo HDFS.  

It also results in improved compressor durability due to reduced heat and refrigerant pressures. The ultimate benefit is that temperatures sensed by the driver and passengers can be up to 10 degrees cooler than with clutch-driven systems.

A vehicle equipped with the HDFS delivers better fuel economy and more horsepower to the wheels, Valeo claims. Another feature of HDFS is that it temporarily reduces fan power draw during rapid vehicle acceleration. In contrast, drivers of vehicles equipped with clutch-driven fans often find that up to 25 horsepower is unavailable for acceleration when the fan clutch is engaged. Even when the clutch is disengaged, these fans waste about one horsepower through ‘parasitic#; losses under normal loading.

HDFS is also said to improve water pump durability because a mechanical fan and fan drive are no longer attached.