Off-highway vehicles operate in the harshest environments, performing in dirty conditions, under tremendous loads, over uneven terrain and in extreme temperatures. Final Tier 4 emissions regulations in the U.S. are placing even greater demands on these workhorses. To meet these stringent standards, off-highway engine manufacturers are employing exhaust gas recirculation (EGR) strategies. EGR systems, such as those supplied by BorgWarner, are proven technologies in cutting emissions. However, more EGR means higher engine coolant temperatures. Consequently, cooling system efficiency becomes critical to achieving optimal engine performance.

Typically, cooling is achieved through a combined effort of air flow through heat exchangers and coolant flow through radiators. BorgWarner’s electronic control and systems integration expertise can optimize the entire cooling system—including the fan, fan drive, and coolant pump—to help our customers achieve tough emissions and fuel economy targets. Recent back-to-back tests have demonstrated that an optimized cooling system, with variable speed fan drives and variable speed coolant pumps, improved fuel economy up to 5% over conventional technologies.

Smart airflow technology

BorgWarner’s electronically actuated variable speed fan drives—known as Visctronic fan drives—provide precise cooling, generating the right amount of airflow at the right time to help the entire engine run more efficiently.

Using calibrated software to communicate with the engine’s electronic control unit, Visctronic fan drives continuously respond directly to the engine’s cooling needs. Because the system doesn’t run when the engine doesn’t need it, fuel is no longer wasted, and emissions are no longer created.

BorgWarner engineers collaborate with the vehicle maker’s engineering teams to create systems that deliver the precise airflow needed to cool a specific condition. This eliminates unnecessary parasitic losses in the engine by reducing the high fan speed spikes common in conventional systems.

The result is more available power to operate the equipment. For engine makers, that means meeting emissions regulations. For operators, it translates into a healthier bottom line through greater fuel savings.

Visctronic fan drives incorporate a robust actuator and heavy-duty, heat-resistant bearings. As a self-contained unit, the fan drive requires no service or maintenance—a definite advantage for off-highway equipment. Visctronic has a track record of proven durability in off-highway applications with over one million produced around the world in the past 12 years

A cooler coolant pump

Engineers at BorgWarner have now applied their electronic control and systems integration expertise to the coolant pump. BorgWarner controlled coolant pump technology provides precise cooling to optimize engine temperature and reduce parasitic losses.

Using a concept similar to the Visctronic system, BorgWarner has developed a new variable speed coolant pump that uses viscous sheer within the pump housing to manage the pump’s impeller speed. Instead of increasing and decreasing speed directly with engine speed, the engine control unit directs the flow requirement based on engine coolant temperature. When the coolant temperature is low, the pump reduces speed to improve engine warm-up times, which improves fuel economy and driver comfort. As the coolant temperature rises, the pump increases speed to move more coolant through the system and cool the engine more efficiently.

Variable speed fan drives and coolant pumps individually improve the efficiency of the engine. However, unless both are optimized as a system, the engine may not be as efficient as it could be. With our expertise in both airflow and fluid systems, BorgWarner can optimize the fan drive and coolant pump as a system so that the powertrain and vehicle run as efficiently as possible. BorgWarner testing has shown up to 5% improvement in fuel economy, with the variable speed fan drive contributing 3.5% and a variable speed coolant pump adding another 1.5%.

BorgWarner’s engineers have developed the expertise to calibrate and balance both systems to work in harmony. Communicating directly with the engine via an SAE J1939 communications network, the fan speed and the pump’s impeller speed can be monitored and augmented to optimize the entire cooling system. Working closely with engine designers, we use our two decades of experience in optimizing and stabilizing viscous-based products to improve engine efficiency.

In addition to improving fuel economy and reducing emissions, the variable-speed fan clutch and coolant pump work together to minimize large thermal spikes that can negatively impact component reliability. Belts, radiators, and charge-air coolers all benefit from the combination of a variable speed fan drive and coolant pump.

As a global product leader, BorgWarner provides a comprehensive portfolio of fans, fan drives, and pumps. A critical aspect of our process is that first we listen to our customers. Once we truly understand their duty cycle and particular regional application needs, we engineer an optimized thermal management solution.

Daniel Paterra, President and General Manager, BorgWarner Thermal Systems, wrote this article for SAE Off-Highway Engineering.