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After many years of successful Visco fan drive applications, Behr has now transferred the Visco technology to the coolant pump drive. The continuously variable Visco drive allows the coolant pump to deliver the optimum flow dependent upon the requirements, therefore reducing the drive power to the minimum possible. Up to now coolant pumps, world wide, have almost always been powered by direct, uncontrolled drives. Consequently, the delivery and the power consumption have been directly related to the engine speed, which, in many conditions, results in an unnecessarily high flow rate. The potential to reduce the flow rate is inherent within the Visco coolant pump. As a concept with continuous control of the impeller speed it has been found to be more fuel efficient than incremental impeller speed control or concepts which only restrict or divert the flow rate. The torque transmission via the shear forces of a silicone oil results in a robust and wear-free drive unit.

Step by step US and European legislation are defining more stringent emission limits for diesel engines. Depending on these limits for NOx and particulate emissions different emission reduction concepts including or excluding cooled exhaust gas recirculation (EGR) appear over time. Most probable cooled EGR will be the solution for US02 and, in combination with particulate traps, for many Euro4 applications. Competitive aftertreatment solutions like selective catalytic reduction (SCR) may need cooled EGR in addition to meet even tougher emission targets. Therefore cooled EGR can be assumed to be a long term task. The impacts on the power train cooling system arise from the need of high performance EGR systems. This results in increased heat rejection from the EGR cooler and increased pressure and temperature loads on the charge air cooling system.