An Innovative Torque Sensor Is Helping To Reduce Engine Emissions And Improve Economy

With engine efficiency under the spotlight like never before, automotive companies are exploring all avenues for improving performance. And because engines have a rotating power output, torque is the key measurement.

Car engines are the bett noir of the environmental lobby. There is no doubt that they are major contributors to carbon build up. But equally they are fundamental to modern life. A true replacement is decades away, so we have to make them as efficient as possible.

Engine lubrication systems are essentially dumb. They have a simple mechanical pump which has been sized to ensure an adequate supply of oil in the worst operating condition. This is typically a hot engine at idle. The pump is thus hugely oversized for most of the rest of the speed range and, as a consequence, nearly 60% of its output is dumped straight back into the sump via the relief valve. It will also deliver the same amount of oil to every part of the engine regardless of what that system might actually need. The pump is also insensitive to engine load and thus the bearings will receive the same oil supply at a given speed regardless of the load. This is a very inefficient system.

In addition the pump forces nearly a ton of oil per hour through the filter, and when the oil is cold this takes a huge amount of energy.

With this in mind a major UK company asked Powertrain Technologies Ltd in Snetterton, Norfolk, to design an intelligent lubrication system and to analyse its effects on engine friction and parasitic losses. They built a highly specialised test rig for the project and since accuracy in measuring small changes in drive torque reliably and repeatably was a critical requirement a key part of the rig is a TorqSense transducer from Sensor Technology in Banbury.