The technology from Rotrak, a joint venture between Torotrak and supercharger firm Rotrex, promises the benefits of supercharging (higher power outputs and response) but by using a variable drive instead of a direct connection to the crank, it removes the usual parasitic losses. Torotrak is talking to Tier One suppliers and vehicle manufacturers about commercialising the technology.
The company’s engineers are running the technology in a B-segment vehicle on a dynamometer and are calibrating the control strategy to prove its driveability, performance, CO2 and fuel economy benefits.
Andrew de Freitas, Rotrak product director, said: “We’re among the first engineers to calibrate a variable drive supercharger. It’s uncharted territory and a lot of work, but the effort we invest in exploring the technology’s operating envelope is establishing new areas of engine performance for manufacturers.
“The intellectual property and know-how we’re generating has enormous commercial value – it provides a new variable in engine control strategies with which manufacturers can increase performance and reduce CO2 emissions.”
The Rotrak variable drive compressor has been conceived with industry CO2 targets in mind. Downsized engines with fewer cylinders now form a significant part of companies’ strategies and ensuring these economical engines still provide the driveability car buyers expect is a challenge for the automotive industry.
“At low speeds, engines with only two or three cylinders find it harder to give the turbo enough exhaust energy to generate the torque drivers need to pull away quickly,” said de Freitas. “The Rotrak variable drive supercharger isn’t limited in this way. Instead we’re taking energy from the crank, passing it through our variable drive and into a centrifugal compressor to boost combustion. It gives the next generation of downsized powertrains ‘big-engine’ response.”
James Shawe, the senior engineer responsible for the calibration project, said the system was performing well. “We are learning to control and apply the technology’s very fast torque-delivery. Torotrak’s rolling road dynamometers provide a controlled environment for the car athat llows us to put the technology through its paces quickly and in complete safety.”
Work to develop a driveable prototype for interested Tier Ones and vehicle manufacturers will continue on the rolling road for the next few months. At the same time, Torotrak will gather data on the system’s efficiency to validate fuel economy simulations.
The Rotrak prototype is undergoing testing on one of two single axle rolling-road dynamometers at Torotrak. The dyno is capable of testing vehicles at speeds of up to 250km/h and the roller has a maximum tractive effort of 6000N. In-cell weather stations monitor atmospheric pressure, relative humidity and ambient air temperature, which can be controlled from 10-30°C.