The circulating lubricant supports the turbine shaft hydrodynamically in the turbine housing by means of floating journal bearing. It also removes heat from the turbine shaft, hence the need for an oil cooler.
Lubricant, in this case Mobil 1 synthetic grade, is pumped at about 2 bar from the sump under the turbo, via an oil cooler and filter, to the turbo. A pressure gauge and pressure transducer is attached to the turbo oil feed. Mobil 1 oil is used because of its low viscosity, which reduces the drag on the turbine shaft, and eases the turbine starting procedure.
The oil pump consists of a 90 Watt Datsun heater motor, coupled to a gear pump from an old Cosworth DFV Indy car engine. Oil pressure is controlled electronically. The pump motor speed is controlled by a simple pulse width modulated switch mode controller, in a closed loop with a transducer measuring the oil pressure.
An oil cooler is fitted between the sump and the oil pump. This is one of the many items needing development, as it currently has no fan or thermostatic switch.
