State any four advantages of ball bearings over plain journal bearings.

1) The ball bearings have a far smaller contact area and thus have a lower frictional drag coefficient. 2) Due to less frictional drag means better response and less power consumption. 3) The turbo can spool up much faster, which reduces turbo-lag and offers a major performance advantage over journal bearing turbochargers at lower to mid turbocharger speeds. 4) The reduced contact area of the ball bearings means that it requires far less lubrication, allowing for lower oil pressure feeds. 5) The ball bearing more reliable. 6) Less expensive. 7) Ball bearings generate less heat and require simple and inexpensive lubrication - by oil ring, oil mist, or oil bath method.