A simplified example of a turbo’s operation is to compare it to an air pump. The turbo is designed to reach peak boost pressure quickly, while creating minimal exhaust back-pressure in order to drive the turbine wheel. Performance turbos differ from stock in a number of ways: most have larger housings (which increase air-flow), larger wastegates (that prevent premature “blow-open”), and some “ball bearing turbos” replace the bushing with ball bearings providing quicker “spool-up”.