As you take your foot off the accelerator the throttle valve to the engine closes. The problem here is that during this process the turbo is still spinning and the boost pressure that it is producing has no where to go. (This is a bit like putting you hand over a hair dryer so the air cannot get out) What happens at this point is the turbo starts to stall, the spinning vanes slow down (incurring alot of stress) and the boost pressure drops. When you open the throttle valve again by pushing down on the accelerator (demanding more power) the turbo has lost its momentum, boost pressure and there is a pause or a "Lag" before the engine is producing the required power once again.To combat this loss of power and stress on the turbo, a recirculation or diverter valve is used. On the Mini, when th.
