VNT control explained - Turbo Geo Metro

The most common question I get asked on this channel is how do you control a variable nozzle turbo on a gasoline engine. I hope this will help explain visually how this works. as many of you know, a variable nozzle turbo effectively has an open and closed setting with an infinitely variable position between those two extremes. by taking a standard wastegate pod and modifying it so there is a port above and below the diaphragm, you can completely regulate the vanes simply by the vacuum or pressure differential. when the engine is under vacuum or no load, that vacuum is pulled from the hose connection on top of the pod. as soon as you press down on the throttle and the vacuum drops, the vanes go into their closed position and the boost pressure starts to rise and begins pushing on the underside of the diaphragm. this is regulated by a boost controller and as soon as the set point is reached comma the vanes will push completely open and self-adjust to regulate the pressure across the entire RPM band this allows near instantaneous boost with a smooth torque curve and very little turbo lag