content_image/574240.jpg
<img src='content_image/574240.jpg'>

The waste gate actuator is a spring-loaded piston operated by engine oil pressure. The actuator, which adjusts the waste gate position, is connected to the waste gate by a mechanical linkage. 

The control center of the turbocharger system is the pressure controller. This device simplifies turbocharging to one control: the throttle. Once the desired manifold pressure is set, virtually no throttle adjustment is required with changes in altitude. The controller senses compressor discharge requirements for various altitudes and controls the oil pressure to the waste gate actuator, which adjusts the waste gate accordingly. Thus the turbocharger maintains only the manifold pressure called for by the throttle setting. 

## Ground Boosting Versus Altitude Turbocharging 

Altitude turbocharging (sometimes called “normalizing”) is accomplished by using a turbocharger that maintains maximum allowable sea level manifold pressure (normally 29–30 "Hg) up to a certain altitude. This altitude is specified by the airplane manufacturer and is referred to as the airplane’s critical altitude. Above the critical altitude, the manifold pressure decreases as additional altitude is gained. Ground boosting, on the other hand, is an application of turbocharging where more than the standard 29 inches of manifold pressure is used in flight. In various airplanes 

using ground boosting, takeoff manifold pressures may go as high as 45 "Hg. 

Although a sea level power setting and maximum rpm can be maintained up to the critical altitude, this does not mean that the engine is developing sea level power. Engine power is not determined just by manifold pressure and rpm. Induction air temperature is also a factor. Turbocharged induction air is heated by compression. This temperature rise decreases induction air density, which causes a power loss. Maintaining the equivalent horsepower output requires a somewhat higher manifold pressure at a given altitude than if the induction air were not compressed by turbocharging. If, on the other hand, the system incorporates an automatic density controller which, instead of maintaining a constant manifold pressure, automatically positions the waste gate so as to maintain constant air density to the engine, a near constant horsepower output results. 

## Operating Characteristics 

First and foremost, all movements of the power controls on turbocharged engines should be slow and smooth. Aggressive and/or abrupt throttle movements increase the possibility of over-boosting. Carefully monitor engine indications when making power changes. 

