b'Soastoadapttheboostpressuretosuitanygiven prevailing load condition and also to protect the engine and turbocharger, a boost pressure control or regulator is required. Depending on the type of turbocharger in question,amechanical-pneumaticcontroldeviceor alternatively an electromechanical one can be used. In the further course of the chapter, we will primarily deal with electromechanical control.Cause of a defective electronic boost pressure control/regulator: Cause of failure Causes of a defect on the turbocharger actuator can be:ELECTRONIC BOOST PRESSURE CONTROL:Rod of control device or guide vanes stiff or defectiveTURBOCHARGER ACTUATOR TESTING Corrosion of the electrical components as a result Useful information and valuable tips on all aspects of electromechanical controlof environmental inluences (water, salt, etc.)settings for adjustable turbochargers Mechanical damage as a result of external impactTodayalmosteverymoderndieselandalsopetrolTroubleshooting- Repair notesengines are equipped with an exhaust gas turbocharger to increase engine performance and eficiency. To ensure that the optimum boost pressure is always present, it hasAs part of troubleshooting, a visual inspection of the to be adjusted to suit the particular load condition. Inturbocharger in the engine compartment should irst be modernvehicles,thisisdonebytheelectronicboostcarried out after the ECU diagnosis.pressure control.Theturbochargerwithitsindividualcomponents The turbocharger uses the energy of the exhaust gases toshould always be considered and diagnosed as one unit. drawinandcompressfreshairforcombustion.ThisMost vehicle manufacturers do not supply spare parts allows a greater volume of air and thus more oxygen tofor VNT/VTG turbochargers. This is not because the enter the combustion chamber. Engine performance and enginetorquearesubsequentlyincreased.Simply explained,theexhaustgasturbochargercontainsan exhaust gas turbine and a compressor turbine, which are connected to each other by a shaft. The exhaust gas low-ing out of the engine drives the exhaust gas turbine andThe required boost pressure is regulated according to a thus also the compressor turbine.map stored in the engine control unit. The engine control Theturbochargeractuator,alsocalledcontrolboxorunit sends the required boost pressure in the form of a boost pressure regulator, is an electronic control devicesignaltotheturbochargeractuatorviaadatabus for adjustable turbochargers and is predominantly usedconnection. The actuator adjusts the guide vanes accord-for Variable Nozzle Turbine (VNT) and Variable Turbineingly in line with the required angle setting contained in Geometry (VTG) turbochargers. the signal.Advantages of an electronic control device In these turbochargers with variable turbine geometry,are: Faster response of the turbocharger already at theactuatorreliablyandpreciselycontrolsthemove- low engine speedsment of the guide vanes. Through the adjustment of the guide vanes, the exhaust gas low onto the turbine wheelExact adjustment of the guide vanes in all speed is inluenced, thus changing the boost pressure whichrangescan then be optimally adjusted to match all speed ranges. 21 12'