Turbocharger and Control System The Rotax 914 engine is equipped with an exhaust gas  turbocharger making use of the energy in the exhaust gas for  compression of the intake air or for providing boost pressure  to the induction system. The boost pressure in the induction  system (airbox) is controlled by means of an electronically  controlled valve (wastegate) in the exhaust gas turbine.  The wastegate regulates the speed of the turbocharger and  consequently the boost pressure in the induction system. The  required nominal boost pressure in the induction system is  determined by the throttle position sensor mounted on the  carburetor 2/4. The sensor’s transmitted position is linear  from 0 to 115 percent, corresponding to a throttle position  from idle to full power.  [Figure 11-12]  For correlation  between throttle position and nominal boost pressure in the  induction, refer to  Figure 11-13.  As shown in the diagram,  with the throttle position at 108–110 percent results in a rapid  rise of nominal boost pressure.  To avoid unstable boost, the throttle should be moved  smoothly through this area either to full power (115 percent)  or at a reduced power setting to maximum continuous  power. In this range (108–110 percent throttle position),  small changes in throttle position have a big effect on engine  performance and speed. These changes are not apparent to  the pilot from the throttle lever position. The exact setting for  a specific performance is virtually impossible in this range  and has to be prevented, as it might cause control fluctuations  or surging. Besides the throttle position, overspeeding of  the engine and too high intake air temperature have an  effect on the nominal boost pressure. If one of the stated  factors exceeds the specified limits, the boost pressure is  automatically reduced, thus protecting the engine against  over boost and detonation.  The turbo control unit (TCU) is furnished with output  connections for an external red boost lamp and an orange  caution lamp for indications of the functioning of the TCU.  When switching on the voltage supply, the two lamps are  automatically subject to a function test. Both lamps illuminate  for one to two seconds, then they extinguish. If they do not,  a check per the engine maintenance manual is necessary. If  the orange caution lamp is not illuminated, then this signals  that TCU is ready for operation. If the lamp is blinking, this  indicates a malfunction of the TCU or its periphery systems.  Exceeding of the admissible boost pressure activates and  illuminates the red boost lamp continuously. The TCU  registers the time of full throttle operation (boost pressure).  Full throttle operation for longer than 5 minutes, with the  red boost light illuminated, makes the red boost lamp start  blinking. The red boost lamp helps the pilot to avoid full  power operation for longer than 5 minutes or the engine could  be subject to thermal and mechanical overstress. The HKS 700T engine is a four-stroke, two cylinder  turbocharged engine equipped with an intercooler.  [Figure 11-14]  The horizontally opposed cylinders house  four valves per cylinder, with a piston displacement of 709  cc. It uses an electronic control fuel injection system. A  reduction gearbox is used to drive the propeller flange at  a speed reduction ratio of 2.13 to 1. The engine is rated at  77 horsepower continuous and 80 horsepower takeoff (3  minutes) at 4,900 rpm and 5,300 rpm, respectively. A total  engine weight of 126 pounds provides a good power to weight  ratio. The 700T has a TBO of 500 hours. HKS 700T Engine Jabiru Light-Sport Engines Jabiru engines are designed to be manufactured using  the latest manufacturing techniques. [Figure 11-15] All  Jabiru engines are manufactured, assembled, and ran on a  11-10 Figure 11-13.  Correlation between throttle position and nominal  boost pressure. Figure 11-12.  Turbocharger control system throttle range and  position. 0% 100% 115% 1,500 1,400 1,300 1,200 1,100 1,000 900 0 10  20  30  40  50  60  70  80  90 100 110 115% 46 44 42 40 38 36 34 32 30 28 hPa "Hg