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rotax 4-stroke - turbo & turbo control unit
912UL, 912A, 912F, 912ULS, 912S, 914UL and 914F Engines
All information provided here is correct at the time of publishing to the best of our knowledge, but Rotax recommendations may change at any time without our knowledge. It is the engine owners responsibility to ensure that the engine is fit for flight at all times. The information is provided here free of charge and with no obligation from us to the consumer. To ensure that you have the correct and most up to date information, you should refer to the current Installation, Operators and Maintenance manuals for your engine. The information provided here may not be valid for aircraft outside the UK. Click here for ConAir SportsTerms& Conditions, including website usage policy.
The 914 engine uses a turbo to boost power. The benefits of the 914 are not only an increased power at sea level, but also the ability to provide greater power at high altitude (100hp @16,000 ft).
In simple terms, a turbo charger uses exhaust gases to turn a turbine on a common shaft with a compressor that is connected to the air intake - the faster the exhaust gases leave the engine, the faster the turbine spins, the faster the compressor spins and the more air into the engine intake, giving the ability to provide more power.
To control the amount of compression “boost” of air on the intake, Rotax use an electronic device called the Turbo Control Unit (TCU). The TCU opens up a valve (wastegate) allowing exhaust gasses to bypass the turbine and limiting the speed of the turbine. The TCU uses a number of sensors on the engine to determine the wastegate position.
The TCU has a data storage facility which can be accessed using a suitable cable and Rotax software. The TCU has an output for 2 lights, one red and one orange - these should indicate the state of the TCU and should be off when the TCU is functioning correctly.
TCU Light Modes:
POWER UP - red & orange lights both light up for a fewseconds
ORANGE FLASHING - sensor failure
RED FLASHING - time in boost too long (limited to 5 mins)
RED ON - overboost (too high airbox pressure)
A switch to isolate the servo motor wastegate should be fitted. The switch should be used as detailed in the Operators manual, but care should be taken to ensure the switch is not used inappropriately as it could cause engine damage.
TURBOS WILL LEAK OIL - small spots of oil out of the exhaust or smoke on the start up are not uncommon. A turbo that has oil in it may not be a problem. A small ball valve in the oil supply line should prevent the turbo filling with oil but the seal is not perfect. If left for a long period, oil will seep into the turbo. This oil could seep into the air filter. Oil dripping from the airbox drains is often from the small amount of oil that can collect in the turbo. If the turbo spins freely and the vanes on the turbo are undamaged it is probably ok.
CHECK THE WASTEGATE LEVER MOVES - regular checks on the free movement of the wastegate lever are a good way to avoid engine damage by over boosting.
ALLOW THE TURBO TO COOL DOWN - always allowthe engine to run for 5 minutes at lowrpm to help prevent coking in the turbo.
TCU part number 996741 can be interrogated (& throttle calibration) using software TLR 4.6 that can be downloaded from the documentation section at www.rotax-aircraft-engines.com
It may be found to be a little bit complicated so you may need to contact us for further advise.