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60 and, below that, a single solenoid- type injector angled at 29 º , pointing downstream. The reed valve is stock, as is its housing, which attaches directly to the centre of the crankcase, while the throttle body bolts to that housing. The engine runs on 87+ octane (RON + MON/2) petrol at a premix of 32:1 for lubrication. The fuel line runs from the tank through a filter to the electric pump, then on to the single injector that feeds both cylinders. This is a return- less system. “The fuel pressure is generally 3.0 bar, but the GCU can take that up to 6.0 bar,” says McRoberts. “With our system we can control the operation of the injector in terms of more than just on and off time – fuel pressure gives us another degree of control. “We designed the ECU ourselves, including the injector driver circuitry. The ECU also controls the ignition, which is internally developed CD. That requires a separate box, which is being developed to be included within the wiring harness. “The CD box does nothing other than create the high voltage for the spark plug – spark timing is handled by the ECU/GCU.” The exhaust can be DA70 stock or a much longer tuned exhaust. McRoberts says, “Where a customer requires silencing there are a lot of off-the-shelf solutions for the DA70, and that was one reason why we chose to work with it. “Using the stock DA70 exhaust the noise signature is much higher than using the optional long tuned exhaust, which also improves volumetric efficiency. The only downside is the increased packaging requirement.” GE70 GCU The GCU is mounted externally to the EGU. It needs to run at 45 C or less, and this will normally be the case if it is in a well-vented location. Designed in-house, the GCU incorporates the ECU, the AC/DC rectification control and a diagnostics facility. All system components and associated sensors communicate with one another through the GCU using CAN. McRoberts says, “The GCU has an ECU microcontroller plus a GCU microcontroller that handles any low- level operation, such as what the engine and the rectifier should be doing; it thus tells the ECU what it should be doing. On top of that, there is what we call the supervisor microcontroller that monitors both of the others. It is responsible for the derived diagnostics – non-real-time stuff. “The supervisor takes the information from the ECU and the GCU, checks on how things are working and identifies if parameters can be modified for the engine to be working more efficiently. “Our Pegasus Advanced Diagnostics suite allows the user to have real-time monitoring of the performance metrics. This data is communicated back to the user wirelessly and will flag any performance issues, track overall usage of subsystems, and relay both operational and maintenance data. “The GCU is the translator of data between our internal comms and the client platform. For example, one company might want a serial interface, another might want CAN. It will handle the necessary translation. Our modules can be reprogrammed to facilitate that communication so that a customer doesn’t have to redevelop their system.” Whose microprocessors are you using? “We are using ARM for high-level control, Freescale for engine control plus a powerful 32-bit microcontroller for real- time control,” McRoberts replies. “Our selection was based on their performance in the given application, as well as their ability to be reprogrammed for that application. For example, a June/July 2018 | Unmanned Systems Technology The GE70 engine/generator unit, seen here with induction located overhead