January 2014

Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.

Issue link: http://experimenter.epubxp.com/i/247918

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Page 36 of 38

The original oil pump gets an additional part (layer) especially made for the turbo charger . The stainless-steel silencer is fitted with a cabin warm air supply orifice; warm air for carburetor heating is not necessary in a turbo installation because the compressed air is much warmer after passing the turbo than the air in front of the charger. For hot environments and those who would like to minimize engine thermal stress, Marchini is testing an intercooler for the compressed air behind the turbocharger. It will be offered as an option beginning in 2014. The turbo kit power-to-altitude graph is not yet available, but the manufacturer gave us the following data: 120 hp at sea level, 100 hp at 14,700 feet. As for engine reliability, Marchini believes that in normal use (not full-time wide-open throttle/full power) he expects that a new 912 engine with the turbo kit will reach 1,500 hours. Of course, Marchini noted that all depends on how the engine is used, adding, "All our customers are happy with the kit, and on our test aircraft we have logged 250 hours without any problem; all our factory engines together have cumulated more than 1,000 hours." Just before publication of the article, Marchini told us that he is testing 90- and 100-hp versions of his turbo kit that are able to keep the engine output constant up to an 18,000-foot altitude. It should be available in two to three months. To learn more about this engine, visit www.Marc-Ingegno.it. TURBOCHARGING EXPLAINED Don't fear—we are not going to get too technical and theoretic. Nowadays, turbocharging and supercharging are commonly used for engine power augmentation. Both systems press more air into the engine compared with a "normal" atmospheric engine, with the result that more air and oxygen under higher pressure gets into the cylinders where, once ignited, it produces more power than the same engine without turbo- or supercharging devices. Each system has its pros and cons, and there are even some crossovers of both systems. A normal atmospheric four-stroke engine is "breathing" air/fuel mixture through the downward piston movement (roughly compared with the suction action of a bicycle air pump) that sucks in the air. Because of this suction of air through the filter, carburetor, intake manifold, and intake valve, the pressure and air density in a cylinder—when the piston is in its lowest point—are lower than the atmospheric pressure. To compensate for this pressure, air (even air pressure higher than atmospheric pressure) can be compressed/blown into the cylinder via a compressor or blower. Two different systems are commonly used: the turbocharger or supercharger. Both systems are forced induction devices. The key difference between a turbocharger and a supercharger is that the supercharger is mechanically driven from the engine crankshaft (by means of belt, chain, gear, etc.), whereas a turbocharger— a centrifugal compressor—is driven by the engine exhaust gasses passing through a turbine. Compared to a mechanically driven supercharger, turbochargers tend to be more efficient but less responsive. EAA Experimenter 37

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