The Scuderi engine, formally called the Scuderi Split Cycle Engine, is a split cycle, internal combustion engine invented by Carmelo J. Scuderi (April 13, 1925 – October 16, 2002). Scuderi Group, an engineering and licensing company based in West Springfield, Massachusetts and founded by Carmelo Scuderi's children, is testing a working prototype of the engine that was officially unveiled to the public on April 20, 2009.
The Scuderi engine is under development by Southwest Research Institute in San Antonio, Texas. Scuderi Group released video footage of a naturally aspirated one-liter prototype of the Scuderi engine firing on its own in the laboratory in October, 2009.
Scuderi engines have paired cylinders, each of which performs two of the tasks (strokes) of a conventional engine. The compression cylinder performs intake and compression. The power cylinder performs combustion and exhaust. Compressed air is transferred from the compression cylinder to the power cylinder through a crossover passage. Fuel is then injected and fired to produce the power stroke.
The power cylinder fires just after the piston has begun its downward motion ("after top dead center", or ATDC). The Scuderi Group says ATDC eliminates a thermal efficiency shortcoming seen in previous split-cycle engine designs. Firing ATDC in a split-cycle arrangement is claimed to eliminate the losses resulting from recompressing the gas.
In a conventional Otto cycle engine, each cylinder performs all four strokes per cycle. This means that two revolutions of the crankshaft are required for each power stroke. The pistons fire every other revolution, while the Scuderi engine fires every revolution. The Otto cycle design convention calls for combustion just before top dead center (BTDC) in order to allow combustion pressure to build.
According to Scuderi Group, tests indicate that the Scuderi engine shows gains in efficiency and reduced toxic emissions over conventional four-stroke Otto cycle designs. The company also says that the Scuderi engine could be used as part of an air hybrid system, allowing recovered braking energy to be stored as compressed air. Laboratory tests of the prototype are said to match earlier predictions generated by computer models.
As can be seen, this engine requires an extra valve per pair of cylinders compared to an Otto engine, but only when in air hybrid configuration. In the standard configuration conforming to the schematic above it could use actually one less valve per cylinder pair than an Otto engine. It also has the same power density (power strokes per cylinder per revolution), even though the power cylinder fires on every rotation, because of the extra compression cylinder. While its fuel efficiency and other advantages may make this a useful modern design, the extra complexity would historically have favored the Otto design, when precision machining was more expensive than fuel savings over the engine's lifetime.
As of August 2011, Scuderi Group said its patent portfolio included more than 476 patent applications worldwide, more than 154 of which have issued as patents in more than 50 countries.
The Scuderi Group has partnered with several automotive engineering companies to assist with engineering the Scuderi engine's complementary components. German automotive supply company Mahle GmbH is working on the pistons, Swedish engine developer Cargine Engineering AB is assisting with the air-activated valves, Denver-based Gates Corporation is engineering the belts, and Germany-based Schaeffler Group is contributing to the valve train assembly. The engineering division of Germany's Robert Bosch GmbH is working on the timing mechanism of the engine.
Various manufacturers, including Honda, Daimler AG, Fiat, and PSA Peugeot Citroën, have signed non-disclosure agreements with Scuderi Group. A Daimler AG scientist familiar with the matter told The Wall Street Journal that the design has potential.
The predicted best brake specific fuel consumption (BSFC) when turbocharged is 233 g/kWh at 1400 rpm, and in the same configuration the engine has a specific power output of 75 kW/litre at 4000 rpm. In naturally aspirated form the BSFC is 269 g/kWh and specific output is 30 kW/litre.
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