A Very Simple Cycle

Simpler

Internal combustion always requires five things: air, fuel, compression, combustion and exhaust. There are two well-known means of using pistons in cylinders to obtain power from the air fuel mixture. These are the four-stroke cycle and the two-stroke cycle.

The four-stroke cycle draws in the air and fuel mixture on its first stroke, the INTAKE stroke. This is followed by the COMPRESSION stroke and then the ignition takes place and the POWER stroke follows. As the POWER stroke ends, exhaust begins; as the piston returns to the top, during the EXHAUST stroke, it drives the remnants of the burned combustion product out of the cylinder, then the four-stroke cycle begins again.

Although LIM engines use only two-strokes, the LIM process is derived from the four-stroke system, and LIM engines resemble conventional four-stroke engines more than they do two-stroke engines.

Once the LIM type engine has started, all four events occur in an only slightly modified sequence. As the power stroke ends, EXHAUST begins, then almost immediately, new air is forced into the cylinder; at the same time that exhaust continues. This new air displaces the remnants of the previous POWER stroke and COMPRESSION then takes place, completing the cycle.

The mechanical resemblance to a two-stroke is only that the piston acts as the exhaust valve. The major mechanical improvement, compared to a four-stroke, is the use of most of the head area for intake valves, since the exhaust leaves through the ports disposed around the girth of the cylinder.

The crank case, as in a conventional four-stroke, is home only to the bearings and crankshaft, the connecting rods and the main lubrication system. Another LIM advantage is that the main lubrication system has nothing to do with the valve train, although it may be involved with lubricating the compressor.

The compressor is external to the cylinder, but is vital to making a LIM type engine what it is. The compressor enables the LIM type engine to resemble a conventional four-stroke because it forces the fresh charge of air into the cylinder, and the coincidental displacement of the remains of the previous cycle.

The LIM Cycle is just three events: Ventilation, Compression, and Power. Two-stroke engines and four-stroke engines are explained in greater detail on other pages in this site.

Smaller

LIM Type engines can be smaller because each cylinder is capable of producing more than 50% more power than a comparable cylinder in a conventional four-stroke engine. This means that in a LIM type engine, four cylinders can easily do the work which in a conventional engine requires six.

Smarter

For less money, an SCDi engine is lighter, less expensive, and can generate more torque and equal horsepower, than most conventional engines costing more. This simple engine will require less fuel for its output, less lubrication, and less maintenance, so a decision to use this engine compared to a more conventional internal combustion engine is SMARTER.

Learn about the Basics

Learn more about the Simple Cycle Engine

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