Power
The rated power of the engine in horsepower (in fact,
the maximum power that the unit can produce in normal operation, without overloads). Despite the popularity of the designation in watts (see below), horsepower (hp) is still quite widely used to indicate the power of internal combustion engines. 1 HP is approximately 735 watts.
In general, the more powerful the engine, the more speed and tractive effort it is able to develop. On the other hand, this indicator directly affects the weight, dimensions, and most importantly, the cost of the unit, while the real need for high power is relatively rare. Therefore, it is worth choosing according to this indicator, taking into account the features of the planned application; specific recommendations on the selection of an engine for a specific technique and tasks can be found in special sources. We only note that models of the same power can differ in speed and "torque"; see "Shaft speed" for details.
In general, performance up to 8 hp. are considered low, up to 13 hp. — medium, more than 13 hp — high.
Power
The rated power of the engine (the highest power it can deliver in normal operation) in kilowatts. Initially, the power of internal combustion engines (ICE) was usually denoted in horsepower, but now it is also common to record in watts / kilowatts; this, in particular, makes it easier to compare the power of internal combustion engines and electric motors. Some units can be converted to others: 1 hp approximately equal to 0.735 kW.
In general, the more powerful the engine, the more speed and tractive effort it is able to develop. On the other hand, this indicator directly affects the weight, dimensions, and most importantly, the cost of the unit, while the real need for high power is relatively rare. Therefore, it is worth choosing according to this indicator, taking into account the features of the planned application; specific recommendations on choosing an engine for a specific technique and tasks can be found in special sources. We only note that models of the same power can differ in speed and "torque"; see "Shaft speed" for details.
Shaft rotation
Direction of rotation of the motor shaft. Usually, it is indicated by the direction in which the shaft rotates, if you look at it from the flywheel side (from the side of the engine from which the power is taken off). The classic option is counterclockwise rotation, but the opposite direction is also found. Anyway, the main selection criterion for this parameter is what direction the car is designed for, under which the engine is bought.
Shaft speed
The highest shaft speed provided by the motor. Before buying, you should make sure that this indicator corresponds to the characteristics of the equipment in which you plan to install the engine — too high a speed can damage the working tool, transmission units, etc.
It is also worth considering that a higher rotational speed (for the same engine power and transmission characteristics) means less torque, and vice versa. Therefore, this parameter allows you to compare engines in terms of the speed / thrust ratio (however, only on the condition that they do not have reduction gears — see "Functions").
Shaft length
It is customary to call the shaft length only the length of its outer part protruding beyond the engine housing. The optimal value of this parameter depends on the characteristics of the machine in which the engine is planned to be installed.
Capacity
The working volume of all engine cylinders. Usually, other things being equal, a larger volume allows you to achieve higher power, but increases fuel consumption and affects the dimensions of the unit.
Piston diameter
The engine piston diameter is a reference parameter — in fact, this data is required very rarely, usually, for repairs and other specific tasks that the average user usually does not deal with at all.
Fuel tank volume
The nominal volume of the engine's fuel tank is the maximum amount of fuel that can be safely filled there. Knowing the fuel consumption (see below), it is possible to estimate the operating time of the unit on a single refill by the volume of the tank by dividing the tank capacity by the consumption.
Large fuel tanks, on the one hand, allow you to work for a long time without refueling, on the other hand, they significantly affect the dimensions and weight of the engine. Also note that many models allow refueling "on the go." When choosing a tank volume, manufacturers take into account these points, as well as the “weight category” and the specifics of the engine application.
Specific fuel consumption
Specific consumption in this case can be described as the amount of fuel consumed by the engine per hour per 1 kW of generated power. The lower this figure, the higher the efficiency of the engine and the more economical it is. Specific consumption data is especially useful for comparing units with different capacities.
