4.11.8 Medium loads
At medium loads (from low loads up to 85% of full load), it is necessary to supply a different amount of air-fuel mixture, but always of the same type - a little diluted, in order to obtain the best efficiency indicators.
Note
Orifice plug is similar to a bolt, only without a head, element with a drilled through hole, the size of which is selected with high accuracy (it is called calibrated).
Note
In the simple carburetor, by selecting an orifice plug of the appropriate diameter and a diffuser, it is possible to obtain a mixture of the required composition only at a certain constant, for example, an average, position of the throttle blade.
With further opening of the shutter, the mixture prepared by the carburetor starts enriching. This happens because in this case the vacuum in the diffuser increases significantly. As a result of this, the resistance to fuel flowing out of the orifice plug becomes less than with a low vacuum in the diffuser. Therefore, the amount of fuel entering the mixing chamber increases, but not proportionally to the increase in the amount of passing air, which leads to an enrichment of the mixture. When the shutter is closed, the mixture starts diluting. In order to maintain approximately constant, the most advantageous composition of the mixture with different openings of the throttle blade at medium loads, i.e., to compensate for the mixture, a special device must be in the carburetor (for example, an economizer).
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