オットーサイクル
The Diesel cycle is assumed to have constant pressure during the initial part of the combustion phase (formula_1 to formula_2 in the diagram, below). This is an idealized mathematical model: real physical diesels do have an increase in pressure during this period, but it is less pronounced than in the Otto cycle. In contrast, the idealized Otto cycle of a gasoline engine approximates a constant volume process during that phase.