= Vanishing-cutoff limit of the Diesel cycle
{title2=$\eta\to1-r^{1-\gamma}$}
For an ideal <Diesel cycle> with compression ratio $r=V_1/V_2>1$, cutoff ratio $\rho=V_3/V_2>1$ and constant heat-capacity ratio $\gamma$, its <thermal efficiency> is $\eta=1-(\rho^\gamma-1)/[\gamma r^{\gamma-1}(\rho-1)]$. As $\rho\to1^+$ the quotient tends to $\gamma$, giving $\eta\to1-r^{1-\gamma}$. The maximum-to-minimum <temperature> ratio tends to $r^{\gamma-1}$, so the limiting efficiency equals that of a <Carnot cycle> between those <temperatures>. Both <heat> input and net <work> vanish in this limit: the result is a limit of their ratio, not a finite-work engine at exactly zero cutoff interval.
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