  We propose a new method to model cluster scaling relations in modified
gravity. Using a suite of non-radiative hydrodynamical simulations, we show
that the scaling relations of cumulative gas quantities, such as the Sunyaev
Zel'dovich effect (Compton-y parameter) and the x-ray Compton-Y parameter, can
be accurately predicted using the known results in the $\Lambda$CDM model with
a precision of $\sim3\%$. This method provides a reliable way to analyze the
gas physics in modified gravity using the less-demanding and much more
efficient pure cold dark matter simulations. Our results therefore have
important theoretical and practical implications in constraining gravity using
cluster surveys.
