Understanding the ignition characteristics of binary hydrocarbon blends is essential for designing high-speed propulsion systems such as scramjets, where ignition under short residence time is a critical challenge. In this work, the ignition delay behaviour of ethylene-acetylene/air mixtures was examined through shock tube experiments and kinetic simulations under engine-relevant conditions. Ethylene was used as the primary fuel and blended with acetylene at 5%, 10%, and 20% by volume to form binary mixtures, at an equivalence ratio of 1.0, temperatures between 560–1030 K, and pressures of 2.5–9 bar. The ignition delay time was determined from peak pressure rise and CH* chemiluminescence behind the reflected shock. Unlike previous blended fuel studies dominated by saturated hydrocarbons, this work presents a comprehensive dataset for ethylene-acetylene blends at low to intermediate temperatures and increasing the acetylene fraction from 5% to 20% reduces the ignition delay time by up to 50–60% in the 700–850 K and 2–5 bar regime. Numerical simulations were performed using ANSYS Chemkin in a closed, homogeneous, constant-volume reactor with the NUIG, ARAMCO, LLNL, and San Diego mechanisms. The sensitivity and rate-of-production analyses reveal that ignition is governed by HO₂–H₂O₂ radical chemistry, with the thermal decomposition of H₂O₂ triggering rapid OH formation. Acetylene enhances ignition by promoting the regeneration of HCCO radicals and accelerating the transition to chain-branching chemistry.