Phase-locked sampling has been applied to hot-wire anemometry in order to investigate the pulsating flow inside two types of automotive exhaust manifolds fitted with a close-coupled catalyst. An isothermal dynamic flow bench has been used to compare the catalyst velocity distribution in steady operation to crank angle resolved velocity distributions measured in pulsating flow. The latter were obtained using phase-locked averaging. A rotating valve and a cylinder head have been used to generate the pulsating flow. Experimental results have proven the addition principle, i.e. the time-averaged velocity distribution in pulsating flow is proportional to a specific linear combination of velocity distributions, resulting from steady flow through each runner.