A self contained field sampling system for measuring engine exhaust emissions includes a mini-dilution tunnel adapted for the collection of proportional samples of emissions to be analyzed, an engine air intake flow measurement instrument, a system controller and data acquisition system, and an optionally portable generator to provide electrical power. Several probes withdraw dilute and undiluted exhaust for emission analysis. Various engine emissions may be isolated. As well, engine emissions mass rate may be calculated by reference to engine RPM, inlet flow rate, exhaust temperature and emissions output rate.