Direct measurement of engine exhaust volume is often required in determining vehicle or engine mass emissions. The most accurate exhaust flowmeters use ultrasonic transducers to measure exhaust gas velocity with 1% accuracy. Available ultrasonic exhaust meters are limited to exhaust gas temperatures of less than 400 degrees centigrade. These exhaust meters are not suitable for use with diesel engines, because the exhaust gas temperatures can exceed 600 degrees centigrade under heavy loads, or when Diesel Particulate Filter (DPF) regeneration occurs. A new type of ceramic ultrasonic transducer that is rated for exhaust gas temperatures greater than 600 degrees C is being developed. An ultrasonic exhaust flowmeter with these high-temperature transducers can be applied to diesel engine and emission tests without limitations for engine size or load.