In 1936 a telegram from Stuck to Kissel started the T 80 project. In 1937 Daimler-Benz AG concluded the design contract with Porsche. At the same time, the search began for the perfect power unit. The Mercedes-Benz DB 601 aircraft engine was an obvious contender: in flying records established in 1938 and 1939 it developed up to 2,036 kW (2,770 PS).
An aircraft engine could only be used if the ministry of aviation gave permission. In February 1937 Mercedes-Benz obtained official approval for installation of a DB 601. Meanwhile, Porsche had made considerable progress with the vehicle concept. The car for the record attempt was to have three axles and a centrally installed aircraft engine with overhead cylinders. Porsche calculated that for a record speed of 550 km/h after a distance of five kilometres, an engine output of at least 1,618 kW (2,200 PS), or better still 1,838 kW (2,500 PS), would be necessary.