Analysis of information sources in references of the Wikipedia article "Porsche 928" in English language version.
After these successful tests on April 5 and 6, 1986, the 928S4 was fitted with its higher rear axle ratio, which was aimed at matching peak power with peak speed. At Nardo the engine had been bumping up against its controlled limit of 6,500 rpm. By the end of April the car was ready for shipping to the United States, where Walter Naher supervised the runs. Al Holbert took the wheel at Bonneville in August, when the salt was at its best. On August 7 he was officially timed by USAC, under the auspices of the FIA, at an average of 171.110 mph for the flying mile and 171.926 mph for the kilometer. It was official; Porsche could declare the 928S4 the world's fastest catalyst-equipped car.
