His father, Kurt Ahrens Sr., was a German speedway champion who competed against his son for five years.

Due to the long Nürburgring track, it was possible to take part in the German Grand Prix in Formula 2 cars.

He participated mostly with Brabhams for the Caltex Racing team, and was invited to drive the Brabham-Repco F1 in the wet 1968 German Grand Prix.

In 1968, Ahrens Jr. joined the Porsche factory sports car team and shared victory with Jo Siffert in the 1969 Austrian 1000 km event.

He had suffered a high speed shunt in April 1970 while testing a long tail Porsche on a wet Ehra-Lessien, with the car disintegrating badly- the car went under the Armco barrier and broke in half (as they were known to do), leaving Ahrens strapped in the back.