What am I doing wrong with my acceleration measurements? Cayenne needs 8 sec from 0-100 🙁

Hello Together, I wanted to measure today the acceleration values of my Cayenne S 4.5L from 2003. I did maybe 6 attempts and got over every time at values of 8.0 seconds or even slightly. Now I have a question for you: Can it be that I do the measurement wrong? Or is it possibly because of the engine? Are engines slowing down over time / less pull-through strong? Would be nice if someone could find themselves with some “racing” experience with my manco Because 8.0 seconds from 0-100 is really not tingling and rather in the Opel Corsa class. Have had a try by my passenger (who held his camera in front of my chest) video-technically recorded:http://www.youtube.com/watch?v=LBM_yGKGVKQ Thank you in advance, Rainer