I was just wondering about something. The basic 2007 XK has the same advertised horsepower as the XK8--300hp. However, the 2007 XKR has 420hp versus 400hp for the previous generation.

Does anyone know how Jaguar tweaked 20 more horsepower out of the supercharged engine but none for the normally aspirated?

Doug

 

I think you kinda answered that one for yourself. From my understanding it was all to do with the supercharger, they fitted a larger bottom pulley and tweaked the ECU slightly.

I am sure Avos will be able to answer this questuion better than me