Originally Posted by Garage19
I would have to say this is utter tosh. If you have ZT engine that starts to tail off at 5.5k, thats down to YOUR turbo choice, ign timing and camshaft timing/choice.
It is not a feature of the engine itself.
At the end of the day, the zetec has a better flowing head and a larger capacity so is always going to make more power with less stress.
On a forced induction engine, the capacity is irrelevent except for when off boost IMO.
Maybe on the later black top engines the power won't tail off as fasts as the earlier engines but from my experience (limited as I must admit) the stroke does play a small part in causing the tail off. From most power graphs I have seen they seem to produce all their torque between 3 an 4.5k ish then.
Of course I do agree that the turbo, cam, port size and ignition timing will all help the reving issue.
Prehaps I haven't experienced as many high power Zetec Turbo engines as yourself. From the bigger power engines I have seen, they all had new rods/crank and thought they had addressed the rod ratio.