Motor alone, there is always a maximum speed limitation
A 450w eZip motor, pushed to 25.9V can output 485w.
485w can provide about 22mph on a mountain bike, 26mph on a race bike.
But only with optimal gearing ...
Gearing too high will actually start lowering motor only speed!
Note - Speed-Torque lines are for gearing ratio comparisons and do not represent "torque curves".
Gearing higher will lessen motor assist for climbing hills and getting up to cruising speed but provide better assist above 23mph for your substantial pedal power.
Sacrificing motor only torque and speed to gain motor assist at just above motor only limit.