Why does my X axis go faster than my Y axis????

When I cut a part out using Mach3 my x axis will move faster that the
y axis.

For example:

I have used a basic shape that has a couple 90 degree corners and a
diagonal back to the start point.

The shape is set to cut at 1300mm/min.

The y axis will cut at 1300mm/min, but when the machine turns a corner
and the x axis starts moving. The feed rated goes over the set
1300mm/min up to 1800mm/min.

Then turns a corner and back onto the y axis and it is fine at
1300mm/min again.

When doing an angle say 45degrees, it will move at 1400mm/min.

What is going on???