A speed tower in OpenSCAD, parametric, you can select speed range and step and feature size.

This OpenSCAD code prints the G-code for Slic3r, clean up the ECHO: prefix and the "" quotes and paste the code into custom G-code "Before Layer change":
{if layer_z >= 1.5 && layer_z < 2.5}M220 S{10100.0/perimeter_speed}{endif}
{if layer_z >= 7.9 && layer_z < 8.9}M220 S{14100.0/perimeter_speed}{endif}

Unlike the temperature tower, there is no G-code to set speed, only the speed multiplier. This G-code will set the perimeter speed to the values printed on the tower, but the other speeds will be rescaled by the same ratio. So you have to go into the Speed tab of the Print settings in Slic3r and set the External Perimeters and Perimeters (at least) to the same speed. If you select the solid tower, then do the same with infill. Note that the base is printed with whatever settings you have in the slicer, speed starts to change when it gets to the towers.

Make sure to reset the speed multiplier at the end of the job if your G-code does not do it (even better, add M220 S100 to your end G-code).