If SPEC is turned off before it ramped up, warp field is instantly set to maximum - and vice versa. One of the results is that it's impossible to use SPEC in small increments other than by setting low velocity.
The reason: warp ramping, whether activated manually or via autopilot, as done in Unit::AddVelocity (src/cmd/unit_generic.cpp) sets ramp counter to full ramp time and then calculates warp field strength from ramp counter.
Anonymous
Fixed by patch from Turbo Beholder