Tested on Factorio 1.0
Seems to work fine on the Spidertron.
Tried it on all trains of your Logistics mod.
It's possible it's just not showing the number correct? but I get 496~ km/h with T3 trains and Nuclear fuel, regardless of what I put in the equipment grid.

Trains have a speed limit applied to them.
Despite what the tooltips say, they effect Acceleration only.
So, they do have an effect on trains, they basically allow them to pull more carriages, or just reach top speed faster.
Speed limits on other vehicles such as the car, tank and spidertron are actually just acceleration vs wind resistance, so more acceleration equates to a faster speed.

Alright, good to know. Thanks for the explanation :)