Yeah this was on a really old car at the time, you had to connect it between the throttle trim and receiver, to be honest I have no idea why it done it. I want to say I put it in the wrong way around but I'm not sure that's possible haha I did have the X4 1st as was cheap and had great reviews...
It was yeah, about 40mph across the field haha I soon upgraded my controller to dumbo x6 and get about 500m range now and a built in fail safe. For some reason the old cars would lock up hard left and accelerate if they lost signal
I once connected the fail safe to an old receiver wrong and when I lost signal it accelerated fully instead of what it should have done which is to break fully, I had to chase my car across the field where it hit a chain linked fence ha