..it's really hard to judge speed watching a vid- of an R/C on YouTube. The frame rate is 24fps second at best which means a lot of frames are being skipped or cut (compared to what one would view w/ their nake eye) -giving the effect of your car travelling faster than it really is in the video.
FPS =frames per second
example, your eye can view well over 100 FPS, YouTube displays at 24 FPS. Therefore it's not a true 1:1 view for us ...we'd have to view your car in real life OR have some kind of speed radar or something to tell us how fast your car is actually going. Viewing a lower frame rate actually makes your car seem faster to us because your cutting out frames of the video (or YouTube in this case).
check out this cool calculator, -it will give you some idea of how fast your car should travel ...you can probably judge whether or not it's close to the speed this calculator outputs: