The sound is most commonly placed midway between beats, in the same place as hi-hats, but can be put in other places for different effects and such. The music it is used in is usually played between 150 and 160 Beats Per Minute.
When dancing, a donk commonly makes the dancer bounce on the donk beat.
Are we goin' donkin tonight?
The people who do it right usually perform engine swaps, transmission regearing, brake upgrades, and throttle programming. The problem is very few people take the time to modify their car correctly, and some take pride in having "haters" and have no ambition to do the project correctly anyways