Hello again, 
Liberador
I have some guesses.
1) You used to set the engine volume to -1000 dB instead of using engine mute to avoid one more step where it would be needed to unmute the sound, right?
2) 1+(abs(Tank.Car.Speed)*0.01 I think 1 is there to play sound in normal speed and then add "force engine sound" to play faster. Example: if tank speed is 100 * 0.01, then it will be 1, and the previous 1 will make it 2, or double the sound play speed, right?
I still don't understand.
3) Why is the truck mark spawner delay based on left track animation speed? Is truck animation speed movement calculated based on tank speed? Why not use something like tank speed compare instead of the current animation frame? Plus, if there is a vehicle that does not have tracks at all, it will need a new formula... Is there any way to skip that left track step and calculate based on tank speed? Can you please explain it to me?
1) Yes.
2) Yes.
3) I did it like this looking for the easiest and simplest solution, but if you don't want the truck mark spawner delay to be based on the left track animation speed, you can use the solutions suggested by 
R0J0hound and 
dop2000 in this thread: construct.net/en/forum/construct-3/how-do-i-8/spawn-objects-quantity-185633