i thinking of doing a dyno on my car after i installed underdrive pulley + ECU upgrade.
is the dyno harmful to the engine? and how long does the dyno take?

 

No the dyno is not harmful to your car assuming the dyno you go to knows what their doing. Time depends on what you want to do with the car while your on the dyno. If you are going to tune it on the dyno then possibly 2-3 hours or more. If you just want to see how much power the car makes and not tune around a hour.