Speed means rapid movement or action. Some of the factors you need in order to make a Co2 car would be aerodynamics. A lot can play in aerodynamics, like the way the dragster is made. Does it allow air to flow easy? Can your wheels run well? Gas mileage helps a car go farther without stopping for gas, we have a Co2 that runs on air so were good.
Important factors in launching your dragster is your wheels and launch hole. Your launch hole has to be just right or it won't launch. Your wheels have to be able to spin good or it won't go fast. The weight of my car is pretty heavy so that't a flaw. I think my car will go at least 3 mph.
The shape of my car turned out as well as I wanted it to. I enjoyed watching the races. I would totally redo the whole shape of my car. My least favorite part was watching my car lose.