Although the car itself may be moving at a blistering pace the air around it is always going to be at a scale of 1:1 Therefore any true (and acurate) comparisons between one scale car and another (say 1/12th to 1/10th or even 1:1) cannot be made. Rather good estimates can be made but it's not going to be perfect.
My suggestion, if your looking for speed is to spend the money and get an EP car with a ton of room on the chassis, add a brushless motor to the car with a huge batt pack (say 10 cells although 7 or 8 would do) and have fun. to get a Nitro car to go fast is too much effort.