I believe this topic has been discussed before(many times),but I really need a SIMPLE formula to predict changes in speed based on changes in hp.For example,if I know that 145hp = 134mph what mph will 200hp yield?
Horespower required goes up as the cube of the speed increase.
Or conversely, speed goes up as the cube root of the horsepower increase.
So in your example, take 200hp divided by 145hp = 1.3793, or in other words you're increasing the hp by 37.93%
The cube root of 1.3793 is 1.1131 (if your calculator doesn't have a cube root function, raise it to the 1/3 power)
Therefore the vehicle can go 11.31% faster on the additional power, assuming it's geared right.
1.1131 times 134mph = 149.15mph that you can go on 200hp.