Thank you all for replying.
@BigClive, That was good one if you are joking and I would just say 'NO' if it was in serious tone. Honestly, I am trying to understand as I always have what? why? when? how? I am going through lot of material but very often I figure out that when we discuss, things become easy to understand.
I have couple of more question related to my initial post. Lets say if I replace my current engine which is having 100 hp @2200 rpm, torque of 289@/1400 rpm with power of 75 hp @ 2000 rpm and torque of 312 nm @ 1500. What automobile loose and what gain? I can see power is decreasing, torque increasing and rpm decreasing at max power, but I would like understand in broad manner.
If I pick the transmission with specification of speeds 1st = 2.9 mph , 2nd = 4.7 mph, and use v= v0 + at to calculate F=ma. Is it correct method to find initial speed v0 and thus acceleration(a).
Please, correct me if I am wrong. I would like to check and compare force available at wheel, speed and acceleration when engine is changed.
Suggestions, corrections and other opinions pleas.