Gilligan said:

**Now, no matter how much the cars weight you would always want to strive for more Force, right? ...**

So a specific engine/trans/rearend combo would always provide the same Force through the powerband, which we want as high as possible, as often as possible?

So why would u want a different setup in a heavy car (often low-rpm power) than in a light car (often high-rev)?

You've already answered your own question, kind of.

You probably DO want the most force as possible, as often as possible. But the heavier car will spend more time in the lower end trying to accelerate, so "as often as possible" happens at a lower rpm than on the lighter car. You haven't defined the requirements for the vehicle so it's hard to prove anything that can't be disproved by pointing out another circumstance.

If a car spends 75% of it's time below, say 3500 rpm because it's heavy and trying to accelerate, then it'd be best to address that rpm range. The lighter car probably won't be spending as much time in that range so there's not as much need to improve that range.

Gilligan said:

But none of you seem able to give me a correct explanation using the two formulas:

Acceleration = Force / weight

Why dont you ALWAYS strive for the most Force, which is:

Force = Torque (at the given moment) X total transmission/rear-end ratio.

Again, use the formulas to prove your knowledge.

You haven't chosen the right formulas to prove anything. Example; I analyze where my car is losing the most time and decide it's because the top end is too low. What force do I need to maintain my desired top speed? Well, F=ma. At top speed, a=0 so the required force must be zero too? Hmmm... air resistance is a drag... (pun intended)

You've oversimplified things by A) not giving any criteria for what you want the car to do, and B) restricting the answer to two formulas to "prove" things, yet the two formulae don't fully describe the requirements the torque curve would be designed around.

There are different set ups because there are different ways to compromise the pros and cons of each option. A heavier car may bias the factors one way, a lighter car may bias them another.