Actually, the decision to shift is based not only on horsepower, but on torque. As you know, gearing is important as well. I'll use my car for example, since I know it well. One thing that is the same for all cars is that lower gears are easier for the engine to turn. Now my car's peak horsepower is 280hp @ 6,200rpm and peak torque is 270 foot pounds at 4,800rpm. As you can see, horsepower and torque are both very high...horsepower is always at or near the car's redline, but this is not always the case with torque. Most Japanese car companies opt to provide maximum horsepower AND torque at higher rpm's, which allows you to take MAXIMUM advantage of lower gearing, because lower gears are easier for the engine to power and all the power of the engine are at those high rpm's, which is perfect for always being in the lowest gear possible. It's a combination of the easiest gear, maximum horsepower, and maximum torque (I know I just said that like 3 times, but bare with me, it's 3AM).
The way BMW typically does it, is they give you that maximum horsepower up top, but maximum torque in the mid-range. This is good for real-world driving because the torque kicks in low for good acceleration when driving around normally, and horsepower takes over up top. Plus, BMW's have a really nice power band so there is still ample torque throughout the entire rev band (keep in mind that BMW firmly believes in high revs), which is why BMW engines are so well-appreciated by auto enthusiasts. It's really cool too, because it allows you have a lot of fun on regular roads....just downshift to 3K-4K rpm and punch it and the car just whips you back in your seat from all that torque.
If we were talking about those older American muscle cars, then it's a different story...they are big V8 engines, so they have mad torque down low, so they would definitely shift earlier than redline (I dunno exactly where, as it's different for each car) because being in the harder-to-turn gear earlier was more worth it, since all the crazy torque was at lower rpm's.
The way BMW typically does it, is they give you that maximum horsepower up top, but maximum torque in the mid-range. This is good for real-world driving because the torque kicks in low for good acceleration when driving around normally, and horsepower takes over up top. Plus, BMW's have a really nice power band so there is still ample torque throughout the entire rev band (keep in mind that BMW firmly believes in high revs), which is why BMW engines are so well-appreciated by auto enthusiasts. It's really cool too, because it allows you have a lot of fun on regular roads....just downshift to 3K-4K rpm and punch it and the car just whips you back in your seat from all that torque.
If we were talking about those older American muscle cars, then it's a different story...they are big V8 engines, so they have mad torque down low, so they would definitely shift earlier than redline (I dunno exactly where, as it's different for each car) because being in the harder-to-turn gear earlier was more worth it, since all the crazy torque was at lower rpm's.
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