The Truth About Horsepower, Torque, and Acceleration

To take this in a different direction, what about fuel efficiency?

If I were an automotive engineer with efficiency in mind, I’d make a car that runs at optimum rpms at 60 mph in fifth gear (’cause that’s supposedly average driving conditions). Under those conditions, the tachometer in my car reads around 2600 rpms. I notice that 5252 / 2 = 2626.

The only explanation I’ve had for this phenomenon is that 2500-2700 rpms is in a magical “power band” of rpms. I try to think of it like this:

Under the power band, it’s like you have a man pushing a large block. It’s not hugely efficient because the brick is hard to push, but as your rpms increase, the man is getting stronger (rpms up -> horsepower up) and the block is getting smaller (car gaining momentum).

There’s a “sweet spot” right at 2600 rpms where the man is using just enough strength to push the block without breaking a sweat — most of his energy is going toward pushing the brick. This is a highly efficient state.

Over the power band, the man is almost too strong for the brick — imagine Arnold Schwarzenager pushing around a regular adobe brick — which isn’t very efficient either… so you change gears, replacing the man with a somewhat weaker (but faster) man.

I understand the concept, but why is that sweet spot right at 2600? Do car engines like hacker quarterlies?

Yeah, leave it to a real geek to bring it back to computers. Ok, ok… the sweet spot is probably around 2626, but then I wouldn’t have been able to use that joke.

“What matters more for acceleration — horsepower or torque?”

“… anyone telling you that either horsepower or torque is more important than the other is significantly off-base.”

“So yeah, the answer to the question is horsepower.”

Um …

:)

Good job dude. Tim does make a point about efficiency, but I think we are mostly talking about performance and not efficiency here.

Here is something to consider when running a car at max performance. We use catalytic converters to help burn off excess CO2 that is emitted while we do normal city driving. If you run your car at mostly high RPMs then the catalytic converter is no longer needed. In fact your car could be far more efficient with out one.

I’m also told that the backpressure from the catalytic converter helps the engine operate more efficiently.

Then again, my dad told me that, and we all know how that goes.

Ken, thanks for that…good point.

Carl, thanks for that as well…lol