Horsepower vs Torque Relevance and Explanation Attempt!

Originally Posted by dsx724

loled at the last one.

Me too. Well done........


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thank you for writting this. Solid points!

Originally Posted by cridge

Understeer is when you hit the wall with the front of the car.



Oversteer is when you hit the wall with the rear of the car.



Horsepower is how fast you hit the wall.



Torque is how far you take the wall with you

Killin it !!

Wow, just wow. All that detail! thanks a lot

As if I was taking Physics again in the 70's. Excellent definitions of basic principles. Wonderful reference material. Thank you.

A well written and thorough explanation. Many thanks for taking the time and sharing!!

This sounded interesting until you made the statement about holding the flywheel of the engine. No way that is right. JMO.

"An engine, even the most powerful around are much weaker than many realize. An average grown human can take the flywheel of most street engines in use today and hold it in place even if the engine is operating at maximum throttle."
What???
I'd love to see someone hold the flywheel of even a small engine when just turned over on the starter motor.
There is a very direct relationship between torque and horsepower. The formula originally posted is the single thing in the OP that is in any way relevant:
Horsepower = (Torque x RPMs) / 5252
The constant of 5252 has a complex calculation behind it that is probably not important to this discussion. The thing to understand is that horsepower is calculated from torque which in turn is physically measured on a dynamometer. But importantly, nothing about this formula has anything to do with the acceleration of the vehicle or the speed of the propshaft. It has only to do with the speed of the engine (RPM) and the torque produced by the engine at specific engine speeds.
The reason why a car cannot accelerate well at low speed in 3rd gear is because the engine RPM at that road speed in that gear is too low to produce torque. This is a characteristic of the engine design.
Just look at a torque curve graph - this is not rocket science.
When you see a car being run on a "rolling road" (dynamometer), do you think they're measuring horsepower? They aren't, they're measuring torque. The horsepower rating is derived from the torque measured.
"If power is merely a calculation . . . ." It's not a case of "if". It IS merely a calculation.
Actually, there is so much wrong with the OP, I'm astonished that this has been given "sticky" status.

I'm glad I read this. Someone above me in the comments said, and im paraphrasing, "a noob that reads this wont gain in knowledge, and will have more questions at the end." I have to say, at 44 I have the amount of time it took me to read this vested in the hp vs Nm's. Aside from 9th grade science and the usual math classes. I now can say, without a doubt, that I understnd what the two units of measurement mean, and why gearing is so important. For the first time in my life i own a car that I want to spend my time and money on. I havent so much as washed a car in 12 years. Til a few months ago. Now i have a kick ass E34 on jack stands in my garage, front end dismantled, and parts in the mail. What does this all mean? I dont have the foggiest. But I do know that if tbis is the quality of info i will find on here, Im gonna love this forum as much as I do my Zombimmer. I tend to ramble, sorry. Great explanation. cant wait to school a few chevy owners. thanx for the knowledge. sincerely

The way I try to think about it:

Torque - What you need to move
Horsepower - How fast you use your torque

Consider two extremes:

- Imagine a massive truck trying to move a space shuttle. It moves very, very slow, but it can pull the shuttle. This is similar to something with high torque, low horsepower: its engine doesn't spin very fast, but it produces a lot of power for each revolution.

- Imagine a small car trying to move a space shuttle. The engine spins very fast, but it can never move the shuttle. This is similar to high horsepower, low torque: it can use the torque quicky, but because there's not enough of it, neither the car nor the shuttle go anywhere.

Torque is what does the work to move you, horsepower is how fast it does the work.

Of course these analogies aren't precisely how reality is, but it's a way to wrap your brain around it.

Originally Posted by NBA Jam

The way I try to think about it:

Torque - What you need to move
Horsepower - How fast you use your torque

Consider two extremes:

- Imagine a massive truck trying to move a space shuttle. It moves very, very slow, but it can pull the shuttle. This is similar to something with high torque, low horsepower: its engine doesn't spin very fast, but it produces a lot of power for each revolution.

- Imagine a small car trying to move a space shuttle. The engine spins very fast, but it can never move the shuttle. This is similar to high horsepower, low torque: it can use the torque quicky, but because there's not enough of it, neither the car nor the shuttle go anywhere.

Torque is what does the work to move you, horsepower is how fast it does the work.

Of course these analogies aren't precisely how reality is, but it's a way to wrap your brain around it.

Fundamentally you are correct but . . . .

As I said in my post above, there is a very direct relationship between torque and horsepower. What this means generally speaking is that an engine developing high horsepower will not have low torque and conversely, high torque will not result in low horsepower.

And if your analogy with the massive truck is taken to the next step, no matter how much torque or horsepower the giant truck has, if it is not geared correctly it will not be able to do any work. E.g. if a heavy vehicle (say a Freightliner Argosy with 560hp, 1,850 lb-ft torque) tries to pull off in top gear, it will not get away, even with no load at all. The high gearing will simply not allow it. But in super low gear it is capable of moving well over 100 tons from stationary.

The useful expression is "Torque gets you up to speed, horsepower allows you to stay there"

Cheers
Andre

That was a great explanation and helped me wrap my head around a few things I struggled to understand in the past.

Originally Posted by cridge

Understeer is when you hit the wall with the front of the car.

Oversteer is when you hit the wall with the rear of the car.

Horsepower is how fast you hit the wall.

Torque is how far you take the wall with you

That is bloody amusing so I am going to steal it.

When i remapped my e39 530dA i increased torque only from 420 to 490 because i dont want to break automatic transmission, but most off all that tork only works about to 3k rpm, after that it doesn't matter, because power depends from horse power So my remapped 258 hp is really enough.