Official 'Let's discuss Torque vs HP thread...

[Hack]

Another "yes and no" here.

You have two cars that both make 400rwhp, one has a torque peak of 400ft/lbs the other has a peak of 350ft/lbs (ignore average torque measurements for now). Are you saying that since they both have the same HP they'll be even in a race?

IF everything else is equal and HP is equal, they will be even. There are a million things that go into a race, including driver reaction, weight, tire grip, gearing, the time it takes to shift gears, aero, etc. If two cars are close, any little thing can mean a tenth or two. I'm not talking about predicting speed exactly, I'm saying that there is a relationship between HP and a car's quickness. That same relationship doesn't exist for torque.

What I am saying is that you can predict hp approximately given car weight and time/speed through a race. There are websites that calculate it for you.

Two cars of about the same weight and average hp will be close (everything else being equal). Two cars can have the same weight and average torque and one could be twice as fast as the other (or even more), even if everything else is equal.

 

[mikemustang289]

http://www.superstang.com/horsepower.htm

Read this, it explains it all and more. Horsepower is just a word, it is calculated from torque and doesn't mean much. Engines make torque; depending on where in the RPM range that torque is made will dictate what the resultant HP will be. Pretty simple stuff.

 

[Hack]

http://www.superstang.com/horsepower.htm

Read this, it explains it all and more. Horsepower is just a word, it is calculated from torque and doesn't mean much. Engines make torque; depending on where in the RPM range that torque is made will dictate what the resultant HP will be. Pretty simple stuff.

Yes HP is calculated from torque and rpm, but your conclusion is totally wrong. HP is calculated because it's needed to understand the performance characteristics of the engine.

If HP didn't mean much, people wouldn't bother to calculate it. Where in the RPM range the torque is made is the most important thing, because it determines whether your car will actually be fast. Torque does not tell you about the ability of a motor to accelerate an object. HP does.

 

[65ShelbyClone]

I was about to explain what torque is and why horsepower wouldn't exist without it, but it has been explained at least several times already. Once I figured it out, I couldn't believe it was so simple.

 

[reenmachine]

I so love this thread...

:SNSign:

 

[67GTA-FB429]

torque is two dimensional. (distance and force)
horsepower is three dimensional. (distance, force and time)

 

[zookeeper]

Does anyone else think that your engine building goals should at least take into consideration cubic inches? I mean, to build a 289 for torque seems pointless, since it simply would never equal the torque output of even a mild big block, so wouldn't you need to move the power upstairs a bit regardless of your goals? By the same token, a big engine is always going to have an abundance of torque, so you get it as a by-product of your hp gains, right? Lets use a modern 4 cylinder sportbike as an example: they produce stunning horsepower but not a whole lot of torque compared to a similar size Harley, which by performance standards is a dog (my apologies to Harley owners). So the bottom line is, wouldn't engine size and intended use dictate your goals?

 

[Crunchyskippy]

This thread has been very helpful to me, as I've never been able to fully grasp the relationship between HP and Torque.

However, I've got one question: If the formula for HP = Torque * RPM / 5252, doesn't that mean that Torque curve and HP curve will *always* cross at 5,242 RPM's???

I've seen a few graphs on this thread that show otherwise (unless I'm confused...which isn't hard to do).

 

[dodgestang]

This thread has been very helpful to me, as I've never been able to fully grasp the relationship between HP and Torque.

However, I've got one question: If the formula for HP = Torque * RPM / 5252, doesn't that mean that Torque curve and HP curve will *always* cross at 5,242 RPM's???

I've seen a few graphs on this thread that show otherwise (unless I'm confused...which isn't hard to do).

Yes. You have to read graphs carefully though. Many times the torque curve is on a different scale than the HP curve which is why 'visually' it might appear they do not cross. At 5252 torque always equals HP because one is a calculation dependant on the other.

 

[Edbert]

I had to do a doubletake on your graph too Dodge.

...and I just wanted to say that 67GTA-FB429 just gave about the most succinct definition I've ever seen

 

[65ShelbyClone]

Does anyone else think that your engine building goals should at least take into consideration cubic inches? I mean, to build a 289 for torque seems pointless, since it simply would never equal the torque output of even a mild big block, so wouldn't you need to move the power upstairs a bit regardless of your goals?

That's just it, though; the goals should dictate engine size. Want to go road racing? That high-revving 289 will be well suited. Want to go dragracing? Lots of ET is cut with a good launch and the torque of a 460 will do it.