Horsepower vs. Torque by Red94Vette

(I promise this will be simple to understand)

First let me explain why I make these annoying posts. My ultimate goal is to teach you something I have learned through years of experience and hard work in school. Why reinvent the wheel if I can tell you and save you the trouble? It’s passing on the torch, If I can show you what I know now, you can take it and better it for the next generation. Do you enjoy your lifestyle today in this electronics age? All this was built upon man’s achievements in the past. Those guys are gone but their work lives on. With that said, here is my best explanation of Horsepower vs. Torque.

Deep breath….

I can write a program that simulates a car accelerating without using one single horsepower number, not one. I use the torque curve to calculate the acceleration. So if it’s torque that moves our car, why do we throw around horsepower figures?

The answer: torque isn’t the only factor, its torque and time.

Torque gives us that kick in the SOTP (seat of the pants). But how long does that kick last? If you make a lot of torque but only for a small range (say over a 1000 RPM band) then you accelerate fast but only for that small amount of time. You also have to talk about time. I can make X amount of torque for Y amount of time.

See where I am going with this? You have to deal with two variables, not one. So, why not talk about the product of the two? If high torque is good and that amount for a long time then the higher the product of torque and time the better, right?

That’s where Horsepower comes in. Horsepower is the same thing as talking about torque and time, all in one!

I want to leave you with an example to give you the “big” picture of torque and horsepower.

EXAMPLE

You have two college students sitting in front of you and you have to decide which one of the two is the smartest. Both students appear normal, they both have ink stamps leftover on their hands from the bars from the previous night.

You only know one thing about each of the students.

1) You know the student (student 1) on the left made a 100% on his last math test.
2) You know the student on the right (a senior) has a 4.0 GPR.

So who is smarter? Well you can’t tell for sure but you can make a wise choice. All you can tell about the first student is he did well on his last test. Did he get lucky? Was the test easy? Did he cheat? All you have is a “snapshot” in time of his performance. But, how did he do on all of his other tests? You don’t know.

Now for the second student, you have his grade point ratio, which is the average of all his classes, grades tests, etc. You can tell by his GPR that he did extremely well on all of his tests and will probably get a good grade on the next test. This information is not a “snapshot” but it is a picture of his timeline and performance, time and performance.

In a nutshell, the first student is torque and the second student is horsepower. With the first student there is a lot of unanswered questions about how smart he really is because you only have one test score. With the second student, you have the single piece of information you need, all of his scores.

That is the sole reason why we talk about horsepower and not so much about torque. It gives you the whole picture.

Torque is the grade you made on your last Basket Weaving test

Horsepower is your GPR (grade point ratio).

(But you must make good on all of your tests to get a good GPR in the long run)

 

Precise, informative and easy to understand!

I needed that... - Keep them coming!

Thank You!! :cheers:

 

The argument that people seem to make is: a higher HP car is a quicker, than a lower HP car. This appears to hold true due to " it takes time to shift".

If you have a LOT of low torque and VERY fast shift,.... higher HP may not be quicker.

Agree/Disagree?

 

Agreed. I powershift at the track and never had a problem with most LT1 cars.

 

:cool:

 

Thank you!!! :cheers: :cool:

 

Thanks professor! Very well done! :cheers:

 

Thanks for the information. :cheers:

 

Very well put!! :crazy:

 

Well just horsepower alone will not win races. There's weight, gears, and traction that also skews the picture.

Powershifting helps out more in the 1-2 shift and 2-3 shift but after that it doesn't have much influence on ET. Think about it, you are already traveling 90-100 MPH and then you powershift or granny shift, you are traveling a lot of distance during that time because of your speed.

What you are trying to describe is a torque motor versus a horsepower motor. A torque motor can be described as a motor that makes more torque than it does HP in the usable range. (torque is always more than horsepower under 5252 RPM)

A horsepower motor makes more HP than it does torque, peak power above 5252 RPM.

If a "horsepower" motor isn't set up with the right gears / converter or clutch then he isn't going to be running his best.

A torque motor doesn't need "low" gears and a big stall to run near it's best time, it's already matched from the factory (close enough).

So if you catch some guy that slapped in some top end parts and didn't do his homework, 9 times out of 10 a torque motor will trailer his butt. I know, I've done just that in my 86 maro for 10 years.

But, if you get a car with higher HP that has the right gears/ converter/ clutch he is going to whip you out of the hole and keep on leaving you, it's a fact. Those are the cars you have to look out for.




[Modified by Red94Vette, 2:41 PM 6/5/2002]

 

So is Autocrossing a L98 in second gear between ~2 and ~4 grand rpm where it can maintain 300+ torque like getting to take the same test you aced every "time"? Therefore you get a 4.0gpa too? :reddevil

 

A+ :)

But remember, it's about the force at the rear wheels.

Take a motor with 350 ft lbs of torque in 2nd gear with 3.45s

Thats 2150 lbs of force. Say your car is 3500lbs take 2150/3500 and you get .61 g's of acceleration.

Now take a motor with less torque say 300 ft lbs in 2nd gear with 4.10's.

That's 2189 lbs of force and .62 g's of acceleration, it's a little bit faster.

Remember it's your torque and gear combo that accelerates your car, not just torque.

A torque monster motor uses the torque of the motor to haul butt.

A high horsepower motor uses the torque of the rearend gear to haul butt (his motor has less torque than torque monster motor but more RPM range to use the gears).


I think you L98 guys need to shut me up, I'm giving the LT1 guys the secret to beat high torque motors :lol:


[Modified by Red94Vette, 3:17 PM 6/5/2002]

 

>The answer: torque isn’t the only factor, its torque and time.

I presume this is the major advantage the LT4 has over the LT1. The LT4 mods seem to be geared toward reliably upping the power band and redline. 'Peak' torque is no more than an LT1 or L98 (maybe less), but I can sure make objects in my rear view mirror shrink when I'm up there in the rpms. :yesnod:

 

Red94, I thoroughly enjoyed todays lesson but you couldn't possibly think you weren't going to get any questions from the class

Notwithstanding your great explanation on the difference between HP and torque, what I want to know is why the 2 measurement medias and what do they mean. I think the HP one is pretty simple...if you had 280 horses pulling on a sled, etc etc,. What I don't get is "foot pounds" tourqe. What is it measuring? Explanation needed if you get a chance...

Thanks professor...i promise to pay more attention in class next time this subject comes up :lol:

Cheers

 

yes , yes, i see now , thanks for the explanation! :cool:

 

Quik86, to answer your torque question:

Think of foot/pounds of torque this way. If you had a bolt in a wall and you put a 1 foot long wrench on it so that the wrench is horizontal. You then hang a 1-pound weight on the end of the wrench. You would just have put one foot-pound of torque on the bolt.

The math then works out to two-foot wrench with one-pound weight 2ft/lbs. 1-foot wrench with 2-pound weight 2ft/lbs. etc...

Your Horsepower analogy was close. One horse power is analogous to the amount of work a horse (no I don’t know which bread :rolleyes:) can do in a hour.

 

I also recall seeing another website where the author went to great pains to compare torque and horsepower--in one example he used a water-wheel analogy (lots of torque but little horsepower). I've heard it said that car manufacturers sell horsepower but you drive torque.

 

Actually, soon, we're going to be driving kilowatts. :D

GM has an experimental Gasoline-to-hydrogen-to-electricity fuel cell running around in some S10 pickups now that makes a whopping 25 kW - that's 33 hp.

I say call me when they get that up to about 560 kW (750 hp).

But that will bring on new and interesting problems - the power will get to the wheels through an ELECTRIC motor/generator, which has a very interesting and quite different torque curve...

 

You know what a force is right? If you push your car through the staging lanes at the track you are putting a force on the car and causing it to move. Say you have to put 50 lbs of force to get it rolling (overcome static rolling friction)

Well torque is almost the same. Torque is a twisting motion. It's the same force applied above that you pushed your car with, but, instead of making the car move, you are putting this force into a twisting motion. You are making something move in a circle rather than in a straight line.

If you take the same 50 lbs of force you were pushing your car with and but push on a 1 foot wrench handle, then you applied 50 ft lbs of "torque"
If you used a 2 foot wrench handle you applied 100 ft lbs.

A "lower" rearend gear is the same as using a longer torque wrench. The same amount of force used with a longer wrench, (bigger gear) will make more torque.

Your tire acts like a backwards wrench. You apply the torque and you end up with a force at the handle. Here length hurts you. If you put a taller tire on your car you just decreased your ground force.

I wish I had more time to better explain torque.

Your engine's output is in torque. The large cylinder pressure above the piston pushes the piston down. The force travels through the connecting rod and the rod pushes on your crankshaft. Your crankshaft is a "wrench" and the force comes from the piston. If you use a bigger crank "stroker" it's like using a longer wrench, thus you get more torque with a bigger stroke.

I hope this helps.

 

I can simplify it a little more...Torque is what gets you to a speed, horsepower is what keeps you there.