Torque vs Power

[gpt]

Not sure if this belongs in this forum, if not please move it.

I have been trying to understand the difference between power and torque and this is my understanding so far, Please correct me where I am wrong.

Assuming everything else is equal between 2 cars the car with more torque will accelerate faster in any given gear.

A car with more power will be able to use a lower ratio gear while going faster.

So by increasing my overall torque, my car will accelerate faster in any gear, by increasing power, my car will be able to maintain acceleration at a higher speed by keeping in a lower gear, and therefore experience less of acceleration that comes from shifting gears.

This being said if you look at the chart below you will see that our cars produce more torque than an RSX-S at most RPM's (the RSX-S) takes over at 6500rpm.

So if you look at the Hondata tune provided, it increases Torque at all RPM's and will therefore make the car feel faster in any given gear. It becomes a lot more complicated when you want to work out what is faster (you have to consider what speed you are going when you shift gears etc.)

Am I completely off?

[Jpax]

torque X RPM = HP

thats all you need to know.

[95 GSR]

"hp is for racing, tq is for burnouts"

[sicivic2002]

A quote I always liked was.

"People buy horsepower and drive torque."

[Dunrick]

Trq is like your 0-30mph, then hp takes over

[myeverlovinsir]

For those confused about the relationship of torque and power.

Torque -> a moment of force, is a measure of the tendency of the force to rotate the body (crank) upon its axis. Usually refered to as the rotational force and mesured in foot-pounds.

Horsepower -> is time based. One HP equals 550 foot-pounds per second.

Horsepower is related to torque, and torque is turning force. Place a lever on the engine's crankshaft and measure the twisting force produced, and you have torque. Note that time is not a factor - torque can be constant over time. Horsepower, on the other hand, is the rate at which the torque is produced.

Horsepower is a measurement of the engine's ability to do work. One horsepower can lift 33,000 pounds up one foot in one minute. Horsepower is measured over time. The more horsepower a vehicle has, the more mass it can move in the same amount of time, or it can move a fairly constant mass (the weight of the car) in less time. In simple terms, to get a vehicle accelerating quicker, we need to produce torque faster.

To achieve good performance, operate the engine at its peak torque, and the lower the rpm this occurs, the stronger it will pull from a stop. Often too many "hot-rodded" engines, all they go after is maximum horsepower at high rpm. If you have a light vehicle, steep axle gearing, and are willing to constantly rev the engine high, then high horsepower numbers will make you go fast. Great for racing.

Imo, it is better to have an engine with higher torque ratings and the lower or broader the rpm range it achieves it the better. Torque is what gets your vehicle moving. For everyday driving, I would pick a vehicle with high torque ratings at low rpm over a high horsepower, high rpm one any time.

...hth:)

[gpt]

myeverlovinsir - thanks that was a really good explanation!:)

[Jpax]

Originally posted by myeverlovinsir

...hth:)

I Hart myeverlovinsir.:*

:D

Good explanation!

[swampdonkey]

Originally posted by myeverlovinsir
For those confused about the relationship of torque and power.

Torque -> a moment of force, is a measure of the tendency of the force to rotate the body (crank) upon its axis. Usually refered to as the rotational force and mesured in foot-pounds.

Horsepower -> is time based. One HP equals 550 foot-pounds per second.

Horsepower is related to torque, and torque is turning force. Place a lever on the engine's crankshaft and measure the twisting force produced, and you have torque. Note that time is not a factor - torque can be constant over time. Horsepower, on the other hand, is the rate at which the torque is produced.

Horsepower is a measurement of the engine's ability to do work. One horsepower can lift 33,000 pounds up one foot in one minute. Horsepower is measured over time. The more horsepower a vehicle has, the more mass it can move in the same amount of time, or it can move a fairly constant mass (the weight of the car) in less time. In simple terms, to get a vehicle accelerating quicker, we need to produce torque faster.

To achieve good performance, operate the engine at its peak torque, and the lower the rpm this occurs, the stronger it will pull from a stop. Often too many "hot-rodded" engines, all they go after is maximum horsepower at high rpm. If you have a light vehicle, steep axle gearing, and are willing to constantly rev the engine high, then high horsepower numbers will make you go fast. Great for racing.

Imo, it is better to have an engine with higher torque ratings and the lower or broader the rpm range it achieves it the better. Torque is what gets your vehicle moving. For everyday driving, I would pick a vehicle with high torque ratings at low rpm over a high horsepower, high rpm one any time.

...hth:)

Thats awsome explaning there. I just wanted to add that HP is a measure of electrical energy with each hp being equal to 250wats. In other words its a measure of WORK not force like torque.

The equation is HP= torque x RPM/5252

[myeverlovinsir]

Originally posted by swampdonkey


Thats awsome explaning there. I just wanted to add that HP is a measure of electrical energy with each hp being equal to 250wats. In other words its a measure of WORK not force like torque.

The equation is HP= torque x RPM/5252

Actually swampdonkey, 1HP equates to 745.6669 Watts mechanically and is 746 Watts exactly electrically. Better check your sources.

HP is a rate of doing work which I mentioned previously and work is measured in joules per second.
1 joule per second = 1 Watt/s = .74 foot-pound (which is a constant force).

EDIT: Your HP equation is the correct one and is an easy way to check what HP you may be making at any given rpm when only torque is provided by a dyno chart or vice versa. This is the internal calculation done by most tortional dynopack meters to report HP. Where as inertial dynos such as dynojet report HP and in turn calculate torque.

...hth;)

[S800Racer]

Originally posted by swampdonkey


The equation is HP= torque x RPM/5252

If your buddies are not real familiar with dyno charts in general and this equation in particular, you can win a few "sucker" bets.
Just bet your buddy $20 that because you are such an expert on engine combinations/torque/HP and based on his combination of mods and engine type that you can predict that his HP curve will cross over his torque curve at, oh, about 5250rpm.;)
Now if he is really a friend, give him the $20 back and tell himm how you did it.