2K7ZO6

The distinction was never clear to me until I read this article. Hope this helps someone else.

http://www.straightdope.com/mailbag/mhorsepower.html

Andi

Decent article but it's aimed at the non-enthusiast, the non sports car, etc. For your tow rig or for your mom's car, low end torque is better than horsepower every time -- that article is right on the money *in those situations.*

For a sports car, horsepower is key*. It does sell cars and it does win races. For an explanation of why..... read this less pithy but much more in-depth primer... (Notice I didn't say peak horsepower... I just said horsepower. Having a nice broad horsepower plateau so you can stay at your hosepower "peak" throughout the race is optimal.)

http://vettenet.org/torquehp.html

Andi

(edit) PS-- having a wide torque band makes a car a lot easier to drive, though, than an equal horsepower car that you have to rev the **** out of to wring those horses out of. That does count for something....

Ruf-Racer

may be found here:

http://phors.locost7.info/contents.htm


Cheers

R

AU N EGL

Leamans terms

Torque gets up off the line or out of corners and up to speed ASAP. or up to 5000 RMPS
Torque is what thoughs you back deep into your seat when your right foot goes to the floor.

"Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. "

Cars that are tuned for a FLAT torque curve will accelerate harder then cars with an increasing torque curve.

HP gives you the top speed over 5000 RPMS

HP = ( Torque * RPM) / 5252

HP and Torque are = at 5252 RPMS

Second

If you are comparing two cars of the same make and model with the same transmission and differential gearing than you should compare the average torque made over the relevant rpm range. What I define as the relevant rpm range is between redline and to wherever the rpms fall to during a shift. In the c6z I believe the transmission drops the rpm to 70% of the rpm at the time of shift. This would take a 7000rpm shift to 4900rpms. In that case I would calculate the average torque between 4900 and 7000 rpms to determine which car has the better power and will win the races.

This will not necessarily give you the same answer as peak hp, but will give you the same result as average hp over the same rpm range. This will not be helpful though if you're talking about comparing two differently geared cars.

To compare 2 differently geared cars you would have to compare average torque X trans gear X diff gear. This would be divided by weight to give you rwtq (geared) per pound. Then you would need to compensate for the speed under which the comparison would be made and if you're really getting detailed, tire size.

So if your point it what header to choose or which blower/ cam / etc.. to choose the answer is the one that make the most average torque over the "relevant" rpm range.

cbgpe

The more average power you have thru the gear pull the faster the car will accelerate. High Peak power with a narrow power band is almost useless unless you have a gear box with enough speeds to allow you to keep it in the narrow power band. The power band of the engine must be matched to the available gear ratios in the transmission.

bob53

Torque is really the only thing the motor is generating. HP is a time/speed derivation of torque.

Velocity Steve

You've got it backwards. The only thing the engine generates is power. The torque is only a way of measuring the horsepower. The only thing that matters, whether drag racing or towing a boat, is rear wheel torque, not engine torque. If you had a continuously variable transmission, you're best 1/4 E.T. or your most effortless boat towing would be accomplished at maximum horsepower, not maximum torque.

Velocity Steve

Leamans terms

Torque gets up off the line or out of corners and up to speed ASAP. or up to 5000 RMPS
Torque is what thoughs you back deep into your seat when your right foot goes to the floor.

Rear wheel torque, not engine torque.

"Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. "

Nothing could be further from the truth. The car will accelerate hardest at maximum horsepower. If you had a continuously variable transmisson, the car would accelerate hardest at maximum horsepower, not maximum torque.

Z06-Goose

In asking that question a while ago, a friend of mine explained to me the difference between HP and TQ in very layman's term: "Horsepower is how fast you hit a wall...torque is how hard you go through it"
-Goose

AU N EGL

that was a quote from here: http://vettenet.org/torquehp.html

Porsches have very small torque curves and need to stay within their power bands of only a 1200-1800 rpms.

LSx motors can be tuned for a flat torque( relativly flat) curve from 2000 rpms right up to 5000 rpms. at 5252 rpms hp and tq are equal. above 5252 HP take over.

When you shift the rpms drop about 1500. So ideally one should shift 1500 rpms above peek HP so that when you do shift you are AT peek HP.

aharte

No. In a given gear, maximum acceleration is at the torque peak.

If you had an ideal CVT, you would indeed set it to stay at the power peak for maximum performance. But that is a different situation. Maximum acceleration in a given gear is reached at the point of peak torque. Maximum acceleration at a given speed is reached by being in the gear which allows the engine to produce the most power. Understanding the distinction here is probably the best way to understand the practical difference between torque and power in a car.

Most of the statements in this thread are either wrong, misleading, or irrelevant... Part of the problem is that torque and power are used with several different (conflicting) definitions in car magazines. The people doing this rarely realize that they're constantly switching definitions. They take a statement which might be correct about one definition, and blindly apply it to another (where it's no longer true). Then everyone reading those magazines picks up on this, and we get threads like this.

JZ

Me likes torque...

bob53

No, a motor exters a force by rotating a crankshaft. This force is torque.

ZeeOSix

All that "low end torque" means is that it's producing "low end horsepower" also.

You can't have one without the other. HP is derived from "torque at speed" -- HP = (T X RPM)/5252 -- by definition.

ZeeOSix

In reality, it's producing BOTH. It's basically producing torque WHILE rotating, which by DEFINITION is HP.

HP = (T X RPM)/5252.

You can produce torque WITHOUT rotation ... but the HP would be ZERO ... again, by definition.

The torque is produced by the air/fuel mixture exploding in the combustion chamber, which pushes the piston down, which rotates the crankshaft, which produces a torque into the drive train, which makes the wheels turn, which make the car move forward.

HP is just torque being produced at a rotating speed.

HP = (T X RPM)/5252

Jagcvette

Right, the ability to move your car is a mixure of both torque and hp. Torque is a measurement of your engine's ability to move 1 lb, 1 foot of distance. That's why torque is measured in lb/ft. Horsepower is how quickly your car can move that weight. To put it in practical terms, if a weight lifter can lift 300 lbs 10 times, that would measure how much torque he is producing to lift the weight. But how quickly can he lift the 300 lbs is measure of horsepower. Will it take him 20 seconds or 200 seconds to lift the weight 10 times? That depends on how much hp he has.

As you launch off the line, it takes more torque (power) to start moving the car. As the car generates more speed, you rely more on how fast (hp) you can continue to move the car as it continues to generate speed. Once you get the weight moving, it takes less torque, but more hp (ability to move it fast). Its just like a sprinter leaving the blocks. Those with super strong legs will get a good jump on the competition, but those with the ability to move faster (hp) will eventually catch up and pass the quick starters. Carl Lewis was great at generating more speed down the stretch, i.e., equivalent to more hp, but less torque, then other sprinters.

AU N EGL

TQMONSTR would be a good Lic plate

Verrückt

He's actually right.

Dynos measure torque then compute horsepower by factoring in RPM. Torque is what the engine produces. Horsepower is the rate.

A motor that makes a lot of low end torque simply makes more horsepower at a lower RPM.

That's a pretty big (false) generalization.

Let me ask you this, what makes more low end torque...the LS7 or the new Porsche Turbo motor?

gonzalezfj

Now you did it!!! Verrückt will be on your case hard. Just watch.

Saying anything even mildly derogatory of a Porsche will not wash with Verrückt.