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Old 03-29-2007, 08:55 AM   #1
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Horsepower vs Torque

Which is more important for maximum "sports" performance? Which would you rather have in your sports car...240 hp engine with 160 lb-ft torque or a 160 hp engine with 240 lb-ft torque? Which will accelerate the fastest?

This has probably been argued before over the net...but those discussions don't count because I didn't take part in them...therefore they are only theoretical discussions that should have taken place given the vast amount of people that "exist" away from me...whatever. We know the truth.

But anyway, I am a firm believer that horsepower is what matters most for best acceleration. But these old "know-it-alls" at the track who speak not from books, but from experience argue that torque is most important and power is just an imaginary number. I give them numerous facts to support my horsepower belief, they give me these f*ckin' recalled instances. Old people... These are amateur racers, I am "What"...who do you side with?


Seriously, what do you believe and why: torque or horsepower?
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Old 03-29-2007, 09:28 AM   #2
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i dont know, id prefer torque though it depends on which wheels are driven i suppose! like RWD in the Vauxhall Monaro, the torque is monsterous! but for circuit races, id say horsepower is better suited as too much torque isnt a good thing (especially for Le Mans cars or WRC cars)
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Old 03-29-2007, 10:44 AM   #3
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But for circuit races, id say horsepower is better suited as too much torque isnt a good thing (especially for Le Mans cars...

Yeah, especially for LeMans cars...how's the diesel Audi R10 doing?

Do you ever make decisions True Brit? Your answer is always "both".
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Old 03-29-2007, 11:46 AM   #4
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up late? j/k

but seriously though, id say a car is best off as perfectly even as possible, 200hp and 200 lb ft of torque would probably best ethier of the others, (assuming everything else is the same, including powerbands and everything else)
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Old 03-29-2007, 12:40 PM   #5
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You would need a good combination of both. Little torque and a lot of isn't good. Too much torque, and too little horsepower isn't good either. Basically, what Nighthawk said.
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Old 03-29-2007, 02:32 PM   #6
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This is retarded. But then again, it's What.

Torque is what you feel. HP is what gives speed. Torque is the twisting force acting on the driveline and wheels, and is multiplied by gear ratios. HP is a number derived from torque and is NOT multiplied by gear ratio. Considering that you can change the gear ratio and change the acceleration by multiplying torque (4.11 final drive will accelerate quicker than 3.23 final drive in the same car), then YOU tell me what's important.

Take your car to it's torque peak rpm and punch the throttle. Feel that? now take the car to it's hp peak rpm and punch the throttle. Feel how little additional force is generated? Go ahead, do it in your own car. I'll wait.

Torque is what you feel around town and on freeway onramps. On the street, torque rules. The more torque, over a wider rpm band, the more flexible and tractable the engine will be.

OTOH, hp is what generates speed, and the higher the hp peak, the longer the engine can pull before it runs out of breathing. That means you can gear up the final drive to multiply torque while still having a decent top speed. This means that while torque is accelerating the car, hp is what allows it to accelerate over distance. For drag racing, then, hp is everything, as you can take advantage of gearing to multiply torque for acceleration. The higher the hp peak the higher the rpm and maximized torque in the next gear up when accelerating, which is why you alway shift at the power peak, not the torque peak when racing.

Confused yet?
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Old 03-29-2007, 06:09 PM   #7
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Quote:
Originally Posted by ChrisV
Confused yet?

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Old 03-29-2007, 06:21 PM   #8
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Quote:
Originally Posted by ChrisV
Torque is the twisting force acting on the driveline and wheels, and is multiplied by gear ratios. HP is a number derived from torque and is NOT multiplied by gear ratio. Considering that you can change the gear ratio and change the acceleration by multiplying torque (4.11 final drive will accelerate quicker than 3.23 final drive in the same car), then YOU tell me what's important.
If torque is multiplied by gear ratios, and HP is derived from torque, doesn't that make HP dependent on the gears as well?

Yes, I am confused, but it's got me thinking.
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Old 03-29-2007, 06:40 PM   #9
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analogy time:

All torque= dump trunk. Its the strength part, It's the grunt, its when you first pick up that heavy ass bag of cement.

Horspeower is the ability to KEEP doing that. Your horsepower is the amount of how much work you can do over time.


Torque=doing the work
Horepower=how much work your getting done


get it?

no?

Yes?

Potato?

Or maybe i'm completely wrong and I should light my head on fire.
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Old 03-29-2007, 07:00 PM   #10
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Quote:
Originally Posted by chris_knows
Little torque and a lot of hp isn't good. Too much torque, and too little horsepower isn't good either. Basically, what Nighthawk said.

I feel differently. I'd rather a 100 lb-ft 300 hp car over a 230 lb-ft 230 hp car. My car would be stressed, but it would be fun. And fast...er than the 230-230 car given everything else equal.


Quote:
Originally Posted by ChrisV
Considering that you can change the gear ratio and change the acceleration by multiplying torque (4.11 final drive will accelerate quicker than 3.23 final drive in the same car), then YOU tell me what's important.


You were about to sound like one of those old guys, but then you said...
Quote:
Originally Posted by ChrisV
...hp is everything
I appreciate torque, but hp has my heart...too?
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Old 03-29-2007, 07:53 PM   #11
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Quote:
Originally Posted by giant016
If torque is multiplied by gear ratios, and HP is derived from torque, doesn't that make HP dependent on the gears as well?


Nope. Torque is multiplied through the gears to the wheels, while hp is not.

Try this little experiment: start your car in first gear from idle. Now try it again in 4th gear. Why does it accelerate quicker in first gear? Why is the top speed in first gear so low?
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Old 03-29-2007, 08:57 PM   #12
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Ok, here is an old man's explanation.

Torque overcomes kinetic energy (objects at rest and all that stuff)

Horse power overcomes friction.

Torque gets you moving. It is needed for the first few seconds of heavy acceleration or major increase in speed. It is what makes those tires burn.

Hp is needed to reach high speed where torque doesn't mean crap-o-la.

A car traveling at 50 mph is still governed by the laws of kinetic energy to a certain extent. that car can still be considered at rest, in terms of drastically increasing it's speed. To increase speed quickly from 50 mph to 75 would be helped by some extra torque. Most cars just don't have that much left at that point.

There is no such thing as which is best. If I want to built a car that races 30 feet, then give me torque. If You want to go 250 mph, you better have lots of Hp.

Here is an example.

Two men, 1 weights 100lbs, the other weights 250.
Now they both are 1 people power/hp.
Which one do you think would pick up a 50 pound weight the easiest?
The big one has more mass/torque, getting that 50 pounds to move from a dead rest is easy for him.
The little guy can probably run faster because of less mass. (better power to weight ratio)

Check out kinetic energy.
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Old 03-29-2007, 11:07 PM   #13
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Why does this old chestnut keep raising it's head? There must be something sadly lacking in the school system that people can't come to terms with basic physics. Dredge the internet and you'll find posts that stroke governs torque output of an engine. That power is derived from torque. That torque discovered the New World.

Torque is simply a crossproduct of two vectors, nothing more nothing less, etch it into your brain and don't confuse units of measure. The basic equation when talking engines is Nm = watts/(2Pi x RPS).

Get back to school, grab that little wooden train, string and weight and redo the year 8 experiment again, but this time learn the principle.

If I bragged to you "my engine has 500Nm of torque", it has as much relevence as "I have 400kW of power". Both are nonsensical statements. But if i said I have 500Nm at xyz revs, then you would be able to get an idea of the power delivery characteristic, engine efficiency, etc.
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Old 03-30-2007, 02:41 AM   #14
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Quote:
Originally Posted by ChrisV
Nope. Torque is multiplied through the gears to the wheels, while hp is not.

Try this little experiment: start your car in first gear from idle. Now try it again in 4th gear. Why does it accelerate quicker in first gear? Why is the top speed in first gear so low?
I understand what you're saying, but if gears can increase torque, than according to the equation: HP=TORQUE * RPM / 5252, the HP will increase when the torque does. Unless maybe the gears are making the peak torque at a lower RPM.

Side question, what is the term for gears that increase torque but make you lose top speed? I know the ratio is higher (3.23 vs 4.10 for example), but don't think anybody calls them higher gears.
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Old 03-30-2007, 03:27 AM   #15
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Quote:
Originally Posted by giant016
I understand what you're saying, but if gears can increase torque, than according to the equation: HP=TORQUE * RPM / 5252, the HP will increase when the torque does. Unless maybe the gears are making the peak torque at a lower RPM.
He's talking about using gearing to increase the torque at the wheels.
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