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Quick question came up when I was reading "HowStuffWorks" first, it was clear when talking to some people including my machine Design teacher that TORQUE was the resposible factor when accelerating. Example: Engine with 200Lb-Ft Flat Flat Flat from 0 - 5,000RPM Max torque: 200Lb-ft throught out Max HP: 190HP Selecting any 2 points for comparison: @1,000RPM: 200Lb-ft & 38 HP @5,000RPM: 200Lb-Ft & 190 HP but because TORQUE was SAME for 1K or 5K RPM the acceleration was the SAME for either point 9even thought you have 5x as much HP) Now i read this at the webpage: Quote:
What a graph like this points out is that any engine has a peak horsepower -- an rpm value at which the power available from the engine is at its maximum. An engine also has a peak torque at a specific rpm. You will often see this expressed in a brochure or a review in a magazine as "320 HP @ 6500 rpm, 290 lb-ft torque @ 5000 rpm" (the figures for the 1999 Shelby Series 1). When people say an engine has "lots of low-end torque," what they mean is that the peak torque occurs at a fairly low rpm value, like 2,000 or 3,000 rpm.
Another thing you can see from a car's horsepower curve is the place where the engine has maximum power. When you are trying to accelerate quickly, you want to try to keep the engine close to its maximum horsepower point on the curve. That is why you often downshift to accelerate -- by downshifting, you increase engine rpm, which typically moves you closer to the peak horsepower point on the curve. If you want to "launch" your car from a traffic light, you would typically rev the engine to get the engine right at its peak horsepower rpm and then release the clutch to dump maximum power to the tires.
Basically, they are saying the MAX ACCEl is achieved at MAX HP and NOT at MAX TORQUE
please give ur opnion.
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"Absolut Rara."
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horsepower is a derived unit, and cannot be directly measured. Horsepower is a basically torque over time, or in the case of an engine torque and engine speed. So to say anyhting about horsepower, you are indirectly referring to torque anyway.
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Originally posted by Rara:
horsepower is a derived unit, and cannot be directly measured. Horsepower is a basically torque over time, or in the case of an engine torque and engine speed. So to say anyhting about horsepower, you are indirectly referring to torque anyway.
Wel... that is clear, but you are not helping because YOU CAN HAVE MAX TORQUE AT SOME POINT AND MAX HP AT ANOTHER.
And when you have this situation (which happens on 90% of the cars) which one is more important ??
And that's how I am proposing the question: shouldn't TORQUE be the one dictating acceleration ???
At the example given, will the car have the same boost @ 1,000 or 5,000RPM or not ????
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All I can say is this: Torque is measured in ft/lbs which is basically how many newtons are exerted on an object over a given distance. Simply put, torque is the force behind a moving object. As for when horsepower comes into play, I'm not sure. I'd think that torque is the most important factor in acceleration. But I'm not completely sure and sorta 
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"Absolut Rara."
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Originally posted by BBorges:
Wel... that is clear, but you are not helping because YOU CAN HAVE MAX TORQUE AT SOME POINT AND MAX HP AT ANOTHER.
And you're not helping BECAUSE YOU CAN'T HAVE HP WITHOUT TQ.
This question is way too simplistic to have a definitive answer, it depends on gearing, vehicle weight, and most importantly the area under the curve.
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Originally posted by Rara:
Originally posted by BBorges:
Wel... that is clear, but you are not helping because YOU CAN HAVE MAX TORQUE AT SOME POINT AND MAX HP AT ANOTHER.
And you're not helping BECAUSE YOU CAN'T HAVE HP WITHOUT TQ.
This question is way too simplistic to have a definitive answer, it depends on gearing, vehicle weight, and most importantly the area under the curve.
No, it is not too simplistic.
It is a conceptual problem.
let's forget about gearing and weight.
All I would like to confirm is at point of the T/HP the engine will accelerate more:
at Max TORQUE or at MAX HP ???
I always thought the TORQUE was the main factor (and then you said they are related, yes they are, BUT the PEAKS occurs at diff RPMs, right?) and that is causing the confusing part.
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Okay, Acceleration from a Dead stop, or acceleration from a certain speed? Gearing DOES come into play. Take for instance a 320hp LS1 F-Body vs. a 320hp 4.6 Cobra. Stock vs Stock, the Cobra will lose because the gearing is too tall for the ammount (or lack there) of torque produced. Throw in some 4.30's or better yet 4.56's and the Cobra will be right with the F-Body through the 1/4 mile. What did the gear change do?? Increase Torque multiplication to the rear wheels, thus increasing acceleration. Torque will get you off the line, Horsepower will give you the speed. The Mustang might not Trap any better with the gears, but it will be quicker off the line (better torque multiplication) and when shifts are made the RPMs drop less keeping it closer to peak Horsepower after the initial acceleration. Did I make any sense?? Because I just rambled... 
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i was kinda confused about this too. my brothers dodge ram turbo diesel has alot more torque then my contour. compared to the tq/weight ratio but yet his car accelerates slower.
what gives this is relaly confusing.
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Good webpage explaining HP, torque, acceleration, and top speed It'll do a lot better job explaining it than I can. Might wanna read it more than once...it is fairly physics heavy. Enjoy! 
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Bear in mind torque has no movement. If you put 100 lbs of force on a 1 ft. wrench, you have 100 ft/lbs of torque even if the wrench doesn't move.
HP adds in the idea of torque and "speed". You can have torque without movement (Force) but no HP because of no movement. As soon as you start moving the wrench with your 100 ft/lbs of torque, you now develop HP. The faster you turn with that wrench with the 100 FT/lbs, the more HP you are developing. SO, peak HP is the point where the AVAILABLE torque from the engine (Which varies because of too many things to go into) and the speed the engine is turning is optimum.
The confusion is from the way torque and HP develop in a recip. gas engine. An electric motor has max torque at stall (Steam Engines Too). As RPM increases, Torque drops but HP goes up. Electric motor have a more linear HP/Torque curve that is a little easier to understand.
The reason your car slows down up a hill is the torque isn't great enough to maintain the force necessary to maintain the speed (hp). As the car/engine slows, HP drops, but torque increases (if your engine RPM is above torque peak). If the torque increases enough , you maintain the new, lower speed (less HP). If you are below the torque peak, you continue to slow down unless you downshift to get above the required torque level.
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