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The BarTender
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I thought I would start a debate on this topic of Horsepower Vs. Torque to generate some much needed information for the site. We have allot of racers, vendors, and members who hold allot of knowlege. Let's hear what you have to say about it! We all know the little 281's are in much need of tourque and the Eaton/KB combo's help tremedously along with N20 and Turbo's, but the centrifugals don't measure up in the torque department. So what will ultimately make your car faster on the street and the track, Is it horsepower or torque?

Razor.
 

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For street driving it's area under the curve of torque versus RPM. Broad, wide curve works best. For drag strip, assuming your gearing matches, peak torque at higher RPM is more useful, which also translates to high HP.
 

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Tq for getting the heavy car moving, once its rolling at speed higher Hp will make the mph needed
 

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Since Horsepower is a direct calculation derived from Peak TQ and the RPMs at which peak tq occurs, I'll have to say that Torque is far more important.

The real question is, what type of torque curve is better. A flat curve(ie: KB 03s), or one that builds to a high peak(ie: Centrifugal powered DOHCs).
 

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The BarTender
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Discussion Starter · #5 ·
hj16 said:
Since Horsepower is a direct calculation derived from Peak TQ and the RPMs at which peak tq occurs, I'll have to say that Torque is far more important.

The real question is, what type of torque curve is better. A flat curve(ie: KB 03s), or one that builds to a high peak(ie: Centrifugal powered DOHCs).
Ah yes, Exactly what I want to know!

Razor.
 

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TORQUE

TORQUE MOVES THE VEHICLE--HORSEPOWER IS JUST A CALCULATION OF OF TORQUE.

THE MORE AREA UNDER THE TORQUE CURVE THE FASTER THE CAR.

A CAR WITH A PEAK TORQUE OF SAY 500 FT LBS AT 4000 RPM AND THEN DROPS WILL NOT BE AS FAST AS A CAR WITH A FLAT TORQUE CURVE OF SAY 475 FT LBS ACROSS THE BOARD.

JUST SOME INFO
JOE
 

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akatherazor4 said:
Ah yes, Exactly what I want to know!

Razor.
Well, it depends on the shift points. If your RPMs only drop down to 5000 then its obvious that a higher peaking torque curve will be more benificial. You want to the RPMs to fall relatively close to your peak torque. If your RPMs fall down to 4000 then a lower peaking/flat curve will work better.
 

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What is important is torque at the rear wheels. What allows torque at the rear wheels to be maximized is horsepower.

For example, if both cars had a flat torque curve, car A has 400 ft lbs up to redline of 3000 RPM, and car B has 400 ft lbs up to redline of 6000 RPM, which would you rather have?

To keep the math simple imagine the both have the same gears in the transmission and rear, When Car A gets to redline, he has to shift, If both cars are '03's, up until the shift, they both had 2.66 x 3.55 x 400=3777 ft lbs at the rear axle.
Now Car A has shifted into second gear and has less overall gear multiplication. He now has 1.78 x 3.55 x 400= 2527 ft lbs at the rear wheels. Car B is still in first for another 3000 RPM! and still has 3777 ft lbs at the rear wheels! Which means car A is getting slaughtered.

The HP number accounts for this, and is what is important.

JT
 

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TORQUE

TORQUE IS WHAT MAKES THE CAR GO---NOT HORSEPOWER

A TORQUE CURVE THAT LOOKS LIKE A STEEP MOUNTAIN---WHICH IS PEAK TORQUE AT THE TOP OF THE MOUNTAIN IS NOT AS GOOD AS A TORQUE CURVE THAT IS FLAT LIKE THE LAND--STRAIGHT ACROSS--IT IS PROVEN EVERYDAY AT THE TRACK---

HORSE POWER IS A CALCULATION OFF OF TORQUE

JOE
 

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Yes, horsepower is calculated from torque. The reason the HP is calculated and used for comparison is that a torque number by itself, doesn't mean anything. I can put out 400 ft lbs of torque, or 800 ft lbs or 2000 ft lbs, just give me a long enough wrench. Torque can always be traded for speed. Put a 10 ft breaker bar on a wrench, and it is no problem to generate torque, although it will take a long time to swing the end of the 10 ft wrench. Torque can be multiplied through mechanical advantage, i.e. longer lever arms, gears, different sprockets. Power does not get multiplied, or divided through mechanical advantage. Some power is transformed into heat (inefficiencies) but it is not "lost".

That is why the power number is, even though it is calculated, is what is important. It tells how much torque you can get to the wheels at speed. Mathematically it is RPM x Torque, and is the representation of how fast the engine can produce torque. Diesel engines put out much more torque than a similar sized NA gas engine They are not real popular for racing because the can't produce the torque "fast enough".

The HP number allows engines with different shaped torque curves to be directly compared.
That is with reasonable gearing appropriate for each engines torque curve, the higher HP engine will always be faster than a higher torque engine, because it will on be able to turn faster and still have more reduction to generate more torque at the drive wheels.

Take an extreme example to illustrate why the torque number is meaningless. Compare in the same car with two different engines, an engine that puts out 50 ft lbs of torque and an engine that puts out 500 ft lbs. Say we are going to race the cars for a given distance with a 1 speed transmission. Which engine will be faster?

Hmmm, can't say right?

Lets say the 50 ft lb engine puts out it's 50 ft lbs to 10000 RPM, and the 500 ft lb engine puts out it's 500 ft lbs to 1000 RPM. Now we are getting somewhere, because before, with out knowing the speeds at which the engines produce those numbers, we don't know how much power they can produce, which tells what gearing they can support in the race to distance without hitting redline.

Now, for the 50 ft lb engine we put in 20:1 rear gears and when we run it on our racetrack we just get to 10,000 RPM right at the finish line. Everything looks good; the gears maximize the potential of the car as it sits for this combination.

Now we put in our 500 ft lb engine, and leave the gears the same. Now the engine redlines about a tenth of the way down the track, the 20:1 rear is no good. We look at the first combination and we know to go the same speed with 1/10 the reline we need 1/10 the gears, right? So replace the 20:1 rear with a 2:1 rear. Now the car will run the same, because both cars have the same HP (RPM x T)/2525 in both cases. They also have the same torque at the rear wheels (50 x 20= 500 x 2). So what number told the tale, the torque numbers, which varied by a factor of 10, or the HP number, which is the same?

In order to not have to calculate rear wheel torque every time you want to compare two cars, or even the same car, you can just look at the calculated HP number. The HP number tells the whole story.

JT
 

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on a street car with a real street tire on it, i personally would rather trade some unusable low end torque for some usable mid to upper end horsepower. the reason i say this is due to traction limitations on the street. what good is it to have an over abundance of torque if you can't hook it. why not trade some of the excess torque for more useable horsepower.
 

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Speed is the answer :)
 

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Just playing. All is true . but the real answer is ----deponds on the car , and weight :) Gear . tire. aerodynamic, ect.
peace
 

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pete,

how have you been? are you still selling kb blower? a friend of mine may be in the market to by 2 or 3 of them for different applications.
 

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Super .......... Just call nitro
staying busy here .
dont have much time for the net . But I will try here and there.
 
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