Professur

http://www.hotrod.com/techarticles/h...sepower_guide/

Easily the best article on the subject I've seen .. and an important one for Olds guys give how much more torque Olds blocks make compared to their chebby siblings. A little math heavy, but it's pretty well spelled out.

Koda

Decent article. I wish they'd actually talk to engineers too. People who build engines do know a whole lot, but basic industry standards are gotten wrong. For instance, people say torque and horsepower. Why? Torque is a force. Horsepower is a UNIT of power, You should say "Torque and Power" or "lbs (force)* ft and "ft * lbs (force)*ft /min" or horsepower. Units and quantities are not the same thing.

Edit: So you can say "I have 500 lbs (force)*ft of torque and 700 horsepower of power." Redundant, but equivalent. Also, lbs (force) does not equal lbs (mass) but that's another discussion entirely.

A basic touching on how force, work, energy, and power function would be good, as well as discussing what the "area under the curve" is actually called (integral).

It's power that moves the car. Application of energy over a period of time. Always has been, always will be. No hot rodding required; it's physics. The problem is the components of the equation, whether you have the high rpm or the high torque, and the answer to what you want to maximize is always dependent on the application.

And nobody talked about gearing either.

Tony72Cutlass'S'

I calibrated the torque/power curve of my cutlass using a butt dyno.

I also did a wheel alignment using a couple pop cans (full) and some string.

oldcutlass

Can't argue with the accuracy of the Butt Dyno, a finely tuned measuring instrument.

Professur

The butt hole gyro is also the superior tool for calculating handling and cornering builds.

Seff

Right up there with the 'tight enough' Three-Finger Torque Meter.

EDIT: To be on topic, it simply comes down to simple physics. Horsepower is torque times RPMs. Torque is force times distance. Distance is the crank offset. Force is the power applied to the piston by the combustion of fuel and air.

Following this logic, torque should be a constant, and horsepower should be a mere calculation. The reason it isn't is because it's partly comprised of a very variable factor, namely the supply of air and fuel into the combustion chamber. This supply varies with intake design, valve sizes, etc. Typically a smallish intake runner will make for an engine with a lot of low end torque, at the cost of high-end horsepower. At low RPM the runner will fill and 'backlog' with fuel and air (due to the venturi effect), which in turn will be forced into the combustion chamber. Once the RPMs increase, though, the engine will be starving for fuel and air due to the small runners not being able to supply the needed amounts, hurting torque and in turn hurting horsepower. On the other hand, large runners will have the opposite effect.

Please correct me if I'm wrong.

BlackGold

I wish you had said instead:
Typically a smallish intake runner will make for an engine with a lot of low end torque, at the cost of high-end torque.

People talk about torque and horsepower as if they're two different things -- as if at low RPM torque is all that matters, while at high RPM horsepower is all that matters. Your engine produces a torque curve, period. That curve includes torque (on the y axis) and RPM (on the x axis). When you do the math you come up with the horsepower curve.

Who cares what the peak horsepower OR peak torque is?! What really matters is the entire curve -- how broad that "peak" is and over what RPM range it falls. And then how the rest of your drivetrain is build to take advantage of it.

Seff

...That was a test, to see if you were paying attention.
>.>
<.<

Tony72Cutlass'S'

Yo man,

Do you have a spare tire I can borrow? I popped two tires on the cutlass tonight and I only have one spare...

I managed to get the car partway home but I've completely lost air in two tires.

Octania

To avoid confusion in the U.S. measurement system, the unit of measure for torque is the pound-foot (lb-ft), while for work it is the foot-pound (ft-lb).
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FAIL. Confusion still reigns.
Most of us, even those of us trained in math and engineering, still refer to foot-pounds when using a torque wrench. I don't think even Snap-on shows a readout in pounds-foot, er, pound feet, uhm, pounds-feet??? Pounds-foot? How many need to be plural?


Suppose it takes a constant 100 lb-ft of torque to spin a nut onto a bolt one complete revolution.
======================
That's one hell of a Nylock if it takes 100 ft-lbs just to run it down the stud.
And, yes, I said FOOT POUNDS.

11307

tru-blue 442

Also works well on the calibration of all drum brakes.

Koda

That's true. Work is not really used in any practical sense.