Which Is Faster - 600hp@6200 or 600hp@7100

[EngineTech1]

Playing the devils advocate here...how is it that there are fast diesel powered trucks then? Does rpm have that much to do with it?

Glad you asked. My example was NA, theres not a diesel in the world as far as know that could do anything without a turbo. In drag racing 4500 RPM will not make any kind of racing TQ converter work without a power adder, the power adder makes the low RPM combo work as always. NA drag racing is about RPM and TQ multiplication and power carry.

NA doesn't change the story. Traction and reaction time aside, drag racing is all about average power to weight. The better your power to weight ratio, provided you can keep it hooked up and apply it, the faster you will run. The vehicle and the tires have no idea how much rpm the engine is turning. They only know how much grip they have, how much the vehicle weighs and how hard the axles are trying to break them loose. Fast diesel trucks make a lot of power and that is why they are fast. It's all about transferring power to the ground.

[EngineTech1]

Geeez, what a bunch of pikers; only 5 pages. Same argument (AGAIN AND AGAIN) took up 93 pages over 5 years here: viewtopic.php?f=15&t=29115&hilit=accele ... start=1365 and more recently another 7 here: viewtopic.php?f=1&t=46939&hilit=acceleration+torque

Hilarious. This topic has come up since the beginning when I joined this board back in 2004. It always attracts the same crazy "power pulses", "RPM wins", "Torque is what accelerates cars", "Gearing multiplies power" etc. type of statements.
Here is one from 2007 that has some way better info in it from a few people.

viewtopic.php?f=1&t=5934

[EngineTech1]

Torque always wins if it makes 600 hp at 6200 it will make much more hp at 7100 than 600. You must reduce torque to limit the 7100 engine to 600 hp so reguardless the average torque must be the same in either engine so if you optimize the car in a lab mathmaticly correct for each engine the outcome should be equal.

So many would be better off if "torque" was erased from the dictionary!
If it was, ALL the race winners and record holders would remain the same.

You dont get it. Without torque you dont have horsepower. What i am saying is with these 2 hypothetical engines the 7100 rpm 600 hp engine makes less torque than the same at 6200 rpm. But if you add the average sum of the lower torque engine's added rpm the over-all average should be the same for both with an insignificant margin of error. As the rpm increases torque doesnt disappear it is just multiplied by the Rpm. So horsepower is not an individual measurement it is married to the torque numbers. I will get flamed for this but her goes. In a way horsepower is just a feel-good calculation based on torque multiplied be rpm

You should get flamed for this. Feel good calculation? Horsepower is a measure of the rate at which work is done.

[user-23911]

It's the measure of the rate of fuel flow.

More fuel flow.......more power.
Less fuel flow.......less power.


All else being the same.

[user-23911]

It's also a measure of the rate of air flow.

[roc]

EngineTech1, what a relief, finally some good sense posts here.

Folks, let me tell ya: on some dynos, it's actually HP that is measured, then torque is consequently calculated. It doesn't matter at all which one is measured and which one is calculated, the order doesn't affect the results.

It's unfortunate that knowledge, education and level headed thinking aren't necessarily priorities nowadays. After all, Seven percent of all American adults believe that chocolate milk comes from brown cows.

[user-23911]

No, doesn't work like that.

On a waterbrake or any other brake dyno...............the load cell measures torque.

If it's an inertia dyno...........it measures the torque from the acceleration of the flywheel of known mass and inertia.


HP is always a calculated number.

[John Wallace]

Try telling a horse he's not real?
He's just a calculation.



Wonder how many RPM's he turns to raise that 33000 pounds 1 foot?

[EngineTech1]

No, doesn't work like that.

On a waterbrake or any other brake dyno...............the load cell measures torque.

If it's an inertia dyno...........it measures the torque from the acceleration of the flywheel of known mass and inertia.


HP is always a calculated number.

HP is a measurement of the rate of work. It can be measured directly with no reference to torque. As a matter of fact when you measure actual power output on certain types of dynos or using accelerometers the torque gets mathematically calculated based on engine rpm. If you don’t have the RPM reference you can still measure the power output, you just won’t have the torque calculation.

What you’re saying is kind of nonsensical.

Try reading this. http://www.madsci.org/posts/archives/20 ... .Eg.r.html

[roc]

No, doesn't work like that.

On a waterbrake or any other brake dyno...............the load cell measures torque.

If it's an inertia dyno...........it measures the torque from the acceleration of the flywheel of known mass and inertia.


HP is always a calculated number.

HP is a measurement of the rate of work. It can be measured directly with no reference to torque. As a matter of fact when you measure actual power output on certain types of dynos or using accelerometers the torque gets mathematically calculated based on engine rpm. If you don’t have the RPM reference you can still measure the power output, you just won’t have the torque calculation.

What you’re saying is kind of nonsensical.

Try reading this. http://www.madsci.org/posts/archives/20 ... .Eg.r.html

X2

... and there are electric dynos that are pretty much a generator, so the horsepower measurement is based on current and voltage (Watts).

[In-Tech]

notshite.JPG

[jacksoni]

Geeez, what a bunch of pikers; only 5 pages. Same argument (AGAIN AND AGAIN) took up 93 pages over 5 years here: viewtopic.php?f=15&t=29115&hilit=accele ... start=1365 and more recently another 7 here: viewtopic.php?f=1&t=46939&hilit=acceleration+torque

Hilarious. This topic has come up since the beginning when I joined this board back in 2004. It always attracts the same crazy "power pulses", "RPM wins", "Torque is what accelerates cars", "Gearing multiplies power" etc. type of statements.
Here is one from 2007 that has some way better info in it from a few people.

viewtopic.php?f=1&t=5934

Hey, now we're up to 22 pages.

[user-23911]

HP is a measurement of the rate of work. It can be measured directly with no reference to torque. As a matter of fact when you measure actual power output on certain types of dynos or using accelerometers the torque gets mathematically calculated based on engine rpm. If you don’t have the RPM reference you can still measure the power output, you just won’t have the torque calculation.

What you’re saying is kind of nonsensical.

Try reading this. http://www.madsci.org/posts/archives/20 ... .Eg.r.html

Who's had a play with a dyno?

How did you calibrate it?
Maybe you don't?

I calibrated ours (waterbrake) by bolting on an arm then loading it up with weights.
That gives a direct reading of torque (from the load cell) and at zero RPM the power is zero.


I've got an inertia dyno at home.
It triggers off the flywheel. That sends one pulse per revolution to the computer.
The flywheel has known (measured) inertia.
What it directly measures is time. It's the change in time interval between revolutions that's directly proportional to the torque applied.
You can measure torque (from the decreasing time interval) but to measure power you need to know the RPM as well and add that to any calculation. You can't calculate the power without calculating torque first.

Electric dynos.......well yes, volts times amps makes power but they make heat too. not very accurate due to not being 100% efficient.
But if you mount it the same as a waterbrake you can add a strain gauge to measure torque and vary the electrical load on the generator.


So what sort of dyno measures power directly?

[EngineTech1]

So what sort of dyno measures power directly?

Inertia dynos, eddy current dynos, chassis dynos. Accelerometers designed to calculate horsepower from measuring acceleration force.

That inertia dyno you mentioned, it measures acceleration of the flywheel (known moment of inertia) and derives power from the rate of acceleration. More power = faster acceleration rate. The torque is just calculated based on the measured power (acceleration) at any given RPM in the sweep.

Chassis dynos can measure the rate of acceleration of the drums and determine the power based on that.

Accelerometers just measure the acceleration forces and determine power based on that.

If you can measure the rate of acceleration of a given mass across a given distance and time you can calculate HP completely independent of torque. Ever notice how 1/4 mile et and speed calculators rely on power and weight for their calculations?

[user-23911]

So you've never calibrated a dyno yourself then?