Torque vs. Horsepower

torque is real. measurement of a force....hp is a calculated unit of work in other words you can have hp without torque. **** good spread sheet too. can't argue with numbers.

You buy horsepower, you drive torque.

Torque is why I love my v-twin!

httc84, just the way you said that makes me think you didn't look at the spreadsheet linked.

I did, and checked it again.

What I'm saying is prevelant in cars and in-line 4's. Sure you've got great horsepower numbers, but they all occur at the upper end. VTECs are a great example of that. Most people look at this one number as the "performance indicator."

The real day-to-day performance is in the torque curve. If the curve is high early and flat, the day-to-day performance is - IMHO - better. You don't have to run around town at 10K just to keep the engine in it's "power band."

Your spread sheet is the other alternative. You can gear a high revving engine to provide good daily performance. The gear spacing is so close, you have to shift more frequently. This too becomes a chore.

To put it plainly, at one point I owned a 924 and the ex had a del sol. Both had similar horsepower numbers. The 924 had a flatter torque curve. The 924 had more "grunt". The del sol would perform, but you had to get RPM up and keep it up.

Clear as mud?

OK, let's try this another way:

You have two similar engines: Both make peak torque at 5000 rpm. Engine A makes peak horsepower at 7000 rpm and Engine B makes a higher peak horsepower at 9000 rpm.

Driveability of both engines is similar as the lower parts of the torque curve are close. Performance of B is better.

You would have to take both to the drag strip. Engine A would be forced to shift earlier to maintain acceleration as torque falls off more rapidly past 5000 rpm. Engine B would hold each gear longer and maintain acceleration longer resulting in reduced ETA's. This is indicated by a higher peak hp at 9000 rpm meaning a higher torque available.

Around town, you would have to exceed 5K to experience the postive effects of greater horsepower.

andyauger said:

I figured you folks should be equally miserable,

Click to expand...

haha, that is awesome andy

andyauger said:

It's a beautiful day and I'm stuck off the bike with a bad cold. I figured you folks should be equally miserable, so I decided to send this link.

http://spreadsheets.google.com/ccc?key=pBCH2ClzmrpkZ6JigLdoxHA&hl=en#

The torque vs. horsepower debate is a common one. I think this simple sheet should clarify the issue.

Click to expand...

All that spread sheet does is explain why you accelerate faster in a lower gear. It does nothing to explain what horsepower means or the "horsepower vs torque" debate (which is a meaningless and pointless debate in my opinion).

When you understand the math and physics behind the two, you can explain it all you want to the horsepower and torque believers, but generally, they're too stubborn to understand.

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Uncalled for ...

httc84, hit the nail on the head!

MotoFusion, I didn't intend to explain HP and torque all that rigorously. What the spreadsheet shows is that with a given amount of HP at the rear wheel the acceleration varies widely. It shows that HP is not related to the rate of acceleration. If it were, then there should be a difference in the HP numbers as the acceleration rate changes.

So if the argument is that HP is what accelerates the vehicle, the problem is to explain why the rear wheel horsepower will always equal the engine horsepower, even in different gears.

Wait, I thought rear wheel hp never equaled engine hp due to driveline inefficiency?

what debate is there? they are two different thing...

andyauger said:

So if the argument is that HP is what accelerates the vehicle, the problem is to explain why the rear wheel horsepower will always equal the engine horsepower, even in different gears.

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This is where the confusion lies. People who don't have an understanding of the two measurements (torque and horsepower) argue against each other without really understanding either.

There's no question that applied torque is what is responsible for the instantaneous acceleration. However, the major confusion here is the instantaneous acceleration vs acceleration over a period of time. Torque has no measurement of time figured in where horsepower does.

For example...

Two rowers in separate canoes: they each can apply the same amount of torque. When they paddle once, the canoes (assuming they are equal) accelerate to the same speed. This is an example of an applied force/torque.

Now imagine the the two rowers apply equally powerful paddle strokes, but one applies them more often. Which one will experience the most acceleration over a period of time? Now you've added the element of time. This is an extremely simple example of horsepower.

Dear God in heaven Andy, not this drivel again!!

MotoFusion said:

For example...

Two rowers in separate canoes: they each can apply the same amount of torque. When they paddle once, the canoes (assuming they are equal) accelerate to the same speed. This is an example of an applied force/torque.

Now imagine the the two rowers apply equally powerful paddle strokes, but one applies them more often. Which one will experience the most acceleration over a period of time? Now you've added the element of time. This is an extremely simple example of horsepower.

Click to expand...

my example would be different

2 canoes, same size, but one has bigger paddles, the other paddles faster

the one with bigger paddles will accelerate faster to its top speed even thouugh the one with smaller paddles might paddle fast enuf to eventually attain a faster speed (more horsepower, less torque)

First, I didn't include friction because I wanted to demonstrate the ideal case. Second, friction would affect both quantities. Friction reduces usable torque, HP is calculated from that torque.

The examples are a bit wonky, folks. To go from HP to change in speed you must convert from HP back to force first. Even the differential solution removes the time factor, and has the relevant conversion factors in it.

Just like in the linked spreadsheet. Your horsepower is 47.6, your weight is 650 pounds, drive wheel radius is 12". What's your rate of acceleration? Now you need the RPM of the rear wheel. Now your units don't work out and (2XPi) begins to look like a usable factor and then........

RandyO said:

my example would be different

2 canoes, same size, but one has bigger paddles, the other paddles faster

the one with bigger paddles will accelerate faster to its top speed even thouugh the one with smaller paddles might paddle fast enuf to eventually attain a faster speed (more horsepower, less torque)

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Randy,

That's not a good analogy for bikes or cars. A bike with more HP will accelerate harder, even if it has less torque. That's why 600cc I-4s accelerate harder at every speed than the SV650, even though their torque is no higher.

RandyO said:

my example would be different

2 canoes, same size, but one has bigger paddles, the other paddles faster

the one with bigger paddles will accelerate faster to its top speed even thouugh the one with smaller paddles might paddle fast enuf to eventually attain a faster speed (more horsepower, less torque)

Click to expand...

You changed two variables at once, so it's not possible to come to that conclusion conceptually.

On each stroke, the canoe with the bigger paddles will experience a higher acceleration than the smaller paddled canoe, however, you cannot come to the conclusion that one canoe or the other will experience a greater total acceleration over a period of time (multiple strokes) without quantifying the variables.

If you're racing, theres absolutely no friggin reason you should ever be outside of your powerband.... reguardless if your power exists between 10k and 12k, or 4k and 6k. And if you are outside of your powerband, you need more training.

Torque is just a representation of the combustion energy thats transfered to the drivetrain... The only way to go faster is to either increase the combustion energy(displacement/# of cyl's), or increase the number of times it happens per second. As long as your head can handle the increased flow, there will always be more power up top.

So that raises the question... which is more efficient?? Consuming mass amounts of energy at low intervals, or consuming less energy at greater intervals... My personal experiences tells me the latter is better for countless reasons.

torque doesn't win races... the available traction does... and 500 lbs of torque at 3k rpm will never be transfered to the ground.

/end rant on ppl attacking high revving engines

RichDesmond said:

Randy,

That's not a good analogy for bikes or cars. A bike with more HP will accelerate harder, even if it has less torque. That's why 600cc I-4s accelerate harder at every speed than the SV650, even though their torque is no higher.

Click to expand...

its only cause the way are geared, torque they put to the rear wheel is higher even though the engine may be putting out less torque

at you can see from the chart andy linked to, maximum torque is made possible by gearing regardless what the actual engine torque numbers are