Hp vs. Torque

[Alastor]

gear ratios effectively multiply your torque...so chalk another one up for torque

Gears are used to multiply torque but nothing is "free". Using gears to increase torque results in a decrease in velocity and conversely an increase in velocity requires a reduction in torque. For example; a 2:1 gear ratio will double your torque but at half the speed. So even though the gears can increase the amount of work being done, the overall rate of work (work per unit time) remains the same (neglecting losses).

Mathematically:

Power = Work / Time

or

Time = Work / Power

Since power is constant we can see that any increase in work (aka Torque) results in an increase in time. Time is a specified interval and must be maintained in that interval to be related with power. The end result is that any increase in work results in a proportional increase in time, and the same power is maintained.

[jcp123]

Gears are used to multiply torque but nothing is "free". Using gears to increase torque results in a decrease in velocity and conversely an increase in velocity requires a reduction in torque. For example; a 2:1 gear ratio will double your torque but at half the speed. So even though the gears can increase the amount of work being done, the overall rate of work (work per unit time) remains the same (neglecting losses).

Mathematically:

Power = Work / Time

or

Time = Work / Power

Since power is constant we can see that any increase in work (aka Torque) results in an increase in time. Time is a specified interval and must be maintained in that interval to be related with power. The end result is that any increase in work results in a proportional increase in time, and the same power is maintained.

this i know. but the end result in terms of the feel of it is a marked increase in torque.

[henk4]

Gears are used to multiply torque but nothing is "free". Using gears to increase torque results in a decrease in velocity and conversely an increase in velocity requires a reduction in torque. For example; a 2:1 gear ratio will double your torque but at half the speed. So even though the gears can increase the amount of work being done, the overall rate of work (work per unit time) remains the same (neglecting losses).

Mathematically:

Power = Work / Time

or

Time = Work / Power

Since power is constant we can see that any increase in work (aka Torque) results in an increase in time. Time is a specified interval and must be maintained in that interval to be related with power. The end result is that any increase in work results in a proportional increase in time, and the same power is maintained.

This is all very well, but the original question was engine related, i.e. short stroke/long stroke and bhp/torque. In which way the result of the engine configuration is translated into speed is only the next step.

[Alastor]

This is all very well, but the original question was engine related, i.e. short stroke/long stroke and bhp/torque. In which way the result of the engine configuration is translated into speed is only the next step.

The original post is asking which is better "power or torque" nothing in regards to the engine configuration.

I was replying to post about the role gear ratios play.

My point was that just because the transmission can significantly increase torque, power is limited by the engine output. So if you multiply the torque on a low power engine you performance increase will be limited to lower road speeds. To benefit from the torque multiplication at higher road speeds requires more power.

In racing the idea is to maximize acceleration at any speed and race cars tend to operate at high speeds so they require large engine power. Furthermore, because applied torque can vary with respect to engine output, power is in this sense a better measure of a vehicles potential performance since it is constant (or the power curve for a range of engine speeds).

[henk4]

The original post is asking which is better "power or torque" nothing in regards to the engine configuration.

power is in this sense a better measure of a vehicles potential performance since it is constant (or the power curve for a range of engine speeds).

You are correct. My point of view in this is that in every day driving you always need torque and very rarely meximum power, and here my favourite, the turbo diesel engine enters into play

[jcp123]

You are correct. My point of view in this is that in every day driving you always need torque and very rarely meximum power, and here my favourite, the turbo diesel engine enters into play

i'll second the motion.

[skoobz]

like what i say, "all the horsepower in the world won't get you anywhere without torque."

[gtrjazz]

If you can get max torque at say 9000rpm it is better than getting the same Torque at 6000rpm you can make use of gearing.

[KnifeEdge_2K1]

If you can get max torque at say 9000rpm it is better than getting the same Torque at 6000rpm you can make use of gearing.

what?
max torque at lower rpms are more useful because that would be more accesible more of the time

high torque at high rpms is the same thing as alot of horsepowerrr

[CdocZ]

ok......i just read everything on this thread at once........my head hurts, but now i really understand alot more

[Slicks]

Im not sure if this has been mentioned yet, but it is ideal to have a long, generally flat torque curve.
Look at the stock numbers of this LS2, notice the torque curve is pretty much the same through the RPM range.

Now look at the torque curve on this particular engine, its a complete joke...

[Matra et Alpine]

Don't let unequal charts confuse you folks.

The REV RANGE of a flat torque is what matters.

So torque from 2000 to 5000 revs on one engine is WORSE than the same torque from 5000 to 10000 revs of another. The first only has 3000 revs of USABLE TORQUE. The latter has 5000 revs os usable torque.

The MORE REVS you have good torque is what matters.
WHERE it occurs is just a gearing and atttide difference.

What an engine does outside of it's usable power and torque is pretty much irrelevant ( Except for those who aren't used to letting an engine 'scream' )

[Slicks]

Don't let unequal charts confuse you folks.

The REV RANGE of a flat torque is what matters.

So torque from 2000 to 5000 revs on one engine is WORSE than the same torque from 5000 to 10000 revs of another. The first only has 3000 revs of USABLE TORQUE. The latter has 5000 revs os usable torque.

The MORE REVS you have good torque is what matters.
WHERE it occurs is just a gearing and atttide difference.

What an engine does outside of it's usable power and torque is pretty much irrelevant ( Except for those who aren't used to letting an engine 'scream' )

oh, so you can read my posts now?

The rev range does matter, and its better if the torque is flat throught the WHOLE rev range, not just at the top.

BTW the charts are just an example, they were not supposed to be "equal."

[Matra et Alpine]

The rev range does matter, and its better if the torque is flat throught the WHOLE rev range, not just at the top.

When an engine runs out of torque, you need to change gears to keep acceleratiing. So a rev range of 3000 revs of peak torque needs more frequent gear changes than an engine with 50000 revs of peak torque. It's failrly clear and cimple arithmetic.

BTW the charts are just an example, they were not supposed to be "equal."

You said "Now look at the torque curve on this particular engine, its a complete joke...", so you did the comparison, slicks.

I only added the comment so those tryign to understand hp and torque and enjoying this thread got the whoel picture and tempered bias.

IF, you had pointed out the peak torque was lower, it woudl have had some relevance. Just trying to keep things so folks understand all the ramifications.

[SlickHolden]

Isn't torque over rated.
Here we have some Cars built that have had more torque and HP about 100kg more weight and th car which is 100kg less in weight and less in torque and down 25kw is faster, Now that same car which is down on HP and torque has also beat in times a car with 55kw more power,
The cars i'm talking about are 2002 Holden VY Commodore SS 235kw 1700kg+.
2002 Ford BA XR8 260kw 1800kg+ and 2003 FPV GT 290kw 1850kg+