Torque and Horsepower

[The Scorpion King]

Guys,
anyone can show the differance between the Torque and Horsepower?
and which enginge is better, for example (210 HP @ 5200 RPM or 190 HP @ 4600 RPM)?
and for desert driving what should i use, the more Horsepower or the more Torque?

[Al Marshoudi]

Horsepower is a power measurement & it defines the mechanical preformance of the engine .. While Torque is a Turning force ( came from Work which is directional force ) & it defines the force delevered by the engine ( to flywheel or tires) ..

190 HP @ 4600 RPM engine is fast responding & quite good but with low Power .. 210 HP @ 5200 RPM engine have more BHP but long dead time to release all that Power ..

the higher HP in Lower RPM will be very good offroading car

[Alosh]

i like that

[NaSeR]

Torque is how fast you will reach a good speed, Horsepower how to keep the speed for long time.. usually for dunes and desert drive you will need more low-end-torque. So it seems the second one will give you more power at low RPM which I would prefer for the desert.. the first one might be good for the highway.

[sandmonkey]

In simple terms I would say Torque determines the accelaration while Horsepower has more of a role to play in the speed the vehicle is capable of achieving... And both play an imprtant role. The best example I can give is the Land Rover Defender which is unmatched when it comes to applications like crawling among rocks or in mud, its high torque at low rpms is what makes it possible. But the vehicle also has a small rev band and runs out of breath soon requiring constant gear changes, this makes it unsuitable for climbing big dunes. So while the HP n Torque play a big role, other things like the gear ratios also matter quite a lot.

[Indy]

190 bhp @ 4900 rpm would translate to 294 Nm of torque, and the 210 bhp @ 5200 rpm translates to a torque of 287 Nm. The margin is quite negligible.
It is better to have torque at more RPM than low RPM. In the second case as torque is available across a wider band, gear changes required will be less frequent while maintaining peak torque..which translates to pulling power/climbing ability, etc..
Torque availability across a wider band is preferable.

[sandmonkey]

190 bhp @ 4900 rpm would translate to 294 Nm of torque, and the 210 bhp @ 5200 rpm translates to a torque of 287 Nm. The margin is quite negligible.
It is better to have torque at more RPM than low RPM. In the second case as torque is available across a wider band, gear changes required will be less frequent while maintaining peak torque..which translates to pulling power/climbing ability, etc..
Torque availability across a wider band is preferable.

This is new info... How do you convert thr HP into Torque?? I thought even the weight of the flywheel matters among other things, so how is that accounted for?

[caprihorse]

Normal 0 false false false MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0mm 5.4pt 0mm 5.4pt; mso-para-margin:0mm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} This is very interesting subject, as there are many rumours going around, as “What is better? High torque or high horse power?”

Actually the answer is in the physics, what we learned about in the 7th grade from Mr. Isaac Newton.

Torque is a force that tends to rotate or turn things. Informally, torque can be thought of as "rotational force". Maybe you heard about “torque wrench” and imagine that you try to turn the nut on the wheel on your car by the hand. You need a lot of force and work.

The same applies for automotive engines. If a force is allowed to act through a rotational distance, it is doing mechanical work. English units of torque are pound-inches or pound-feet; the SI unit is the Newton-meter. Notice that the torque units contain a distance and a force. To calculate the torque, you just multiply the force by the distance from the centre.

The formula is:

HP = Torque [lbf-ft] * RPM / 5252

Or

Torque [lbf-ft] = HP * 5252 / RPM (Here you will get the result in lbf-ft, to convert in Nm, multiply it by 1.35)

The constant 5252 is not a house number, but it is just lump of several different conversion factors together into one number, to make the calculation simpler.

Actually HP is calculated from Torque. Torque can be directly measured on special stands called Dynamometer, where the car is tested how an engine or power train performs, in terms of producing power and torque, under a given condition. There is tested the whole range of RPM on the special stand, to measure a torque and establish a performance curve. The car is ‘driving’ on the stand, similar to brakes test machine, with the right octane fuel, tyres and pressure, weight and other significantly influencing parameters.

Horse Power is then calculated at certain RPM to give to a car some specific HP information at certain RPM. That’s why sometimes you read in car’s technical specification Horsepower = 240 @ 6,000 RPM and Torque (lb-ft) = 265 @ 3,200 RPM. Actually these numbers give a little hint about the car performance, until you use the above formula.

Such a testing is done on new engines or when the cars are modified. Actually mods lovers should perform Dynamometer testing before mods application and after mods, just to see how much the car gained or lost of the torque.

Taking your numbers into Excel and making some calculations, to compare the results at same inputs, it comes out that both engines are differing just by 6 Nm, i.m. they are more less the same power.

[caprihorse]

190 bhp @ 4900 rpm would translate to 294 Nm of torque, and the 210 bhp @ 5200 rpm translates to a torque of 287 Nm. The margin is quite negligible.
It is better to have torque at more RPM than low RPM. In the second case as torque is available across a wider band, gear changes required will be less frequent while maintaining peak torque..which translates to pulling power/climbing ability, etc..
Torque availability across a wider band is preferable.

Your calculation is correct, I got exactly the same results. However it is important to understand the torque curve of your car at the given gear. It significantly differs if you are driving first gear or third. The climbing ability is different. On the other hand the acceleration is also important. Normal 0 false false false MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0mm 5.4pt 0mm 5.4pt; mso-para-margin:0mm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising.

[Indy]

Yes Capri, you are right.. assuming both cars are in the same gear, & everything else is the same, a wider torque band seems more preferable.