mart360

Clarkson describe torque as an item akin to bhp???

Quote"

it has 280 torques under the hood

Unquote"

erm it dosent ,


why cant he just explain it laymans terms rather than make it sound like bhp, of which, we know it isnt!!


Mart

GaryCat

BHP = Torque (lbft) x RPM
-------------------
5252


So... I would say, torque is very akin to bhp.

mart360

yes torgue is akin to bhp, but its not like individual hp

ie a 420 bhp engine has the brake horse power = to 420 horses,

it dosent have 420 torques,, it has a torque value, derived from one motion,

**
laymans term


torque is best described as a twisting action, akin to twisting a tea towel as tight as possible,

***

the way clarkson describes it, is there are 420 of these torques happening at once, when in fact its a sum action

(i think )

MArt

Turbohot

<nods>

sherlock

iTrader: (1)

I think he said on one of the top gear shows, that he could not explain what it was and it's just him ......being him. I think

Sherlock

NotoriousREV

But having "420 horses" is also a sum action

rgv_stu

clarkson = tosser

plain and simple

ALi-B

iTrader: (1)

I know that 600lb/ft with 450bhp is much more "interesting" than 600bhp with 450lb/ft on the road.
On the race track - its the other way round.

bhp is outright oomph, torque is the kick in the back when you plant it the throttle (ok that might be response). That's the best I can do to explain it

GaryCat

Here's a full explanation from the Honda CRX group I'm on....

The first thing to remember is that BHP is not measured on a dyno - only torque, BHP is a factor of torque and engine speed - its just a theoretical calculation!

First, power, what do we mean by that?

Well, we usually express power in terms of the amount of time it takes to do a certain amount of work... for example, one horsepower is measured as the amount of work required to lift 33,000 lbs over 1 foot in 1 minute (huh -that's obvious, ). As this is such an obviously Scottish measurement (as James Watt first devised the calculation) , we have a metric equivalent... the metric horse could lift 4,500Kg a metre in a minute... 98.6% of a good British horse. The Europeans decided to call it a PS (Pferde Starke - German for Horse power!)instead of an HP to cover their shame. Also, in the newfangled metric system, 1hp is the equivalent of 746 Watts of electrical power. So, to recap briefly:

1 HP = Roughly the amount of work a horse can do lifting coal up a mineshaft, assuming his heart was really in it = 1.014 PS = 0.746 KW - easy huh

Now we need a way to measure this output - so we use a defined force or "brake" to see how much energy we need to apply to stop it - Hence "Brake Horsepower" - and is defined as it's maximum performance at a certain rpm.


The other thing we babble on about is Torque... Torque is the amount of force applied to turn something multiplied by the distance from the axis of it's rotation... sounds all weird, until you realise that we use the engine to rotate the front wheel, so torque is something that would be nice to calculate. Something interesting is that 1hp is 550ft/lbs of torque per second.

Now, it's fairly easy to measure torque... this is where the dyno comes in, and we calculate horsepower from an engine's torque output multiplied by the revs...


A dynomometer is just a heavy drum (brake), an accelerometer and a computer... if you know the weight of the drum, and you know how fast it's being accelerated, you can calculate the torque that must be being applied to the drum. What you also want to take into account are the frictional losses on the drum, and the air temperature at the time (which is why you'll see air temperature, pressure and a correction factor calculated by the software... as air temperature goes up, so the effective power output goes down, so the correction factor has to go up to normalise this).

So, to measure torque, we strap the car to the dyno, start it up and run it up in the gears to 3000RPM the dyno operator holds the car at a steady 3000 for 6-7 seconds and the dyno learns the road speed for that car at 3k. ( Some dynos use an inductive loop to accurately measure RPM - but the rev counter method works fine for most modern cars) - now with a given road speed the RPM can be calculated.
... cars tend to do their power runs in 4th gear, as it's the best gear for acceleration at speed and less chance of the wheels slipping, as the calculation errors get smaller the bigger the numbers are. 4th is used because on cars these days 5th gear tend to be a bit of an overdrive.
The throttle is gently floored, and the dyno slowly allows the speed of the engine to increase - this measures the torque of the engine. When the engine reaches maximum RPM, the operator puts the car in neutral, and allows the wheels to decelerate of their own accord - this measures the losses of the transmission,driveshafts,bearings brakes (if they are sticking!) and tyres

Now here comes the maths

BHP = Torque (lbft) x RPM
-------------------
5252

This means that BHP is always equal to torque at 5252rpm - if its not then there is something wrong!

As discussed what we actually measure is torque, expressed in ft/lb, and then we calculate actual horsepower by converting the twisting force of torque into the work units of horsepower.

Visualize a one pound weight, one foot from a fulcrum on an "invisible weightless" bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (pi times a two foot circle), and, we have done 6.2832 foot pounds of work.

OK. Remember Watt? He said that 33,000 foot pounds of work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we've done per revolution of the weight into 33,000 foot pounds, we come up with the fact that we have to rotate that weight at the rate of 5,252 revolutions per minute in order to do 33,000 foot pounds per minute of work, and thus do work at the equivalent rate of one horsepower.
Therefore, the following formula applies for calculating horsepower from a torque measurement:

Horsepower = ( Torque * RPM ) / 5252

Thats where the 5252 comes from


Torque is only half the story. While torque is the force created, it doesn't account for the importance of revs.
Imagine trying to remove a wheel nut from a car with a standard wheelbrace and all the torque you could produce can't loosen the "Kwik fit special" airgunned super tightened wheel bolts. You apply lots of force, i.e. torque, but you still can't generate any rpm. Therefore nothing is accomplished, no power generated despite your cursing and kicking. So - Without rpm, torque is useless!

Two engines may make 125 foot/pounds of torque, but if one is a ford turning at 5,000 rpm and another is a Honda turning at 10,000 rpm, the Honda is doing more work than the ford, therefore generating more power.

HP = Torque x RPM / 5252

so the ford makes 125*5000 / 5252 = 119HP,
but the Honda makes 125*10000 / 5252 = 238HP - must have been an S2000

Brendan Hughes

Maybe he was talking about the complex construction - Torx heads??

harvey

iTrader: (48)

To go back to the original question, Clarkson is just a sometimes entertaining clown and it would be unwise to place much credence on any technical explanation he may give as his talents are obviously of a more frivolous nature.

Chip

Torque is a force that tends to rotate or turn things. You generate a torque any time you apply a force using a wrench. Tightening the lug nuts on your wheels is a good example. When you use a wrench, you apply a force to the handle. This force creates a torque on the nut, which tends to turn the nut.

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 center. In the case of the nuts, if the wrench is a foot long, and you put 200 pounds of force on it, you are generating 200 pound-feet of torque. If you use a 2-foot wrench, you only need to put 100 pounds of force on it to generate the same torque.

A car engine creates torque and uses it to spin the crankshaft. This torque is created exactly the same way.

http://vettenet.org/torquehp.html

Chip

Sticky Stuff

Has everyone missed the point, or just me?

I always thought it was a bit of 'tongue-in-cheek' taking the p1ss out of those anally retentive enough to walk around quoting BHP and torque figures.

davyboy

....or indeed discuss them at length on the internet.

Leslie

BHP is a maeasure of power as a rate. Torque is a measure of the twisting force generated at the flywheel.

Max torque rarely occurs at the same RPM as max BHP.

Les

Peanuts

iTrader: (15)

Les, max torque can only = max bhp if peak occurs at exactly 5250rpm, shirley?

MattN

in fairness to clarkson he also said ...

"" no one actually knows what torque is ""

so you get the impression he's taking the pi55. I'm no expert but I reckon someone on the planet knows how torque is calculated

_Meridian_

iTrader: (1)

Who does that sort of thing then?


M

NotoriousREV

Only if the max torque figure is the same in lb ft as the max power figure is in bhp (i.e. if you had 100bhp@5252 and 100lb/ft@5252). The lines cross at 5252 as this is the constant used when calculating bhp from torque.

Leslie

Thank you Not Rev. The statement I made above was correct.

Who is Shirley?

Les