hi, is there a relationiship between the two in terms of some kinda equation? i.e. if you increase the bhp by 20, does the torque go up by a certain amount? i've tried searching google and the forum for something like this but no clue.

For a given torque, the equivalent power may be calculated. The standard equation relating torque in foot-pounds, rotational speed in RPM and horsepower is:

P [ {\rm hp}] = {[\Tau / ({\rm ft \cdot lbf})] [\omega / ({\rm r/min})] \over 5252}

Where P is power, τ is torque, and ω is rotations per minute. Outside the United States, most countries use the newton meter as the unit of torque. Most automobile specifications worldwide have torque listed in newton meters. The standard equation relating torque in newton meters, rotational speed in RPM and power in kilowatts is:

P [ {\rm kW}] = {[\Tau / ({\rm N \cdot m })] [\omega / ({\rm r/min})] \over 9549}

These are based on Watt's definition of the mechanical horsepower. The constants 5252 and 9549 are rounded.

5252 comes from (33,000 ft·lbf/min)/(2π rad/rev),

and 9549 comes from (60 s/min)(1000 W/kW)/(2π rad/rev).

Source.

Put very simply, torque is how much twisting force an engine produces. You get more power if it can carry on producing lots of torque and still rev fast.

For a given torque, the equivalent power may be calculated. The standard equation relating torque in foot-pounds, rotational speed in RPM and horsepower is:

P [ {\rm hp}] = {[\Tau / ({\rm ft \cdot lbf})] [\omega / ({\rm r/min})] \over 5252}

Where P is power, τ is torque, and ω is rotations per minute. Outside the United States, most countries use the newton meter as the unit of torque. Most automobile specifications worldwide have torque listed in newton meters. The standard equation relating torque in newton meters, rotational speed in RPM and power in kilowatts is:

P [ {\rm kW}] = {[\Tau / ({\rm N \cdot m })] [\omega / ({\rm r/min})] \over 9549}

These are based on Watt's definition of the mechanical horsepower. The constants 5252 and 9549 are rounded.

5252 comes from (33,000 ft·lbf/min)/(2π rad/rev),

and 9549 comes from (60 s/min)(1000 W/kW)/(2π rad/rev).

Source.

or, roughly roughly, hp=( torque*rpm)/5252 where torque is measured in lb.ft

or, roughly roughly, hp=( torque*rpm)/5252 where torque is measured in lb.ft

Which is why on rolling road print outs the power(bhp) and torque(lbft) curves cross at 5252rpm.

Well on good ones they should.

Under steer is when you hit the wall with the front of the car.

Over steer is when you hit the wall with the rear of the car.

Horsepower is how fast you hit the wall.

Torque is how far you take the wall with you.

BHP is a fictional number created by people that drive petrol engined cars to try and say that they are better than diesels when in fact we all know deep down that torque is the only thing that really matters

BHP is a fictional number created by people that drive petrol engined cars to try and say that they are better than diesels when in fact we all know deep down that torque is the only thing that really matters

To give you some idea

A very small (in terms of power) tractor engine peak power of 110hp at 2200rpm and peak torque of 480Nm at about 1500 or 1600rpm...

Put that in a pulling match against a 110hp petrol engine and guess which would win

To give you some idea

A very small (in terms of power) tractor engine peak power of 110hp at 2200rpm and peak torque of 480Nm at about 1500 or 1600rpm...

So what does one of those sod off big 'racing tractor' type things push out then?

So what does one of those sod off big 'racing tractor' type things push out then?

Dunno, but take same engine and put it in a dragster and you have some serious clag!

http://www.cumminsracing.com/

So what does one of those sod off big 'racing tractor' type things push out then?

Well I'm not sure if you meant the proper "tractor racing ones" - in which case I have no clue, but the average tractor you see towing trailer fulls of potatoes will be pushing out around 1254nm @ 1600rpm and 280hp for a range of around 600rpm or so (from 1600rpm to 2200rpm).. see http://www.deere.co.uk/en_GB/products/agriculture/tractors/8030/8030_specs.pdf for more info - and look at the "constant power range"

get your same tractor and race it against the same car over a 1/4 mile and see which wins

a tractor is a tool for a specific job and not an all round vehicle, it might as well be a spanner or hammer.

Under steer is when you hit the wall with the front of the car.

Over steer is when you hit the wall with the rear of the car.

Horsepower is how fast you hit the wall.

Torque is how far you take the wall with you.

Very good explaination but I like this one best-

For a given torque, the equivalent power may be calculated. The standard equation relating torque in foot-pounds, rotational speed in RPM and horsepower is:

P [ {\rm hp}] = {[\Tau / ({\rm ft \cdot lbf})] [\omega / ({\rm r/min})] \over 5252}

Where P is power, τ is torque, and ω is rotations per minute. Outside the United States, most countries use the newton meter as the unit of torque. Most automobile specifications worldwide have torque listed in newton meters. The standard equation relating torque in newton meters, rotational speed in RPM and power in kilowatts is:

P [ {\rm kW}] = {[\Tau / ({\rm N \cdot m })] [\omega / ({\rm r/min})] \over 9549}

These are based on Watt's definition of the mechanical horsepower. The constants 5252 and 9549 are rounded.

5252 comes from (33,000 ft·lbf/min)/(2π rad/rev),

and 9549 comes from (60 s/min)(1000 W/kW)/(2π rad/rev).

Or maybe the other way round.

Torque is for pulling caravans.

get your same tractor and race it against the same car over a 1/4 mile and see which wins

a tractor is a tool for a specific job and not an all round vehicle, it might as well be a spanner or hammer.

Was just trying to explain what torque was. EDIT: ... in relation to power (sorry, missed that bit off)

Edited 22 May, 200917 yr by yegnold

a diesel might well have more torque, but its over a much shorter rev range therefore potentially not as usable as you'll be changing gear more often.

IMO diesel torque makes you feel faster than you are cos it comes in big masive lumps.rather than smooth spread, i believe the new CR engines to be sligtly better though.

Well I'm not sure if you meant the proper "tractor racing ones" -

I meant the big ones you see towing trailers up and down the roads near you .

Was just trying to explain what torque was.

badly

diesel's high torque definitly gaives a huge impression of performance, brothers ibiza cupra feels very fast when booting it about where as swmbo's V6 vectra feels lazy and slow in comparison yet the cupra is every so slightly slower in reality.

The original question was

hi, is there a relationiship between the two in terms of some kinda equation? i.e. if you increase the bhp by 20, does the torque go up by a certain amount? i've tried searching google and the forum for something like this but no clue.

I was showing that large power figures could be achieved at low RPMs if the torque figure was high, using tractor engines as an example...

i may be mis-remembering but i think i was told:

bhp is how much work an engine does

while torque is how quickly it gets it done

but that could have been rubbish to start with and i've may made it worse by forgetting!

i'd say its the other way round myself.

i'd say its the other way round myself.

lol i knew it was those words in some order i just got the most important bit wrong!

Horsepower & Torque

Saw this a while ago, thought it a really good analogy/explanation.

Also, had a mate in the police, and he said they had petrol and diesel Rav4's. He always felt that he was going faster in the diesel ones because he'd feel the torque more and also run for a shorter time in the power band before changing gear. However, he figured that actually his speed at the end of the road from the police station was the same in both, as the petrol ones obviously revved longer.

Anyway, in real life we all know that figures don't matter, my petrol fabia's slower than your diesel ones on torque and hp!

a diesel might well have more torque, but its over a much shorter rev range therefore potentially not as usable as you'll be changing gear more often.

IMO diesel torque makes you feel faster than you are cos it comes in big masive lumps.rather than smooth spread, i believe the new CR engines to be sligtly better though.

I love those posts in threads like this. As a owner of a 2.0T that makes 280bhp+ and having coming from a modified PD130 with 220bhp+ i'd be nervous coming up against my old PD130

Both the 2.0T and PD130 has 6 speeds boxes and to be honest gearchanges were no more than in my PD130. The TDI box is higher ratio and i can practically nearly get the same speed out of each gear as the 2.0T. It's not that simple of narrow powerband

blah blah gear ratios make up for different power bands. BHP for BHP there won't be much difference petrol vs diesel. I know i have had both.

Ok my octy maybe a bit faster but if it had only 220bhp my old TDI would have kicked it's ***.