BHP and Torque
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What is Horsepower?
Power is the creation of mechanical energy. Horsepower was a term that first came about as a measurement for judging the relative power of various methods of lifting coal from a mine. An engineer called James Watt established a unit to compare work rates against that of a work horse. The unit was fixed at 33,000 foot pounds of work in one minute, whilst not the most scientific or useful measurement it stuck. Thus giving birth to man's striving to achieve more power in order to achieve greater propulsion and speed.
Measuring Horsepower in an engine
Standard methods of measurement use a Dynamometer (or Dyno). This works by placing an engine under load and measuring it's output and this can be done either directly at the crank or by methods such as a rolling road. Measuring the amount of load that an engine can handle at given engine speeds gives us a torque figure. Torque being a product of power (as below) and can be converted to give us the benchmark power figure.
What is Torque?
Torque is a force that turns, twist or rotates. The spinning crankshaft of the engine thus creates torque. Torque is defined as force multiplied by distance.
Torque and power are related by the following equation.
Power = Torque x RPM / 5252
The above formula varies if the measurement units are not BHP and lb/ft.
Cheekly stolen from dyno-plot...
but i belive its all there
I belive you are correct to a extent that torque gives you better accel and bhp gives you better top speed.. but thats very general
Power is the creation of mechanical energy. Horsepower was a term that first came about as a measurement for judging the relative power of various methods of lifting coal from a mine. An engineer called James Watt established a unit to compare work rates against that of a work horse. The unit was fixed at 33,000 foot pounds of work in one minute, whilst not the most scientific or useful measurement it stuck. Thus giving birth to man's striving to achieve more power in order to achieve greater propulsion and speed.
Measuring Horsepower in an engine
Standard methods of measurement use a Dynamometer (or Dyno). This works by placing an engine under load and measuring it's output and this can be done either directly at the crank or by methods such as a rolling road. Measuring the amount of load that an engine can handle at given engine speeds gives us a torque figure. Torque being a product of power (as below) and can be converted to give us the benchmark power figure.
What is Torque?
Torque is a force that turns, twist or rotates. The spinning crankshaft of the engine thus creates torque. Torque is defined as force multiplied by distance.
Torque and power are related by the following equation.
Power = Torque x RPM / 5252
The above formula varies if the measurement units are not BHP and lb/ft.
Cheekly stolen from dyno-plot...
but i belive its all there
I belive you are correct to a extent that torque gives you better accel and bhp gives you better top speed.. but thats very general
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Ziggy gives a brillitant explanation above so I'll only add a little.Zip said:
Torque = measure of force created by 1 revolution.
BHP = measure of power over time (per seccond I think). This is everything when determining how fast a car is at a given point.
Both change through the engine rev range. A Honda can have a realatively high BHP at 9000 revs, but have a relatively lower BHP at 2000 revs than a family desiel.
If you were to accelerate a car in 2nd gear from tickover (1500 revs) to the red line. The fastest car to get there would may not be the one with the highest listed BHP figure. Fastest would be the one with the greatest area under its dyno printout graph (divided by weight of the car etc etc).
This is why desiels can feel fast in day to day driving.
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BHP is about willy-waving.
There is a point where Torque (in lbs per square foot) matches bhp...I think it's 4,700rpm but don't quote me on that.
Put it this way: I'd rather have an engine with 200bhp and 300lb/ft of torque than one with 300bhp and 200lb/ft of torque.
*n
There is a point where Torque (in lbs per square foot) matches bhp...I think it's 4,700rpm but don't quote me on that.
Put it this way: I'd rather have an engine with 200bhp and 300lb/ft of torque than one with 300bhp and 200lb/ft of torque.
*n
penski said:
I won't because it's 5250rpm, which follows from the equation ZG002 quotes. To show you, here are the power and torque curves for an Impreza STi, then the same with the PPP. Note where the lines cross, and note that the extra power PPP leaves the lines crossing in the same place.
M
penski said:
Nonsense, bhp isnt about willy waving at all. They are both linked and it isnt just one or the other as said many times before.
In your above example the first car will drive pretty much like a diesel and the second a petrol. The first car would make peak power at around 3501 rpm and the second at 7878 rpm. To make the first car any near as fast as the second would need long gears which reduces torque to the wheels.
If you like to pull caravans then yes the first one would be better, for a performance car I'd take the second car everytime.
The problem with quoted torque figures, which means they can get confusing, is that they refer to peak torque. An engine with a turbo (such as a turbo diesel), will have lots of torque, but only in once the turbo kicks in. This means that the lag up to this point causes a performance loss. A flat torque curve is far more importnat than a high maximum torque.
Like bhp measure, the torque measure is simply an indication of an engine's characteristics. They do not go the full way to describing the performance of the engine.
My 2p.
Like bhp measure, the torque measure is simply an indication of an engine's characteristics. They do not go the full way to describing the performance of the engine.
My 2p.
penski said:
If the 300bhp engine has a relatively flat torque curve I'll take that one thanks, it will be much quicker with the appropriate gearing.
Torque by itself is useless, i.e. static torque. You need a combintaion of high torque and high RPM...and that gives you high BHP.
The shape of the torque curve is at least as important as the quantity.
Soldato
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Deffo agree with Penski, nice one quoting Carol Shelby too 
A sorted race car will always have just the right amount of BHP and just the right amount of Torque, but its BHP that sells cars/bikes - its silly, BHP nowadays is all about willy waving.
A sorted race car will always have just the right amount of BHP and just the right amount of Torque, but its BHP that sells cars/bikes - its silly, BHP nowadays is all about willy waving.
My earlier comment was aimed at those who go on about their bhp levels..."I have 280bhp!" "Well I have 298bhp!"
And?
Show me a flat torque curve with a lot of space under it and I'll be more impressed than if you show me an extra 10bhp at 7krpm.
*n
And?
Show me a flat torque curve with a lot of space under it and I'll be more impressed than if you show me an extra 10bhp at 7krpm.
*n
great advice said:Deffo agree with Penski, nice one quoting Carol Shelby too
A sorted race car will always have just the right amount of BHP and just the right amount of Torque, but its BHP that sells cars/bikes - its silly, BHP nowadays is all about willy waving.
So how much torque does an F1 car have compared to BHP ?? Not having a clue myself, but Im willing to bet the BHP figure is huge compared to the torque figure.
Soldato
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Bear said:
They keep that under wraps but i think its about 700bhp and 500/lbs. Torque curve and power delivery will be smooth as a baby;s bum
I never said they have equal amounts but the torque figure is equally as important as the BHP figure when it comes to racing.
