in lamens terms to simpletons like myself.... the difference between torque and bhp. how they are produced and how they seperately determine performance e.g acceleration, top speed etc...?? im not sure if this is an obvious question or a particularly interesting one for alot of people but hey ho!! it interests me and would appreciate someone taking a minuit to give me a quick run down
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could someone explain.....
- Thread starter matt hartas
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Compare blender motor and tractor motor.
Blender motor can spin a small wheel at ridiculous RPMs. But if you were to grab the wheel between your fingers, it would stop spinning. So while it can spin fast, there's no power behind the spin.
In a tractor, the wheel would spin slooowwww....but try stopping a tractor wheel from turning when the engine is turning it. You'd need a loaded HGV.
So...the tractor engine has heaps of turning power, and the blender motor very little.
Torque = turning power.
For acceleration you want torque to essentially nullify the weight of the car within the boundaries of grip of you tyres on the road.
Loads of torque and loads of capability for the wheel to spin quickly (mix of blender and tractor) would give you wheel spin all day long.
Bhp is more to do with the amount of power tw engine can generate.
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Blender motor can spin a small wheel at ridiculous RPMs. But if you were to grab the wheel between your fingers, it would stop spinning. So while it can spin fast, there's no power behind the spin.
In a tractor, the wheel would spin slooowwww....but try stopping a tractor wheel from turning when the engine is turning it. You'd need a loaded HGV.
So...the tractor engine has heaps of turning power, and the blender motor very little.
Torque = turning power.
For acceleration you want torque to essentially nullify the weight of the car within the boundaries of grip of you tyres on the road.
Loads of torque and loads of capability for the wheel to spin quickly (mix of blender and tractor) would give you wheel spin all day long.
Bhp is more to do with the amount of power tw engine can generate.
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As you can tell there is no short and easy explanation.
Lots of BHP can loooosely translate to high top speed
Lots of torque loosely translates to acceleration...but only if there's enough BHP as well
hehe...
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Lots of BHP can loooosely translate to high top speed
Lots of torque loosely translates to acceleration...but only if there's enough BHP as well
hehe...Sent from my iPhone using Tapatalk
Right mate. I'll try lol.
Torque is the turning force produced by the engine. Imagine trying to hold the flywheel still as the engine is running, the force of the engine turning the flywheel is torque, and is measured in lbs/ft. Torque is the measurment that affects the rate of acceleration of a car.
BHP (horsepower) is a measurement of the amount of work an engine can do over a given time and is the measurement that relates to top speed of a car.
Torque and bhp are directly related to each other too and are also dependent on the rpm of the engine when you measure them.
There is a simple mathmatical formula that links the 2 things (BHP and torque) together that uses the number 5252 (don't ask me why it's that specific number,lol).
The formula for working out the BHP of an engine is: BHP = Torque x RPM ÷ 5252
The formula for working out the torque of an engine is: Torque= 5252x BHP ÷ RPM
A few of examples of 3 ways to get 300BHP for you
Imagine that all these engines are running at their maximum RPM too
1. An engine producing 584lb/ft of torque at 2700rpm would= 300bhp
2. An engine producing 343lb/ft of torque at 4600rpm would= 300bhp
3. An gas turbine engine that can achive 41000rpm! but only produces 38lb/ft of torque would also= 300bhp
So lets say a seat leon needs 300BHP to achive it's top speed, any one of the above engines running at the rpm stated above would have the same 300BHP and could power it to the same speed at their own different maximum RPM's
As you can see from those examples BHP is just a measure of the amount of torque produced and the RPM at which it is produced.
Not sure if that is any help,lol
Torque is the turning force produced by the engine. Imagine trying to hold the flywheel still as the engine is running, the force of the engine turning the flywheel is torque, and is measured in lbs/ft. Torque is the measurment that affects the rate of acceleration of a car.
BHP (horsepower) is a measurement of the amount of work an engine can do over a given time and is the measurement that relates to top speed of a car.
Torque and bhp are directly related to each other too and are also dependent on the rpm of the engine when you measure them.
There is a simple mathmatical formula that links the 2 things (BHP and torque) together that uses the number 5252 (don't ask me why it's that specific number,lol).
The formula for working out the BHP of an engine is: BHP = Torque x RPM ÷ 5252
The formula for working out the torque of an engine is: Torque= 5252x BHP ÷ RPM
A few of examples of 3 ways to get 300BHP for you
Imagine that all these engines are running at their maximum RPM too
1. An engine producing 584lb/ft of torque at 2700rpm would= 300bhp
2. An engine producing 343lb/ft of torque at 4600rpm would= 300bhp
3. An gas turbine engine that can achive 41000rpm! but only produces 38lb/ft of torque would also= 300bhp
So lets say a seat leon needs 300BHP to achive it's top speed, any one of the above engines running at the rpm stated above would have the same 300BHP and could power it to the same speed at their own different maximum RPM's
As you can see from those examples BHP is just a measure of the amount of torque produced and the RPM at which it is produced.
Not sure if that is any help,lol
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That is one of the best explanations I've seen to date. It's far easier to understand the variables once you know the basic theory,
Indeed!!
Good one. Good mix of the science and practical example.
You should teach
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Good one. Good mix of the science and practical example.
You should teach
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Well, you asked for it. I can quote the lecture I usually trot out when the petrol-vs-diesel argument gets around to torque-vs-power in another post, but here's some descriptions of the basic units.
Torque and power are related but are not the same thing. Torque is an instantaneous measurement whereas power is a rate of supplying force over time.
Torque is measured in units such as foot-pounds. A torque of, say, 240 ft-lb is the same as having a 24-pound weight on the end of a 10-foot pole hung off your front axle.
Power is measured in units such as horsepower: 1 HP = 916 foot-pounds per second, which means the standard horse can pull 916 pounds one foot upwards every second.
So if you attached this standard horse to that ten-foot pole (pointing straight up for the purposes of this somewhat unlikely thought-experiment) it would be able to produce a torque of 9160 ft-lb every second.
You may be seeing some relationships here, and you'd be right. Torque and horsepower are related by engine speed, rpm, which is pretty obviously measured in units like "per second".
The relationship is Power(bhp)=Torque(lb-ft) x rpm/5252.
Now it starts to get a bit more complicated.
Torque is a useful measure of what the engine produces because it can be easily visualised as the amount of push given to the piston by the explosion in the combustion chamber. The bang pushes the piston down which pushes the crankshaft round, which is measured as torque. So obviously the size of the bang is directly related to the torque that the engine produces. So a bigger engine produces more torque (bigger combustion chambers) and a turbocharged engine produces more torque than a naturally-aspirated one (more air in the combustion chamber, so more fuel and a bigger bang).
You may have noticed that the engine doesn't just do one bang, it does lots and the thing is spinning round all the time. Various mechanical limitations mean that the engine does not produce the same torque from zero revs upwards; instead the torque changes from almost nothing at very low revs rising to something usable at 1000-2000 rpm then rising further up to the rev limit (where it all falls apart due to valve bounce and other things).
So taking the torque figure at any given rpm, the power *at that rpm* can be calculated by the equation I quoted earlier.
What this means is that your car is not producing the same power all the way through the rev range. The BHP so beloved of car salesmen and petrolheads is the manufacturers quoted max horsepower, and is only produced at max rpm. This has ramifications that we can discuss in another post, if anyone is interested.
Torque and power are related but are not the same thing. Torque is an instantaneous measurement whereas power is a rate of supplying force over time.
Torque is measured in units such as foot-pounds. A torque of, say, 240 ft-lb is the same as having a 24-pound weight on the end of a 10-foot pole hung off your front axle.
Power is measured in units such as horsepower: 1 HP = 916 foot-pounds per second, which means the standard horse can pull 916 pounds one foot upwards every second.
So if you attached this standard horse to that ten-foot pole (pointing straight up for the purposes of this somewhat unlikely thought-experiment) it would be able to produce a torque of 9160 ft-lb every second.
You may be seeing some relationships here, and you'd be right. Torque and horsepower are related by engine speed, rpm, which is pretty obviously measured in units like "per second".
The relationship is Power(bhp)=Torque(lb-ft) x rpm/5252.
Now it starts to get a bit more complicated.
Torque is a useful measure of what the engine produces because it can be easily visualised as the amount of push given to the piston by the explosion in the combustion chamber. The bang pushes the piston down which pushes the crankshaft round, which is measured as torque. So obviously the size of the bang is directly related to the torque that the engine produces. So a bigger engine produces more torque (bigger combustion chambers) and a turbocharged engine produces more torque than a naturally-aspirated one (more air in the combustion chamber, so more fuel and a bigger bang).
You may have noticed that the engine doesn't just do one bang, it does lots and the thing is spinning round all the time. Various mechanical limitations mean that the engine does not produce the same torque from zero revs upwards; instead the torque changes from almost nothing at very low revs rising to something usable at 1000-2000 rpm then rising further up to the rev limit (where it all falls apart due to valve bounce and other things).
So taking the torque figure at any given rpm, the power *at that rpm* can be calculated by the equation I quoted earlier.
What this means is that your car is not producing the same power all the way through the rev range. The BHP so beloved of car salesmen and petrolheads is the manufacturers quoted max horsepower, and is only produced at max rpm. This has ramifications that we can discuss in another post, if anyone is interested.
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power = top speed.
torque = how fast you get there.
however this is a little too simplist..
another way to think of it is to consider a gear box as a torque converter. In that the engine produces the same power in any gear, but the torque being delivered to the wheels increases or decreases depending on the gearing. (ie you accelerate faster in 2nd gear than 5th gear).
Many people forget this, they compare diesels to petrols and think the diesels have massive torque, which to be fair they do, but as they dont rev as high you need a taller gear and so the torquw that might be delivered to the wheels at a set speed may be reduced by the taller gear.
torque = how fast you get there.
however this is a little too simplist..
another way to think of it is to consider a gear box as a torque converter. In that the engine produces the same power in any gear, but the torque being delivered to the wheels increases or decreases depending on the gearing. (ie you accelerate faster in 2nd gear than 5th gear).
Many people forget this, they compare diesels to petrols and think the diesels have massive torque, which to be fair they do, but as they dont rev as high you need a taller gear and so the torquw that might be delivered to the wheels at a set speed may be reduced by the taller gear.
wow cheers guys... will have to read these several times for them to sink in lol but great explanations from all! many thanks
PlymLeon
Guest
Torque is how much turning force the engine has. BHP is a combination of how much turning force the engine has and how many times it can do that force in a set time which is where RPM comes into it.
Its kind of like you can have a lot of force to do something or you can use less force but do it more times to get same result!
Its kind of like you can have a lot of force to do something or you can use less force but do it more times to get same result!
As I've said before (e.g. post #12 in this thread) , torque is how big a bang you can make (in the cylinder), power comes from how soon you can make the next bang.
just to clear one thing up however torque is actually measured in Newton Metres (Nm), lbs/ft is an american/ye olde imperial measurment.
it has been explained very well, the simplest way i think of it is :-
TORQUE - turning/twisting force - when this is related to an engine its how much of a turning force is exerted on the crankshaft (diesel= bigger bang, more torque, petrol= small bang, less torque)
BHP - this is simply a MEASUREMENT OF POWER and is related to torque but dont get the two mixed up - when this is related to an engine/car BHP is the amount of power made available by the engine before and transmission losses happen, ie shafts, hubs, wheels etc
it has been explained very well, the simplest way i think of it is :-
TORQUE - turning/twisting force - when this is related to an engine its how much of a turning force is exerted on the crankshaft (diesel= bigger bang, more torque, petrol= small bang, less torque)
BHP - this is simply a MEASUREMENT OF POWER and is related to torque but dont get the two mixed up - when this is related to an engine/car BHP is the amount of power made available by the engine before and transmission losses happen, ie shafts, hubs, wheels etc
Nm is metric, ft-lb imperial, but everyone can envisage a 24-lb weight, whereas I for one can't visualise a 65 Newton weight, on the end of a 5 meter pole or anywhere else.
Newton-metres and ft-lbs both have the dimensions of ML, mass x length.
Newton-metres and ft-lbs both have the dimensions of ML, mass x length.
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