your engine produces torque and horsepower so what exactly is the
difference between torque and horsepower and which is more
important to understand horsepower and torque we
need to first understand the concept of work and we don't mean your job unless
your job is applying force to something to get it to move
like a mechanic's job in this case you really are working in the scientific
sense the force you use to move something is
measured in pounds a pound of force is equal to the
gravitational force on a mass of one pound on the surface of the earth
work is the force you apply to something to move it
so pounds multiplied by the distance you move it in feet
work is measured in foot pound which can get a bit confusing since the
technically correct measurement for torque is pound
foot foot pound pound foot i guess it might give teachers some fun
cork is a twisting force that's applied at a distance
so take a wrench for example you apply a force on the wrench which becomes
amplified by the distance of the wrench lever
and supplies a torque at whatever you're tightening or loosening
the greater the distance from the axi the greater the torque
think about a door you don't push the door open closer to the hinges because
it's harder the further the distance you are away
from the hinges the easier it is to open the door
so how do we measure torque let's go back to our wrench example
if you apply one pound of force and use a one
foot long wrench this is equal to one pound foot of torque
torque is force multiplied by the distance of the lever
you can apply more torque by applying more force or increasing
the distance from the axi so if you apply
two pounds of force and use a one foot wrench that equals two pound feet of
torque but you could also apply one pound of force and use a two foot
wrench and that would also equal two pound feet of torque let's see
how the supplies in an engine the explosion is created in the
engine this creates a force the force of the
expansion pushes the piston downwards which applies force on the crank pin
that turns the crankshaft so torque is equal to the amount of
force on the pistons multiplied by the distance of that force from the center
axis you can increase the torque by
increasing the force on the pistons created by the explosion
or you can increase the torque by increasing the distance from the center
axis of the crank pin to the center axis of the crankshaft you
can also add gearing somewhere down the system but we won't get into that for
now so that's torque now let's move on to
horsepower
power measures how quickly work is done so if two people were to tighten the
same bolt by applying the same force but one did it in half the time
the net person is more powerful of course we use horsepower when talking
about cars or engines why horsepower well that's an
interesting story it's the mid 1700s the place is green
rock scotland a young boy sees a kettle boiling he
notices the steam forces the lid to rise and sparks an interest in the
power of steam the boy is james what you say his name every time you talk
about a light bulb so james is into power
he doesn't invent the steam engine but his improvements to it are so radical
he's known as the father of the modern steam engine
james simply adds a condenser this increase efficiency
so much that it can produce the same power as the competitor engine
while using 75 percent less fuel this invention kick-starts the industrial
revolution but before this happens james needs to
sell his engine so he has to figure out a way to explain
the huge technical advantage of his engine to ordinary people he could just
say my engine does the same thing as a newcoming engine but uses 75
less fuel but this is a bit of a mouthful
so he has to figure out a different way now of course steam engines are pretty
much new in those days people didn't really
understand steam engines or what they can do
what people did understand was horses if you want to pull something heavy you
get a draft horse to do the job so james needs to find a common way to
compare horses with steam engines and being an engineer he loves numbers
so he decides to figure out how much work a horse can do in a given time
there are different stories about how he does this for all we know they might all
be true perhaps he did more than one demo to
sell his engine anyway one story goes that watt measures
the work the ponies do lifting out the coal of a mine he works
this out by multiplying the weight of the coal by the distance is lifted
that's foot pound which is work then he calculates how long it takes for the
work to be done because that is power on average
each pony can do 22 000 foot pounds of work in a minute
and maintain that rate throughout the day so the measurement of pony power is
22 000 foot pounds of work in one minute
james simply increases by 50 percent to convert the horsepower why
well horses are about 50 bigger than ponies
so the measurement of horsepower is 33 000 foot pounds of work in one minute
you can adjust the combination so one horsepower can raise 330 pounds
of coal 100 feet in one minute or 33 pounds of coil 1000 feet in one
minute or 1000 pounds of coal 33 feet in one minute
so long as it's 33 000 in one minute you have one horsepower
horsepower can be converted into other units as well so
1 horsepower is equivalent to 746 watts if you take a one horsepower horse
that's a horse that can raid 33 000 foot pounds in one minute and put it
on a treadmill it could operate a generator producing a continuous 746
watts so the value of horsepower is not absolute but the
apples to oranges comparison works wonders for james
it helps the owner of a draft horse know that a steam engine can do five times
more work than a single draft horse does so that's the story of how horsepower
was invented and here's the thing we can't
actually measure car horsepower it's a man-made number but we can figure out
what it is if we know torque and rpms and we can measure torque in rpms using
a dynamometer or dino the earliest version of a dyno
invented to measure torque was in 1821. it was called the prony brake if you're
thinking shouldn't it be pony brake horsepower pony brake makes sense
actually no it was the prony brake because it was
named after its inventor gaspard deproni the similarity of pony
in horses is just weirdly coincidental or is it modern
dinos can measure torque and revolutions per minute are rpms we then use
math to work out horsepower torque times rpms
divided by 5252. but why 5252 that's a whole lot more math but
basically the faster the crankshaft spins with the same amount of force
the more power the car will have remember the two people tightening the
boat they both turned the bolt using the same torque
the one who did it in half the time is more powerful
so let's talk about torque and horsepower when it comes to diesel
versus regular engines diesel engines produce more torque while
petrol engines produce more horsepower why is this
well imagine we have a diesel regular gas engine
and say for the purpose of this example they're exactly the same
size and diameter compression is higher in a diesel engine
that's because a diesel engine must compress the fuel air mix
so much that it spontaneously explodes in a petrol engine mixture is ignited by
a spark instead the explosion spreads from the spark
outwards in the diesel engine the explosion occurs simultaneously
everywhere in the engine this creates a more
forceful explosion also since the piston has to travel further in the diesel
engine the distance from the center of the
crankshaft to the center of the crank pin
or throw can be greater so this is more force multiplied by a greater distance
which makes more torque but this also means it takes
longer in a diesel engine for the crank to complete a revolution
the shorter throw and stroke of the gasoline engine results in higher
revolutions per second which creates more horsepower
now it's not surprising that torque and horsepower get confusing
it's a complicated relationship it gets even more complicated
when you introduce other factors like weight and gearing into the equation
so what does it mean for you cork gives you lots of low-end power if you need to
do a lot of work like toning a horse or pony
or you're traveling long distances then torque is what you need
if you're traveling shorter distances you want speed and the ability to
overtake on a highway then what you need is an engine
optimized for speed and torque in other words horsepower
a lightweight sports car can operate on high rpms
which will give it high horsepower even though it has relatively low
torque but it's not going to tow your boat
so what's more important horsepower or torque they both are but for different
reasons we have more exciting car content coming very soon so
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