What is Torque?
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 wheel 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.
English 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 lug 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:
A force is applied at a distance.
In the combustion chamber as the piston reaches TDC (Top Dead Center)
the point where the only to go is back down,
once the spark has ignited the mixture the force propels the
piston back down which forces the conrod (connector-rod) down
which turns the crankshaft and because this point is furthest away
from crankshaft center it creates torque (from a leverage point).
In short, Torque is pullingpower i.e momentum to move parts and
get the cycle going. A steamroller has little BHP but alot of torque
to get it moving.
Producing More Power
Using all of this information, you can begin to see that there are
lots of different ways to make an engine perform better.
Car manufacturers are constantly playing with all of the following
variables to make an engine more powerful and/or more fuel efficient.
Increase displacement - More displacement means more power because
you can burn more gas during each revolution of the engine.
You can increase displacement by making the cylinders bigger or
by adding more cylinders. Twelve cylinders seems to be
the practical limit.
Increase the compression ratio - Higher compression ratios produce
more power, up to a point. The more you compress the air/fuel mixture,
however, the more likely it is to spontaneously burst into flame
(before the spark plug ignites it). Higher-octane gasolines prevent
this sort of early combustion. That is why high-performance cars
generally need high-octane gasoline -- their engines are using
higher compression ratios to get more power.
Stuff more into each cylinder - If you can cram more air
(and therefore fuel) into a cylinder of a given size, you can get
more power from the cylinder (in the same way that you would by
increasing the size of the cylinder). Turbochargers and superchargers
pressurize the incoming air to effectively cram more air into
Cool the incoming air - Compressing air raises its temperature.
However, you would like to have the coolest air possible in the
cylinder because the hotter the air is, the less it will expand when
combustion takes place. Therefore, many turbocharged and supercharged
cars have an intercooler. An intercooler is a special radiator
through which the compressed air passes to cool it off before it
enters the cylinder.
Let air come in more easily - As a piston moves down in the intake
stroke, air resistance can rob power from the engine. Air resistance
can be lessened dramatically by putting two intake valves in each
cylinder. Some newer cars are also using polished intake manifolds
to eliminate air resistance there. Bigger air filters can also
improve air flow.
Let exhaust exit more easily - If air resistance makes it hard for
exhaust to exit a cylinder, it robs the engine of power.
Air resistance can be lessened by adding a second exhaust valve
to each cylinder (a car with two intake and two exhaust valves
has four valves per cylinder, which improves performance -
- when you hear a car ad tell you the car has four cylinders and
16 valves, what the ad is saying is that the engine has four valves
per cylinder). If the exhaust pipe is too small or the muffler
has a lot of air resistance, this can cause back-pressure,
which has the same effect. High-performance exhaust systems use
headers, big tail pipes and free-flowing mufflers to eliminate
back-pressure in the exhaust system. When you hear that a car has
"dual exhaust," the goal is to improve the flow of exhaust by
having two exhaust pipes instead of one.
Make everything lighter - Lightweight parts help the engine perform
better. Each time a piston changes direction, it uses up energy
to stop the travel in one direction and start it in another.
The lighter the piston, the less energy it takes.
Inject the fuel - Fuel injection allows very precise metering
of fuel to each cylinder. This improves performance and fuel economy.
Guide written by Dazza & Scooby.
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