Premium Gasoline and Engine Knock
Most internal combustion automobile engines, whether they're four, six or
eight cylinders, operate on a Balenciaga Bag Sale
fourstroke cycle known as the Otto cycle. The four strokes are: intake,
compression, combustion and exhaust. To put it in the simplest of terms, each of
the vehicle's pistons moves up and down within a cylinder. As the piston moves
to the bottom of the cylinder, a mixture of fuel and air flows in. The piston
then moves upward, toward the top of the cylinder, compressing the air and fuel
mixture as it does so. Just as the piston reaches the top of the cylinder, that
cylinder's spark plug ignites. The spark creates a small, controlled explosion
that forces the piston to the bottom of the cylinder. In the final stroke of the
cycle, the piston moves upward to push the exhaust gas out of the cylinder. Once
the exhaust gas has been pushed out, the entire cycle begins again. For a much
more indepth look at how an internal combustion engine operates, you may want to
read How Car Engines Work.
As long as this process works as described above, the engine runs smoothly.
But occasionally the pressure of the piston itself will cause the air and gas
mixture to ignite prematurely during the compression cycle, creating a smaller,
less powerful explosion. This is called preignition and it's the cause of engine
knock, the erratic rattling or pinging sound you may occasionally hear
underneath your car's hood. A little bit of engine knock isn't necessarily bad
for your engine, but it's not desirable, either. It means that your engine isn't
running as efficiently as it could be, and left unchecked, it could eventually
cause damage. Engine knock reduces your car's performance, too, so you
definitely want to avoid it. How, you may ask? Well, lowoctane gas is more
likely to ignite under the pressure of the piston alone, so it's also more
likely to produce engine knock.
Does this mean you should always use highoctane gas? Not necessarily. It
really depends on the compression ratio of your engine. This is the ratio of the
volume within the cylinder when the piston is at its lowest point to the volume
within the cylinder when the piston is at its highest point. The higher the
compression ratio, the more http://www.balenciagatop.com/
compressed the air and fuel mixture becomes and the more likely it is
to ignite before it's supposed to due to pressure alone. Cars with a low
compression ratio don't need premium gas because there's little danger of the
air and fuel mixture igniting improperly. But highperformance engines, which
have a high compression ratio, are more prone to preignition and can truly
benefit from premium fuel. This would include the engines in most luxury
cars.
Even so, premium gas isn't always necessary for these engines. We'll find out
why on the next page..
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