Engine Knocking
Knocking (also called knock, detonation, spark knock, pinging or pinking) in spark-ignition internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front.
The fuel-air charge is meant to be ignited by the spark plug only, and at a precise time in the piston's stroke cycle. Knock occurs when the peak of the combustion process no longer occurs at the optimum moment for the four-stroke cycle. The shock wave creates the characteristic metallic "pinging" sound, and cylinder pressure increases dramatically. Effects of engine knocking range from inconsequential to completely destructive.
Knocking should not be confused with pre-ignition. They are two separate events, however, pre-ignition is usually followed by knocking.
Read more about Engine Knocking: Normal Combustion, Abnormal Combustion, Pre-ignition, Causes of Pre-ignition, Detonation Induced Pre-ignition, Knock Detection, Knock Prediction
Famous quotes containing the words engine and/or knocking:
“The machine unmakes the man. Now that the machine is perfect, the engineer is nobody. Every new step in improving the engine restricts one more act of the engineer,—unteaches him.”
—Ralph Waldo Emerson (1803–1882)
“Once we begin to appreciate that the apparent destructiveness of the toddler in taking apart a flower or knocking down sand castles is in fact a constructive effort to understand unity, we are able to revise our view of the situation, moving from reprimand and prohibition to the intelligent channeling of his efforts and the fostering of discovery.”
—Polly Berrien Berends (20th century)