Engine Knocking is a phenomenon known to mechanics also as terms like “knock”, “detonation”, “spark knock” or “pinging” and was discovered by Harry Ricardo in a series of experiments undertaken in 1916-1919 aimed at discovering the reason for aircraft engine failure.
This phenomenon happens only in spark-ignited internal combustion engines, or better said… gas engines and most of the time it’s confused with pre-ignition. This is the case since almost all pre-ignition events are followed by engine knocking.
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Under normal circumstances a 4 stroke engine works exactly in the fashion described by it’s name.
It’s movements are divided into 4 elements:
In this animation… you can see the proper way that a 4 stroke engine works, burning the air/fuel mixture in an organized and controlled fashion.
Combustion is started by the spark plug and the ignition advance allows time for the combustion process to develop peak pressure at the ideal time for maximum efficiency. As combustion continues, a mixture of fuel/air is burned and gases in the combustion chamber rapidly expand and push the piston downwards. Pressure smoothly rises to a peak and after that, the exhaust valve opens and the piston moves up to eliminate the resulted burned gas.
This is fine and dandy but sometimes things don’t go as planned and abnormal circumstances appear.
Engine knocking usually appears when a low octane rating or otherwise bad fuel is used. This convergence can also occur when the engine and fuel injection or carburetors are out of tune… or the most common cause occurs when deposits (carbon build-up) can be found in the cylinder.
Thankfully the engine and fuel timing don’t just go out of tune by themselves generally, so that leaves us with low octane rating, bad fuel and/or carbon deposits.
These two elements prevent the fuel from being burned efficiently and completely. The remainder or leftover usually “sticks” to the cylinder wall, piston tops, and valves as a part of internal combustion. This little area heats up and is known as a “hot spot” which can trigger the air/fuel mixture to detonate earlier that usual. Usually detonation or engine knocking tends to occur when the piston is starting it’s travel upwards in it’s compression stroke and before the actual detonation time. This provokes a “shock” wave that travels throughout all the engine internals and instantly creates a peak of cylinder pressure while the piston is also compressing these gases.
For example, this can happen at the rate of at least 800 times per minute when your engine is idling! Although this occurrence at idling is rare, an engine under load can have these stresses grow tenfold in short order.
Moderate engine knocking provokes particle wear that is absorbed by the oil and pushed around the engine’s oil system causing unnecessary wear and tear on other internal engine parts before it reaches the oil filter and remains there in most cases. This type of wear has a look similar to erosion, abrasion or “sandblasting” effects.
Severe engine knocking however, can lead to engine and component failure in the form of burned holes in pistons, broken pistons, connecting rods or even worse a complete and total engine failure. This is especially true in higher performance turbocharged applications, when engine knocking becomes so severe as cylinder heat and pressure overcome the internal components strength and things begin to break apart. Many a good engine has succumb to pre-ignition, detonation and the resultant engine knocking that by the time the driver is aware of this condition, it is far too late to get out of the throttle to save the engine before complete failure.
Many newer engines are higher compression designs and require better fuels and/or higher octane ratings than a mere 85. This combined with the growing popularity of direct injection and how direct injection actually allows for higher buildups of carbon deposits, is of particular concern.
5 Tips to Protect your Engine from Engine Knocking
- Fill up your tank only from reputable gas stations
- However often you can afford, use fuel with higher octane ratings or be sure to follow your owner’s manual on recommended minimum octane ratings
- Make sure your spark plugs are regularly changed as recommended by your owners manual
- Whenever you hear any type of pinging or engine knocking, reduce the throttle immediately
- Eliminate or prevent carbon deposit buildup by using a quality fuel additive designed specifically to reduce carbon buildup
One way to make your life easier is with the use of a quality Engine Oil. An Engine Oil such as DuraMax has the capacity to protect your engine even when the fuel you use is of a lower octane. DuraMax is different in the fact that it is a fuel catalyst and allows your engine to burn fuel more efficiently and more completely than it can on its own. Years of testing have proven its effectiveness for internal combustion engines of all designs, compression ratios and includes turbocharging, direct injection, supercharging and naturally aspirated engines.
DuraMax has the necessary cleaning components in it’s DNA with a formula which eliminates carbon deposits and prevents them from appearing, which is a root cause of detonation and engine knocking. Read more about DuraMax and discover how a small investment of a few cents per gallon, which actually saves you money with improved performance and gas mileage, can end up being profitable when you factor in the overall longevity of your investment. DuraMax is full synthetic too. Check it out today and see the many testimonials of others using DuraMax