What is engine detonation and how can one prevent it?

What is engine detonation?

Engine detonation takes place when excessive heat and pressure in the combustion chamber of an engine causes the air/fuel mixture inside to ignite on its own. 

Engine detonation or engine knocking is a common problem that occurs in vehicles. This can cause serious damage to the engine and other internal parts of a bike or car. 

Generally, turning on the engine sparks the air/fuel mixture. This then ignites a single flame kernel to propel the vehicle forward. However, when heat and pressure ignite this mixture, instead of one, multiple flames are created. 

These flames then collide with huge force and cause sudden rise in cylinder pressure. 

This sharp rise in pressure then causes various internal parts like pistons, rings, bearings, gaskets, etc. to become overloaded, which is known as detonation or knocking. 

What are the symptoms of engine detonation?

Whenever engine detonation takes place, it causes a pinging or knocking sound which can be heard during acceleration or throttle tip-in. This sound is different from normal exhaust noise since it is high-pitched and is emitted from the engine compartment. 

What are the effects of engine detonation?

Once detonation happens, it can cause fair to severe damage to an engine, which can be irreversible or at least, very costly. Detonation can melt spark plugs, crack piston rings, hammer rod bearings and blow gaskets. 

Reference Video - What is engine knocking?

What should be done when detonation occurs?

If you hear such a knocking or pinging sound, you should take the foot off the throttle immediately and stop the vehicle. It is also important to take it to a service station to check for damage before using it again. 

Using it while knocking occurs can exacerbate the damage and lead to long term issues. Furthermore, it can also be unsafe for the rider.

It is clear that engine detonation can cause significant damage to a vehicle. Here are some ways to prevent detonation from occurring:

Use high octane fuel

The octane number of the fuel indicates its ability to resist self-ignition. Therefore, the higher the fuel octane, the better the fuel’s ability to resist self-ignition and the lower the chances of detonation. 

Standard 87 octane protects most engines, but engines with high compression or forced induction may require higher octane fuel. 

Reduce the compression ratio

Compression in the cylinder determines the heat in the chamber and thus, one can control the other. In order to ensure that the heat and pressure remain stable and not exceed limits, the compression ratio should be controlled.  This can be done through use of different cylinder heads, pistons and head gaskets. 

Check the ignition timing

Over advanced timing in an ignition can cause the pressure in the cylinder to rise too fast. This can lead to detonation. It can be helpful to check the ignition timing and reset it according to the manufacturer’s specifications.

Use a colder spark plug

The tip of a spark plug is many times the main source of self-ignition. A plug that is too hot can retain too much heat and cause a detonation. Switching to a spark plug in a colder heat range can often resolve this issue. This would reduce the chances of self-ignition. It would help if you use a spark plug guide before you decide the one to buy.

Increase cooling capacity

Heat is usually the main cause for detonation. Excess heat can often be due to an ineffective cooling system. Improving the cooling system of the vehicle by replacing the radiator, installing a better fan, fan shroud or coolant can help with increasing the cooling capacity. 



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