What is knocking and detonation in IC engine?

Knocking (also knock, detonation, spark knock, pinging or pinking) in spark ignition internal combustion engines occurs when combustion of some of the air/fuel mixture in the cylinder does not result from propagation of the flame front ignited by the spark plug, but one or more pockets of air/fuel mixture explode …

What is Preignition in an engine?

Pre-ignition is the ignition of the air- fuel charge while the piston is still compressing the charge. The ignition source can be caused by a cracked spark plug tip, carbon or lead deposits in the combustion chamber, or a burned exhaust valve, anything that can act as a glow plug to ignite the charge prematurely.

What is knocking and detonation?

Knocking vs Detonation Knocking is the making sharp sounds due to uneven combustion of fuel in the cylinder of a vehicle engine. Detonation is the process of pre-ignition or auto-ignition of a fuel in an engine’s combustion chamber.

What is Preignition explain?

Pre-ignition is a situation in which the fuel-air mixture in a spark ignition engine ignites before the timed spark, because of contact with a hot surface. Over-heated spark plugs and exhaust valves are the main causes of pre-ignition. Pre-ignition might be the consequence of the spark plug tip getting too hot.

What are the differences between detonation knocking and preignition?

Detonation is an uncontrolled combustion event which occurs after the spark event. Pre-ignition is an uncontrolled combustion event which occurs before the spark event. Knock (pinging) is the actual noise that can be audibly heard if detonation is bad enough.

What is detonation in gas engine?

Detonation—sometimes called knock or pre-ignition—is a pinging sound that can sometimes be heard during acceleration and throttle tip-in. Unlike normal exhaust noise, detonation is a higher-pitched, raspy note that emanates from the engine compartment.

What causes detonation and preignition?

Preignition is caused by the presence of something in the cylinder hot enough to act as an ignition source. Detonation is caused by anything that adds heat to the last small volumes of unburned mixture out near the cylinder wall.

What is detonation in piston engine?

Detonation is the abrupt combustion or explosion of the fuel charge inside the cylinder. In simplified terms, when detonation occurs, the fuel charge ignites quickly in an uncontrolled explosion, causing a pounding or hammering force on the piston rather than a steady push.

What is detonation in engine?

What causes detonation?

Detonation is generally caused by excessive heat, excessive cylinder pressure, improper ignition timing, inadequate fuel octane or a combination of these. Of the previous, excessive heat is usually the culprit. As an engine is modified to generate more power, additional heat is produced.

What is preignition how can it be detected?

Mild preignition can be detected, regardless of the location of the source, and the results also clearly indicate the difference between preignition and detonation. An oscilloscope is used to identify preignition; detonation is determined by its audible knock.

What is the difference between knocking or detonation in SI and CI engine?

In S.I. engines detonation is caused by the auto-ignition of end gas towards the end of combustion whereas knocking in CI engines is due to auto-ignition of the first charge at the start of combustion. The air fuel mixture that self ignites in SI engines is homogeneous.

What is the difference between detonation and pre-ignition?

As far as the engine itself is concerned, one of the key differences between detonation and pre-ignition is that an engine can be designed and built to tolerate light-to-moderate detonation, but not necessarily so with pre-ignition. Neither, however, is desirable as neither aids in combustion stability and control.

When does detonation occur in a combustion engine?

For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts. The key point here is that detonation occurs after you have initiated the normal combustion with the spark plug. Pre-ignition: Pre-ignition is defined as the ignition of the mixture prior to the spark plug firing.

What does it mean when a car pre ignits?

Pre-Ignition Pre-ignition (self-ignition) occurs when the fuel mixture in the cylinder burns before the spark-ignition event at the spark plug. Pre-ignition may or may not cause permanent engine damage, but it does lead to engine inefficiencies and may cause engine damage if it is a severe or continuous event.

Where is the detonation point on a 4 valve engine?

In a four valve engine with a pent roof chamber with a spark plug in the center, the chamber is fairly uniform in distance around the spark plug. But one may still may see detonation by the exhaust valves because that area is usually the hottest part of the chamber.