Detonation in an internal combustion engine is primarily caused by using fuel with a lower-than-recommended octane rating.
Detonation (often called engine knock or spark knock) occurs when the air-fuel mixture spontaneously ignites due to excessive heat and pressure inside the cylinder after the spark plug has fired. Instead of a smooth, controlled burn, the remaining mixture explodes violently, causing rapid pressure spikes and potential engine damage.
If the air/fuel mixture is compressed too much, it can detonate. Low coolant or a bad water pump can cause the engine to overheat. Too much heat can cause the air/fuel in the chamber to detonate.
Detonation occurs when excessive heat and pressure in the combustion chamber enable the air fuel mixture to autoignite. Instead of a single flame kernel in the combustion chamber there will now be several flame fronts.
Moderate to severe detonation could be noticed as engine roughness, vibration or loss of power and eventually engine damage. A pilot should always be looking for unexpectedly high Cylinder Head Temperatures (CHTs) or Exhaust Gas Temperatures (EGTs) which may be a sign that detonation is occurring.
The condition most likely to lead to detonation in a reciprocating engine is the use of fuel with a lower-than-specified octane rating.
A detonation is a rapid and violent type of combustion where an explosive shock wave propagates supersonically through a material. Reaching speeds greater than the speed of sound, it produces extremely high temperatures and pressures, causing much more destruction than standard burning.
Low-Octane Fuel
Another problem that causes detonation engine knock is fuel that has octane lower than what your engine requires. Higher octane fuel burns more quickly. Lower octane fuel does not burn fast enough in high-performance engines, and, as a consequence, it will detonate multiple times.
There are 4 main reasons why detonations occur in 2-stroke engines: ignition timing, squish, combustion chamber volume, and octane rating. In all cases, what you must avoid is rod knock, a situation that leads to irregular combustion and detonations.
Preventing engine detonation (knock) requires managing cylinder temperature and pressure, primarily through higher octane fuel, lower compression ratios, proper ignition timing, and cooler intake air. Key strategies include using premium gasoline, reducing boost on forced induction engines, avoiding overheating, and ensuring proper air/fuel mixtures.
Based on this analysis, the stoichiometric fuel mixture is the factor that does NOT contribute towards detonation.
Because of the noise that it makes, detonation is called “engine knock” or “pinging” in cars. High heat is detrimental to piston engine operation. Its cumulative effects can lead to piston, ring, and cylinder head failure and place thermal stress on other operating components.
Detonation is caused by excessive cylinder temperatures and pressures. This doesn't happen with an excessively rich mixture, ever. It can happen if leaned to peak at high power.
A detonation produces a supersonic shockwave that causes immediate, devastating destruction. The four primary effects are blast overpressure (crushing shockwaves), thermal radiation (intense heat), fragmentation (flying debris), and seismic/crater effects.
Yes, a lean fuel mixture is a primary cause of engine detonation (also known as engine knock). When there is an insufficient amount of fuel relative to the air, the combustion process burns more slowly and creates dangerously high temperatures within the cylinder.
A plug that's too hot will retain too much heat, causing detonation. A change to a colder heat range plug is often all that's needed to shut down unwanted detonation. Be aware, though, that too cold a plug can cause the opposite problem of fouling, which is when a plug fails to fire the air/fuel charge altogether.
Other causes of detonation are improper ignition timing, high inlet air temperature, engine overheating, oil in the combustion chamber, or a carbon build up in the combustion chamber.
Slight detonation shows up as a small roughing of the area, appearing much like it has been lightly sand blasted. There may also be scoring down the side of the piston due to molten piston material being splattered onto the bore and disrupting the lubricating film of oil. 2. Lower the compression ratio.
If we take the moment of combustion of the mixture at the top as a starting point, the two-stroke engine works as follows: when the piston reaches the top dead center, the mixture is burnt by the spark from the spark plug and explodes, and this explosion launches the piston down to the so-called bottom dead center.
To fix engine detonation (spark knock/pinging), immediately switch to higher octane fuel, retard ignition timing, and check for cooling system issues. Detonation is caused by excessive heat and pressure, so reducing cylinder temperature, lowering compression, or using better fuel can eliminate the dangerous pre-ignition.
Detonation is another cause of head gasket failure because it damages the armors or fire rings, allowing cylinder pressure to leak past the armors.
It seems common to have people think that they are hearing detonation at idle. Detonation, almost always, requires engine load in order to exist. There is little to no load on the engine during idling. Having said that, the higher the rpm the least likely it is for detonation to occur.
A detonation is an extreme type of supersonic combustion where a shock wave and chemical reaction front travel together, causing violent, rapid destruction. Detonation speeds range from 2,000 to 8,200 meters per second.
To detonate is to explode or cause something to explode. If a bad guy lights the fuse of a stick of dynamite, run before it detonates! In war, there is a lot of detonating, which is when something violently explodes, like bombs or grenades. When someone steps on a landmine, it detonates.
There are three categories of electrical detonators: instantaneous electrical detonators (IED), short period delay detonators (SPD) and long period delay detonators (LPD). SPDs are measured in milliseconds and LPDs are measured in seconds.