Are "pre-ignition" and "detonation", the same thing?
If not; can they have the same consequences?
Bob, JC gave a good description. I would change it slightly though.
Preigniton is as he described. Burning of the fuel prior to the spark plug igniting the fuel. Preignition begins as the fuel burning, ignited by anything from hot carbon, to a sharp metal edge and so forth and hopefully continues as fuel burning.
With detonation, the fuel does not burn, but rather explodes. This violent explosion is almost instantaneous and creates huge stress within the engine.
A normal engine burns the fuel in a controlled manner. Terms such as flame front are often used. In comparison, a flame front could be considered similar to a weather front. Rather predictable and following a path.
Preignition compared to weather may be a front traveling along a path. Let's say expecting to drop rain in the city late in the day. As the weather moves, it is forced to travel over the mountains, this change lets the front begin to drop rain early. Bad example but maybe the idea of something other than the spark plug igniting fuel is realized.
Comparing detonation to weather sort of. Consider an earthquake. All seems good at one moment, the next moment it's as if a huge force disturbed everything.
Often, people are unaware of the technical differences. Engine tuners, from Kart racers to Nitro Funny Car racers know all to well of detonation. Preignition is not that common.
Ultimately much of this relates back to internal cylinder pressures. Variables such as throttle setting, ignition timing, fuel quality can come into play, and fuel air ratio mixture.
It is also possible for an engine to begin a proper burn of the fuel. However if the fuel was ignited by the spark plug at the improper time (advanced timing), the fuel could begin its burn, then as the pressure inside the cylinder increases, the possibility exists to detonate.
Hope it helped.
PK
:2thumbs:
