What exactly does detonation hurt in an engine?

Discussion in 'Fox 5.0 Mustang Tech' started by stangboy, Feb 11, 2004.

  1. I know detonation kills an engine, but what exactly is it killing and how is it killing it? I'm wondering because I faught a detonation problem with my car for the longest time and I'm about to put H/C/I on my car and I just want to know if my engine is week now since I faught that detonation problem so long. i don't want to put all that stuff on and have the bottom end of my motor go out on me.

    Oh, and just to make sure I'm right, pinging is detonation, right?
  2. Most common is melted pistons, or even a rod through the side of your block. Detonation causes extreme heat. Things like to melt when its around
  3. Yes, pinging is detonation. It always occurs after normal combustion is initiated by the spark plug. The initial combustion at the spark plug is followed by a normal combustion burn. 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. Yup, melted pistons, rods through a block, block splitting, crank walking, you name it detonation will do it...
  4. Well, I sure hope i don't have melted pistons and rods and whatever else. I'm not ready to rebuild my shortblock yet.
  5. it really depends on the severity of detonation and the parts being used. slight detonation caught early could have no noticable effect. as it worsens you could start to melt electrodes of your spark plugs, burn holes in pistons, break connecting rods, chew main/rod bearings to sh**.

    when the a/f mix spontaneously combusts too far in advance of TDC due to excessive heat it tries to push the piston against its existing rotation, so even if you are lucky enough to save your pistons etc the bearings could be fudged necessitating a rebuild.

    in your case stangboy i'd recommend doing a compression test before slapping on the new hci. if the engine isn't making any bad noises at this time it is probably ok.


    edit: if anyone sees a problem with the above statement(s) please let me know, i'm not afraid to learn :nice:
  6. Pinging or spark knock is not the same as detonation.

    Pinging is preignition of the fuel air charge by some source of ignition other than the spark plug. The source of the ignition can be a hot spot in the combustion chamber such as carbon, a spark plug insulator, side electrode, or a sharp edge on a valve. It occurs before the spark plug can fire and while the piston is still on its upward movement towards TDC. That is the cause of the characteristic ping or ringing sound, much like shaking a coffee can full of BB’s.

    Detonation is the uncontrolled explosion of the fuel air charge after the spark plug fires and starts to burn. In a properly running engine, the spark plug ignites the fuel air charge and it burns slowly and evenly across the combustion chamber, much like a fire as it burns its way across a grassy field. When detonation occurs, the ignited fuel air charge causes an increase in the combustion chamber pressure and temperature. The remaining fuel air charge that has not been burned self–ignites explosively causing tremendous heat and pressure. The source of secondary ignition can be the same as preignition, or can be simply due to the heat and pressure. Detonation is what damages engine parts because of the excessive heat and pressure.

    Pinging can lead to detonation, and the results are the same: engine damage because of the excessive heat and pressure
  7. thanks jrichker :nice:

  8. Is detonation exhibited only on INITIAL start-up of the engine or does it exist/experienced throughout the driving of the car.

    How do you sense if you have a detonation problem? Does the car overheat, does the engine knock loudly, are there driveability issues such as vibrations coming from the engine/car shake.

    Does the car over heat as a result of detonation?

    More info please on the signs of detonation.
  9. Detonation will usually occur at higher power levels due to the extra heat generated by the combustion process. An engine that overheats is more prone to detonation.

    A loud knocking is one of the signs of detonation, along with overheating if allowed to continue. In most cases, the engine will do severe damage to itself before it gets to overheat.

    A good example of what detonation sounds like is what happens when you use ether as a starting fluid. The rattle and clanging noises you'll hear are detonation at a low enough level that it won't hurt the engine.

    Some input from the forced induction guys as to their personal experience would help to better explain some of the symptoms and signs.
  10. So, the pinging sound I used to hear coming from my engine at high rpms(above 4k rpms) is or isn't detonation? Thats what I'm trying to figure out.
  11. try forcing a piston down when it is not able to, something has got to give sooner or later...
  12. I wish I had looked at your sig more carefully. The 94-95 engines seem to have more ping problems than the earlier models. It has to do with the computer and the spark & fuel tables from what I understand. Repost your questions in the 94-95 Specific forum and maybe you'll get some working answers rather than just an explaination of what it is and why.