new pinging question

[CHR!S]

i searched and could'nt find the answer to these questions:

what can pinging do to your engine, specifically,
what does pinging sound like,
and is race gas (either complete or pump/race mix) necessary to ward off pinging in a 250 two stroke? what octane rating can withstand 9:1 to 10.6:1 compression, paired with an fmf sst?

 

[76GMC1500]

The term pinging is descriptive of the sound the problem makes. Technically, pinging is the collision of two seperate flame fronts within the cylinder. Normally, when fuel ignites, a flame front travels outwards from the sparkplug until all of the fuel in the cylinder is consumed. But, certain conditions can generate a second flame front started elsewhere in the cylinder. The second flame front is usually started by a hot carbon deposit. As for the damage, pinging doesn't really do any damage itself, but it can lead to detonation which melts down pistons and breaks spark plug electrodes filling your cylinder with shrapnel. Detonation is the explosive ignition of fuel. Detonation sounds like marbles in a can, but is usually fairly faint. You might not be able to hear it over your exhaust. If you experience detonation, you are using the wrong fuel, your spark plug is too hot, or your engine is improperly tuned.

 

[John Cena]

I think I read somewhere the SST pipe is bad for making bikes ping, could be wrong.

 

[uts]

The term pinging is descriptive of the sound the problem makes. Technically, pinging is the collision of two seperate flame fronts within the cylinder. Normally, when fuel ignites, a flame front travels outwards from the sparkplug until all of the fuel in the cylinder is consumed. But, certain conditions can generate a second flame front started elsewhere in the cylinder. The second flame front is usually started by a hot carbon deposit. As for the damage, pinging doesn't really do any damage itself, but it can lead to detonation which melts down pistons and breaks spark plug electrodes filling your cylinder with shrapnel. Detonation is the explosive ignition of fuel. Detonation sounds like marbles in a can, but is usually fairly faint. You might not be able to hear it over your exhaust. If you experience detonation, you are using the wrong fuel, your spark plug is too hot, or your engine is improperly tuned.

I always thought pinging was the sound made by detonation ie the are they same and they are bad. Try a higher octane fuel.
UTS

 

[76GMC1500]

Detonation makes more of a knock than a ping.

 

[john3_16]

When you raise the compression it makes fuel easier to ignite...So you need a higher octane to offset this...If you have an easily ignited 90 octane gas and add compression you increase the likelyhood that the fuel will ignite at the wrong time resulting in a knocking sound...


From what I understand the SST pipe affects the pressure wave that goes back to the cylinder and it raises cylinder and piston temps...When it runs hotter that extra heat may also generate combustion at the wrong time and result in a knock...This is my best guess as to why the sst pipe causes knocking so I'm not 100% sure...

I've ridden a CR250 with raised compression (Terry Varner cylinder) with an SST pipe and even with VP red it knocked pretty badly when rolling on the gas right off idle...The jetting was about as clean as you could get so perhaps running a tad richer would cool things down a bit.