mrx

Hi,

first of all i know the difference between knock and pre-ignition but there is one issue that is unclear:

if i have pre-ignition from too advanced ignition timing is it a must to have knock before the pre-ignition or is it possible that i have NO knock but a pre-ignition situation.

i know that you can have a pre-ignition without knock if you have an external ignition source but my question is only of pre-ignition from too advanced timing!

Hope someone can help...

0mtber

iTrader: (2)

Detonation occurs in the combustion process when the advancing flame front, which is pressurizing and heating the unburned mixture ahead of it, does so at such a rate that unburned fuel in that zone achieves its auto-ignition temperature before the arrival of the actual flame front. The result is that the unburned mixture combusts "spontaneously" and over the entire zone where the auto-ignition temperature has been achieved. The apparent flame speed in this zone is many orders of magnitude faster than that in conventional combustion initiated by a normal flame front, with the result that the local rise of pressure and temperature is significantly sharp. This produces the characteristic "knocking" or "pinking" sound, and the local mechanical devastation that this can produce on piston crown or cylinder head can be considerable. Actually, "knocking" is the correct terminology for what is a really a detonation behavior over a small portion of the combustion charge. A true detonation process would be one occurring over the entire compressed charge. However, because detonation in this strictly defined sense does not take place in the spark-ignition engine, the words "knocking" and "detonation" are used interchangeably in the literature, without loss of meaning, to describe the effects just discussed.

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mrx

Hi,

thats what i allready know... my problem is (thats why i ask) i had an engine:

B16, 10.2:1 CR, Stock internals with 6.5psi of boost with 25,9° of timing and the engine had a damage because of pre-ignition.

i know the timing was too much for this engine, thats clear but!

at the tuning there was absolutly no sign of detonation. not at the knock sensor and no sign on the spark plugs (befor/at/and after peak tourqe).

The car runs great for a few weeks and then one time he get pre-ignition.

why can this happen? i thought it was because of the to advanced timing but what was strange is that there was never any sign of detonation/knock

mrx

bump for the night

mrx