Quote:
Originally posted by Stubman
Duke higher compressions engines risk pre-ignition due to the higher compression and if that occurs heat or hot spots on the pistions etc. could cause damage. Hence the need for higher octane gas that won't ignite before the spark plug ignites it(proper point in the stroke).
If you don't have pre-ignition then higher compression engines don't always equate to hotter EGTs.
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What???
Preigntion is causes by "hot spots" that act as a source of ignition and is equivalent to advancing the timing. Retarding timing heats up the exhaust gas and the combustion chamber boundaries, so retarding the timing can lead to preigntion, which leads to detonation. This was common on seventies and eigthies vintage engines that had retarded (from ideal) idle timing. Since the EGT and combustion chamber walls would heat up at idle they would often detonate once a load what applied when accelerating.
All other things being equal a higher compression engine will have lower EGT.
Duke
03-15-2004, 11:56 AM
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