dished vs. flat top piston.
dished vs. flat top piston.
(OP)
Most OEM Gasoline engines use a dished piston. I'm assuming that there is an advantage in reduced ignition advance timing requirements and/or reduced emmissions. I've asked a number of custom piston manufactures but no one seems to know. Any thoughts or information? -----Phil





RE: dished vs. flat top piston.
malbeare
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare
www.sixstroke.com
RE: dished vs. flat top piston.
I'm not sure that the practice is anything more than a cost saving device for the mfgrs as in a race/performance design, the practice is non existent...save for a couple extreme and, rare cases.
Rod
RE: dished vs. flat top piston.
ISZ
RE: dished vs. flat top piston.
RE: dished vs. flat top piston.
Since the edges of the combustion chamber are usually the zone in which detonation is initiated, accelerating these gases towards the centre of the chamber (where the plug is generally located) means that more ignition advance can be used without being knock limited. There is also a corresponding increase in flame kernel development and reduction in burn time (and improvement in combustion stability) due to this mechanism.
That said, issues arise when the geometry is such that at lower piston speeds quench occurs, with a corresponding increase in pollutants due to incomplete combustion of the charge.
MS