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2,413 Posts
Bob Sheaves noted:
The Hemi design combustion chamber is one of the poorest designs for emissions - why do you think it took so long to get it into production? It almost did NOT make emissions test requirements even with the modifications. NOx is the problem due to the cool temp flame front inherent in the design (also why it builds so much torque). There is also a little problem called "flame quench" (which causes additional NOx) with a true Hemi design, as was used on the V16 aircraft engine and the automotive engines produced in the 1950s. Today's Hemi is that (a "Hemi") in name only. [Editor's note: Bob is referring to the head design. It is not a true hemispherical head, but looks vaguely like a hemispherical head with parts filled in.]
The Hemi design combustion chamber is one of the poorest designs for emissions - why do you think it took so long to get it into production? It almost did NOT make emissions test requirements even with the modifications. NOx is the problem due to the cool temp flame front inherent in the design (also why it builds so much torque). There is also a little problem called "flame quench" (which causes additional NOx) with a true Hemi design, as was used on the V16 aircraft engine and the automotive engines produced in the 1950s. Today's Hemi is that (a "Hemi") in name only. [Editor's note: Bob is referring to the head design. It is not a true hemispherical head, but looks vaguely like a hemispherical head with parts filled in.]
