Dr.Jeff
True Classic
This is specifically regarding the exhaust manifold (header) to cylinder head interface.
I've seen two theories about the flow of exhaust gas from the head to the exhaust system. One is basically to have the smoothest possible transition between the two components with the ports perfectly matched. The other is to have an increase in diameter in the manifold's ports, or "step" transition, to create a reversionary pulse effect. Some tubular exhaust headers have more than one step increase as the gases transition along the tubes. But with a cast manifold it would be just at the junction to the head.
Frankly I do not know if there is any clear advantage to either design. I've seen a few tests that claim to show each is better than the other. So that really does not help. But I'm also not too current on this subject. Anyone have more info about this? And for the 'stepped' concept are there any basic criteria for how it should be designed?
I've seen two theories about the flow of exhaust gas from the head to the exhaust system. One is basically to have the smoothest possible transition between the two components with the ports perfectly matched. The other is to have an increase in diameter in the manifold's ports, or "step" transition, to create a reversionary pulse effect. Some tubular exhaust headers have more than one step increase as the gases transition along the tubes. But with a cast manifold it would be just at the junction to the head.
Frankly I do not know if there is any clear advantage to either design. I've seen a few tests that claim to show each is better than the other. So that really does not help. But I'm also not too current on this subject. Anyone have more info about this? And for the 'stepped' concept are there any basic criteria for how it should be designed?