Fluid dynamics, Cale is a thinking man !
Okay, what happens to the exhaust gases as they travel further away from
the engine ? It cools off. What happens to gases as they cool ? They
contract. When the gas contracts , it slows down. This minimumizes
scavenging. How do we speed it up to scavenge better ? We reduce the
pipe size. I think exhaust systems should be designed with ever
decreasing diameters every couple feet to keep the flow pulses velocity
up for scavenging and to hold some pressure for the break into the
atmosphere. If the gasses are below atmospheric pressure like with a
pipe too large, why would the exhaust gas exit ? The higher pressure
inside the pipe sucks the exhaust out into the atmosphere.
A true dual exhaust on a V8 engine makes it run like two four cylinders
mechanically attached, and scavenging is cut in half with only half the
pulses pulling twice as far apart.
Thanks,
Eugene
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