"Ron Soave" <redlotus@spacey.net> writes:
>My understanding: A header is a manifold that has pipe lengths and
...
>are chosen so that there is what is sometimes called an ejector effect (AKA
>shock wave tuning or inertial extraction) where the pulse from one cylinder
>is timed so that the momentum of the slug of exhaust leaves an area of low
>pressure behind it that will cause an increase in intake charge during the
>overlap period (TDC) by "sucking" in more on intake (no Monica Lewinsky
A minor point: that's a nice and very common idea to explain header
tuning, but the physics is wrong. It has more to do with reflection of
shock waves back towards the ports (and when they arrive there) than
momentum creating suction. That's one reason why "stepped" headers are
beneficial - they create a series of smaller spaced-out reflections, which
widens the power-band. Read a good book on exhausts or the book that comes
with a software-dyno (I forget the title).
--
Randell Jesup, Scala US R&D, Ex-Commodore-Amiga Engineer class of '94
Randell.Jesup@scala.com
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