Theo,
Sounds like my Lionel train track layout. ;-) Can't see any value in
multiple turnings and flow redirections in a system that is best
straight through. The purpose of a cross over is to take advantage of
the rarefaction wave timing in the individual exhaust pipes on each bank.
Since each cylinder fires at a different time, the attached header pipe
is filled with a "sausage" of exhaust gas from each cylinder as the
exhaust valve opens, releases gas, and closes. The volume for the pulse
varies with the pressure in the cylinder that is decreasing as it
empties, after merger in the tube collector.
In firing order, each exhaust collector junction is filled with a train
of pulses (and pressure). The opposite side of the engine is doing the
same thing, but the phasing (time of occurrence of the wave) is not the
same.
The concept of a Cross Over is to take a high pressure zone on one side
and transfer the gases into the other bank during it's low pressure
zone. Sort of like a train of sausages, and transferring excess, when
there is some.
It is more efficient, and actually quiets a loud system. The benefits
are marginal, but acceptable. (~5%)
I do not understand how going to plumbing extremes, in this simple
pressure equalization scheme, pays off for the work and weight involved,
if it does any measurable good at all.
Willing to learn.
Steve
Theo Smit wrote:
>Steve, and Listers,
>
>Larry's exhaust is a (very nice) example of an H-pipe crossover. A popular
>modification on late-model Mustangs is to install an X-pipe crossover, so
>dubbed because the pipes have 45 degree elbows immediately aft of the header
>collectors, the pipes meet in the middle, and then have a 90 degree bend so
>that they again separate at 45 degrees (relative to the long axis of the
>car). This is supposed to give some slight performance benefit over H pipes,
>but obviously is hard to do on an installation as tight as the Tiger's, at
>least if you use production headers like Rick's or CAT's. If you were to do
>up a custom header set where the collector exits were already aimed at 45
>degrees inward, then you might save enough room front-to-back to get it all
>to fit in.
>
>http://www.ampperformance.com/store/bxpipe.htm
>http://www.mustang50magazine.com/techarticles/4376/index1.html
>
>Best regards,
>Theo
>
>
>
>
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Steve Laifman
Editor
http://www.TigersUnited.com
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