>But since the engine RPM is lower, you don't want
>the pressure wave to come back too early, so you want a longer pipe. I
>really goofed there. Sorry for the confusion.
BINGO!
My bad for even bringing 2 strokes into the equation as they do require the
reflection from the convergence cone at the end of the pipe, or baffle on
muffled pipes. Now the only reason you even need the reflection of the pulse
is as you said to hold the intake charge in the cylinder. 4 strokes do not
have that problem, as much, do to valve timing. If you were to place a valve
on the exhaust, then you would not need the convergence cone and the engine
would run extremely well on just a header, ala 4 stroke. But now I'm going
way off in some abandoned field and talking to the butterflies about how to
make this a perfect world :)
But all of this holds true with 4 strokes as well, as long as you look only
at the expansion of the pulse and how it scavenges the other cylinder. If
the exhaust pulse moves at a constant speed regardless of RPM, and you are
running low RPM's then you must delay it from entering into the collector
where it creates a vacuum to scavenge the other cylinders. Lower RPM/longer
tube. As it takes longer to travel a longer distance there by giving the
engine a chance to open an exhaust valve on another cylinder. If you are
running high RPM's then you want a shorter tube to get that pulse (actually
a shockwave) into the collector where it will expand and scavenge the next
cylinder to open its exhaust valve.
I'm not trying to start a battle of terms and theories, just that the part
you mentioned on shorter headers = lower RPM's was backwards. I'm personally
torn between the DT's and something else that works as well that can be
coated to try and beat the heat. Preferably stainless so I won't have to
worry about rust or oxidation blowing them out in just a couple of years.
John
98 Dak CC 4X4 Sport, 5.2L, Auto, 3.92LSD, T&H Package, Power Everything,
Billet Grill, Nerf Bars, Rhino Liner, Snug Lid, DDBC, home brew FIPK 2.
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