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I was doing some flow calculations at work for a Hi-Pressure Steam system (1000PSI to be exact). What was interesting is, once we regulated the pressure, we needed to create a low pressure zone on the downstream side. Now, what does this have to do with exhaust. Technically, once you get the collector length optimized, you effectively need to "kill" the scavenging effect. Way back this was easy - everyone ran open exhaust, so the collector length was whatever it needed to be and you were done with it.

Where am I headed with this? I think there may be power to be made by running the smaller diameter primaries [ie 1.75" for a big block] with a standard 3" collector, then instead of running the same or smaller diamter pipe, running a somewhat larger diam - say 4". This should create a low pressure zone. The high pressure gases will hit the low pressure zone and should effectively increase the siphoning effect of the smaller tubes as the cooling gases try to fill the larger space. Added benefit, the gases will cool more rapidly and require less volume as they exit the larger space. If the theory is correct, you would need smaller tubes and less split on the exhaust side of the cam due to much higher velocities in the primary tubes. This is basically proven theory in twostroke expansion chamber design.

Hey what can I tell you, spent 8 hours today behind the wheel of my pickup. 3-1/2 hours out, unloaded a full load of furniture, misc boxes and supplies, up 1 rather high flight of stairs I might add, 1 hour of local runs, then immediately drove back another 3-1/2 hours. The mind starts to wonder. Food for thought anyway. Besides. we needed a new "philosphical" theory in the performance section. Things have gotten too serious in here.
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